Zbigniew Pokryszka
email: zbigniew.pokryszka@ineris.fr

Christian Tauziède
email: christian.tauziede@ineris.fr.

Candice Lagny

Yves Guise
email: yves.guise@charbonnagesdefrance.fr

Rémy Gobillot
email: remy.gobillot@charbonnagesdefrance.fr

Jean-Maurice Planchenault

René Lagarde

Gas Migration from Closed Coal Mines to the Surface RISK ASSESSMENT METHODOLOGY AND PREVENTION MEANS

Keywords: gas, coal, mine, closure, risk gaz, mine, charbon, fermeture, risque

French law as regards renunciation to mining concessions calls for the mining operator to first undertake analyses of the risks represented by their underground mining works. The problem of gas migration to the surface is especially significant in the context of coal mines. This is because mine gas can migrate to the earth's surface, then present significant risks: explosion, suffocation or gas poisoning risks. As part of the scheduled closure of all coal mining operations in France, INERIS has drawn up, at the request of national mining operator Charbonnages de France, a general methodology for assessing the risk linked to gas in the context of closed coal mines. This article presents the principles of this methodology. An application example based on a true case study is then described. This is completed by a presentation of the preventive and monitoring resources recommended and usually applied in order to manage the risk linked to gaseous emissions.

Introduction

French law as regards renunciation to mining concessions calls for the mining operator to first undertake assessment of the risks represented by their underground mining works in terms of people, property and the infrastructure present on the surface. In cases where significant levels of risk are identified, the operator must furthermore define and implement the appropriate preventive measures.

The problem of gas migration to the surface represents one of the major aspects of this risk assessment, especially in the context of coal mines, for these works very often combine the three components needed to trigger the appearance of the feared phenomena: the presence of residual mining voids which, together with the natural porosity of the strata, forms underground reservoirs. Taken together, given the conditions of French coal seams, these reservoirs could represent 25 to 35% of the total volume of coal extracted [START_REF] Degas | Stabilité de la surface après l'exploitation totale du charbon et l'arrêt des pompages d'exhaure minière[END_REF], the presence of dangerous gases, the possibility that these gases could accumulate and migrate, in significant concentrations, to the surface.

Mine Gas and the Dangers Linked to its Presence

Coal seams very often contain significant amounts of endogenous gas (firedamp), whose main component is typically methane and sometimes carbon dioxide. Firedamp can be released from unmined parts of the seam for a relatively long time after the end of mining operations.

It accumulates in residual mine spaces at the same time as other gases from the transformation of materials present in the old workings and/or in the air that may still be able to circulate through the old workings (nitrogen, carbon dioxide, carbon monoxide, hydrogen sulphide…). The combinations of these gases form a mixture called "mine gas". Very often, this mixture is severely lacking in oxygen or even virtually oxygen free.

Mine gas can migrate to the surface where its presence can then induce significant risks: risks of explosion, suffocation or poisoning. In France and in other coal mining countries affected by mine closures, a number of accidents and incidents linked to releases or build ups of mine gas have been reported in the literature [START_REF] Sizer | Methane and other gases from disused coal mines : the planning response -Technical report for the department of the environment -Wardell Armstrong -The Stationery Office[END_REF][START_REF] Burrel | The effect of mine closure on surface gas emission[END_REF][START_REF] Kral | Methane from closed-down mines in the soil[END_REF][START_REF] Jackson | Our mining heritage -Presidential address delivered to the North-East branch of the Institution of Mining and Metallurgy on 21 Oct[END_REF][START_REF] Łukowicz | Prévision et prévention du risque lié au grisou à la surface de mines fermées[END_REF][START_REF] Pokryszka | Evaluation of gas emission from closed mines surface to atmosphere[END_REF][START_REF] Robinson | Mine gas hazards in the surface environment[END_REF][START_REF] Novotny | Reduction of uncontrollable mine gas emission in the Czech part of Upper Silesian hard coal basin devastated by past mining activity[END_REF].

The most common situations that have caused these incidents or accidents are:

Local, concentrated, releases of mine gas through a direct path between the old workings and the surface (mining opening, faults, crack...); A build up of gas in confined or semi-confined spaces (basements or underground locations, or in buildings themselves as well as in underground networks, etc.);

The unintentionally connection of a post-mining voids to the atmosphere (e.g. due to drilling or excavating work conducted close to old workings...).

Mine Gas Migration to the Surface

The transfer of gas from post-mining voids to the surface may be driven by a number of mechanisms: the rising water level within the old workings; feeding the reservoir with gas by its release from the coal left in place; variations in barometric pressure; natural draft. These different possible causes of gas releases on the surface may occur simultaneously. Nevertheless, the period during which the water level rises once pumping stops represents the most critical phase.

The possible appearance and intensity of gas emissions on the surface from old workings will essentially depend on three main factors: the gaseous (firedamp) nature of the post mining reservoir present, especially represented by the type of gas that is present, the importance of its "production" in the reservoir and the volume of the voids; the degree of differential pressure between the reservoir and the surface generated in combination by the various mechanisms mentioned above; the resistance of the environment to gas migration, simultaneously represented by former mine-surface links and by the covering strata, including water bearing horizon within it.

This shows the importance of knowing the underground mining reservoir (the structure and distribution of any residual voids, their position in relation to the surface…), their geological environment and their hydro-geological behaviour, so as to best appreciate the problem posed by the migration of mine gas to the surface.

Gas may rise to the surface: preferably through former works linking the mine and the surface (shafts, adits, access galleries) which constitute individual gas emissions points, if they have remained open or are not sufficiently tightly sealed off; through the covering ground itself, especially in areas of only slight thickness and/or where permeability is greatest. This is because a slight thickness in the covering ground, when naturally permeable (with high built-in permeability, the presence of cracks…) or made permeable as a direct consequence of mining operations (induced fracturing), is the situation that is most likely to favour gas releases; to a lesser extent, through water release or with the water from mine drainage (dissolved gas).

Figure 1 illustrates the various possible paths used by mine gas when migrating towards the surface.

Risk Assessment Methodology

Considering the shutdown of all coal mining operations in France, INERIS at the request of Charbonnages de France, drew up a general methodology for assessing gas related risks. This methodology, drawn up in its initial version around 1995 for the specific context of coal mines closure has since been improved and expanded to take into account the experience gained from handling a larger number of real life cases.

The methodology is based on taking into account and analysing various types of information and data: Data relating to the underground reservoir: the firedamp characteristics of the seams, the volume and extent of the residual mining voids, their position in relation to the surface...; Data relating to covering strata: type, structure and overall thickness of the covering strata, thickness of the various specific bedrocks and their permeability. The latter parameter may be strongly dependent on the fissuring induced by the workings; Information relating to hydrogeology: type, thickness, shape of the water bearing horizons, their position in relation to the mine workings and their evolution over time; Elements relating to seam structure: here the aim is especially to identify any possible presence of formations likely to encourage the accumulation and migration of mine gas; Data relating to ground occupation: geographic position and density of built up areas for rising gases result in a risk that is all the more significant if there is a human presence in the area and a possibility that gas will accumulate on the surface.

The superimposition and mapping of the various data and information is carried out on a map background using a scale chosen to obtain a result that provides enough overall coverage while being sufficiently precise. This work is performed in line with the following major steps: collecting the knowledge available on the firedamp nature of the mining concession studied, from archive documents completed by any reconnaissance and measurements taken on field; information on the mine workings and the geological and hydro-geological context; identification of areas that may potentially release gas, based on geological and hydrogeological data and on working characteristics that are specific to the mining area; identification of risky areas, based on surface occupation; definition of the means of prevention and/or monitoring applied to manage the risk.

In cases where the hydrodynamic situation of the studied area has not yet stabilised (the water table is rising and the former workings are progressively flooded), the analysis of the problem of gas migration to the surface is performed separately for the two consecutive hydrogeological configurations:

for the rising water level phase, and for the phase that follows the stabilisation of the hydrodynamic situation. This general approach is presented in graphic format in Figure 2.

Conclusions on the Firedamp Nature of the Former Workings

This step aims to define the potential for former mine workings to release and to accumulate mine gas as well as to identify the type of gas likely in time to transit to the surface.

The analysis is performed through the search for numerous quantitative or simply qualitative data. The following especially should be retained:

reports of the appearance of firedamp in the underground workings as stated in the reports filed by the operators or the authorities in charge of supervising the mines, or even various works describing the history of the mining operations.

administrative ranking of workings in relation to firedamp that appeared in France towards the end of the 19th. Century.

implementation during mining operations of firedamp prevention measures: safe explosive, safe lamps, mechanical ventilation, firedamp meters… reports on firedamp related accidents.

results of the various measurements taken of firedamp releases during mining operations.

This data can be collected, more or less exhaustively, from the various archives available, those kept by mining operators, the mining administration or national or local public archives. This approach can be completed by reconnaissance on field and especially taking gas release measurements from mining openings where this is still possible.

The data collected is then compared and summarised so as to determine to what extent the workings being studied and their various sectors are affected by the presence of mine gas.

Criteria linked to the coverage of residual voids

Criteria linked to surface occupation

Mapping Residual Mining Voids and Analysing Geological and Hydro-geological Data

This work comprises analysing and summarising the various elements relating to the workings considered and are necessary to evaluate the sensitivity of the old mine being studied to gas accumulation and its transfer towards the surface, namely:

-a cartographic presentation of the main working areas and any underground links that may exist between these areas, -identifying the upper mined out areas in the former mine workings that form "potential mine gas traps" and their position in space, -the thickness of the overlying covering strata in the upper mined out areas, -information relating to the structure, type and aeraulic characteristics of this covering strata as well as the degree of fissuring affecting it (both natural and that induced by the workings),

-information relating to overlying water tables above the upper mined out areas, -current hydrological situation and the way it changes over time and in space, for the rising water phase as well as the future stabilised phase, -the presence of any geological structures that favour the accumulation and/or migration of gas.

Defining and Mapping Areas that could potentially release Gas on the Surface

This step serves to locate and to set out a hierarchy, where possible, those areas that may contain mine gas and release it to the surface. This work is performed using the data acquired during the previous step.

The analysis requires setting out a number of criteria, the two main ones being:

thickness and type of soil covering the upper mined out areas in the post-mining reservoir.

From a general point of view, a covering thickness of more than 200 meters is sufficient to obstruct the rise of gas in any way other than in a diffuse way. This limit thickness has been adopted on the basis of models developed in Europe for predicting the release of firedamp from a coal exploitation by caving longwalls, one that is the most penalising in terms of weakening the overlying strata.

These models consider that there is no significant influence by mine workings on the aeraulic properties of the covering strata in excess of a height of some 150 to 170 meters above the seam [START_REF] Gunther | Mécanisme et prévision du dégagement grisouteux -Publication CERCHAR n°1588[END_REF]Coal Directorate, 1980;[START_REF] Pokryszka | Estimation of the extension of the zone of increased permeability in the goaf. Application to mine gas drainage techniques -Workshop on the recovery and enduse of coal-bed methane -Katowice[END_REF].

Depending on the refinement of the analysis, it is also possible to introduce intermediate limits in the covering thickness thereby ensuring partial protection in relation to gas migration.

At the same time, depending on the hydro-geological context of studied mining area, one takes into account when setting out the criteria, the existence in the covering strata of impervious beds (clay for example) or even water bearing beds, on condition that these are thick enough and continuous in order to form an efficient obstacle to rising gases.

degree of flooding in the former workings still in contact with the unmined seam.

This aspect is especially relevant for the stabilised hydrodynamic phase, in cases where the workings or some of its parts remain insufficiently flooded. This is because, in this case, the gas contained in unmined seams may potentially continue to be released and transit to the surface.

For lack of studies or relevant past data, dedicated research work has been undertaken in order to be able to propose criteria relating to this aspect. This study covered the behaviour of the gas (methane) adsorbed in the coal in the presence of a hydraulic load created by the flooding water.

Experiments performed in the laboratory showed that finely split flooded coal, with no significant hydrostatic pressure may still, despite this, release gas. However desorption kinetics are very weak, some ten times less than with dry (not flooded) coal.

When the hydrostatic pressure caused by the flooding rises, the gas release kinetics falls.

If the water pressure approaches that of the adsorbed gas, then the quantities of gas released become highly insignificant: they are in this case in the order of a few percent of the volume that can be desorbed. Figure 3 shows and example of the results obtained. All of these results have made it possible to detail the notions of "coal seam gas pressure" and the "minimum flooding level" as the basis for setting out criteria that correspond to the degree of flooding affecting former workings. Applying these criteria makes it possible, for example, to eliminate from the rest of the risk assessment, those areas that are sufficiently flooded at a given time, by considering that in this configuration, the water present effectively inhibits any significant release of firedamp from the residual coal still in place.

In the analysis of areas that may potentially release gas, it is also considered, in parallel with the upper areas in former underground workings, those geological or tectonic structures that favour the accumulation or the migration of gas towards the surface (porous and permeable layers, anticlines, faults…). This entire step leads to drawing a map of "areas likely to release mine gas". As an example, Figure 4 shows an excerpt of the mapping of such areas for a part of the French Nord-Pas-de-Calais coal mining area, representing some 13 square kilometres.

Analysing and Mapping Surface Risks

This step comprises identifying, from among those areas that could potentially release mine gas, those which are occupied on the surface by gas sensitive elements. This analysis is done by superimposing the aforementioned map of areas that could potentially release mine gas over a surface occupation map.

In this analysis, special consideration is of course given to built up areas occupied by buildings and industrial installations, for any release of can all the more frequently result in accidental events when there is a human presence and possibilities for mine gas to accumulate in buildings or in surface infrastructures. Built up areas therefore increase surface vulnerability and consequently, with the same likelihood of gas releases, the degree of risk.

Significant likelihood

Slight likelihood

Negligible likelihood

Virtually no likelihood

Consequently, when enough information is available, the analysis is conducted so as to result in a hierarchy of risk, based on geographic location, the type and density of vulnerable areas. It should be noted that the risk mapping that is generated in this way is valid for the occupation of the surface in question, as it was when the study was conducted.

This step results in a so-called map of "mine gas emissions risk area". Figure 5 illustrates the result of this mapping effort drawn up for the same part of the French Nord-Pas-de-Calais coal mining area as presented in the preceding subsection.

Defining Compensatory Measures and Monitoring Methods

Compensatory Measures

Once the risk linked to the rise of gas to the ground's surface is quantified and mapped, it is necessary to define the preventive or compensatory measures well suited to the context. These measures should make it possible to reduce the risk to a technically and financially acceptable minimum.

Two types of measures are possible to minimise the rise of gas to the surface: active treatment and passive treatment of the mine gas.

Capturing firedamp (drainage) from the surface represents an especially efficient active treatment of the problem. It usually creates a more or less significant vacuum in the mine reservoir compared with the surface level, but one that is sufficient to stop any uncontrolled release of gas on the surface. For example, large scale gas capture installations have been set up in the Nord-Pas-de-Calais mining area where a majority of the former mine workings are now under a vacuum of up to -500hPa.

Very significant risk

Significant risk

Insignificant risk

Negligible risk

This costly and complex method is most often practised in very gassy mining areas in order to industrially capture the gas and it is technically difficult to apply to low firedamp content seams. It is however possible, in some cases, to set up a local capture station intended to avoid any uncontrolled gas releases at local level [START_REF] Robinson | Mine gas hazards in the surface environment[END_REF] or even a mobile installation that can be temporarily connected to capture points set up ahead of time in those areas where mine gas periodically appears on the surface [START_REF] Novotny | Reduction of uncontrollable mine gas emission in the Czech part of Upper Silesian hard coal basin devastated by past mining activity[END_REF].

In mines where firedamp collection systems have been set up in the past during mining operations, whether for safety reasons or gas exploitation, it may be interesting to keep such mechanisms in service even after coal mining stops, so as to control the water flooding phase for as long as possible. This is the case with the capture installations operating in the eastern and central parts of the Lorraine coal mining area.

Passive treatment comprises implementing, in areas of risk, priority escape routes for the gas, by building decompression installations (existing shafts suitably fitted out or drilling performed specially). This is because it is necessary for the gas contained in the reservoir to find a priority escape route to the outside atmosphere, i.e. one that considerably less resistant than the former mine-surface connections that are closed off or the covering strata.

The drilling required, which does not necessarily necessitate a very large diameter to be efficient, must aim for the high parts in the mining reservoir, in order to favour the decompression of the voids that are the closest to the surface and to allow the release of gas for as long as possible during the rising water phase.

Figure 6 illustrates the operating principle of a decompression borehole connected to a flooding post-mining reservoir. Given the normally very limited level of the unitary gas flows involved, one can easily assume that the releases from all of the system components (postmining reservoir, covering, shafts and decompression works) are mainly laminar [START_REF] Couillet | Mathematical model for firedamp reservoirs -Proc. of the International Conference on Coal-bed Methane Technologies of Recovery and Utilisation -GIG[END_REF]. In this case, the distribution of the gas flow migrating to the surface spread among the three possible paths, i.e. the covering strata, the former adits or shafts and the decompression works will take place proportionally to the relative aeraulic resistance of each of these paths. The gas will therefore generally be released mainly by the one or more decompression devices as these offer the circuit with the least resistance.

It should be noted that prevention systems of this type have been proposed and/or implemented in a number of mining countries: in France, but also in Germany, Great Britain [START_REF] Jackson | Our mining heritage -Presidential address delivered to the North-East branch of the Institution of Mining and Metallurgy on 21 Oct[END_REF], in Poland [START_REF] Łukowicz | Prévision et prévention du risque lié au grisou à la surface de mines fermées[END_REF], in the Czech Republic [START_REF] Novotny | Reduction of uncontrollable mine gas emission in the Czech part of Upper Silesian hard coal basin devastated by past mining activity[END_REF][START_REF] Prokop | Gas leak effects on environment of Ostrava basin[END_REF], etc.

Installing decompression works requires implementing specific safety measures in relation to the risks linked to the gas that can emerge from the post-mining voids (inflammation, suffocation, poisoning). In the same way, once completed, these works must be made safe in view of their often long term operation by fitting them with safety equipment such as cut off valves, flame arrestors…, and made inaccessible to the public.

For those drillings where it is assumed that they will become highly active, it is also necessary to establish a protection area that takes into account the above mentioned risks. An example of how to define this area in relation to the thermal effects caused by accidental gas (methane) inflammation conducted by INERIS on a drilling in the Lorraine coalfield, is presented in Figure 7. It should be noted that these decompression installations should play a part during the entire time taken to flood the underground works, the most critical phase, but that they may also need to be retained in situations where flooding of post-mining voids will never be complete. As an example, Figure 8 presents the change, over a three-year period, to the activity of a decompression borehole placed into service in Cransac in France's Decazeville coalfield that is flooding. The intensity of the gaseous release from this borehole, as established from one-off measurements of the methane content and gas flow clearly show the beneficial effect that this kind of installation can have in terms of reducing the pressure level in the post-mining reservoir and in reducing the amount of gas likely to migrate uncontrollably to the surface.

Special Measures and Land Management

In those special cases where implementing efficient prevention methods is technically impossible or where the action of all of the means implemented turns out to be insufficient, the appropriate administrative approach must be undertaken as regards the urban development of those areas classified as being the most likely to release gas to the surface.

Depending on the local context, this may require:

temporarily ruling out any urban development in the affected areas or the banning of new building projects without any additional preventive measures, at least during the rising flood water phase;

the mandatory inclusion as part of any building permit, of technical and/or constructive measures that inhibit the penetration and accumulation of gas within the buildings envisaged.

These measures which have to be set out on a case by case basis, must come with the appropriate inspection and monitoring procedure.

Inspection and Monitoring Means

Whatever the treatment mode chosen and implemented, monitoring the operating parameters of the underground mining reservoir and the presence of any mine gas on the surface is necessary to ensure that the preventive measures taken are effective.

It is especially necessary to regularly check the correct operation of the decompression shafts or boreholes (or the gas drainage system) so as to be sure that the reservoir is not placed under pressure. This check must be carried out throughout the service life of the system.

Post-mining site monitoring can be performed by: manual checks and measurements (covering gas content, pressure, direction of release, flow...) performed periodically at strategic locations or those that are most exposed (decompression boreholes, former mine-surface links, locations where build-ups may occur such as in underground networks and basements…), using portable devices; implementing automated measurement or remote monitoring systems. A system of this kind has, for example, been installed by Charbonnages de France in the Nord-Pas-de-Calais coalfield, to monitor the overall behaviour of the post mining reservoir from some twenty observation points; direct measurements of gas flows on the surface. These measurements are especially effective in assessing the importance of the actual transfer of gas towards the surface [START_REF] Pokryszka | Method of measuring surface emission of methane -Proc. of the International Conference on Latest Achievements in the Field of Mine Ventilation -Fire and Methane Hazard Fighting -GIG[END_REF]. This is recommended for sensitive built up areas, if the presence of gas is observed using the aforementioned monitoring measures.

The means available for use in checking and monitoring post-mining sites are described in greater detail in a communication dedicated to this problem [START_REF] Besnard | Gases emission monitoring in a post-mining context[END_REF].

Conclusions

The risks linked to the rise of mine gases to the surface represents a problem that is especially important in the context of closed coal mines. This aspect should be taken into consideration during regulatory investigations prior to a mining operator relinquishing their mining concessions.

A methodology for analysing and assessing this risk has been developed by INERIS in cooperation with Charbonnages de France. It is based on compiling and analysing multiple data relating to the studied mining area: historical data, the characteristics and the behaviour of the post-mining reservoir, the geological and hydro-geological characteristics of the seam… It results in a quantified mapping of risks and in defining those preventive measures that should possibly be implemented. This method has been applied to all closed down mines belonging to Charbonnages de France in the various French coalfields where an analysis of the risk relating to migration to the surface of mine gas turned out to be relevant. Furthermore, even if there remains a number of phenomena that are insufficiently understood 1 , the development and research work undertaken in the context of establishing this methodology have made it possible to improve knowledge of gaseous phenomena in the context of shutdown coal mines and to move along the understanding of the behaviour of post-mining reservoirs in a complex geological and hydrological environment.

The knowledge acquired and those elements of the methodological approach established can be used or derived to evaluate the risks linked to gases in other post-mining contexts other than closed coal mines. It can be also used in the context of setting out Mine Risk Prevention Plans (Plans de Prévention des Risks Miniers or PPRM) described in a communication dedicated to this regulatory tool [START_REF] Didier | The MRPP: A powerful operational regulatory tool to prevent and manage post-mining risk -Actes du Colloque International Après-mine[END_REF].

Figure 1

 1 Figure 1 Mine gas migration paths towards the surface

  Conclusions on the firedamp nature of the former workings Mapping residual mining voids and analysing geological and hydro-geological data Defining and mapping areas that could potentially release gas on the surface Analysing and mapping surface risks Defining compensatory measures and monitoring methods

Figure 2 .

 2 Figure2. General approach applied to the analysis of the problem of mine gas rising to the surface

Figure 3 .

 3 Figure 3. Example of the influence of water on coal gas desorption kinetics.Laboratory experiment using finely split coal.

Figure 4 .

 4 Figure 4. Excerpt from the mapping of areas potentially likely to release gas produced for the Eastern part of the Nord-Pas-de-Calais coal mining area

Figure 5 .

 5 Figure 5. Excerpt from the mapping of areas with a mine gas emissions risk produced for the Eastern part of the Nord-Pas-de-Calais coal mining area

Figure 6 .

 6 Figure 6. Operating principle of a decompression borehole linking a post-mining reservoir that is flooding

Figure 7 .

 7 Figure 7. Example of the definition of the protection area around a highly active decompression drilling in relation to the thermal effects linked to accidental gas inflammation (methane outflow 0,3 m 3 /s)

Figure 8 .

 8 Figure 8. Example of the activity of a decompression borehole in the Decazeville coalfield

For example: the evolution of gaseous properties of post-mining voids and their hydro-chemical behaviour over the long term, the durability of decompression works…


Katia Besnard

Zbigniew

Gases emission monitoring in a post-mining context

come

GASES EMISSION MONITORING IN A POST-MINING CONTEXT

BESNARD Katia 1 , POKRYSZKA Zbigniew 1 1 INERIS, Unité Eaux Souterraines et Emissions de Gaz -Parc Technologique Alata -BP 2 -60550 Verneuil-en-Halatte -France. Katia.Besnard@ineris.fr; Zbigniew.Pokryszka@ineris.fr ABSTRACT: Closed mines are often sources of dangerous gas emission. Flammable and/or toxic gases or deoxygenated air can be transmitted to the surface through existing aerodynamic links like abandoned shaft or galleries and fissures in rock. The gases issued from closed mines may generate public health and safety concerns and these problems are encountered for nearly all mine types. For the last 10 years, INERIS has developed in situ gas monitoring methods whose objectives are (i) to characterise gas emissions and to improve our knowledge of the processes governing their migration; (ii) to allow their risk evaluation and, eventually, to enable gas detection and alarm triggering. After briefly presenting each method, we will focus on some typical examples of monitoring by continuous automatic in-situ measurements that we have set up. KEYWORDS: gas emission; abandoned mines; monitoring; in-situ measurements. RESUME : Les mines abandonnées sont fréquemment le lieu de dangereuses émissions de gaz. Des gaz inflammables, toxiques et/ou de l'air désoxygéné peuvent migrer vers la surface à travers les anciennes infrastructures minières (puits, galeries…) ou des fissures dans le recouvrement. Les émanations de gaz à partir des mines abandonnées peuvent poser des problèmes de sécurité et de santé publique. Au cours de la dernière décennie, l'INERIS a développé des méthodes de monitoring in situ dont les objectifs sont (i) de caractériser les émissions de gaz et approfondir notre connaissance des processus gouvernant leur migration et (ii) d'aider à l'évaluation des risques et, le cas échéant, de permettre la détection des gaz et le déclenchement d'alarmes. Après avoir brièvement présenté chaque méthode, nous nous attarderons sur quelques exemples de surveillance par des mesures in situ en continu que nous avons mis en place. MOTS-CLEFS : émission de gaz; mines abandonnées; surveillance; mesures in-situ.

Introduction

Problems of mine gas issuing at the surface have been encountered all over the world in all types of active or closed mines.

Mine gas develops in underground reservoirs formed by residual voids left by the mining activity. It can migrate to surface under the effect of several mechanisms and thereby presenting considerable hazards for individuals and property (explosions, intoxication, asphyxia, etc). Therefore it is crucial to have technical means to monitor gas emissions characteristics.

The intent of this paper is to briefly present the various methods that we have at our disposal. We then focus on three sites in a post-minig context in which we have set up gas monitoring systems.

Mine gas hazards on surface

Mine gas

In underground closed mines, they are often residual cavities resulting from the mining activity: abandoned rooms and pillars sectors, partial filling in, caving, galleries… or voids due to the increase in the porosity of surrounding strata resulting from their distressing and fracturing. This forms a true underground reservoir in which gases can build up. The composition of the gas mixtures in this volume considerably varies from one mine to another.

The gases most commonly found in mining contexts are oxygen, nitrogen, carbon dioxide and methane, and less often, hydrogen sulphide and carbon monoxide. In a simplified way, one can distinguish two origins for these gases: they can be geological gases, contained in rock before mining or the result of (bio)geochemical reactions in the deposit or in surrounding rocks, during or after mining. Thus the coal spontaneous combustion in abandoned mines causes frequently toxic gas emissions to the surface.

The major noxious gases are the very poisonous carbon monoxide and carbon dioxide. Hydrogen sulphide is extremely poisonous, but rarely occurs in dangerous quantity. Moreover mine gas is generally accompanied by a variable degree of oxygen depletion. Mine gas consequently presents several hazards including asphyxia, due to the oxygen concentration being too low, intoxication, due to the presence of carbon monoxide and hydrogen sulphide and, to a lesser extent, carbon dioxide, and finally ignition or explosion, due to the presence of hydrocarbons. These hazards are, of course, increased when the mine gas rising to the surface accumulates in locations accessible to the public.

Factors governing the migration of mine gas to the surface

Noxious gases or deoxygenated air can be transmitted on the surface through existing aerodynamic links like abandoned shaft or galleries and fissures in rock.

The gaseous mixtures build up in the reservoir formed by residuals voids can be transmitted to the surface when the pressure within the reservoir is higher than the atmospheric pressure. The different reasons for such a positive pressure differential between the reservoir and the surface are mostly:

• A dilatation of the atmosphere in the mine, due to a decrease of the atmospheric pressure at the surface; • An increase of the pressure inside the reservoir due to :

• The hydrostatic pressure imposed by rising water levels. The displacement of gas and reduction in storage volume add to the effect ; • The release of gas initially trapped;

• The production of gas by geological gas desorption and/or (bio)geochemical reactions that can lead to local overpressures within residual voids.

Any thermal gradient between the underground reservoir and the surface will also lead to gaseous migration. In this case, the air flow may reverse direction from one season to another.

These causes of surface gas emissions may occur simultaneously.

Therefore the gases issued from closed mines may generate public health and safety concerns and these problems are encountered for nearly all mine types.

Incidents caused by gas from closed mines

In France, few accidents or incidents associated with emissions or accumulations of coal mine gas after mine closures have fortunately been reported. Some cases have, however, been reported and looked into [START_REF] Pokryszka | Evaluation of gas emission from closed mines surface to atmosphere[END_REF]. In the United Kingdom, on the other hand, ten or more incidents of this type have occurred over the last 50 years [START_REF] Robinson | Mine gas hazards at the surface environment[END_REF]. Other incidents or accidents have been reported in some countries with coal mining industries [START_REF] Kral | Methane from closed-down mines in the soil[END_REF][START_REF] Novotny | Reduction of uncontrollable mine gas emission in the Czech part of Upper Silesian hard coal basin devastated by past mining activity[END_REF].

Some residential areas of the iron basin of Lorraine (in the Northeast of France) are affected by noxious gas emissions (under-oxygenated and noxious gas loaded mixtures). The most spectacular phenomenon occurred in the built-up area of Moyeuvre-Grande in Moselle, especially in the district of the town located very close to the former underground mine workings in which some inhabitants observed faulty working gas cookers and boilers [START_REF] Grabowski | Noxious gas emissions from the closed iron mines to the builtup areas on the surface[END_REF].

The occurrence of gas in salt and potash mines and caverns has often been mentioned in the literature and in the historical reports of mine operations. Numerous mines in operation have experienced sudden, usually unexpected, expulsions of gas or continuous gas emissions. Incidents or accidents, sometimes very spectacular, occurred in mines due to gas emissions. At the beginning of the century, several potash mines of northern Europe were abandoned because of problems caused by gas outbursts (Gimm, 1968). In the early history of salt mining (prior to the current practice of evacuating the mine prior to blasting), many fatalities resulted from gas outbursts. A large portion were due to secondary factors, such as a methane explosion, suffocation, and poisoning (Dorfelt, 1966). Even with the practice of mine evacuation, outburst gases have in some cases filled the mine, blown out of the mine shafts, and caused fatalities at the surface. In one case, the heavier-than-air gas (CO2) gas blew out of the mine shafts for 25 minutes, flowed down a hill into a populated area, and killed 3 people. Several potash mines were abandoned due to a high number of casualties (Baar, 1977). These types of incidents can also occur after mine closures.

Gas monitoring methods

In-situ direct gas measurements or/and gas sampling and laboratory analysis

The gas composition can be determined by in situ direct measurements with portable gas sensors.

The sensors have to be frequently calibrated with several gas standards covering the range of interest. Relative uncertainties in the readings are generally <5%. Portable gas detectors can either monitor :

• a single specific gas, e.g. methane, carbon dioxide, etc ;

• all volatile organic carbon (VOC) gases, or total hydrocarbons ;

• all flammable gases as a total ;

• oxygen ;

• a combination of flammable gas(es), oxygen, carbon dioxide and other gases such as hydrogen sulphide or nitrous oxide. Separate sensors being used for each gas/ group of gases and the values being reported separately.

Portable gas detectors are point source detectors. They measure the concentration of the gas at the sampling point of the instrument. The unit of measurement is % volume ratio, % lower explosive limit (LEL) for flammable gas, ppm for low-level concentrations (and toxic gases) or mg/m 3 . There are a number of techniques used for gas detection.

Those detectors give a first idea of gas composition in an area. They allow the measurement of numerous points and numerous gases but there are just periodic and limited measurements.

Gas samples may conjointly be collected in order to be analysed in laboratory. Such analyses are more precise concerning gas concentrations.

Continuous automated monitoring of old mining sites

Gas monitoring can be accomplished by an automatic continuously operating station located on site. Continuous gas emission monitoring systems refer to a package of gas sampling system, gas analysers and other sensors of aerodynamics or meteorological parameters that are integrated with a data acquisition and data logging system. Continuous automated gas measurements can be performed in former mine workings, in soil, in air and at particular gas emissions points on surface (old shafts, fumaroles, faults…).

In a continuous emission monitoring system, a sample of gas is continuously withdrawn from the chosen source point and presented to various gases or other parameters sensors. Gas concentrations and other parameters are measured, recorded and stored as data. The data is used to generate reports, alarms... This system offers the advantages of choosing the most appropriate analysis technique for the desired components and concentration ranges.

Gas flux measurements on surface.

The measurement of the gas flow out of soil is probably the best method to detect and estimate the importance of gas emissions at the surface. It can be measured by placing accumulation chambers at discrete locations on surface and monitoring the rate of gas that accumulates in the chamber.

INERIS has been developing and validating such methods since 1992 [START_REF] Pokryszka | Development and validation of a method for measuring biogas emissions using a dynamic chamber[END_REF]. These methods, which were originally intended for landfills and contaminated ground, quickly found an application in mines [START_REF] Pokryszka | Method of measuring surface emission of methane[END_REF].

The method uses a chamber that avoids perturbing too much the environment (cf. Figure 1). The gas escapes from the covered area then accumulates in the chamber. In this way it is possible to monitor how the atmosphere becomes enriched in a studied gas. A sample of the mixture is fed to an analyser and then returned to the chamber. By monitoring the rate at which the recirculated mixture is enriched in the gas, it is possible to deduce the local gas flow at the given point. The dimensions of the chamber and the operating parameters of the method were optimised at the design stage on a test rig using known gas flows. The measurement system used is relatively simple to operate. The total time necessary for an individual measurement is of the order of 5 to 10 minutes, so that a large number can be made daily (from 40 to over 60 points according to the difficulties of the site). The method has already been applied in an operational manner for methane on the surface emissions diagnostics and appraisal on number of old mines sites in France, Czech Republic and Spain. The procedures involved in this method are protected by a European patent No. 96-05996.

The research work is now in progress at INERIS to adapt this method for CO 2 and radon emissions measurement on the surface of closed mines.

Examples of gas monitoring

Gases concentrations and aerodynamics parameters measurements in a closed iron mine

An automatic continuously operating station has been set up at the entrance of a former gallery connected to a closed iron mine in Lorraine, in Moyeuvre-Grande area. This area is affected by noxious gas emissions (under-oxygenated and noxious gas loaded mixtures).

In order to estimate the importance of these possible gas emissions, we have studied the influence of the aeraulic conditions within the underground voids on the gas flow from the old workings to the surface. We thus measured some aeraulic parameters in a former gallery, and interpret them in terms of process.

The monitoring device measures some aerodynamics parameters and gases concentrations. It is constituted by: • A temperature sensor, that measures the air temperature old mining workings ;

• A barometric pressure sensor;

• A differential gas pressure sensor that measures the pressure difference between the old workings and external atmosphere; • An O 2 and a radon gas sensors that measure the air composition in the gallery ;

• A data acquisition and data logging system.

Table 1 summarises the monitored parameters, their measure range and the sensors' characteristics. Figure 2. shows the monitoring station. We also have at our disposal a measure of the outer atmospheric temperature.

The continuous monitoring of aeraulic parameters in the former gallery shows us that:

• The differential pressure between the outer atmosphere and the measured point in old workings, which is relatively close to the entrance (400 m), is low, in a range of -1 to 7 Pa. It is positive in summer and fluctuates around zero in winter; • Theoretically the possible gas flow to the surface is low and goes preferentially through the fractures. This flow is higher in summer than in winter when it tends to zero and can even reverse.

These results give us data about the gas emissions from the former workings to the surface through the overburden. However, we need to perform other measurements in order to assess the importance of the flux through the fractured rocks.

Monitoring of gas emission in deep boreholes in an operational salt mine

We have set-up an automatic continuously operating station in the context of an active salt mine in Lorraine. There, the salt is mined by the method of solution mining. Fresh water is injected through wells drilled into the salt bed, around 200m deep, to dissolve the salt and the resultant brine is then pumped to the surface. Dissolution of the salt forms a cavern in the salt deposit.

The objective of the experiment are (i) to identify the presence of gas within the salt deposit and (ii) to qualify and quantify the gas emission during the salt dissolution until the cavern collapses.

A continuous monitoring of the gaseous composition above the salt roof is allowed by the mean of an equipped drilling that emerges near the salt cavern. The gas mixture is measured by a withdrawal of the gas at the bottom of the drilling and its analysis by a specific device. The withdrawal and analysis of the gas are done continuously in a closed cycle (the gases are injected back in the drilling). This drilling is closed and allows the build up of the gases that can potentially be emitted at the salt roof.

The device is constituted by: • Two flexible pipes: one channels the gas from the bottom of the drilling to the measure system and the other injects back the analysed gas at the bottom of the drilling; • An automatic continuously operating station with :

-Gas sensors; -A pump; -A data acquisition and data logging system.

The methods of analysis are non-destructive; therefore the gases can be injected back in the drilling in order to modify the composition of the gas and the pressure in the drilling.

Since the drilling has been equipped, in 2004, the system works under in-situ conditions. However, the salt exploitation is stopped and until now the composition of the air above the salt is the same as the atmosphere.

Moreover in situ direct measurements with portable gas sensors have been realised several times in the neighbour drillings above the future collapsed area. For that we insert a flexible pipe in the drilling. The CO 2 , CH 4 , H 2 S, CO and O 2 concentrations are measured for each drilling. We noticed a spatial heterogeneity of the composition of the air in the drillings. The air is sometimes similar to the atmosphere and is sometimes enriched by methane or hydrogen sulphur.

Underground fire monitoring in an old mine of brown coal

On the site of the former lignite mine of Bois d'Asson, in Provence-Alpes-Côte d'Azur (SE of France), a spontaneous combustion has been noticed in 1999 through an old adit located close to the surface. Since the gas emissions on the site have been monitored by periodic in situ direct measurements with portable gas sensors.

We have set up a monitoring system in order to monitor the evolution of the combustion by measuring the underground temperature at various locations. This system also allows data logging and acquisition and transmission of these data by GSM. The system consists of:

• Four temperature sensors placed in particular points of the site (Figures 3 to 5):

• In the affected gallery;

• In a fumarole at the surface above the gallery;

• In the soil, 0,5m depth in a location where there is no influence of the coal heating;

• In the atmosphere in a sun-protected location;

The two least points are references in order to take the meteorological and climatic conditions into account.

• A station for data acquisition, data logging and data transmission by GSM (cf. Figure 6);

• An autonomous electric supply with two batteries, a loader and a solar panel (cf. Figure 7).

After one year, the experience has shown that the system works well. Thanks to the temperature measurements and the data teletransmission, it is possible to better follow the evolution of underground fire on this old mining site.

Conclusion

After mine closures gas emission risks may persist. Gases accumulated in post-mining voids can migrate to the surface through aerodynamic links. This may lead to risks of accidents on surface like explosions, asphyxia or intoxications.

Methods have been set up to monitor the sites where there are risks. Continuous automated systems associated with data teletransmission appear to be the best method to monitor old mine sites.

INERIS has developed efficient methods that have been validated in several post mining sites. These methods can now be used in the case of gas hazards in other closed mines sites.

Figure 1 .

 1 Figure 1. INERIS method of gas flow measurement on the soil surface

Figure 2 .

 2 Figure 2. Automatic continuously operating station at Moyeuvre-Grande

Figure 3 .Figure 4 .

 34 Figure 3. Temperature sensor at the entrance of the gallery

Table 1 .

 1 Monitored parameters and the sensors' characteristics

	Parameter	Sensor's measure range	Sensor	Sensor's accuracy	Acquisition frequency
	O 2	0 to 25 (%vol.)	Polytron 2, Dräger	1% (± 0,1% O 2 )	30 min
	temperature in the gallery	-20 to +40 (°C)	PT 385, Prosensor	± 0,3°C	30 min
	Atmospheric pressure	600 to 1060 (hPa)	Analogic barometer, PTB 101B, Vaisala	± 0,15 hPa	30 min
	Differential pressure	-1 to 10 (Pa)	FCO 332, Furness Control	1%	30 min
	radon	0 to 10 000 (Bq/m 3 )	Barasol probe, Algade	65 Bq/m 3 h -1 (±0,8 imp.)	50 min


Lionel Aufauvre
email: lionel.aufauvre@ineris.fr

Ruddy Branka
email: ruddy.branka@ineris.fr

FRENCH APPROVAL PROCEDURES FOR PYROTECHNICAL AUTOMOTIVE SAFETY EQUIPMENTS

Pyrotechnical articles for civil uses may be subject to national procedures before placing on the market. According to the French decree n°90-153, 16 February 1990 as modified; explosives that are dispensed with EC marking and that are not excluded of the decree application have to conform to approved types. Pyrotechnical automotive safety equipments such gas generators for airbag modules or seat-belt pretensioners, pyrotechnic relay compositions and/or igniters inside those gas generators fall into that case. The approval procedure, test methods and criteria relating to those equipments are described. For a practical use, a flow-chart of the overall procedure applied to obtain the approval is given. 1

INTRODUCTION

For three decades pyrotechnic articles appeared in automotive industry and their uses grew rapidly as they showed their efficiency to save lives. In parallel, it was known that those articles by nature were potentially dangerous, that lead the French Government to require compulsory approval for pyrotechnical automotive safety equipments.

A BRIEF REVIEW

Since 1990 and the publication of the decree n°90-153 of February 16, 1990 1 few evolutions concerning directly pyrotechnical automotive safety equipments have been done. The order of November 12, 1991 2 clearly specify that pyrotechnical devices for automotive safety, relay compositions and igniters in such devices have to be approved to be produced, sold, imported, exported, shipped, held or used. The order of July 30, 1997 3 approved the manual of test methods for pyrotechnical automotive safety equipments, see paragraph 5. WHAT THE DECREE N°90-153 SAYS?

Here we summarise some statements of the decree n°90-153 concerning the approval of pyrotechnical automotive safety equipments.

WHAT ARE THE ITEMS RELATED TO AUTOMOTIVE SAFETY TO BE APPROVED?

Considering the fast development of pyrotechnical automotive safety technology, one could difficulty give an exhaustive list of all items entering in that category. Even so such a list would not stay up to date very long. But the following families can be use to classify those items:  Gas generator (found for example in airbag modules, sea-belt pretensioners…);  Pyrotechnic relay composition;  Igniter (electrical or not).

Taken separately or part of another object these items have to be approved before to be produced, sold, imported, exported, shipped, held or used. In addition, for production in EU and subsequent putting on the market, substances like gas generating material, propellant in seat belt equipment should be CE marked according to the Council Directive 93/15/EEC of 5 April 1993.

METHODS AND CRITERIA FOR APPROVAL

The manual of approval test methods and criteria for pyrotechnical automotive safety equipments can be obtained on demand at INERIS. According to items concerned specific test methods apply. All test methods required for the approval have been chosen with a view to ensure an acceptable level for public safety. The procedure of approval does not guarantee any performance reliabilities in the final use of the safety equipments. All trials have to be carried out on representative samples of the model to be approved.

GAS GENERATOR

Whatever the use that is intended for the gas generator submitted to approval, it is subjected to the eight test methods listed in table 1. To be carried out those tests usually required 11 representative gas generators of the model to be approved. Besides of those test methods, compatibility of all components, ageing, effects of mechanical and climatic stresses, electromagnetic environment effect and properties in case of criminal uses are considered according to technical data submitted. Information regarding safety in a shaped of warning notice or information leaflet similar to material safety data sheet (MSDS) are also considered.

The minimum criteria to pass for the tests are:  The normal operation in test N7 after each single test J8, I10, E10 and before any of them;

 No splitting during test M7;  Gas concentration in test R8 below 20 ppm/l of inflatable bag 5 for CO (carbon monoxide) and below 2 ppm/l of inflatable bag for NO x (nitrogen oxides).

RELAY COMPOSITIONS

Such compositions to be approved are subjected to the nine test methods listed in table 1. The quantity of pyrotechnical composition required to perform all the tests is between 1 and 2 kg. The material safety data sheet (MSDS) required is also examined. The criteria to pass the tests performed are the same than for other pyrotechnical compositions in those tests.

IGNITERS

A1 Description • • • • • • • • • • • J8 Vibrations • I10 Fall • E10 Stability • N7 Operation • • • • I11 Impact • • • • M7 a) Heating • R8 b) Combustion products • • Igniters A1 Description • • • • • • • J8 Vibrations • I5 Fall • E10 Stability • N7 Operation • • • • P8 Detonability • • • Relay compositions A1 Description • A3 Particle size distribution • B1 Density • E1 Stability • I1 Sensitiveness to impact • J1 Sensitiveness to friction • K1 Sensitiveness to electrical spark • F2 Progressive heating • M8 Deflagration to detonation transition • a)
Performed only for gas generator designed for air-bag module. b) Not necessarily performed, in particular for hybrid gas generator.

DESCRIPTION OF TEST METHODS

Hereafter we briefly describe the test methods listed in table 1.

Test method Description A1 Description

Description and comparison of the item sent to be approved with the technical data or drawing submitted.

J8 Vibrations

The object is submitted to vibrations (frequency 50 Hz, amplitude 0.5 mm) during 60 minutes.

I10 and I5 Fall

The object is dropped on a hard floor from a height of 1.20 m.

E10 Stability

The object is submitted to a temperature of 50°C and a relative humidity of 60% during 4 weeks.

N7 Operation

Operation of the object is compared to what it is suppose to be.

I11 Impact

The gas generator is struck with a 30-kg fallhammer dropped from 0.25 m and 0.50 m high on 2 different directions.

M7 Heating

The gas generator is heated with a gas burner until reaction.

R8 Combustion products

Analysis of the nature and quantities of the products emitted when the gas generator is initiated in a 2.5 m 3 chamber.

P8 Detonability

The igniter is used to initiate a cartridge of pentrite. A3 Particle size distribution 100 g of pyrotechnical composition are screened through sieves of different mesh sizes. B1 Density Determination of the normal loading density.

E1 Stability

The material is submitted to a temperature of 75°C in an oven during 48h.

I1 Sensitiveness to impact

The material is submitted to various energy of impact and the energy corresponding to a probability of reaction of 50% is determined.

J1 Sensitiveness to friction

The material is submitted to various energy of friction and the energy corresponding to a probability of reaction of 50% is determined. K1 Sensitiveness to electrical spark A 3-mm-thick layer of pyrotechnical composition is submitted to electrical spark of different energy, a level of minimum energy of no-reaction is determined.

F2 Progressive heating

The material is progressively heated (heating rate 5°C/min), the temperature of runaway is determined. M8 Deflagration to detonation transition Determination of the length after which the deflagration of the confined material turns into detonation.

FLOW-CHART OF THE OVERALL PROCESS

In the given chart (see below) we describe the main steps of the process to obtain an approval according to decree n°90-153. The time to get through the entire process can usually be estimated between 3 to 6 months.

CONCLUSION

As pyrotechnic articles are out of the scope of the Council Directive 93/15/EEC of 5 April 1993, the regulation we commented in this paper applies in France. In the coming years, pyrotechnic articles like pyrotechnical automotive safety equipments should fall under a Council Directive in preparation in which the requirements are the same than those cited in the 93/15/EEC Directive:  Type examination (product certification) in accordance with some Essential Safety Requirements;  Examination in term of periodic audits of the manufacturing and inspection conditions, audits depending of the level of quality existing in the manufacturer.

  Request for the approval of a model should be submitted to the Ministry in charge of Industry by a natural or legal person established within a state of the European Community. Together with the request, one has to joint a record that at least should:  Describe the product and its components (part drawings, characteristics, composition, origin…);  Mention the trade name of the product;  Justify the ability of the applicant to guarantee the future conformity of the product to the model.INERIS as Official Laboratory (authorised by Order ofDecember 20,1996 4 ) is commissioned by the Ministry to carry out the approval test methods on representative samples of the model. If any, results of equivalent methods already done by relevant laboratories can be considered. INERIS writes a report on the base of the results obtained and the technical file provided and presents it in front of the "Commission des Substances Explosives CSE" (French Committee of Explosives). Then the Ministry in charge of Industry delivers the approval after consultation of "Commission des Substances Explosives CSE". The approval bears the name of its holder and any transfer of it from the holder to another person requires a notice from the Ministry in charge of Industry to be done. At any time, the Ministry in charge of Industry can prescribe tests or controls in order to check the conformity of a product to an approved model.

  Igniters either electrical or not are subjected to the six test methods listed in table 1 to be approved. Besides of those test methods, electrical properties and sensitivity, compatibility of all components, effects of mechanical and climatic stresses, electromagnetic environment effect are considered according to technical data submitted. In the case of non-electrical igniters, electrical features that are not relevant are replaced as needed. Usually 7 igniters of the model to be approved are required to carry out all those tests. Information regarding safety in a shaped of warning notice or information leaflet similar to material safety data sheet (MSDS) are also considered.

	INERIS test reference	Name	Sample number 1 2 3 4 5 6 7 8 9 10 11
	Gas generators

The minimum criteria to pass for the tests are:  The normal operation in test N7 after each single test J8, I5, E10 and before any of them;  No initiation of a detonation of explosive cartridge in test P8. Table 1: List of test methods performed within the scope of the approval according to the decree n°90-153

INERIS issues an examination report and submit it to the "Commission des Substances Explosives", which is gathered periodically (2 or 4 times a year).

The "Commission des Substances Explosives" reaches a decision which is communicated to Ministry in charge of Industry and the applicant.

Additional information are required from the applicant before.

An approval number is delivered to the applicant and the decision is published in the French OJ

The applicant amends its file.

The amendment is evaluated

Two cases possible

The applicant affixes the approval number on the item approved


Cécile Honore
email: cecile.honore@ineris.fr

Laurence Rouil

Frédérik Meleux

Laure Malherbe

Bertrand Bessagnet

Robert Vautard

Nathalie Poisson

Vincent-Henri Peuch

Anne Dufour

Cécile Honoré

Frédérik Meleux1

Laure Malherbe1

Bertrand Bessagnet1

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

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

INTRODUCTION

Numerical simulations of pollution events with deterministic models hâve become easier for thé last décade thanks to increasing computer skills. Hence three-dimensional chemistry-transport-runs can be performed on a single workstation for long-term simulation or real-time forecast over large scale areas. Furthermore, fast Internet download and high file storage capacity in data processing make it possible to use a wide database of meteorological parameters and pollutant concentration measurements.

The PREV'AIR System rests on those technological progresses for delivering daily air qualiry forecasts in operational conditions. In fonction since summer 2003, it is thé visible part of a wider collaborative project -thé PREVAIR project -launched by thé French Ministry for Ecology and Sustainable Development (MEDD), aiming at: (1) providing technical support on atmospheric pollution management in Europe, in thé framework of negotiations on trans-boundary air pollution;

(2) providing large scale national air quality information based on numerical simulations and observations. The PREVAIR System is a complementary monitoring tool with respect to thé local information delivered by thé French qualified associations in charge of régional air quality monitoring (AASQA 3 ). It relies on a chain of numerical tools: air quality simulation models, modules ensuring thé provision of meteorological and air quality input data to thèse models, modules enabling thé extraction and use of thé numerical data computed by thé System. The outputs of thé PREVAIR system (secondary pollutants forecasts and maps) are archived to build up a large scale air quality simulation database over Europe.

The following public organisations are involved in thé PREVAIR project:

Reliability and scores of thé PREV AIR System

Forecasting mode: Statistical performance indexes are updated every day and published on thé PREV'AIR web site.

The availability of thé AVN data is of primary importance (thé missing data is responsible for 5 % of thé forecast failure). Some performance indexes (see A sensitivity study was conducted to assess thé efficiency of the correcting procédure. Two 15-day test periods were selected in thé summer 2003 season. 103 ozone monitoring stations, mostly of rural type, were used in thé kriging process. 2 rural, 42 suburban and 151 urban monitoring stations were kept for validation. At thé end of thé tests, différent error statistics were calculated. As they indicate, thé choice of thé kriging parameters is satisfactory and thé agreement between model and measurement in rural and suburban areas is significantly improved. For example in cross validation, when averaged over thé whole period and thé 103 stations, thé normalised bias and thé root mean square error decrease by 60% and 26% respectively whereas corrélation increases by 10%. In validation at thé suburban stations, thé normalised bias and thé root mean square error decrease by 51% and 22% whereas corrélation increases by 8%.

USE OF THE PREVAIR AIR QUALITY FORECASTS AT THE LOCAL SCALE

In relation to thé second objective of thé PREV AIR project, numerical air quality forecast data hâve been put at thé disposai of air quality related organisations. The only requirement for thé demanding organisations is to fill in a form specifying thé exact domain on which thé data are to be delivered. Numerical data are then put every morning on thé users page of thé PREVAIR web site. Two kinds of data are available over thé specified domain: ozone and nitrogen dioxide surface data and 3D data for 22 chemical species. Up to now, about 40 organisations hâve 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 and forecast models. In that context, several initiatives gathering thé skills and resources of différent AASQA were born in France. In thé SYRSO (Régional System for Ozone Monitoring) and OCARINA (Interrégional Air Quality Mapping Tool) projects, PREV'AIR forecast maps are reprocessed at a local scale and broadcast on thé AASQA websites. In thé ESMERALDA and AIRES régional modelling platforms, which involve AASQA respectively from thé North and centre part of France and from thé Provence-Alpes-Côtes d'Azur région, PREV'AIR numerical outputs are used as boundary conditions for high résolution modelling.

PERSPECTIVES

Différent ways of improving thé system are being investigated or are planned for thé next months:

Ozone forecasting and simulation

Observation data can be used not only to correct D-1 simulated maps but also to increase thé accuracy of forecasts. This is particularly relevant in régions of complex terrain, where thé model résolution is not sufficient to reproduce some local pollution patterns.

According to data availability, thé domain considered in thé analysed maps could be extended by including observations from surrounding European countries. -In thé framework of the GMES PROMOTE and GEMS European projects, PREV'AIR will quickly evolve in thé next few years, including developments both for meteorology and chemistry-transport modeling (CTM). The main goal is to evaluate and improve thé model behavior on thé vertical dimension. Thereafter, satellite data assimilation will be carry out. Finally, thé feasibility of using several models to deliver a single forecast (multi model approach) will be investigated, by example coupling CHIMERE and MOCAGE models.

Aérosol forecasting

Aérosol forecasts hâve been delivered since winter 2003 (starting end of October). The most important improvement expected for aérosols concerns thé implementation of a more detailed chemical schème for secondary organic formation. More observation data will be used in thé analysis and vérification processes (Italy (ARPA-EMR), Switzerland (NABEL/SAEFL), Poland (institute of Environmental Protection, Katowice), Germany (UBA)...).

Figure 2 - 3 -

 23 Figure 2 -Ozone peak and PMio daily mean forecast issued on June 28, 2005 for thé same day

•

  INERIS (National Institute for Industrial Environment and Risks) is a public institution, under thé supervision of thé MEDD, Its mission deals with assessment and prévention of accidentai and chronic risks due to industrial plants, chemical substances and underground opérations, France joined thé System in 2004. The organisation develops another air quality model, MOCAGE, and ensures its operational implementation for thé needs of PREV'AIR. OOh UT to D+3, OOh UT. The first 24 hours of forecast are actually rather simulations whereas thé next 72 ones are strictly speaking forecasts. The meteorological predicted fields necessary to run CHIMERE are obtained in two steps: 1. Low résolution meteorological forecast data are downloaded from thé ftp server of thé American National Weather Services, where they are produced by thé Global Aviation Model (AVN) model; 2. High résolution meteorological forecast data are then locally computed using thé MM5 model.Emission data corne from thé EMEP program 4 , with hourly, weekly and monthly temporal profiles from 1ER 5 . Contrary to meteorological data that change from day to day, émission data are set once and for ail.Observed air quality data are also used by thé PREV'AIR System (see hereafter). They are transmitted by various European organisations. For example, thé French real-time air quality data are downloaded from thé BASTER ftp server and used both to evaluate thé model skills and to correct a posteriori thé CHIMERE air quality (D-1) simulations.

	hereafter). Moreover INERIS carries out air quality studies for thé MEDD including reporting
	and prospective analysis.
	• IPSL (Pierre-Simon Laplace Institute) is a research institute in thé field of environment, under
	thé supervision of thé National Centre for Scientific Research (CNRS). IPSL ensures thé
	development of thé chemistry-transport model(s) -thé CHIMERE model(s) -used within thé
	PREV'AIR System.
	• ADEME (Agency for Environment and Energy Management) is a public institution under thé
	supervision of thé Ministries in charge of research, ecology and energy. It helps implementing
	public policies in thé field of energy and environment at local, national and international levels.
	ADEME ensures thé gathering, archiving and transmission of real-time air quality data locally
	collected by thé AASQA. By this way, ADEME builds up thé BASTER database used by thé
	PREV'AIR System.
	• Météo-
	towards health effects and environment. Within thé PREVAIR project, INERIS is in charge of
	developing thé PREVAIR architecture, delivering daily information about air quality; providing
	and archiving air quality data produced within thé PREVAIR system. The institute also
	participâtes to thé development of thé CHIMERE model in collaboration with thé IPSL (see

The MEDD financially supports thé PREVAIR project through thé funding of INERIS activity. The PREV'AIR System is briefly presented hereafter, as well as thé first conclusions drawn front two years of opération.

ARCHITECTURE OF THE PREV'AIR SYSTEM, INPUT DATA AND OUTPUTS

The PREV'AIR System provides daily air quality forecasts at three spatial scales. Global forecasts are produced by Météo-France with thé chemistry-transport model MOCAGE and transferred every day to thé PREV'AIR System. Continental and national forecasts are computed by thé chemistrytransport model CHIMERE implemented in thé PREV'AIR forecasting chain. In thé "continental" set up, pollutant concentrations are computed over Western Europe with a 50 km*50 km résolution. In thé "national" set up, pollutant concentrations are computed over France with a 10 km* 10 km résolution.

Ozone and nitrogen dioxide forecasts hâve been delivered for two years. In october 2003, forecasts were extended to particulate matter. PM10 are assumed to be composed of sulfate, nitrate, ammonium, primary particles, anthropogenic and biogenic secondary species. The aérosol module accounts for 6 bins from 10 nm to 40 \xm. From spring 2005, PM10 account for désert dust, sulfates and carbonaceous compounds advected from thé domain boundaries. A spécifie émission module hâve been built to account for soil particles emitted from érosion and resuspension processes. Each day (D), hourly concentration levels are predicted over a four-day period going from D-1,

  table below) hâve been computed for thé last two summers, using thé ozone peak concentrations measured in France and calculated for D+0 by thé PREV'AIR System. Regarding thé ozone peak, thé performances of thé System are quite satisfying.

	Statistical Indexes
	Observed mean ozone
	peak (ug/m3) (nuber of
	observations used)
	Simulated mean ozone
	peak (jig/m3)
	Normalized Bias (%)
	Normalized	Mean
	Square Error (%)
	Corrélation

Coopérative Program for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe 3 Institut fur Energiewirschaflt und Rationelle Energieanwendung, University of Stuttgart

Long-Range Trans-boundary Air Pollution of thé United Nations -Economie Commission for Europe.


Marc Dur1f
email: marc.durif@ineris.fr

Use of commercial sphagnum moss to estimate thé géographie impact of a battery of recycling plant

published or not. The documents may come

Use of commercial sphagnum to estimate the geographic impact of a battery of recycling plant

Introduction

We used an active bioaccumulation method known as moss-bag. This technique rests on thé exposure of small nylon nets filled with bryophytes for one given period. The bryophyte dépends primarily on thé atmosphère for their nutrition. They absorb there thé traces éléments (deposit dry and wet) they need but also other éléments nonessential with their survival of which heavy metals. The bryophyte, having a strong capacity of cations exchange, they will act like metals hyper-accumulators and their complexes. Thèse compounds will be fixed at thé cellular walls of which numbers components hâve negatively charged groupings.

Contrary to thé traditional techniques of assessment of pollution, thé bryophyte are living organisms, and their capacities of accumulation are thus prone to variations of a biological nature in relation to their environment. Consequently, thé exploitation without précaution of thé results obtained by thé biosurveillance is unsure. There are several sources of variability of thé rétention capacity of thé éléments in thé bryophyte [START_REF] Galsomies | Retombées atmosphériques de métaux en France : estimation par dosage dans les mousses[END_REF] :

The species: Thèse variations, related to thé différence of morphology and growth are at thé origin of thé difficulties of interprétation at thé time of thé comparison of thé results for thé in situ studies. At small scale, it is relatively easy to find a species présent on ail thé selected sampling points. But on greater scales, it is often necessary to take other species when thé species of référence are missing. The interprétation of thé results is then more critical. In this case, comparisons inter species are to be realised. Those are difficult to carry out since variability inter species must be quantified in relation to thé régional variations [START_REF] Halleraker | Reliability of moss (Hylocomium splendens and Pleurozium schreberi) as a bioindicator of atmospheric chemistry in thé Barents région: Interspecies and field duplicate variability[END_REF]. This variability source makes also critical thé comparison of studies "transplants" realized with various species. -The élément: thé rates of rétention also differ according to thé élément considered [START_REF] Rûhling | Sorption and rétention of heavy metals in thé woodland moss Hylocomium splendens (Hedw[END_REF][START_REF] Vasconcelos | Atmospheric métal pollution (Cr, Cu, Fe, . Mn, Ni, Pb and Zn) in Oporto city derived from results for low-volume aérosol samplers and for thé moss Sphagnum auriculatum bioindicator[END_REF].

The environmental conditions: sources and mechanisms, others than air pollution, can influence thé métal contents of thé bryophyte [START_REF] Steinnes | A critical évaluation of thé use of naturally growing moss to monitor thé déposition of atmospheric metals[END_REF]:

1. The marine factor: exchange cations on thé surface of thé bryophyte with sea sait ions; 2. The ground factor: minerai particles coming from thé local ground and transported by thé wind; 3. Effects related to thé acid rains (exchanges of ions) and thé transport of thé soluble compounds at thé time of thé long periods of contact water/soil/bryophytes (snow melt); 4. The climatic conditions play an important part in thé absorption of thé éléments, thé intensity of précipitations, thé wind speed [START_REF] Clough | The déposition of particles on moss and grass surfaces[END_REF] is one of thé principal parameters which modified thé process of absorption [START_REF] Ceburnis | Investigation of absolute métal uptake efficiency from précipitation in moss[END_REF],

Contrary to certain studies [START_REF] Al-Radady | A new design of moss bag to monitor métal déposition both indoors and outdoors[END_REF], we did not seek to maintain thé bryophyte under optimum conditions for life. This approach can seem contradictory with thé use of living organisms, and we could almost speak about "necro-sensor". We made this choice in order to use a biologically inert material, to free itself from any interférence of thé metabolism of thé bryophyte with thé collection of metals (élimination, défense...). Indeed, an alive bryophyte used in thé technique of thé transplants is under permanent stress. This has conséquences on its capacity of accumulation then involving différences in response from an intake point to another.

The principal operational difficulty when one works with this type of material is thé provisioning. Sphagnum mosses, because of particular ecosystem that they shelter, are often protected species. We thus tested thé possibility of using of Sphagnum mosses of culture used in thé horticulture in substitution of thé natural sphagnum mosses.

The aim of this study was also to show thé benefits of this kind of technique to evaluate thé géographie impact of diffuse émission. We worked on thé contribution to lead, cadmium, arsenic, barium and antimony déposition coming from a battery recycling plant. For comparison, we also used gauges to measure thé déposition with a conventional methodology.

Materials and methods

Moss-bag origin

The moss used is of Sphagnum mosses type. They came from Chile where they were dried then eut into pièces of 15cm after harvesting. They were then, conditioned and dispatched ail over thé world. They are identified "Chile" in this study. The results obtained with this material hâve been compared with those obtained with Sphagnum mosses collected alive in its natural environment (Sphagnum papillosum). in Forest of Coye (close to Chantilly) far from any polluting anthropic activity. They are identified "Coye" in thé remainder of thé study.

Préparation

Ail thé containers, utensils were rinsed with diluted nitric acid (1%), then with deionised water.

During ail thé opérations (harvest, treatment, exposure...) thé sphagnum mosses and thé mossbag were handled using plastic gloves without talc. The collected sphagnum mosses (Coye) were placed in a hermetic plastic bag, then stored at around 4°C. The Sphagnum mosses Chile were directly taken in thé conditioning of thé supplier. The sphagnum mosses were cleaned (élimination of thé old sphagnum mosses, other plants, insects...) then eut into pièces of 5-6 cm. Thé pièces were washed with thé water de-ionised and then with thé diluted acid (HNO3 with 1%). After a last rinsing with deionised water, thé Sphagnum mosses were dried with air (clean room) until complète dehydration. Approximately 0,4 g (dry weight) of mosses were laid out in a nylon net (meshs of 2 mm X 2 mm) so as to form a sphère of a diameter ranging between 2,5 and 3 cm. The moss-bags were then placed in hermetic plastic bags in order to avoid any possible contamination before exposure. The moss-bags were then set up approximately at 1,70 m above thé ground level.

Post-exposure treatment

The moss-bags were collected in clean plastic bottles. The samples were dehydrated in a drying oven. The whole of thé sample is analysed, which makes it possible to avoid problems of distribution of thé analyte in thé sample. Thé whole of thé moss-bag is poured in matras then mineral-bearing with thé furnace microwaves in a nitric acid solution to 65% (Suprapur).

Sampling strategy

The location of thé sampling points around thé site was selected according to thé modelling of stack émissions (figure 1 Fourteen sampling points equipped with sensors of thé moss-bag type and gauges were set up in a perimeter of 2 km around thé site (figure 1-right side).

A référence sensor of each system of measurement was also located at approximately 4 km in thé south-west of thé site, far from any source of heavy métal émission. In order to evaluate thé level of background contamination.

The measurement network was focused on a perimeter of 500 m around thé site in order to evaluate thé possible impact of thé diffuse émissions. In order to calcuiate thé repeatability of each system of measurement, 6 moss-bags and 6 gauges were sirnultaneously exposed on zones expected to coliect strong (point C) and weak déposition (point K) (figure 1-right side).

The sensors were exposed during one month (from 03/06/03 to thé 04/07/03). During this period, some of thé moss-bags were exposed over a fifteen days shorter duration (from thé 03/06/03 to thé 19/06/03) in order to evaluate thé duration of minimal intégration necessary to get a good quality of thé results. The formalism J+15 and J+30 will distinguish thé two exposure times in thé remainder of thé document.

The parameters of atmosphère dispersion (force and direction of thé wind to 10 meters height, pluviometry and température on thé ground), were obtained thanks to thé establishment of a measuring site on thé factory site.

On each sampling point, three moss-bags from each origin (Coye and Chile) and of both duration (J+15 and J+30) were exposed in order to give a good estimate of thé average metals concentration.

For each system of measurement, blank samples were also carried out (samples that underwent ail handling without never being exposed). This makes possible to evaluate thé initial contaminations but also those likely to occur at each stage of thé protocol: taking away, preexposure treatment, transport, handling, post-exposure treatment, analyses.

On thé whole 204 moss-bag and 25 gauges were exposée!during thé campaign.

Analyses

According to thé concentrations expected in thé varîous samples, two analytical techniques were used: ICP-AES (atomic émission spectrophotometer of coupled to an induced plasma) for thé hight concentrations and 1CP-MS (mass spectrometer coupled to an induced plasma) for thé low concentrations. A semi-quantitative analysis in ICP-AES was carried out on some samples in order to choose thé analytical technique.

Resuîîs and discussion

Repeatability Thé 6 moss-bag and 6 gauges exposed in parallel on thé points C and K made it possible to caiculate a confidence interval (IC) to 95% for two levels of concentrations (weak and strong). This IC correspond to thé interval including/understanding with a probability of 95% thé true value of thé average (u).

\ x J

métal, each type of support and each exposure time. The repeatability of thé technique of thé moss-bag is of 15-20%, therefore comparable with that of thé technique of thé gauges. For lead and cadmium thé repeatability is constant in thé range of studied concentrations. We wiil apply this assumption to thé whole of metals for this study.

Accumulation rate

The accumulation rate of thé moss-bag varies with thé exposure time. This variation is more important than thé variation of repeatability, but ït is équivalent at thé same moment on thé whole of thé points (placed in a comparable climatic environment). This intrinsic property of thé moss-bag thus makes critical thé comparison of thé results of campaigns carried out over différent durations and perhaps even from différent periods. A séries of fifteen days measurement is sufficient to evaiuate thé barîum and antimony, and lead levels accumulated in thé moss-bags. For weak cadmium background noises, a 30 days exposure îs préférable.

Comparison Coye/Chile

The corrélation between this two types of material is very good (figure 2). The Coye moss-bags are slightly more sensible than thé moss-bags of thé Chile type but thé sphagnum mosses cultivated remains a good alternative to thé "natural" sphagnum mosses for thé design of mossbag.

Arsenic Baryum

..----' "

• • • • « • • • • .• ,....-•

Cadmium Plomb

Comparaison Moss-bag / Gauges

The corrélation between thé measurements carried out with thé gauges and thé moss-bags Chile is less good than that between différent type of moss-bags (figure 3). The moss-bag and thé gauges are subjected to thé same particulate métal concentrations in thé ambient air. In order to compare thé quantities measured with thèse two Systems of measurement, thé métal concentrations measured in thé moss-bags (u.g/g of ms) were converted into ng/m 2 .day to be in a comparable unit with thé measurements carried out with thé gauges. The ratio of thèse quantities is higher than one (from 1.4 to 3.9) for ail thé éléments (figure 4). Thèse results are in contradiction with thé surface of exposure of thé moss-bags which is theoreticaily smaller than thé section of opening of thé gauges (Surface Gauges = ~2.6 x Surface moss-bag). By making thé assumption that thé two Systems hâve identical cut-off diameter, it seems that thé moss-bag has a surface of exposure that wouid actually range between 3 and 10 times that of thé gauges. The greatest effectiveness of thé moss-bag is probably thé resuit of a combination of two factors. First, thé fibrous internai network of mossbag offers an important exchange surface to thé particles. In this network, thé particles are better captured on thé végétal surface (adsorption and/or mechanical trapping) than on thé plastic surface of thé gauges (stop and go phenomenon). In addition, comparatively with thé gauges, one estimâtes that thé moss-bags collect a broader spectrum of particles [START_REF] Al-Radady | A new design of moss bag to monitor métal déposition both indoors and outdoors[END_REF]. Indeed, thé gauges collect only thé particles of size higher than 5|im of diameter [START_REF] Hendrickson | Air sampling[END_REF] and thé finer particles, generally forming a deposit by impaction [START_REF] Chamberlain | Interception and rétention of radioactive aérosols by végétation[END_REF], are retained better in thé fibrous network of thé moss-bag. Thèse two factors compensate probably thé losses of matters collected by thé moss-bag (scrubbing, agitation, problem of adsorption of thé métal éléments traces on thé nylon net not analysed...).

Baryum A A. A * -• " ' A A A ^ --^- A A At, A _..-"' A A A A*' A ,-' ' A/-"'' ,-'A
There is a good corrélation between thé moss bags and thé gauges. The moss bags seem to be more sensitive than thé gauges.

Contribution of thé plant

For ail thé metals, thé contents measured within thé limtt of property of thé factory are higher than those measured outside. According to metals, thé contents measured at thé point G are between 7 and 6194 times those of thé référence sample (table 1). For ail metals, thé point D corresponds to thé maximum of thé contents measured outside thé site.

Tableau 1 : Ratio of concentration measured at différent locations to thé référence

Outside thé limits of thé site, thé ratio obtained for barium drops quickly and is relatively uniform whatever thé direction of sampling. For lead, cadmium, arsenic and antimony thé ratios are a function of thé distance that séparâtes thé sampling points and thé site. The shape of thé curves is similar for thèse four metals (figure 5). The concentrations measured increase through site. According to thé directions of dispersion, south-west/north-east and north-west/south-east, they reach a maximum respectively at 370 and 217 m under thé wind of thé installation. The points located at thé NorthEast of thé site, reveal more important contents compared to those of thé three other directions. This distribution is consistent with thé wind rosé and recorded précipitation direction. The plant obviously seems to be a probable source of lead, cadmium, arsenic and antimony.

Conclusions

For thé ievels of exposure met in this study, thé sphagnum mosses of culture are a good alternative to natural moss-bags. This limits thé difficulty of supplying sphagnum mosses in natural and protected area. The technique of thé moss-bags is a powerful tool of qualitative survey (implemented simple, inexpensive, allowing to carry out many intake points) which has many advantages (lower confidence interval, low cost of implementation, easy to use...). This technique brings essential qualitative information where other approaches are less reliable: modelling in degraded situation (diffuse émission). This tool makes it possible to optimise and reduce thé costs of conventional quantification campaigns by quickly determining thé géographie impact of a plant. It however does not exempt to implement a séries of "traditional" measurement to complète thé characterization of thé impact of a site.

This study shows thé importance to follow a strategy of measurement which makes it possible to hâve thé necessary éléments to thé objective exploitation of thé results (référence sample, blank, détermination of thé repeatability...)

  a/2 r : Student coefficient, for which y is thé degree of freedom (y = n -l), and thé probability 1'-a/2, x : averaged concentrations measured in Cor K jU : thé true value of thé averaged concentration measured in CorK s : standard déviation calculated at points CorK flC \ The relative confidence interval, -=-xlOO was calculated of each point C and K for each

Figure 2 :

 2 Figure 2 : Corrélations between Chile and Coye moss-bags (exposed during 30 days)

Figure 3 :

 3 Figure 3 : Corrélations between Chile moss-bag and gauge (exposed 30 days)

Figure 4 :

 4 Figure 4 : Ratio of surface déposition measured by moss-bags and gauges

Figure 5

 5 Figure 5 : £ J Témoin

  -left side).

	o	;io	400	6«n	100	ia,i>	i DQ >4iw	is'io	eo^	2 or

Figure 1 : Left stde : Lead concentrations calculated by modelling of thé lead émissions from stack (10" 2 ng/m 3 ) -Plant position : 1000 ;1000. Right side : Position of the 14 sampling points around thé plant (biue circte)

Université du Littoral Côte d'Opale -Centre Universitaire de la Mi-Voix -MST « Expertise en pollution du milieu naturel, environnement et risques » -Calais

Université de Lille 2 -Faculté des Sciences Pharmaceutiques et Biologiques -Département D'études et de Recherches Toxicologie, Santé Publique, Environnement -DESS Biotoxicologie Environnementale et Industrielle -Lille.