METROPOLIS : a thematic network in support of precautionary sciences and sustainable development policies

METROPOLIS

Measurements play a very important role in modern society to define the quality of manufactured products, determining the safety of food, checking compliance with established limit values and quality standards, etc. Environmental measurements, in particular, are fundamental to understand the environment in which we live, current trends and understand the causal relationships between the pollution produced by human activities and its effects on ecosystems.

Many environmental measurements are carried out in the various EU countries, mainly to meet requirements set by EU and national legislation. The data collected represent a great source of potentially valuable information in support of decision-making. Unfortunately, the quality of the data available is still highly variable: some of the collected data have to be critically examined to establish whether they provide a suitable basis for decision-making. Why is this so? The following critical areas can be identified:

• lack of traceability: it is impossible to base decisions on data that are not sufficiently documented (not traceable to well established references and therefore not reliable). • lack of harmonisation of the procedures applied by laboratories (starting with the sampling procedure, but also including the approach adopted for the calculation of the uncertainty). This lack of harmonisation makes the data obtained from different sources difficult to compare • lack of representativenes s: data that do not reflect the reality that we want to represent are simply not fit for purpose. • too high a level of uncertainty associated with the data collected makes the process of decision-making critical (on the other hand, in some cases the uncertainty is not expressed at all!) • lack of metadata: information about the data (what, how and when measurements were made, who owns the data, and so on...) and the way they are reported / used is an essential requirement to allow the use of the data for other purposes (e.g. compilation of databases).

All this emphasises the role of metrology (basic infrastructure for measurement sciences) as a means of ensuring the quality (traceability and therefore comparability) of the data obtained from the various EU monitoring programmes, throughout the whole "measurement cycle" (i.e. from the collection of the data to the delivery of the information to decision-makers).

METROPOLIS

The METROPOLIS [START_REF]Metropolis (Growth Programme -contract[END_REF]2] network was created in July 2002, under the 5th Framework Programme, to respond to the need for an overall, cross-sectoral assessment of the state of the art of measurements and monitoring systems in the environmental field in Europe. The objectives of Metropolis include:

• gathering information and knowledge about the problems/ shortcomings that we face today in environmental monitoring • identifying the fields where research and further work are needed in order to improve the quality and comparability of environmental data across Europe. Each work package deals with a different aspect of the "measuring cycle" as illustrated in the figure 1.

The purpose of measurement: what and why to measure? The measurement strategy: how to ensure correct spatial and temporal representativeness of the data obtained. The actual measurement operation: reference methods, quality assurance and quality control systems, standardisation process, reference materials, etc. The data processing step: statistical analysis, modelling, interpretation and generalisation of the data collected. The presentation (delivery) of data to the final user & support to decision-making: ensuring that data are converted into meaningful information and recommendations for decisionmaking.

Figure 1. The measurement cycle

The Metropolis network explores the main areas of concern throughout the measurement cycle, from the definition of the measurement strategy for the collection of representative data, to the aspects relating to harmonisation of measurement data and the evaluation of uncertainty, down to the interpretation and presentation of the results to policy-makers. For each of these critical areas Metropolis proposes a number of actions which lead to the publication of reports and guidance documents, the organisation of workshops, seminars, internet discussion fora, etc.

In the area of QA/ QC, Metropolis will produce: • a critical review of significant national and / or EU documents and standards for the calculation of uncertainty, with recommendations on new guidance material, at EU level • a study of the status of PTS (Proficiency Testing Schemes) in the EU in the environmental field, as a follow-up to the EPTIS database • a list of FAQs (Frequently Asked Questions) to help testing laboratories to work in accordance with ISO 17025 • a guide on the use of Reference Materials in the environmental field.

One of the outcomes of Metropolis in the field of measurements and measurement methods will be the development of the database on bio-monitoring assays and chemical analytical measurements. This is a database with a dynamic web interface to collect and make publicly available information about existing standard analytical chemical methods and bio-monitoring assays and alternative methods/ assays that are not yet standardised. Information provided for each method entered in the database includes, for example: EU legislation regulating the substance, limitations of the method/ assay, application range, QA/ QC information, links with other web-sites where more detailed information can be found, etc. Although there is always room for further improvement, this database can be considered a valuable resource for identifying available information and current knowledge & data gaps in measurement techniques. It will provide an opportunity for improving the exchange of information between the legislator and practitioners, including academic researchers, as regards the knowledge currently available and the appropriate analytical responses available today.

But Metropolis also deals with aspects such as the role of Geographic Information Systems (GIS) in environmental monitoring and the difficulties associated with the use of the measurement results in decision-making.

The outcomes of Metropolis regarding the role and gaps in the use of GIS in environmental monitoring today will be revealed in another presentation. As for the presentation of the measurement data in support of decision-making, Metropolis is exploring in particular, the role of expert judgements for measurements that cannot be measured (because of technical difficulties, ethical problems, etc.) and the use of measurement results in decision-making when dealing with data that are affected by large uncertainty. The report that will be produced by Metropolis in this area will provide a survey of the existing decision-making theories (focusing on non-conventional theories fitting into the socalled "precautionary principle") and will try to conclude whether the existing uncertainty models used in metrology can be harmonised with the existing decision-making theories.

A number of discussion fora have been opened on the Metropolis web-site on various items of environmental metrology and five workshops will have been organised during the project. Three of those workshops are:

• "Techniques for data presentation and data distribution" (Gothenburg, September 2003), • "The State of the art and new trends in the use of reference materials in environmental monitoring and analysis" (Paris, 13-14 April 2004), which will involve the participation of experts from NIST, BAM, IRMM, ENEA, etc.. • the one that will be organised by JRC-ISPRA on 3-4 June 2004 on "Practical experience from air quality legislation to effective local abatement and public awareness".

As a final outcome Metropolis would like to ensure that an overall consistent message is conveyed to the final users. To this purpose a tool illustrating how the tasks and the final outcomes of Metropolis interrelate and how they can respond to the needs of the different categories of users will be made available on the Metropolis web-site.

All final documents and reports will be available at the end of the project (June 2004) on the Metropolis web-site (http://www.metropolis-network.net). We hope that these two years of work and the results of this project will help to provide the basis for long-term opportunities for concerted actions in the field of environmental monitoring as a follow-up to the activities of Metropolis.

Table 1 .

 1 Work packages organisation

	The Metropolis network is co-ordinated by INERIS
	(France) and brings together 38 participants from the most
	significant organisations and research institutes dealing with
	environmental metrology in 17 European countries, plus DG
	Environment itself in an advisory capacity.
	The project started in July 2002 and will end at the end
	of June 2004. The work is organised in six scientific work
	packages co-ordinated by INERIS (7th work package). As
	illustrated in table 1.


Isabelle Zdanevitch

Nicolas Moser

Caroline Charpentier

Alexis Moquet

Hervé Borrel

Measurement of ozone in ambient air with microsensors : on-site campaign

Ozone is actually one of the most important atmospheric pollutants in industrial countries. Measurement is well achieved by continuous monitors but a better information on ozone levels would be given by a denser monitoring network, made possible by using a lighter and cheaper technique like microsensors. Such sensors have been tested successfully in the laboratory. We have therefore undertaken a large on-site campaign, on air quality monitoring stations of the French Networks, to validate the use of microsensors on-site. First results of the campaign were improvements in conditioning and calibration procedures. Then, stabilised sensors showed most ozone values within an interval of +/-30 % of the concentrations given by the monitors.

INTRODUCTION

Ozone is a secondary pollutant produced by photochemical reactions between NOx and VOCs. It is one of the major atmospheric pollutants in Europe, specially in summer, and during hot years like 2003, is suspected to be the cause of numerous deaths [1,2]. Therefore, it is very important to precisely measure ozone when it occurs, so as to predict the evolution of the concentration, in order to reduce the sources of primary compounds. Measurement is generally done by continuous monitors installed in automatic stations distributed over the industrial countries where the primary pollutants are largely produced. But the monitoring stations are sometimes not situated at the locations where the ozone concentrations are the highest, in remote places like countryside or mountains, because of the needs (electrical power, data communication..). Also, continuous monitors are very sensitive and stable but expensive, so lighter and cheaper measurement techniques, which can be used in numbers, are very desirable. The possible use of microsensors sensitive and specific to ozone, besides the classical techniques of continuous monitors and the diffusion tubes, could be a very interesting alternative. After a promising evaluation of such sensors in the laboratory completed by on-site tests in Switzerland [START_REF] Zdanevitch | Abstract book 9 th IMCS[END_REF], we have decided to undertake a large on-site campaign in France, during 5 months of the summer 2002.

EXPERIMENTAL

Description of the campaign

Prototypes equipped with ozone microsensors, developed by MICS, have been installed on 13 continuous monitoring stations of the French Air Quality Networks, between early May and the end of September 2002. Stations were chosen to be representative of the various sites encountered in France, such as urban, industrial, rural, seaside, mountain sites, located from East to West and North to South of France. All the stations comprised at least a continuous ozone monitor for comparison.

Description of the apparatus and data acquisition

Prototypes were lightweight : they consisted in a solid plastic box, containing the electronics, with two holes at the bottom, for the ozone module and the temperature sensor. Electronics in the prototype emulated the sensor, which is heated at 400 °C, and allowed the calculation of ozone concentrations, corrected for ambient temperature, using the individual calibration factors determined individually for each sensor. Humidity variations were not corrected. The sensor module comprised the ozone microsensor, protected by an hydrophilic membrane, and a small memory which carried the calibration factors. Sensors modules were dismounted by the staff of the networks every 15 to 30 days, and sent to INERIS for recalibration. Prototypes had two connections wires of 10 meters : one for the electrical supply (220 V -50 Hz), and the other one for acquisition of the sensor signal, in a 0-1 V range. This cable was connected to the data acquisition system of the monitoring station, like for the continuous monitors, allowing the staff to collect the data on the central system of each network. Ozone concentrations given by the microsensors and the monitors were averaged over periods of 15 minutes. Raw data from the microsensors were also stored in the prototype and collected every time the sensor modules were dismounted. The staff of each Network sent all the data every 2 to 4 weeks to INERIS and MICS.

RESULTS AND DISCUSSION

New sensors are already sensitive to ozone, but as it is generally the case on most chemical sensors, the response is not constant over the first days of functioning. This corresponds to a rearrangement of the structure of the metal oxide. Over a period of 15 days, the difference between ozone concentrations, calculated from the sensor response and given by the monitor, increases dramatically : see fig.

CONCLUSIONS

The previous study [START_REF] Zdanevitch | Abstract book 9 th IMCS[END_REF] showed that these ozone sensors are very little sensitive to NOx, which could be the major interferents for ozone monitoring in ambient air. With a temperature compensation, good conditioning and calibration procedures, these ozone microsensors are an interesting technique to complement continuous monitors. They could be used in more locations than the monitors, with a good accuracy, which would allow a better mapping of ozone concentrations over a large area.

  1. It corresponds to a change during the time, of the sensor calibration curve with ozone concentration : see fig.2. The third and fourth calibration curves become more similar and linear with ozone concentration, indicating a stabilisation of the sensor response. Such conditioned sensors give very good stability results at all atmospheric concentrations encountered (see figs.

  3 and 4), within +/-30 % of the monitor response.

Fig. 1 :Fig. 2 :Fig 3 :Fig. 4 :

 1234 Fig. 1 : drift of the sensor response to ozone during the first 2 weeks


Sylvain Geffroy
email: geffroy@lasim.univ-lyonl.fr

Emeric Frejafon
email: frejafon@ineris.fr

Patrick Rairoux
email: rairoux@lasim.univ-lyon1.fr

ATMOSPHERIC AEROSOL SIZE RETRIEVAL FROM LIDAR DATA APPLYING GENETIC ALGORITHM APPROACH

In this paper we present a novel approach using a genetic algorithm (GA) to solve the Lidar "ill-problem". It is inverting aerosol size distribution from multiwavelengths Lidar data in the UV-VIS-IR spectral range. This method do not need any predefined size distribution shape and its also running with data having poor S/N. Numerical convergence test of the GA have been done on both simulated data and on Lidar field measurements performed during the French POVA [4] Campaign. It shows that size distribution is retrieved in millisecond range, which represent a considerably decreasing in computing time consuming. Comparison between GA size distribution retrieval and SMPS ground-based measurements has been done showing an excellent agreement.

1.

METHOD Retrieving the atmospheric aerosol size distribution remotely is a non-trivial problem where several authors [START_REF] Bôckmann | Hybrid regularization method for the ill-posed inversion of multiwavelenght lidar data in the retrieval of aerosol size distribution[END_REF][START_REF] Millier | Microphysical particle parameters from extinction and backscatter lidar data by inversion with regularization[END_REF][START_REF] Ligon | Aerosol properties from spectral extinction and backscatter estimated by an inverse Monte Carlo method[END_REF] have made important contributions. The main difficulty for retrieving the atmospheric aerosol size distribution based on remote sensing data is to find the solution of a "ill-posed" problem. In particular, in a single scattering regime, a first kind Fredholm integral expressing the extinction coefficient for a system of particles a(A,z) should be solved. In term of aerosol size distribution the extinction coefficient is given by: a(A,z) = [START_REF] Bôckmann | Hybrid regularization method for the ill-posed inversion of multiwavelenght lidar data in the retrieval of aerosol size distribution[END_REF] where n(r,z)

is the size distribution (product of ;V(z)the number of aerosol and p(r,z) the normalized size distribution), r is the radius of the particles and z is the distance of the particles from the Lidar position. Q^{i~ ,X,m) is the extinction efficiency, m the refractive index, A the wavelength. The relation between the optical extinction and the size distribution can be expressed, as a matrix, where a discretization of the integral should be made using kernel and error function [START_REF] Bôckmann | Hybrid regularization method for the ill-posed inversion of multiwavelenght lidar data in the retrieval of aerosol size distribution[END_REF][START_REF] Millier | Microphysical particle parameters from extinction and backscatter lidar data by inversion with regularization[END_REF].

where is the extinction Kernel.

^32 ^1064

>"

Based on predefined kernel function, a genetic algorithm (GA) is applied to solve the matrix system

(3), obtaining also a discretized size distribution pt(z)

and then the number of particle 7V(z) using equation [START_REF] Bôckmann | Hybrid regularization method for the ill-posed inversion of multiwavelenght lidar data in the retrieval of aerosol size distribution[END_REF].

Figure 1 : Principle of genetic algorithm.

Genetic algorithms have been widely used [START_REF] Herrera | Tackling Real-Coded Genetic Algorithms: Operators and tools for the Behavioural Analysis[END_REF][START_REF] Hogson | Genetic Algorithm to the Determination of Particle Size Distribution from Light-Scattering Data[END_REF], as they are efficient for solving complex optimization problems.

Applying GA for solving our problem, a standard presentation related to live science can be used (show figure 1). The algorithm is based on natural survival mechanisms to the involved quantities by mating, and mutation. These mechanisms are applied to a set of vectors, which represents a population. They correspond to chromosomes in the context of GAs, which are all possible solutions of the problem and are characterised by a specific "fitness", i.e. their performance with respect to objective functions such as chi-squared values. Vectors having low fitness may then enter the mating population to produce an offspring for the next generation, while vectors having high fitness are cancelled. Applying crossover and mutation -operations on these vectors will then create a new population as input for a new iteration. After a given number of generations, an optimal solution is then obtained, which corresponds to the most relevant vectors. Finally, a GA searches the solution space of a function by using simulated evolution where the fittest individuals reproduce and survive to the next generation, thus improving successive generations. However, inferior individuals also have a chance to survive and reproduce. Through this technique, all regions of the state space are explored. In many situations, particularly when complex optimization problems with numerous local optima should be solved, genetic algorithms provide an effective alternative. Genetic operators are used to create new solutions based on existing solutions within the population. There are two basic types of operators: crossover and mutation. Crossover takes two individuals and produces a new individual, while mutation alters one individual to produce a new individual.

In our investigation, the initial population is [/?,],

where vectors are generated randomly from uniform distribution and each variable is chosen within prescribed limits. The number of individuals in the population remains fixed and it is chosen at initialization. The GA then moves from generation to generation until a termination criterion met the optimized fitness. The stopping criterion is a specified maximum fitness ( % test). The process is monitoring by plotting the value of the fitness as the generation progress.

J.Ot-1 l.OE-3

RESULTS

To test this retrieval method based on remote sensing measurements, simulated and experimental data were used. Results obtained on numerical data using 355, 532, 1064 and 3370nm as Lidar wavelength are presented in Figures 2 and3. To approach real measurement condition, random errors have been added on simulated data in order. For the first test of the algorithm (see Fig. 2). A real size distribution measured in urban area (Lyon [7]) has been considered for optical extinction simulation. In figure 3 a tabulated "remote continental" [8] size distribution has been used for optical data simulation. In both case, the GA could retrieve the shape of the distribution with an error on the concentration depending on the S/N of the optical data (10 % relative error on optical data has been considered). Hence, measurements at four wavelengths (293, 400, 532 and 1064 nm) have been performed for this purpose. Typical data is shown in figure 5.

The Figure 4 shows a typical Lidar profile measured in the VIS spectral range, showing a strong vertical stratification of the aerosol in the atmosphere and this especially at 500 m above ground level (agi). The genetic algorithm was applied on extinction profile provided by two multi-wavelengths Lidar at an altitude of 500 m agi. A discretization at 6 different sizes was considered, covering the 20 nm to 2.5 urn size range. Computation of the kernel functions in regard to the 4 wavelengths were made considering spherical and fractal particles. The retrieved size distribution is shown in figure 6. Ground based SMPS (Scanning electric Mobility Particle Sizing) is also presented in this figure for validation purpose. The SMPS, which has a sizing range between 15 nm and 700 nm, shows a main mode centred at 100 nm and two other modes at the edges of its operating region. The GA retrieves the 100 nm mode and in the same way, two secondary modes. The mode in the micrometer size range could not be validated by the SPMS due to its size cut-off by 700 nm size.

3.

DISCUSSION AND OUTLOOK

he first results of this novel approach in solving the Ldar "ill-problem" using field measurements are promising in regards to the first validation. Moreover, GA approach bring several advantages in remotely atmospheric aerosol sizing. The first one is the low computation time (less than a second using a desktop computer). Secondly, Lidar signals at least 4 different wavelengths with low S/N (in the 10% range) are necessary to evaluate the main modes of the size distribution. However, several improvements should be made and this especially on the particle refractive index, which is taken as parameter in the actual GA. In further work, the refractive index retrieving will be included in the GA. The particles radius range of the retrieving procedure will be also investigated to monitor bigger aerosols size. For this, several algorithms, each dedicated to different size range can simultaneously run due to the fast computation time. Further validation of this algorithm will be made on different type of atmospheric aerosols, as for example background aerosols, Sahara dust, haze and clouds. Infield measurement, combing 3D scanning multi-wavelengths Lidar and standard ground-based device could rise to a quasi on-line measurement of the spatial and time distribution of the atmospheric particles size.

Passive optical remote sensing measurements of the atmosphere like sunphotometer data will be also explored with this algorithm and also extra-terrestrial aerosols of Mars and Titan.

8. Jaenicke R., Troposheric aerosols, in Aerosol-Cloud-Climate Interactions, edited by P.V. Hobbs. Academic Press, San Diego, CA; pp. 1-31 (1993).

4.

Figure 2 :

 2 Figure 2: Convergence test of the genetic algorithm (dash) performed on optical extinction data calculated with urban size distribution (line).

Figure 3 :

 3 Figure 3: Convergence test of the genetic algorithm (dash) performed on optical extinction data calculated with a tabulated size distribution as remote continental (line).

Figure 5 :

 5 Figure 5 : POVA field experiment in Chamonix (summer 2003). The two mutli-wavelenghts lidar instruments are shown: on the right the UV-VIS INERIS device and on the left the VIS-IR CEA/LSCE system.

Figure 4 :

 4 Figure 4: Typical Lidar signal at 400nm during POVA campaign.

Figure 5 :

 5 Figure 5: Field experiment results. Chamonix, July 2003. Comparison between SMPS measurements and genetic algorithm output at an altitude of 500m above ground level using multi-wavelengths Lidar measurements performed at 293,400, 532 and 1064 nm.

ACKNOWLEDGEMENTS

This work was supported by the French Ministry for Ecology and sustainable Development (MEDD), the Agence de L'environnement et de la Maîtrise de l'Energie (ADEME), the French National PRIMEQUAL2 program and the Institut National de l'Environnement Industriel et des Risques (INERIS). Results were obtained by coupling INERIS LIDAR and CEA/LSCE LIDAR during the POVA campaign. We gratefully thank Patrick Chazette from the CEA/LSCE providing VIS-IR Lidar profile, Jean Luc Jaffrezo from the LGGE and Didier Chappuis from the Alpes Air quality Network (AIR-APS).


Cécile Honore

Laurence Rouil

Frédérik Meleux

Laure Malherbe

Bertrand Bessagnet

Robert Vautard

Nathalie Poisson

Joëlle Colosio

Cécile Honoré^

FrédérikMeleux Laurence Rouil'

Bertrand Be-Ssagnet'

Robert Vantard

Nathalie Poisson-*

The PREV'AIR system, an operational system for large scale air quality forecasts over Europe : applications at the local scale

Keywords: atmospheric pollutants, database, deterministic model, forecast, ozone

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

operations, towards health effects and environment. Within the PREV'AIR project, INERIS is in charge of the PREV'AIR architecture development, delivering daily air quality related information; providing and archiving air quality data produced within the PREV'AIR system Moreover INERIS realises air quality studies for the MEDD including reporting and prospective analysis.

• IPSL (Pierre-Simon Laplace Institute) is a research institute in the field of environment, under the supervision of the National Centre for Scientific Research (CNRS). IPSL ensures the development of the chemistry-transport model(s) -the CHIMERE model(s) -used within the PREV'AIR system. 2 displays the ozone peak analyzed on the 09 th of August for D-l. Figure 3 displays the absolute difference (in ptg/m3) between thr ozone peaks simulated by the CHIMERE model and the analyzed peaks. Reliability and Scores of the PREV'AIR System _ During 2003 summer season, 174 days of forecasts have been issued: 85 % of forecasts realized without any problem; 4 % of the problems were related to hardware problems; J1% to software or data problems. The availability of the AVN data is of primary importance (the missing data is responsible for 5 % of the forecast failure). Some performance indexes (see table below) have been computed for the summer season, using the ozone peak concentrations measured in France and calculated for D-l and D+0 by the PREV'AIR system. Regarding the ozone peak, the performances of the system are quite satisfying.

Statistical Indexes

USE OF THE PREV'AIR AIR QUALITY FORECASTS AT THE LOCAL SCALE

In relation with the second objective of the PREV'AIR project, numerical air quality forecasts data have been made available to air quality related organisms. The only requirement for the demanding organism is to fill in a form specifying the exact domain on which the data are to be delivered. The numerical data are then put on a daily basis on the PREV'AIR web site. Two kinds of data are available over the specified domain: ozone and nitrogen dioxide surface data and 3D data for 22 chemical species. Up to now, about 15 organisms have applied for this service, for various applications: Downscaling and mapping of pollutant concentrations: Support to local expert forecasting; Provision of boundary conditions to local scale air quality simulation / forecast models.

Example of the Provence-Alpes-Côte d'Azur (PACA) region

This Mediterranean region is complex from an air quality modeling point of view: it is a coastal region with' complex terrain and meteorology (sea and valley breezes) with strong industrial emissions (Etang de Berre). It is beyond the scope of the PREV'AIR system to represent the detailed patterns of air pollution over such a region. Since June 2003, the feasibility of coupling the PREV'AIR system to a local air quality simulation system over PACA has been tested by AIRMARAIX, one of the AASQA in charge of air quality monitoring over this region. Daily high resolution (3 km) air quality forecasts have been issued for the Marseille area. Boundary conditions came from the CHIMERE continental model; high resolution air quality forecasts were performed using the MM5 and CHIMERE models. The high resolution emission inventory derived from the ESCOMPTE exercise. The feasibility exercise showed the capability of the local air quality simulation system to catch the patterns of air pollution around Marseille. The implementation of the system is planned to begin at the end of October 2003, and the same set up as the one tested during summer 2003 should be ready by May 2004.

PERSPECTIVES

In June 2004, a smaller domain only covering France has been added up to the continental one in the same outline apart from the horizontal resolution increased to approximately 10x10 km. This high resolution model should give more accurate forecasts, which in case of high ozone events should be provide to policy makers and media : (i) for people information and (ii) to take measure for reducing ozone level. An other French model, MOCAGE, freshly including to the PREV'AIR system carries out some forecasts at global scale. Aerosol forecasts have been delivered since the last winter season (starting end of October).

More observation data will be used in the analysis and verification processes (Italy (ARPA-EMR), Switzerland (NABEL/SAEFL), Poland (Institute of Environmental Protection, Katowice), Germany (UBA)...). Sensitivity studies will be done regarding the analysis process.

A general effort towards a more public-and user-oriented web site will be done.

  Figure 1Ozone, pic en ug/m3, le0&XÎ&2003 Krigeage des innovations (el observations)

  • ADEME (Agency for Environment and Energy Management) is a public institution under the supervision of the Ministries in charge of research, ecology and energy. It helps implementing public policies in the field of energy and environment at local, national and international levels. ADEME ensures the gathering, archiving and transmission of real-time

	Emission data come from the EMEP	simulated ozone peak. The resulting
	program4 , with hourly, weekly and monthly	maps are referred to as "analyses".
	temporal profiles from 1ER. Contrary to	Figure
	meteorological data that change from day to
	day, emission data are set once and for all
	within the PREV AIR system.
	Observed air quality data are used by the
	PREV'AIR system (see hereafter); they are
	transferred by various European organisms.
	For example, the French real-time air quality
	data are downloaded from the BASTER ftp
	server time and used to correct a posteriori
	the CHIMERE air quality (D-l) simulations.
	Numerical air quality
	forecast data*
	« Real-time » observations:
	'France (BASTER, ADEME)
	• Emilia Romagna (ARPA-EMR)
	measurements. The PREV'AIR system is supported by these technology progresses for 'Swiss (NABEUSAEFL)
	delivering daily forecasts in operational conditions. Germany (UBA)
	The PREV'AIR system is briefly presented hereafter, as well as the first conclusions that have
	been drawn after the first summer season of operation. Some examples of possible applications Air quality related organisms
	and use of the PREV'AIR system at local scale are presented.
	Since the 2003 summer season, the
	following output data have been made ARCHITECTURE OF THE PREV'AIR SYSTEM, INPUT DATA AND PRODUCTS available on a daily basis and freely through
	the Internet: The PREV'AIR daily air quality forecasts are computed using the CHIMERE chemistry-transport model(s). The CHIMERE model is used in its "continental" set up: pollutant concentrations are computed over Western Europe, with a 50 km*50 km resolution. Last summer season, ozone and nitrogen dioxide forecasts were delivered. Each day, • Maps of daily maxima and averaged forecast concentrations of ozone and nitrogen dioxide were available for D-l, D+0, D+l and D+2. Figure 1 displays the ozone peak forecast issued on the 08 th of August for D+0. • Each day, the ozone peak observation data have been used to correct the D-l	simulation, whereas the following three days are "true" forecasts. The meteorological forecasts necessary to perform the air quality forecasts are done in two steps: Low resolution meteorological forecast data are downloaded from the ftp server of the American National Weather Services, where they are produced using the Global Aviation Model (AVN) model. High
		resolution meteorological forecast data are
	Co-operative Program for Monitoring and	then locally computed using the MM5
	The first day of forecast is actually rather a Evaluation of the Long-range Transmission of Air -Pollutants in Europe	model.	'
	Institut fur Energiewirschaft und Rationei'e
	Energieanvvendung. University of Stuttgart

INTRODUCTION

Numerical simulations of pollution events with deterministic model has become easier during the last decade since computer ability increase. Then 3-dimensional chemistry-transport-model runs for long-term simulation or real-time forecast are allowing over large scale area on a single workstation. High file storage capacity in data processing and fast internet download give the opportunity to use a large database of meteorological parameters and pollutant concentration the forecast begins the day before (D-l), OOh UT and ends 96 hours later (D+3, OOh UT).

CAFE (Clean Air For Europe) project managed by the European Commission, and to the Convention on Long-Rangé Trans-boundary Air Pollution of the United Nations -Economic Commission for Europe. .

• Météo-France joins the system in 2004. air quality model which will be tested during the summer.


Billah Elmountacer

Rene Elabbassi

De-Seze

MOBILE PHONE USE AND TEMPORAL SKIN HEAT SENSATION

Keywords: Mobile phone, electromagnetic field, biological effects, heat, skin temperature

Epidemiological investigation of mobile phone (MP) users reported symptoms of discomfort feeling, warmth behind/around or on the ear and heat sensation of the cheek. These symptoms may be due to thermal insulation, conduction of the heat produced in the phone by the battery currents and running of the radiofrequency (RF) electronic circuits, and electromagnetic field (EMF) energy absorbed by the user's head. Using a Luxtron 790 fiberoptic thermometer we measured the temperature of the temporal skin due to GSM 1800 MHz MP radiated power (125 mW). We suppressed the EMF exposure by switching the RF signal from the antenna to a 50 £7 load. The ambient air temperature was 23°C and the MP was held in the normal position of use for 30 minutes to reach the thermal steady state. With a switched off MP, the increase in skin temperature was statistically significant 1.88°C. When MP was switched on, the increase was 2.93°C in reception mode, 3.29°C in emission mode without load and 3.31°C in emission mode with load. The temperature difference with or without load was not significant (t i7 = 0.707; p = 0.489), which means that the contribution of EMF absorption to skin heating is negligible. The result suggests that the heat sensations reported by the MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling time.

Introduction

Mobile phone "cell phone" use has dramatically increased over the last decade, but doubts remain over its safety. Many epidemiological investigations of MP users [START_REF] Oftedal | Symptoms experienced in connection with mobile phone use[END_REF][START_REF] Sandstrom | Mobile phone use and subjective symptoms. Comparison of symptoms experienced by users of analogue and digital mobile phones[END_REF] reported symptoms of discomfort feeling, warmth behind/around or on the ear and heat sensation of the cheek. These symptoms may be due to changes in the thermal exchange between the skin and the air due to the contact between the phone and the skin (thermal insulation), conduction of the heat produced in the phone by the battery currents and running of the radiofrequency (RF) electronic circuits transmitted to the tissue, and of a part electromagnetic field (EMF) energy absorbed by the user's head. The head exposure to EMF presents particular problems due to the close proximity between the source of emission (MP antenna) and the head of the user. A major part between 40-50 % of MP EMF energy is absorbed by user's head [START_REF] Bernardi | Specific absorption rate and temperature increases in the head of a cellular-phone user[END_REF] and the absorption is highest in the skin ~ 38.5 % [START_REF] Dimbylow | Characterisation of energy deposition in the head from cellular phones[END_REF].

The aim of this study is to quantify the temporal skin warming of the MP user in the normal position of use and to investigate the contribution of different parameters to skin increase temperature especially EMF energy.

Methods

The mobile phone used in this study was a GSM 1800 MHz Motorola mr 20 with a test card to control the use mode of the MP. It was used at maximal power during emission and their batteries allowed continuous emission without loss of power for the whole duration of the experiment. The emission parameters were as following: frequency: 1800 MHz; frequency of repetition of impulses: 217 Hz; duty cycle: 1/8; peak power/average power: 1 W/125mW.

We suppressed the EMF exposure by switching the RF signal from the antenna to a 50 Q load. During experiments the MP was: switched off; switched on in reception mode, in emission mode without load and in emission mode with load.

Temperature was measured using a fiberoptic thermometer (Luxtron 790) with 4 SFF-5 surface temperature sensors which can be used in normal listening conditions. The temperature was measured every minute during the experiment until thermal steady state was reached and the data automatically recorded on a computer. The accuracy of measures was ± 0.1 °C.

The sensors were calibrated at the beginning of each experiment in a water bath at ambient temperature (controlled by a mercury thermometer). For each volunteer, three sensors were used, one placed on the temple of the subject (skin sensor), another on the mobile phone surface in contact with the temple (phone sensor) and the last measures air temperature (air sensor). The 'skin sensor' was placed perpendicular to the line starting from the tragus in alignment with the lip edge, at the level of the temporo-mandibular joint, and held in position with porous adhesive tape (Figure la). The 'phone sensor' was placed on the flat surface between the screen and the keypad on the middle line using adhesive tape (Figure Ib). When the phone was in the normal using position, the two sensors were both parallel and contiguous. The use of these two sensors allowed the measurement of the kinetics of the raise in temperature at the skin-telephone interface until thermal equilibrium was reached. After calibration, the sensors were placed on the skin and MP in their reference positions. The temperatures of skin and MP surface switched off at room temperature were measured before beginning measurement at normal using position of MP. Then mobile phone switched off was held in the normal using position and the variations in temperature recorded until temperature equilibrium was reached (approximately 30 minutes). The same experiment was done with switched on MP: in reception mode in emission mode without load and in emission mode with load suppressing EMF exposure.

The MP was held in the normal using position "Cheek position" (CENELEC Standard 50361) to have the maximal contact between the MP surface and the skin of the MP user (Figure 2). This position may modify heat exchange between the skin and the ambient air and make the MP and the antenna close to the head of the MP user. In all experiments, the mean value of ambient air temperature (T air ) was 23.0 ± 0.8°C, the relative humidity was 50 ± 10 %, the air flow rate in the room was 0.01 m.s" 1 (natural convection) and the MP was held in the normal position of use for at least 30 minutes to reach the thermal steady state.

Results

Load EMF suppress efficacy:

To test the efficacy of the EMF suppress by switching the RF signal from the antenna to a 50 £2 load the SAR of the MP was measured by the SAM phantom (Figure 3). Using the MP connected to the load, the maximal value of SAR (SAR_10 g max = 0.01 W.kg" 1 ; SAR_1 g max = 0.02 W.kg" 1 ) was 15 to 19 times less when compared to the SAR using the MP without load (SAR_10 g max = 0.19 W.kg' 1 ; SARJ g max = 0.32 W.kg' 1 ). A commonly accepted SAR limit is: SARJO g max = 2 W.kg' 1 .

We can conclude that using this load is efficient to suppress the head EMF exposure from the MP antenna. This load can then be used in this study for testing the possible EMF effect on the heat sensation and skin temperature increase on the cheek.

Temperature measurements:

Temperature is recorded until equilibrium was reached around 30 min after the beginning of the experiment.

The mean value of temperature measurement concerns the steady state period.

The initial mean skin temperature (T Mn ) of volunteers at normal room temperature (23.0 ± 0.8°C) was 33.8 ± 0.6°C (reference). The study of the raise in skin temperature due to the physical contact with the phone showed that the equilibrium temperature at the 'skin-phone' interface was 35.7 ± 0.2°C. This was due to the decrease of the skin heat loss with the environment (Table 1). The mobile phone contact causes heat insulation of the skin surface. The temperature increase is equal to + 1.88°C (Figure 4).

The mobile phone temperature -as the skin temperature-increases when the MP is in contact with the skin surface. The skin and the phone sensor were face to face and give the same value at thermal equilibrium at skinphone interface. The skin temperature difference between the mobile phone switched on in emission mode with or without load experimental condition was not significant (t, 7 = 0.707; p = 0.489). There is no significant supplemental skin heating due to RF emission from the MP antenna, which means that the contribution of EMF absorption to skin heating is negligible.

Temperature increase at skin-phone interface and thermal equilibrium:

An example of the kinetics of the raise in temperature at the skin-telephone interface is presented in Figure 5. To reach the skin-phone interface thermal equilibrium we must wait at less 30 min. The calling time is an important parameter for heat sensation and discomfort feeling. More important is the time calling with MP skin contact more is the prevalence of warmth sensation.

Pain threshold:

The highest temperature increases detected during these experiments (T skin = 37.1°C) are in the environmental range and are experienced by the surface skin during hot summer days. No skin damage by thermal insult is experienced for T s id n < 44°C [START_REF] Hardy | Pain sensations and Reactions[END_REF], whereby a pain sensation replaces the feeling of temperature elevation in humans. No thermal skin damage can be suspected using MP in normal use.

Conclusions

The results show that the heat sensations reported by the MP users are exclusively caused by thermal insulation and heat conduction from MP associated with long calling time. The power of EMF emitted by the MP antenna is not sufficient to cause increase in cheek skin temperature when using MP. These results suggest an awareness of the symptoms, but no damaging health problem.

Figure 1 :

 1 Figure 1: Skin (a) and phone sensor (b) positioning.

Figure 2 :

 2 Figure 2: Phone held by the hand in normal user position "Cheek position".Three healthy male volunteers 25, 26 and 30 years old have participated for this study. For each trial 18 measurements were made to assess the repeatability of the measures. The mean values are given with one standard deviation (± 1 SD). The difference between experimental conditions was computed by Student's f-tests. The lvalues are given with their corresponding of degrees of freedom (subscripts beneath /-values). The accepted level of significance was p < 0.05.

Figure 3 :

 3 Figure 3: SAR measurements (W.kg" 1 ) averaged over tissue masses of 1 and 10 g using SAM phantom with mobile phone in emission mode without (a) and with load (b).

Table 1 :Figure 4 :

 14 Figure 4: Mean skin temperature increase at thermal equilibrium in contact with mobile phone (switched off, switched on in reception mode, in emission mode without load, in emission mode with load) compared to the initial temperature of the skin surface (reference) without mobile phone skin contact.

Figure 5 :

 5 Figure 5: Skin (T s kj n , °C) and mobile phone temperature (T mp , °C) plotted against time (min), with MP switched on in reception mode (2), in emission mode without load (3) and with load (4) during one experiment. Thermal equilibrium was reached around 30 min.

Acknowledgements

We are greatly indebted to the Regional Council of Picardy and the Ministry of Ecology and Sustainable Development (BCRD 2003, DRC02-03) for their financial support, and to France Telecom R & D for the SAR measurements they provided us.


Olivier Salvi
email: olivier.salvi@ineris.fr

Myriam Merad

Nelson Rodrigues Ineris

AN INTEGRATED VISION TO ASSIST THE EVOLUTION IN INDUSTRIAL RISK MANAGEMENT PROCESS IN FRANCE

Keywords: Risk management, Multiple-criteria methodology, multi-disciplinary approach

Management in the field of environmental protection and risk prevention has evolved to the increasing participation of all stakeholders in the decision-making process. It certainly results from the development of the Information society and the global increase of knowledge of the population, combined with the concerns of the populations related to a sustainable development of our civilization. Our "risk society", following the big industrial disasters (Flixborough,Tchernobyl, Bhopal, Challenger, and more recently AZF), has also developed a cautious attitude towards the role of the expertise when it comes to assessing risks, along with a question of the ability of science to give definite answers. This has lead in particular to the adoption of the Aarhus convention in 1998 and the evolution of several regulations in the developed countries. For example, in France the new law n°2003-699 of 30 July 2003 about the "prevention of the technological and natural risks and to the compensation for the damages" has introduced an important innovation into the process of technological risks prevention.

This law has enabled the involvement of the stakeholders in the decision-making process related to risk prevention and has urged the development of specific tools to deal with the complexity of risk management issues, in particular for those related to land-use planning.

As technical support to decision-makers in risk management from both public and private sectors, INERIS has played an important role for the evolution of the French risk management system. This paper describes an analysis on the difficulty to control major accident hazards in an evolving context where the industrial systems becomes more and more complex and where the expectations of the civil society has increased. Then, the authors describes how an integrated vision for industrial risk management has emerged in France and is being implemented in a new law adopted after the Toulouse disaster.

Introduction and context

France is known to use a deterministic approach in the control of major accident hazards [START_REF] Christou | Guidance on land-use planning as required by the council directive 96/82/EC[END_REF]. In the deterministic approach, the term deterministic means that the major accidents that are assessed in the risk assessment process are pre-defined and considered independently of their likelihood, which is not assessed. The underlying philosophy is based on the idea that if measures exist sufficient to protect the population from the worst accident, sufficient protection will also be available for any less serious incident. The deterministic approach gives a first importance of the limitation of the consequences of possible accidents. This idea appeared first in an imperial act in 1810, then in a law published in 1917 on hazardous and insanitary plants, but it was clearly reinforced with the law n°76-633 dated 19/07/1976 that became the 'Environment Code' on 18th September 2000.

The adoption in 1999 of the Seveso II directive within the European Member States has initiated evolutions in the various national risk management systems. In France, it has reinforced the importance of the prevention chapter of the risk management as the operator has to demonstrate the implementation of a safety management system. This has lead the authorities to admit that risk management can not only be organised with the limitations of the consequences of accidents.

At the same time, the ISO/IEC standard 73 was adopted and has described risk management as a decision making process based on a risk assessment. For the control of major accident hazards, this means that potential accidents and the way they are controlled have to be assessed in their context.

This paper describes the difficulty to control major accident hazards in an evolving context where the industrial systems becomes more and more complex and where the expectations of the civil society has increased. Then, the authors analyse how an integrated vision for industrial risk management has emerged in France and is being implemented in a new law adopted after the Toulouse disaster.

1. Difficulty to control major accident hazards as required by the Seveso II directive

The number of major accidents in Europe seems to remain more or less the same, despite of the efforts developed to control the major accident hazards since 1982 with the first Seveso directive.

A recent communication from the Commission (European Commission, 2002) indicates that the number of accident collected in the MARS database (Major Accident Reporting System of the European Commission) is between 25 and 30 major accidents par year, (see Figure 1) Using these data, the frequency of major accidents is estimated at about 3.10"^ per year if we consider the number of accidents reported in the database versus the number of hazardous installations throughout the European Union.

The 1999 annual report from the European Environment Agency [START_REF] Pettitt | Environment in the European Union at the turn of the century, Chapter 3.8 Copenhagen[END_REF] has also indicated that in spite of measures on major industrial accidents in force since 1984, the trend in accidents shows that many of the often seemingly trivial 'lessons learned' from accidents have not yet been sufficiently evaluated and implemented in industry practices and standards.

There are probably many reasons of the stagnation of the number of major accidents in the studied period. They will not be discussed in details in this paper. But as a remark, it is important to notice that if the number of accidents would have been normalised with the total production of hazardous products, the number might decrease.

According to these elements, a positive interpretation is suggested. The relative stagnation of the number of industrial disasters might show that the efforts in risk control have been efficient despite of the increase of the complexity of the industrial systems and the production. If not, we should have observed a growing number of industrial disasters. As a matter of fact, it appears that the limits of the technical systems like the chemical processes are better known and the instruments to control them are more reliable.

Evolutions in both the industry and in the society

2.11ncrease of the complexity of industrial systems

Long term structural changes have occurred in the industry, in particular through the concentration of companies in some branches. Moreover, often these structural changes were carried out with staff reductions, that may have an impact on the ways to manage the safety aspects in a given plant.

At the same time, the complexity of industrial systems has considerably increased in the last decades. It is due to the increasing of the knowledge in the technological fields and also to the development of technologies. Sciences have become wider, deeper and quicker, and the technological systems, that integrate knowledge from various disciplines, have become more complex for the operators.

These statements might explain that the number of major accident is not reducing as described in the previous paragraph.

Evolution towards a knowledge society and increase of society awareness

Several industrial catastrophes have strongly marked the public opinion : Bhopal (December 1984) in the chemical Industry, Chernobyl (April 1986) in the nuclear industry, the explosion of the shuttle Challenger (January 1987) in the aerospace sector. More recently the catastrophe of Enschede (May 2000, pyrotechnical material) and the catastrophe of the AZF factory in Toulouse (September 2001, ammonium nitrate storage) have shown that politicians and risk-decision makers are facing difficulties to manage technological risk. This situation is probably due to, on one hand, the complexity of the issue, and on the other hand, citizen's loss of trust in politics, since in a knowledge-based society, citizens expect more access to information and require transparent decision-making processes. Thus, the awareness of the general public about technological risks has increased and as well the demand for effective, consistent and adequate risk management. All these catastrophes have showed that the dialogue and the consultation of the public as of the various actors were not independent of the risk management process whose objective is to ensure long term safety of the populations. Thus the maintaining of an industrial activity is strongly dependent of the acceptance of the risks which it generates.

In general, three tactics of implication and communication with the various actors of risk prevention process are used.

The first tactic consists in being unaware of the opinion of the different actors (public or other). Our "risk society", following the big industrial disasters, has developed a cautious attitude towards the role of the expertise when it comes to assessing risks, along with a question of the ability of science to give definite answers.

The second tactic consists in providing the necessary information in order to convince the various actors "knowledge based theory approach" [START_REF] Maharik | Public views of using nuclear energy sources in space missions[END_REF]. This second approach is in the starting point of various current practices (e.g. the communication phase of the risk prevention process is a linearly posterior phase to the risk analysis one; the use of the concept of "grid of acceptability" within the framework of the safety studies, etc).

The third tactic consists in taking into account the opinion of the various actors upstream and during the decision-making process related to risks prevention: "value-oriented approach ". That it is on the international scale, with the Aarhus convention (1998) on "access to information, public participation in decision-making and access to justice in environmental matters" translated at the According to the discussion presented here, the key issues seem to be both scientific and societal.

Increase of the public participation in public decisions

Thus, management in the field of environmental protection and risk prevention has evolved to the increasing participation of all stakeholders in the decision-making process. It certainly results from the development of the "information society" and the global increase of knowledge of the population, combined with the concerns of the populations related to a sustainable development of When the various stakeholders are aware of risk issues, and involved in early stage of the decision-making process, the solutions inevitably become more sensible and legitimate. The quality of stakeholders participation in risk decision-making is often determined by how well informed they are about the nature of risk issues, and how responsible institutions deal with them.

The participation of the various stakeholders became possible by taking their different opinions and preferences in the risk decision-making process. The multiple-criteria decision-making methodologies can be really useful to aggregate this different opinion (criteria, preference, weight) to choose the most appropriate decision both at the national and local level.

One of the most famous problem in risk management dealing with both national and local constraints is the "land use planning around the industrial zones". INERIS has an important experience in land use planning dealing with natural risk: Natural Risk Prevention Plans [START_REF] Didier | Evaluation du risque d'instabilité en surface à l'aplomb d'une ancienne carrière souterraine-Principes d'une analyse par configurations types[END_REF], Mining Risk Prevention Plans [START_REF] Merad | Use of multi-criteria decision-aids for risk zoning and management of large area subjected to mining-induced hazards[END_REF]. INERIS has developed a new methodology based on a multiple-criteria method to control the urbanisation around the Seveso sites. This methodology in line with the increasing participation of the public will be presented in chapter 4.3.

A vision for a global risk management system

As written in the Third Assessment from the European Environment Agency [START_REF] Pettitt | Europe's environment : the third assessment[END_REF], "holistic approaches, which take an integrated perspective, are becoming more prevalent, with increasing attention to the reduction of risk of long-term environmental impact as well as acute health and property damage from accidents".

As technical support to decision-makers in risk management from both public and private sectors, INERIS has an important experience in risk prevention and is urged to answer to actual needs in technological risk prevention. To help risk decision-makers, INERIS has made its structure evolving and it has developed a integrated vision for risk assessment and management.

Evolution of the structure of INERIS team

The By working on research projects on the development of an integrated risk assessment approach, INERIS facilitated the opportunity to develop a team expertise combining the two cultures. Now, this team can offer to the industry integrated and global audits by multi-skilled teams, that allow studying the hazard of a plant and the appropriateness of the safety management system implemented. The requirements of the Safety Management Systems are therefore proportionate to the hazards of the plant. This is a quite innovative point in the risk control of the chemical process industry.

The constitution of the multi-skilled teams was a great step forward in the direction of global risk assessment, but the maturity of the team still has to be developed thanks to the introduction of systemic (science of complexity) concepts in risk assessment and management.

Development of an integrated vision for risk management

At the same time when the structure evolved, INERIS has initiated several projects both at European and national level to develop an integrated vision for risk assessment and management.

This paragraph describes several integrated projects carried out by teams with multi-disciplinary skills.

The ARAMIS method

In order to characterise the hazard potential and to demonstrate that the associated risks are controlled, an integrated risk assessment methodology has been developed within a project called ARAMIS for "Accidental Risk Assessment Methodology for Industries in the framework of the Seveso II directive". [START_REF] Hourtolou | ARAMIS Project : Development of an integrated Accidental Risk Assessment Methodology for Industries in the framework of SEVESO II directive[END_REF] The Development of an integrated technical and management risk control and monitoring methodology for managing and quantifying on-site and off-site risks, n°ENV4960243.

Beside, there was a need to establish a method that is capable to assess the risk level of an installation by integrating the preventive measures implemented by the operators. Such a method is a prerequisite in order to reach the goals of the Seveso II Directive, that are to improve the prevention linked in particular with the safety management.

So, the ARAMIS methodology proposes to characterise the risk level with an integrated risk index composed with independent parameters related to the consequence severity evaluation of scenarios, the prevention management effectiveness and the environment vulnerability estimation describing the sensitivity of the potential targets located in the vicinity of the hazardous establishments. The application of this method will result in a more consistent and harmonised risk evaluation and safety management strategy in all European Countries. The innovation in this method relates to the integration of the 3 parameters. Moreover, for the evaluation of the prevention management effectiveness, not only formal aspects of the safety management system are assessed, but also the safety culture in the plant. This is done by human factor specialists who built questionnaires and interviews methods.

ARAMIS is therefore a good example of the new kind of methods that have to be developed to assess risks in plant with a global approach.

Risk assessment in France

The same questions as discussed at the European level where risen also in France.

In 2000, the French Ministry in charge of the Environment asked INERIS to take stock of the situation regarding risk assessment and land-use planning in France. Then, several studies were launched both on technical issues and also on risk decision making process to analyse in particular, the procedure to write the safety reports required by the Seveso directive, and the relation with land-use decisions and zoning according to major accident hazards.

The following lines describe several examples of the projects launched.

-Risk analysis methods and scenario identification that takes into account risk reducing measures This project consists in defining a method to choose a set of scenarios that will help for the demonstration that the risks are properly controlled by the operators and for the determination of the safety distances to be used for land-use planning and emergency plans. In this project, INERIS has suggested to move from the deterministic approach used until now to resolve purely technician concerns to a multiple-criteria decision-making method.

This type of projects needs to be addressed through multi-disciplinary approaches combining physical and natural sciences with human science as disasters have been revealed to be the product of the interface of technology with human activities.

-Assessment of the scenario consequences As described above, the original competencies of INERIS related to the knowledge of dangerous phenomena like fire, explosion and atmospheric release of toxics. These projects continued to be funded in order to improve the comprehension of the phenomena and therefore, to enable the development of models to predict the consequences of accidents.

-Decision making process to improve the efficiency of the risk assessment This project leaves the only competence of the technician and relates to the choice of urbanisation measures on the residential areas concerned with high risk levels. These measures are the result of concerted choices between various groups of actors (industrialists, representatives of the local communities, local associations, committees of hygiene, safety and the working conditions CHSCT, administrations, etc.). Such a project depends on the ability to generate appropriate criteria. In the project, INERIS has proposed to develop and use a dialogue grid to help the various stakeholders in the choice of the most adapted solutions to both the local and the national context.

In relation with the last project, the team has worked on a project that relates to the creation of an inclusive risk culture through the integration of the various visions and the various analyses produced by the different groups of actors implied in the dialogue process and the risks prevention decision process. This European research project (TRUSTNET-in-ACTION) is carried out within a multi-field and pluri-cultural group.

All these projects combine multi-disciplinary expertise from engineering sciences, social sciences and management. They have contributed to develop an integrated and global vision to accompany the evolution of the industrial risk management process in France. As far INERIS is concerned, it lent its technical assistance to the IGE during the administration enquiry set up after the explosion and wrote 6 reports added in the annexes of the IGE report.

The Toulouse disaster : food for thought and catalyst for changes

Thus, the Toulouse disaster initiated a large debate and a deep thought that ended up with the proposal of a new law to improve the risk management system. Several ideas brought to the fore after the accident were developed thanks to the studies and the projects mentioned in the previous paragraph. The Toulouse accident operated as a catalyst for changes that made the politicians aware of the need to make the system evolving by taking advantage of the preparatory work carried out by INERIS.

The new law for risk management

The new law n° 2003-699 of July 30th, 2003 about the "prevention of the technological and natural risks and to the compensation for damages" introduces an important innovation into the process of technological risks prevention.

Methodology to establish a hazard zoning for the Technological Risk Prevention Plans

To establish a hazard zoning, INERIS has developed a multiple-criteria methodology. This methodology consists in characterising the hazard partially, according to a set of criteria, and then aggregating this different evaluation to choose the appropriate decision.

A factory site can join together several companies (firms) from which the activities are sometimes different. Each site comprises several installations (Figure 2). In case of a failure of one of these installations, toxic release, thermal effects, missile or overpressure can harm people or the environment.

The path which goes from the failure of the installation to the appearance of an effect is called "accident scenario" noted Sc. One can thus counted, for each installation, a set of accident scenarios S imlallalimt gathered by group of effect (toxic, thermal effect, missile or overpressure).

For each installation, the set of accident scenarios is evaluated according to five criteria, which characterise the hazard (Table 1).

A ranking of the scenarios by installation and by type of effect is carried out on the basis of a multiple-criteria method called ELECTRE III. The head scenarios by type of effect are selected for the hazard zoning by installation (Figure 3).

The selected scenarios by group of effects are retranscribed in the form of a zoning (cartography) in four levels of hazard: very high, high, medium and low (Figure 4).The limits between these four levels of hazard are represented respectively by the three distances which come to characterise each scenario of accident: the insulating distance with a lethality threshold of 5% (In1), the distance with a lethality threshold of 1% (In2), and outdistance with the irreversible effects (In3).

The result of ranking is translated to a hazard-zoning map for each installation and for each effect (Figure 5 and6).

At the end of this procedure, information are presented to the decision:

• A total pre-order (ranking of all the scenarios) ;

• ELECTRE III graph;

• a visualisation of the scenarios that present the highest level of hazard according to each effect and to each installation using a geographic information system (GIS).

Conclusion

To improve risk management process and reduce the number of major accidents, new approaches are urged to address the complexity of the issue in a context where industrial systems are evolving and where the civil society expectations become more difficult to satisfy in terms of consistency and transparency.

In France, the Toulouse disaster has initiated a deep reflection in the society and at the political level, and finally a new law was adopted. This law mainly clarifies the way the procedure to determine the safety distances for land-use planning, increases the participation of the employees in the risk prevention and enables the involvement of stakeholders in the decision-making process.

The global approach advocated by the law, that address both scientific aspects and societal issues, has taken advantage of the preparatory work carried out by INERIS in several projects based on a systemic view of risk management. Moreover, a specific methodology to establish a hazard zoning was developed to take into account the complexity of the criteria contributing to define the hazardous zones.

As a matter of fact, because of its characteristics (contextual, wholeness, multidimensional and complexity), the risk management process needs to be carried out by specialists and generalists.

The role of the specialists is to provide in depth-information, data, analyses to know where are the hazards related to the products, the processes, to quantify or estimate the damage and the probability of possible accident, and of course to assess the performance of the safety measures implemented. To sum up, technical specialists are needed for the risk assessment step and in the risk reduction step. Specialists are also needed in economy, in communication ... for the other dimensions of risk management. The role of the generalists could be seen as collecting and integrating the information provided by the specialists that the generalists would have identified as relevant to solve the risk-related problem. The generalists have also to overcome the interface difficulties generated by the selected views given by the specialists from the engineering side but as well as from the social side, where psychologist, sociologist... who bring their specific insights to relevant issues that need to be addressed. This mutation urges multi-disciplinary expertise from engineering sciences, social sciences and management and the development of the use of multiplecriteria analysis.

Therefore, considering the evolutions mentioned above, the risk regulation systems should also evolve with the increasing participation of the stakeholders and in particular of the industry in the risk control requirements. Since the industry has the best knowledge to control risk on site, regulations should move from prescription to goal-oriented one. It will enable the development of pro-active solutions to improve risk management. It seems to be the only way to build a sustainable and consistent risk management policy. (4) Fast.

(3) Fast but backward.

(2) Fast but highly backward.

(1) Long but immediate.

French

  national scale by the law n° 2002-276 of 27 February 2002 relative to "the democracy of proximity". More recently in France the law n°2003-699 of SOJuly 2003 relative to "the prevention of the technological and natural risks and to the compensation for the damages" has provided a great step in the direction of the implication of the various stakeholders (e.g. Public, elected officials, etc.) in the decision-making processes related to the prevention of the risks.

  our civilisation. By nature, technological risks are required to be treated at both national and local levels. The national level should define general rules, and the local level should apply the rules and reach agreements according to the local socio-economic, political and cultural context. It has long been recognised that increasing public participation is an essential element in improving environmental and risk-related legislation (Aarhus convention, 1998).

  missions of the collaborators of the Accidental Risks Division of INERIS are to provide technical support to the industry and to the Competent Authorities, thanks to the expertise gained by combining research work and practitioner experiences. On one hand, INERIS helps the industry to identify the hazards and to control the associated risks, on the other hand, INERIS gives support to the Competent Authorities to develop methods and tools to facilitate the implementation of regulations and control industrial installations. Five years ago, to do its job, the Accidental Risks Division of INERIS employed only engineers and researchers with technical background in the "hard sciences". The engineers were able to find technical solutions to complicated problems related to risk management. Then, in 2001, the staff was reinforced with new skills, in particular from the "human sciences". Engineers and human factor specialists started to work together, sharing premises and interacting on a regular basis. It was not easy to develop common view and to establish a common language according to the different backgrounds and cultures. Hard science is synonym of equations, quantification... on the opposite, human science is more qualitative and tends to use mathematics and numbers only for limited areas within their field of research.

  ARAMIS project initiated by INERIS was submitted for funding in the 5 th Framework Programme of the European Commission. This 3-years project started in January 2002 and builds further on methods studied in the 4th Framework Programme such as in ASSURANCE 1 project (Christou, Nivolianitou, Lauridsen, Amendola, Markert, Crossthwaite, Carter, Hourtolou, Molag, Spadoni, Tiihonen, Kozine, Aneziris, Gadd & Papazoglou, 2001), a benchmark exercise on the uncertainties in risk analysis, and developed in I-RISK project 2 , which provides a methodology for in-depth judgement of safety management requirements for the design, operation and maintenance of major hazards plants. The development of ARAMIS was justified by the need of the elaboration of a methodology giving consistent rules for the identification of scenarios that take into account mitigation devices and some aspects of safety management, and being recognised by risk experts from Competent Authorities and Industry. \ Assessment of the Uncertainties in Risk ANalysis of Chemical Establishments, n°ENV4970627

  4. A new law about the prevention of the technological and natural risks and to the compensation for damages A new law about the prevention of the technological and natural risks and to the compensation for damages was adopted in France in July 2003 after a deep debate initiated by the Toulouse accident. This paragraph describes the Toulouse accident and its consequences, and the main elements of the new law, in particular the evolution in the definition of the safety distances for landuse planning.

A

  terrible explosion of ammonium nitrate occurred on 21st September 2001, in Toulouse, in the AZF plant belonging to Grande Paroisse Company, TotalFinaElf Group. It killed 30 persons and injured up to 2242 people. The plant was located in the suburbs of Toulouse and the extent of damages was very large both on and off site with a cost estimated by insurers of 1.5 billion Euro. The plant produced mainly ammonium nitrate, ammonium nitrate-based fertilisers and other chemicals including chlorinated compounds. The explosion took place in a storage warehouse where roughly 400 tons of off-spec materials were stored. The TNT equivalent mass of the explosion was estimated in a range of 20 to 40 tons of TNT. After the accident, several studies, enquiries and analysis where initiated by the Authorities, the operator and several governmental services. • Enquiry by the IGE (General Inspectorate for the Environment) to report one month after the disaster to French Prime Minister about the administrative aspects, • Regional and national debates that lasted 3 months reported to the Prime Minister by the high level public servant, • Analysis by 2 rapporteurs of the Parliament who wrote more than 80 recommendations covering structural, organisational, scientific, administrativejuridical and financial aspects, • Study by the FFSA (French Federation of Insurance Companies) to analyse the reparation of the damages, • Enquiry by ATOFINA, the operator of the plant to explain the technical causes of the accident, Moreover, other governmental services like INVS (National institute for sanitary watch) or the ministry in charge of urbanisation and public equipment released also their report in the two years after the accident.

First

  , the new law enables the involvement of the stakeholders in the decision-making process related to risk prevention. This involvement is performed into a local structure of information and dialogue called "Local Committees for Information and Dialogue" (CLIC). Second, the system defined by the new law promotes the participation of the Local Committees in the elaboration and implementation of Technological Risk Prevention Plans (PPRT) devoted to draw up the configuration of the urbanisation around hazardous plants with a long term view. This innovation reveals the concern in giving solutions to two practical needs: (i) to combine a controlled urbanisation and a sustainable economic development in the area around hazardous plants; (ii) to rehabilitate the local decision in the risk prevention process and contribute to the creation of a risk culture.

Figure 1 :Figure 3 :Figure 4 :Figure 5 :

 1345 Figure 1 : Extract from the Report on the application in the Member States of Directive 82/501/EEC of 24 June 1982 on the major-accident hazards of certain industrial activities for the period 1997-1999 (2002/C 28/01) : cumulated number of accidents in the MARS database versus time

Table 1 :

 1 Set of criteria which characterises the hazard


Rémy Bouet

Stéphane Duplantier

Olivier Salvi
email: olivier.salvi@ineris.fr

AMMONIA LARGE SCALE ATMOSPHERIC DISPERSION EXPERIMENTS IN INDUSTRIAL CONFIGURATIONS

Keywords: atmospheric dispersion, large-scale experiments, ammonia, modelling

A programme of large-scale experiments for atmospheric dispersion was carried out by INERIS over a period extending from December 1996 to April 1997. The objectives of the test campaign were to measure anhydrous ammonia concentrations in a range of few meters to 2 km from the release, in order to generate data to be used to improve 2-phase release modelling.

The discharges were released from a 6-tonne storage tank of pressurised liquid ammonia and through a discharge device with an outlet diameter of 2 inches. Fifteen trials were carried out with various release configurations corresponding to industrial situations (impinging jets on the ground and on a wall at various distances, release through a flange without seal...). The quantity of ammonia discharged from the liquid phase varied according to the tests, from 1.4 ton to 3.5 tons for durations between 7 and 14 minutes and, therefore, at flow rates between 2 and 4.5 kg/s. Approximately 200 sensors were settled downwind to measure ammonia concentrations and temperature in the plume. These tests showed that for discharges with identical flow rates the distances corresponding to the same concentration vary a lot according to the configurations. These distances tend to be reduced by the presence of obstacles or bounds that collected liquid ammonia. In the paper, the main experimental results are presented in order to enable the comparisons with numerical predictions.

Introduction

The study of the atmospheric dispersion of ammonia is of major interest for two reasons. Firstly, ammonia is a common substance, which has many uses owing to its chemical and physical properties.

Secondly, ammonia is a substance that is extremely toxic, corrosive, flammable and explosive in certain conditions. It may be remembered that the failure of a 22-tonne storage tank of ammonia in Dakar on March 24, 1992, caused a large number of fatalities (129 dead and more than 1,100 injured) some of which were due to the toxic nature of ammonia and occurred several weeks after the accident.

In the framework of the large scale atmospheric dispersion of pollutants done before the INERIS trials, ammonia specificity was not taken into account such as : the jet formation, the aerosol generation, reactions with the moisture of the air, etc ... Several significant experimentation campaigns ware carried out by [START_REF] Resplandy | Etude expérimentale des propriétés de l'ammoniac (conditionnant les mesures à prendre pour la sécurité du voisinage des stockages industriels)[END_REF], [START_REF] Goldwire | Desert Tortoise series data report -1983 pressurized ammonia spills[END_REF], [START_REF] Wheatley | Discharge of liquid ammonia to moist atmospheres -Survey of experimental data and model for estimating initial conditions for dispersion calculations[END_REF] and [START_REF] Nielsen | Fladis Field Experiments[END_REF]. They all produced data related to the general aspects. These trials highlighted :

• the influence of the weather conditions ;

• the ammonia cloud behaviour which disperses as a heavy gas when it is released from a pressure tank at the ground level ;

• impinging jet on the ground made it possible to collect 70 % of rejected.

Thanks to these trials, models were developed that are used for risk assessment and quantification of accident consequences in safety reports. But to improve the relevance of the predictions related to industrial conditions, risk assessors have data on :

• the characterisation of the release source term and diphasic jet formation in the case of releases under pressure and in particular the generation and the evolution of the aerosol ;

• impinging jet with more significant flow rates.

Therefore, INERIS launched in 1996 a programme of large-scale trials with the aim of improving understanding of the mechanisms of atmospheric dispersion following an accidental ammonia leak. The tests were conducted in configurations corresponding to situations which can typically be found on industrial plants (discharge outlet diameter of 50 mm, impact on obstacles, etc...).

Description of the means implemented a) Field-test description

Ammonia dispersion trials on a large scale were performed on the experimention field of the CEA-CESTA (Center of Scientific and Technical Studies of Aquitaine) near Bordeaux (FRANCE).

The site (see figure 1) has a surface of 950 hectares. It is entirely enclosed and its access is controlled permanently. The site is completely flat and is deprived of any obstacle. This ground, of approximately two kilometres of ray, has, in its middle, a square concrete flagstone of 10 meters side and approximately 15 cm thickness where releases have been performed.

b) The release point

In the close vicinity of the release flagstone, three tanks of ammonia, 12 m 3 each one, were installed.

Liquefied ammonia was stored under its saturating vapour pressure.

During trials, only one of these tanks was connected to the release device located in the middle of the flagstone. This one was equipped with 5 thermocouples and pressure sensors, in order to follow the evolution of the conditions of pressure and temperature inside the tank during each test both in the liquid phase and in the gaseous phase.

The pressure sensor was located in the gaseous phase. This sensor is located P3 on figure 2.

The tank was also connected to a nitrogen tank making possible to pressurise it, or to maintain the constant pressure during a test, or even to purge, after a test, the pipe connecting the tank to the release device.

To perform the fifteen releases defined within the programme framework, two manual valves with a 2 inches diameter were placed on the tank : one was connected to the gaseous phase and the other one to the liquid phase. These two identical valves have not integral passage, and their real diameter is 3/2 inches.

Connection between the tank and the release device was ensured by a flexible pipe of 50 mm diameter and 10.4 m length.

Lastly, the release device was composed of a pipe of 2 inches instrumented by valves, thermocouples and pressure sensors (see figure 3). Note that the axis of the point of release is 1.015 m above ground level.

c) Atmospheric conditions measurements during trials

For the atmospheric conditions measurements, a 10 meters height weather mast was installed at 350 meters of the outlet (reference mark M on figure 1). This one was composed of three cup anemometers, located at 1.5, 4 and 7 meters height, a wind vane at 7 meters and an ultrasonic anemometer at 10 meters.

A weather station was also installed beside the control unit where temperature measurements, relative humidity and solar flux were recorded. These measurements were carried out at 1.5 meter height. The frequency of acquisition of these parameters was 1 Hz, except for the ultrasonic anemometer whose frequency was 10 Hz.

d) Ammonia sensors

To carry out the full-scale experiments, INERIS chose to use autonomous measuring equipment to be easily moved according to the weather conditions (especially for the variations of the wind direction).

Batteries ensured power supply of the sensors. For each series of measures, the data storage was carried out on EEPROM (Electrically Erasable Programmable Read Only Memory).

Thus, the measuring equipment of ammonia concentrations consisted of an electronic box on which it was possible to connect up to 4 sensors of different technologies. On the whole, 70 identical electronic boxes were used for this program.

The electronic box has an internal clock, which starts and stops the system at specified hours. For this period, the EEPROM records the measures of the sensors at a predetermined rate. For the tests, a frequency of 0.25 Hz was chosen (that is to say a measure every 4 seconds), which allowed, taking into account the capacities EEPROM, to record during 8 hours.

To carry out the choice of the sensors to be installed on the 70 electronic boxes, planned releases were modelled using integral dispersion models. These results were considered as orders of magnitude and were adjusted according to the results of preliminary trials. Thus, sensors were chosen according to the expected concentration at different points placed downwind.

Each measurement technique has a specific validity domain. The domains are orders of magnitude which can be wider according to the sensors characteristics. Finally, the sensors connected on the electronic boxes were :

• 60 catalytic sensors of pellistor type, specific to ammonia (EEV VQ 41) allowing to measure ammonia concentrations ranging between 0,1% and 15% (between 1,000 ppm and 150,000 ppm). In order to simplify the installation of the electronic boxes before a release, the test-field was beforehand equipped of more than 150 masts of 3 meters height. These masts could receive 4 sensors at different heights, namely 0.1, 1,2 and 3 meters. They were laid out on 7 circle arcs of 180° centred on the release flagstone and whose rays were 20, 50, 100, 200, 500, 800 and 1,700 meters (see figure 1). On the first two arcs of circles located at 20 and 50 meters, 41 masts were installed, spaced each other with an angle of 4.5°, and on all the other arcs of circles, 21 masts were installed with 9° spacing. Moreover, 60 thermocouples (type K, diameter 1 mm, classifies 1, stainless, length 5 m), were used to measure mean temperature. These thermocouples were installed beside each catalytic sensor until the distance of 100 meters since the outlet, and this in particular in order to appreciate temperature variations in the jet. The resolution of the measurements is made by step of 0.3°C, from -40°C to +40°C.

e) Selected configurations

The fifteen release configurations are briefly described beside each general diagram on table 1. They are numbered of 1 with 8b in the chronological order of their realisation. For each one of these configurations, the hose diameter is 2 inches (50.8 mm). Except specific indication (tests 2, 3, 4p, and 2b), the circular opening is also with a 2 inches diameter and the height of the nozzle is 1.015 m above ground.

For all the performed tests after the 3 rd , no overpressure of nitrogen was used, and the tank pressure was not maintained constant for the duration of the trial. Thus, for each test, it was observed a fall of tank pressure more or less significant according to release conditions.

Main results

Graphs on figures 4 and 5 present the conditions recorded during trial n°4.

Typical evolution of the pressure conditions in the tank and in the pipe during a release is shown on figure 4.

For trial n° 4, changes of the temperatures located at various heights in the tank and located in the pipe are given in figure 5.

These figures show in particular that temperature and pressure tank decreased slowly during trial n°4.

For each of the 15 tests described previously, the atmospheric conditions are listed in table 2.

Concerning the general atmospheric conditions during tests, the following remarks could be noticed :

• From the test n° 4, no more rain was falling on test field. Thus, rather low relative humidity during the day were observed (only 20% for the test n° 10).

• The visible part of the plume varies much. That is mainly due to the relative humidity of the atmosphere.

Indeed, the ammonia cloud is relatively cold (approximately -40°C on the axis of the release at 20 meters of the outlet) because of the presence of ammonia droplets which will take heat, in particular to the ambient air, to vaporize. The low reached temperatures make that water vapour presents on the plume trajectory condenses and forms a visible cloud until the plume is heated by dilution with ambient air. According to studied phenomena, there are various possibilities of carrying out the analysis of the concentration fluctuations which were recorded during the tests. In this paper, concentrations values which will be presented are average values of the concentrations measured on the axis of the plume (see table 3).

To obtain these values, we picked, for each step of time (of 4 s), the value of maximum concentration on each of the 6 circle arcs located at 20, 50, 100, 200, 500 and 800 meters of the outlet. Then, we carried out on each circle arc an average of the whole of the maximum values recorded in the course of time by excluding the first and the last minute of exposure for each sensor. The beginning of sensors exposure was given by considering a time of advection of the cloud. This time was taken equal to the ratio of the distance between the arc of circle considered and the outlet by the mean velocity of the wind during the release.

Discussions

On the basis of the analysis carried out at this time, the following comments can be made. Other detailed interpretation of the results will be published in other coming papers.

• The ammonia cloud behaves like a heavy gas and no elevation of the cloud is observed.

• The temperature in the ammonia jet can fall to approximately -70°C.

• Solid obstacles (wall or ground) located at a few meters from the discharge point, have a considerable effect on the concentration values measured downwind the obstacle (see trials 5, 6, 7, 8, 8b, 9). In this test campaign, concentrations measured downwind the obstacle were approximately half of those measured for the same discharge into a free field, which is why it is important to take into account the obstacles in the vicinity of installations when determining safety distances.

• When discharge is released towards a surface with bounds, a large amount of liquid ammonia is retained. For trials 8b and 9, more than 50% of the total discharged mass were collected in liquid form at a temperature of approximately -60°C.

• Liquid ammonia pool formed after impact with an obstacle does not evaporate quickly.

•

Water screens (peacock tails) located across the cloud trajectory had little effect on the dispersion of ammonia cloud in the test conditions.

• Comparisons have been made between the experimental results and the results obtained using integral dispersion models. When suitable calculation hypotheses are used, especially for flow rates, these models can calculate downwind concentrations of a discharge in a free field that have the same order of magnitude as results obtained by experiments. For impinging releases, big differences exist between integral dispersion models and experimental results, these models don't take into account obstacles near the discharge point.

Conclusions and perspectives

The trials, carried out from a 6 ton tank of ammonia and through a discharge device an with outlet of 2 inches, led to release more than 2 tons of ammonia per trial. For all trials, sensors were located downwind of the outlet in the test field. Those trials made it possible to examine in particular the fluctuations of ammonia concentrations on circular radius located up to 1,700 meters and to determine the influence on the dispersion of the following parameters : impinging jet on a wall, impinging jet on the ground, release through a flange and presence of water curtains.

Comparisons have been made between the experimental results and the results obtained using integral dispersion models. These models can calculate downwind concentrations of a discharge in a free field that have the same order of magnitude as results obtained by experiments. However, at the present time, integral models are not able to predict downwind concentrations for the case of a discharge impacting an obstacle located a few metres away. The calculation results obtained using these models can be very different from the experimental results, unless the models are adjusted beforehand to take into account the quantity discharged into the atmosphere in the form of vapour or aerosol after the impact.

The results obtained in these tests led us to draw up a new programme in 1999 with the particular aim of developing a model which would take into account the interaction between a liquefied gas discharge and an obstacle. This model could constitute an additional module in integral models, optimising the study of specific industrial configurations. Release identical to the n°4. The temperature of liquid ammonia inside the tank was lowered to -12°C before the test.

Release identical to the n°2 with an opening of 1 8 mm diameter.

Vertical release impacting the ground starting from a height of 1 m in a retention dike of 1 Om x 1 Om of surface and 5 cm height (5 m 3 ).

Table 1 : Characteristics of the 15 configurations tested in the project

  These sensors were placed in the close field (up to 200 meters of the outlet); resolution is made by step of 250 ppm of value EEPROM 0 up to 130, then by step of 560 ppm of value EEPROM 131 up to 255 ; • 50 electrochemical cells (SENSORIC NH3 3rd 1000) measuring ammonia concentrations ranging between 10 and 1,000 ppm. These sensors were laid out in the far field (from 200 meters to 1,700 meters of the outlet); resolution is made by steps of 10 ppm up to 2,000 ppm. It should be noted that pellistors EEV VQ41 and electrochemical cells SENSORIC NH3 3rd 1000, have been tested at INERIS in laboratory and during middle-scale releases (releases through 0,5 mm to 8 mm nozzle diameters).

  Thus, for almost identical conditions of release (tests 4 and 11), the visible part of the plume decreased from approximately 500 meters to approximately 70 meters for a relative humidity which decreased from 82 to 24 %. Solar flux varied much between the tests, with very low values at the beginning of the test campaign (0.04 kW/m 2 ) and raised during April (1 kW/m 2 ).

Figure 1 :Figure

 1 Figure 1 : Schematic representation of the test field

Table 2 : Average atmospheric conditions recorded during each trial

 2

Acknowledgements

The experimental programme was mainly funded by the Ministry in charge of Environment and by industrial sponsors : Norsk Hydro (Norway), Grande Paroisse (France), Veba Oel (Germany), SKW Piesteritz (Germany), CEA-CESTA (France) and Rhône Poulenc (France). They are sincerely acknowledged.