Specificity of damage to agriculture due to storms: first recommendations produce flood damage functions Pauline Brémond 1 , Frédéric Grelot 1 and Daphné Durant 2 1. Background

Method to analyze specifity of saline floodings

We conducted interviews with 8 farmers, 8 agricultural experts and 2 cooperatives in Vendée and Charente-Maritime that have been impacted by Xynthia or have supported farmers recovery after Xynthia. Those interviews conducted 8 years after Xynthia allowed us to consider short, mid and long term effects as well as the duration of recovery. Two interview guides have been used: one for the farmers and one for the agricultural experts. All the interviews were transcribed and analysed.

Vineyard

Height of flood (cm)

Conclusions Key messages

Reconstruction of new protections Cost Benefit Analysis

After Xynthia, local communities asked for fundings to reconstruct and implement new protections.

In France, funding from the State need to be asked through the procedure PAPI (Programs of Actions to Prevent Floodings). In this PAPI, Cost Benefit Analysis (CBA) is mandatory.

As a consequence, to conduct CBA, Avoided Damage need to be evaluated. In France, National Flood Damage Functions have been elaborated for non saline floodings and for every category of assets (dwelings, economic activities, agriculture and public infrastructures).

The adapatation of Flood Damage Functions have been proposed for saline floodings for dwelling and economic activities but not yet for agriculture.

Storm Xynthia, 2010

French littoral and particularly Vendée and Charente-Maritime departments have been seriously impacted by storm Xynthia which occured on the 28 th of February 2010 . 32 000 ha of agricultural lands representing 956 farms were flooded with saline water. 55% of farms impacted had more than 50% of their land plots impacted by saline submersion. The main crops impacted by Xynthia were cereal crops or mixed crop-livestock farming systems and viticulture.

French littoral is protected by dykes: first rank dykes protect mainly agricultural areas whereas urban areas are rather enclosed by second rank dykes. A lot of infrastructures, in particular first rank dykes have been destroyed by Xynthia.

Results

Specificity of damage, specific actions and duration of the recovery

General result

No consolidated expertise on mid and long term effects of storm Xynthia on agriculture have been carried out.

Only one precise feedback experience has been found on the INRA experimental farm of Saint-Laurent-de-la-Prée (Durant et al, 2018). The only other submersion that occurred in this area is Martin (December, 1999) . With this only two events, it is difficult to analyze potential effects on crops for every season.

Damage to vineyard (fig. 11) Vineyard mortality due to saline water differs from mortality observed with non saline water. In non saline context, except in spring, mortality is very low. After Xynthia, vineyard mortality occured and was high and delayed in time (sometimes two years after). The factors that influenced vineyard mortality were : the age of the vineyard, the type of soil and duration of submersion. The duration of the recovery varies between two and seven years.

Damage to soil are specific due to salinization (fig. 5) and mud deposit composed of sand and algae (fig. 6). To evacuate salt, gypsum has been applied on fields (fig. 7). From our interviews, 20t / ha of gypsum during 3 years have been applied which represents a total cost of 990 €/ha. Efficacity of gypsum also depended on wether rain occured after treatment. On vineyard, gypsum could not be applied due to technical constraints and organic matter has been applied. Damage to drainage equipment (fig. 8) is also specific. Crops along the littoral are equiped with a system of drainage which relies on pump engines and canals. Reparation costs should be considered in damage functions.

Damage to cereals / leguminous plants

Crop losses on winter durum wheat after Xynthia was 100%. Depending on crop type, crop losses varied between 50% and 100% the year Xynthia occured.

Contrarily to what happens after a non saline flooding, crop losses were endured the years after Xynthia. Effects on yield have been observed between five to seven years after Xynthia due to soil salinity.

Damage to potatoes . Potato crop is often coupled with viticulture in this area. After Xynthia, crop loss were 100%. However, no effect was observed the year after on crops.

Vienna | Austria | 7-12 April 2019 The main effect on livestock farms was due to flood impacts on grassland. The shortfall induced for feeding cattle has been compensated by buyng fodder. The duration of recovery of grassland fields was about three years. Specific damage functions which take into account this linkage should be developped.

  1 G-EAU, Univ Montpellier, AgroParisTech, Cirad, IRD, Irstea, Montpellier SupAgro, Montpellier, France 2 INRA, Unité Expérimentale 057, Saint-Laurent-de-la-Prée, France Correspondence: P. Bremond (pauline.bremond@irstea.fr) This work benefited from fundings of the French Ministry of Environment (CGDD convention n° 2201138418)

Figure 1 :

 1 Figure 1: French littoral impacted by Xynhtia storm in 2010

Figure

  Figure 2: Ile de Ré during Xynthia, 2010

a 1 .

 1 To what extend the mechanisms that induce damage due to saline flooding are specific? 2. To what extent mid and long term effects should be considered? 3. How long is the recovery of farm after submersion? 4. Which adaptations of the damage functions to agriculture should be done?

Figure

  Figure 3: Example of flood damage function

Figure 4 :

 4 Figure 4: Fields in Saint Laurent de la Prée

Figure 5 :FigureFigure 8 :

 58 Figure 5: Impact of salinity on soil structure Figure 6: Mud deposit on soil

Figure 11 :

 11 Figure 11: Vinegrowers in their field after Xynthia


domain: sde shs

text:
Pauline Brémond

Nina Becker

Volker Meyer

Characterization and evaluation of farm vulnerability to flooding using EVA methodology: Comparison of two case studies in the South of France and Saxony

1 MuldEVA project

Introduction

Scientific collaboration

This project has been carried out in the framework of PEER network in which IRSTEA and UFZ are involved. On the basis of this collaboration, Pauline Bremond, researcher at IRSTEA Montpellier, has been doing six months of mobility at UFZ within the Department of Economics (division of social sciences) from March to August 2012.

Common research interests in the field of 'economics of natural hazards' with regard to methodologies developed and objects studied, have been identified between researchers of IRSTEA (Pauline Brémond, Frédéric Grelot, Katrin Erdlenbruch) and of UFZ (Volker Meyer, Reimund Schwarze). This common interest relies mainly in the analysis and evaluation of natural hazard effects on social systems in a context of climate change. This collaboration was intended to strengthen the collaboration and mutualize the efforts carried both by UFZ and IRSTEA to improve the economic assessment of natural hazards.

On the one hand, the work carried out by Pauline Brémond, who achieved a Ph.D. in economics on the evaluation of farm vulnerability to flooding, closes some gaps, at the micro scale, in the systemic analysis of effects of natural hazard on assets. On the other hand, the UFZ group coordinates several projects on the topic of cost evaluation of natural hazards that aim at improving the assessment of natural hazard effects on society based on a systemic approach of looking at social systems vulnerability and resilience like for example the MEDIS, Floodsite project and CONHAZ project (Costs of Natural Hazards). This project, called thereafter MuldEVA, aimed at enhancing exchange on the methodologies to assess the costs of natural hazard. Specifically, within the six months, three main objectives were tackled:

1.

to determine the possibility and conditions to transfer the model developed by BremondP2011a to appraise flood damage on agricultural areas to a case study in Saxony; 2.

to better understand vulnerability to flooding in a case study in Germany, the Mulde River area; 3.

to compare farm vulnerability to flooding on the two case studies i.e. the Rhône River downstream and the Mulde River.

Presentation of EVA model

The farm vulnerability model, called thereafter EVA (Evaluation of the Vulnerability of Agriculture), has been applied in France, on the Rhône River downstream on typical farms. The following section gives a brief description of the EVA model. For more details, see BremondP2011a and BremondP2012a.

Purpose and links with other models

The purpose of the model EVA is to evaluate flood consequences on farms with quantitative indicators in order to assess their vulnerability. In particular, EVA aims at evaluating impacts of a change in flood parameters and/or asset vulnerability. Concerning flood scenarios, EVA uses as inputs flood parameters such as duration, height, occurrence period and speed arising from hydrologic and hydraulic modelling. Concerning changes in asset vulnerability, EVA uses as inputs modified farm's characteristics.

1.1.2.2 Spatial and temporal scales

The system considered is a farm represented as a collection of physical components: on the one hand, buildings containing machinery and stocks of inputs; on the other hand, land plots containing crop production and orchard or vineyard. During and after the flood, these components are characterized by their usability which is a combination of their accessibility and state (normal, damaged, destroyed). The usability defines if the component can be involved in the production process. As an example, as long as a machinery is unusable, it cannot be used to achieve a production task which requires its use. EVA model crosses farm and flood temporalities. Without flooding, farm task planning relies on the crop management sequence defined as a parameter of farm. When a flood is simulated, task planning is reorganized at the weekly time step until the end of the production cycle. Production tasks can be delayed or partially achieved and recovery tasks (cleaning) are added to the list of tasks to do.

Outputs of EVA

This model aims at describing the flood effects on farms with several indicators. Three main indicators are produced by EVA:

1. the chronology of the usability of every farm physical component; 2.

a quantification of changes induced in needs and availability of production factors , mainly workforce and machinery, required to carry on production and recovery tasks, at the same time ; 3.

a quantification of induced damage, in monetary terms, by the achievement using external resources or the undoing of some production tasks depending on farmer's capacity to access to external resources.

Data requirement

EVA finally models the consequences of flooding on farm components and on farm functioning. This modelling approach requires data that can be classified into five types as presented on Figure 1.

1. data related to farm description; 2.

data on field operation achievement; 3.

data on recovery task achievement; 4.

data on direct damage assessment (damage functions); 5.

data required to monetize damage.

Conceptual framework for EVA model

The definition of risk which is adopted in this approach is based pn the Global Assessment Report (GAR) of the United Nations Office for Disaster Risk Reduction (UNISDR, 2011a) and the SREX report of the Intergovernmental Panel on Climate Change (IPCC, 2012a).

According to this, risk, or mean annual damage, is a function of hazard, exposure and vulnerability.

Hazard refers to the flood probability and characteristics and exposure refers to the number (and value) of people or assets in the hazard-prone area. Vulnerability can be distinguished into susceptibility (or sensitivity) and coping capacity as suggested by Gallopin (2006a). Susceptibility/sensitivity refers to the potential of elements at risk to suffer harm or loss while coping capacity describes their potential to cope with these losses and to recover afterwards. All these risk components can be altered by mitigation/adaptation measures (i.e. explicit risk management measures).

In the case of farm vulnerability to flooding,  the hazard characteristics that are critical to consider are the period of occurrence, the height, the velocity and the duration;  the exposure depends on the spatial configuration of the farm i.e. area and type of land plots as well as type and number of buildings flooded;  the sensitivity of several physical elements has to be considered i.e. crops, cattle, soil, perennial vegetal material, buildings and contents (machinery, stocks of inputs or forage)  the coping capacity as showed by Bremond (2011a), mainly depends on the availability of internal resources (workforce, machinery) and the capacity to access external ones (solidarity, service providers).

Research questions

Two mains research questions have been addressed in for the MuldEVA project:

1.

Knowing that the EVA model is highly data demanding, which are the conditions and difficulties to transfer EVA model to a case study in Saxony? 2.

Can different patterns of vulnerability to flooding be identified between the farms on the Rhône River downstream and on the Mulde River?

2 Presentation of the case studies

Case study area on the Rhône River downstream

The French case study is located on the Rhône River downstream. It is briefly described in this section. The description is much more detailed in Bremond (2011a) since this area was the case study for the application of EVA model.

Localization

The Rhône River with 812 km, is one of the main river in France (Figure 2). It has been frequently impacted by severe floods. The flood of reference occurred in May 1856 and caused huge impacts on cities such as Lyon and agricultural areas. According to the Figure 3, the highest probability of for flooding is between October and January (autumn and winter floods).

Flood damages

In 2003, the total amount of damage on the Rhone River downstream has been estimated to 850 millions € among which 76,8 millions € i.e. 9%, correspond to agricultural activities (SIEE, 2005c). -2006). More than 3 000 farms exposed to flood risk have been identified representing 88 690 ha of agricultural areas. Moreover, 70 % of the farms exposed to flooding have their buildings in the flood plain.

Flood management and place of agriculture

Case study area in Saxony

Localization

Research carried out by the UFZ group dealing with flood vulnerability and resilience has mainly been focussed on the Mulde River catchment. More specifically, on the Vereinigte Mulde River which was heavily affected by the flood in August 2002, causing high damages in many towns and villages along the river (RiskMap, 2011a). The Mulde River is one of the main tributaries of the Elbe River (Figure 4). The 124 km long course of the Vereinigte Mulde is formed by a Western branch, the Zwickauer Mulde, and an Eastern branch, the Freiberger Mulde.

Flood characteristics

Period of occurrence

Considering agricultural damage, particular attention has to be paid to the period of occurrence of the flood. The table 1 (LfULG2009b) summarizes some characteristics of the main flood events that occurred on the Mulde watershed area. The flood height is measured in a city located in the Vereinigte Mulde area (Grimma). The extreme floods mainly occur in summer (July, August) but even if it is less frequent some can also occur in winter (December).

The 2002 flood

Last extreme flood that impacted the Elbe catchment, including the Mulde area, occurred in mid-August 2002. The areas in red in the Figure 4 correspond to the flooded areas in 2002. This flood has begun on the 12th of August at the smaller catchments in the Ore mountains (Erzgebirge) and has lasted until the 22nd of August at the Elbe river (Staatregierung, 2002a). Depending on the area, the return period of this flood was between a 50-year and 500-year return period as depicted on Figure 5. At the Vereinigte Mulde, where the case study is located, the return period for the 2002 flood was defined as in between a 200 and 300-year flood.

Flood damages

Flood damages in 2002

The 2002 flood caused huge damages in Saxony. 21 persons died and 110 were injured (Staatregierung, 2002a). In terms of economic damages, the report from the Sächsischen Staatsregierung (Saxon federal government), which is in charge of the management of claims and compensation after 2002, mentions a total amount of damage of more than € 6 billions, for the economic sectors as described in the Table 2.

This amount does not include structural damage and loss of profitability after the flood. For example, concerning buildings, induced damage due to the flood occurred after the frost period. For economic activities, the induced damage due to the loss of profitability has not been estimated (Staatregierung, 2002a). The total amount of damage has been estimated to 79 millions € and divided per agricultural activity as depicted in Table 3. A total of 1 375 farms have been affected in Saxony. The damage assessment is based on surveys of the Offices of Agriculture and experts. The damage to agriculture represents only 1,3 % of the total damage. This flood was an extreme event and has impacted areas that are not used to be impacted by more frequent flooding. That could partly explain why the share of agricultural damage is particularly low.

Land use in the flood plain

The total flood area on the Mulde River represents 13 381 ha of which:

 1 558 ha on the Freiberger Mulde,  229 ha on the Zwickauer Mulde,  11 594 ha on the Vereinigte Mulde.

The analysis of the land use provides some insights on the type of assets impacted by the flood.

Figure 6 shows a focus on an area flooded in 2002 at the Vereinigte Mulde. Most of the areas impacted are agricultural ones and mainly grassland. However, arable land is also located in the floodplain. For extreme events, some assets such as cities, industries can also be impacted. Then, the share of damage related to those sectors is high. However, agricultural assets are the most represented in the floodplain and may be more frequently impacted. In this case, the share of agricultural damage in the Mean Annual Damage (MAD) at regional level, may provide another insight in flood impacts. If agriculture is more frequently impacted, the share of agricultural damage in the MAD may be higher than expected. However, no literature was found on this topic. The Saxon Flood Center (Landeshochwasserzentrum, LHWZ), within the LfULG, is also a main actor for flood information and early warning, particularly since 2002. It provides relevant flood information directly to each authority with flood defence responsibilities.

Flood management and place

The local representative of farmers in flood management decision processes are the regional farmers' associations (Regionalbauernverband). These associations are the local level of the national association, der Deutsche Bauernverband.

Role of agriculture in flood management

After 2002, the potential role of agriculture in helping to prevent flood risk has been questioned. Several options were considered (Stahl, 2005a, LfULG, 2007a):

 to lower or relocate dikes which protect agricultural areas,  to create some areas of controlled flooding (polder) on agricultural areas,  to prevent water run-off by adapting farmers' practices in the upstream watershed.

To also understand which of these options have been implemented since 2002 and how, was part of the interviews we carried out in the case study of the Mulde River region.

Focus on agriculture

In this section, we compare data at the regional level which does not correspond to the scale of the both case studies. The French case study on the Rhone River downstream located on two political regions i.e. Languedoc-Roussillon (LR) and Provence Alpes Côte d'Azur (PACA). The German case study is entirely located in the Federal State of Saxony. This section provides some general information on agriculture characteristics in these regions.

Agriculture and employment

The proportion of people working in the agricultural sector in Saxony is close to the proportion in Languedoc Roussillon and Provence Alpes Côtes d'Azur (Table 4).

Agriculture and land use

Agricultural areas in Saxony represent 55 % of the total area, exceeding the national average for which agricultural areas represent 50 % of the total area. The proportion of agricultural areas in Saxony (Figure 7) is higher than in the two regions of France. Prevalent crop types differ a lot for the two case studies (Figure 8). In Saxony, most of the arable land is cultivated with cereals (wheat, barley, oat, rye), followed by pulses and industrial crops among which production of oil seed such as rape. The grassland represents also a large share of agricultural land (20 %) and is part of the grazing system for animal production (milk cows).

Comparatively, in LR and PACA, the proportion of vineyard, orchard and market gardening is much higher. Crop types in Saxony are much more capital extensive.

Specifically, on the Rhone River downstream, some information exists on the characterization of agriculture in the floodplain (CRAM-R1-2006). The highest numbers of farms in the floodplain are farm specialized in arboriculture, market gardening and vineyard (Figure 8). In terms of areas, cereals, livestock farming then arboriculture represent the most important areas within the floodplain (Figure 8).

Farm size

In Saxony, farm structure is still very influenced by the reform implemented during the GDR (German Democratic Republic) system (collectivization). Mainly two types of farms coexist: the big entrepreneurial structures and the familial farms which can be full time or part time activity.

The size of the farms can be diverse (Figure 9) but in general, many of the farms are bigger than on the French case study. On the Rhone River downstream, farm size is generally smaller. As for examples:

• 4 300 farms are specialized in arboriculture in the five departments of the Rhone River downstream. Among them, 2 031 farms have less than 15 ha (average UAA is 8 ha) and 2 266 farms have more than 15 ha (average UAA is 38 ha).

•

The size of farms specialized in viticulture ranges from 12 to 42 ha on the case study area and the average farm size is 22 ha.

Legal forms of the farms

German farms' legal form are either corporate bodies or natural persons. Among corporate bodies, the most common forms are (Dieckhoff, 2008a):

 registered co-operatives (eingetragene Genossenschaft, e.G.) which are constituted by at least 7 co-operators,  Ltds and similar (GmbH and AG).  Natural persons can be (Dieckhoff, 2008a):  partnership (GdBr),  individual farmers.

Farm distribution within these categories is given in the Table 5. Individual farmers (main activity) 1 803 137 400

Existing studies on farm vulnerability to flooding

Few works have been carried out on flood vulnerability of German farms. Mainly, three studies deal with this topic:

 ForsterS2008a wrote an article dedicated to the evaluation of the efficiency of a retention area on agricultural land,  BMBF2004a published a book on the potential development of polder,  ThiekenA2010a published a book summarizing works on flood damage.

The most detailed work on the characterization of flood impacts on farms, results from BMBF2004a. They recommend to consider the following damage categories:

 surface damage on crops (loss of harvest, fodder) and soil (recovery costs),  damage to buildings and contents (inputs, machinery),  fatalities to cattle.

Methodology

The project has been structured around the following steps:

1.

Literature review in English and German concerning the case study area, flood damage and agricultural context 2.

Identification of existing data sources (English and German) and analysis of their importance for the study 3.

Selection of contacts for interviews 4.

Preparation of interview guides (German and English) 5.

Interviews with representatives from administrative bodies and transcription 6.

Identification of contacts to farmers 7.

Preparation of interview guides and data collection framework for farms 8.

Interviews with farmers and transcription 9.

Data collection and formatting 10. Synthesis

Interviews with representatives from administrative bodies

Presentation of the contacts

We carried out 6 interviews with representatives from administrative bodies (Table 6). These include the three main institutions involved in flood management and the farmers' associations of the regions mostly affected. In addition, we carried out an interview with an experimental farm which is located in the floodplain area on the Elbe river to contrast from qualitative interviews with administrative bodies and have more insights at farm level.

Within the farmers' assocation (Regionalbauernverband, RBV), we met Mr Eggert who was the representative of the Delitzch region and Mr Freiberg who was the representative of the Muldental region (Figure 12). These two regions were the most impacted ones during 2002 flood.

Objectives of the interviews

The interviews focused on:

1. the description of agriculture and farm organization in the region, 2.

the characteristics of the 2002 flood and its impacts on agriculture, recovery and role of the administration during this event, 3.

the place of agriculture in flood management policies under discussion and their implementation since 2002, 4.

the discussion about the exat location of the case study and the contacts with some farms which have been impacted by the 2002 flood.

Interviews with farm managers

Selection of farms

Four farms that have been impacted by the 2002 flood in the case study area have been identified and interviewed (Table 7)

Objectives of the interviews

Interviews were organized around four topics:

1. presentation of the project and objectives of the interview, 2.

general presentation of the farm (legal form, short history, crops, workforce), 3.

collection of farm data (areas, crops, workforce, machinery, etc.); 4.

data on damage and recovery after 2002 flood.

Methodology for data collection and organization

Presentation of the data

Due to the important number of data to be collected, we proceeded to a fine description of each data as presented on the next page. For each piece of data, we define:

 at which level and category, the data corresponds to (this level and category correspond to those of Figure 1),  if the data is numeric or text,  what the unit is,  how this data has been collected in France and in Germany.

Every indicator described in the following table refers to EVA model components.

Identification of existing data sources

To identify which method should be used to collect data in Germany, we had an interview with researchers from IAMO (Leibniz-Institut für Agrarentwicklung in Mittel-und Osteuropa). It helped us to identify data bases such as the data produced in Germany by the KTBL (Kuratorium für Technik und Bauwesen in der Landwirtschaft) which provides data on production tasks (crop management sequence) giving the list of tasks and their timing on the year and the resources needed.

Data at farm level

Besides the questionnaires, we used excel files to collect data with farm managers. Data concerning farm have been collected using 13 Excel sheets:

 Farm-Spatial corresponds to the list of plots (size, type of crops, area impacted in 2002), buildings (size, area impacted in 2002) and animals (number, location);  Labour establishes the amount of internal and external workforce on farm required to achieve crop management sequences;  Machinery gives the list and quantity of the pieces of machinery;  Stock gives the list of inputs and their location;  Flood parameters corresponds to the description in terms of height, period of occurrence and duration of flood events that have impacted the farm;  Crop damage gives for each crop the area impacted and yet harvested for 2002 flood;  Soil damage gives the list of recovery tasks that have been carried out after 2002 flood to restore soils;  Building damage gives the list of recovery tasks that have been carried out after 2002 flood to restore buildings;  Animal damage gives the list of fatalities endured by the farm after 2002 flood;  Input damage gives damage on the stock of inputs;  Stock damage gives damage on other stocks;  Machinery damage gives damage on machinery;  Compensations gives the list of compensations the farm has benefited after 2002 flood.

Methodological differences for data collection at farm level for the two case studies

Two different methods were used in the Rhône River downstream and in the Mulde River area. On the Rhône River downstream, typical farms have been constructed based on data from regional statistics and technical expertise. That means, data at farm level do not correspond to a real farm but to a standard farm. Table 8 gives a summary of the characteristics of these typical farms.

On the Mulde River, data has been collected directly at farm level during the interviews with farm managers. This choice was made for two reasons:

 From a research point of view, it was interesting to test if data collection of farm data was possible directly during the interviews.  From a practical point of view, we could not identify the relevant database to construct typical farms and we found less expert studies on agriculture in the floodplain on the Mulde River area than on the Rhône River downstream area.

Table 8. Description of the typical farms on the Rhône River downstream

Results

Data collection and formatting

Framework to collect data

Since most of the interviews had to be carried out in German, it was essential that the colleagues from UFZ know exactly which data and in which format the data needed to be collected. Efforts have been done to produce a framework to collect data and to make it as much transferable as possible.

Some learning from this experience

We present here some learnings from our experience about the transfer of a modelling approach and the data collection in two culturally different regions:

 A clear presentation of data is needed (name, explanation, units). This is the framework we presented earlier.  The way the data is used in the model needs to be clearly explained so that the importance of the data to be collected is really understood. This point was made even more essential since the colleagues from UFZ had to carry out the interviews in German.  Language presents a difficulty that should not be neglected to achieve the interviews and data collection. To overcome this, some time for discussions and exchange is needed to be sure that the data we are talking about are really the one needed.  To identify existing data bases, a good way to proceed is to identify people specialized in the field. In our case, the challenge was data related to agriculture because the UFZ expertise does not focus on this field. It was really useful to speak with researchers at IAMO to better understand available data bases. Sufficient time need to be allotted for these discussions because there is also a need to discuss about the model to really ensure we are talking about the same concepts and data.

Qualitative analysis of interviews with representatives from administration

The representatives from administration were asked about:

 an overview of agriculture in Saxony and specifically in the Mulde area,  flood management policies and the place of agriculture,  flood impacts on agriculture mainly after 2002 flood.

Agriculture in Saxony

Farm size

As it was expected from statistics, experts suggested that farm size is in average very big.

 Big farms have 1.000 -2.000 ha in average,  Small professional farm would have 100 ha,  An average cattle would be 100 cows for milking production.

Purchase and storage of farm inputs

Most of the farms buy inputs from private enterprises which store them. The consequence in terms of flood damage is that damage on inputs should be affected to the buildings of those companies rather than to farm buildings.

Crop rotations

 Rotation should alternate wheat, raps, corn and barley.  The rape needs to be sowed before the end of August. This implies that the plots need to be prepared by this time.  Winter crops have better yield and quality than summer crops but are more risky due to the winter kill and loss of yield due to pre-summer droughts.

Flood management and agriculture

4.2.2.1 Agriculture in the flood plain  Areas in between the dikes and the river are usually used by farmers for arable crops or grassland, with the farmers bearing their own risk.  Currently, there is more grassland than arable land in between dikes and the river.  There is no difference in terms of crop management sequences between the flood plain and other areas.  Organic farming can also be located in these areas.

Conversion of arable land in the floodplain

There is a will to incite farmers to convert arable land into grassland in the floodplain. From an ecological point of view, the opinion prevails to have only grassland in these areas. However, farmers do not agree and prefer to keep arable land even if, in that case, they bear themselves all the damage on crop (no insurance, no compensation). Farmers' representatives argue that the decision criteria which motivate farmers not to convert arable land into grassland is the economic one, above the risk aversion one. Farmers do not want to convert arable land into grassland because is not economically profitable to have more cattle. The economic market leads to the impossibility to increase the offer in cattle and as a consequence to the refusal of farmers to convert arable land into grassland in flood plain.

It could be interesting to test if the optimization criteria is still true considering flood damage.

Land use regulation in the floodplain

Contrarily to France, converting grassland into arable land in the flood plain is restricted by law.

Controlled flooding and dike lowering

There are two ways to give more room for water in flood management policies:

1.

the so-called non controlled flooding policies, which consists in a complete removing or lowering of dikes; 2.

the so-called controlled flooding or polder, which consists in the construction of new dikes to create a retention area.

After the 2002 flood, both of these options have been considered. Some cases of dike lowering have been discussed between farmers' association and water managers. LTV2003a is a guideline established at the federal level, to define the strategy for the flood protection concepts in Saxony after 2002 flood. According to this guideline, the indicative protection level for agricultural areas is only Hq5 (i.e. a 5-year flood event). In a footnote, it is further specified, that "For agricultural areas there is no or only minor entitlement for protection. Generally, a cultivation adapted to the situation has to be conducted." Generally, farmers' association have tried to limit the dike lowering but some compromises have been done.

Farmers' associations are generally in favour of the controlled flooding option which provides compensations to farmers in case of flood damage within the polder area.

Actual implementation of these policies

Finally, these policies were little implemented on the Mulde River. Currently, most of the dikes have been reconstructed. Depending on the land use, they have been reconstructed even higher than before as for example to protect cities. However, there are examples where the main dikes have been relocated and agricultural areas are only protected now by small dikes (e.g. the village of Erlln)

The contribution of agriculture to flood management has also been oriented towards upstream retention by the use of soil conservation practices (tillage). These measures can also be compensated by the means of Common Agriculture Policy which makes them much more attractive.

Flood impacts on agriculture

From the interviews with representatives from administration, we already collected some information on flood damage on agriculture.

Classification of flood damage by order of importance

From the point of view of experts from administration, main damages for the farmers have consisted in removing litter, mud and deposit from soil. Most of crop damages were compensated. Animals were, most of the time, evacuated. Damage on machinery was limited since few buildings were impacted and most of the machinery was evacuated. Some problems occurred also with oil tanks.

Variability of the loss of harvest

In 2002, due to heavy rain during summer, the harvest date had a huge variability depending on very local conditions. Theoretically, wheat should have been harvested everywhere but that was not the case. The variability induced in damage is huge (0 or 100%).

Flooding induces not always such negative impacts

Some experts related their experience of a plot of wheat flooded and frozen during more than a week in winter and on which, the wheat has not been destroyed but rather this event increased the yield.

Soil damage

Assuming expert knowledge, this type of damage is more dependent on the current than the height of water. In 2002, the flood reached generally high levels but it has induced less litter deposit since the current was higher. However, this remark is really local dependant because the deposit from flood has certainly occurred somewhere upstream or downstream.

Recovery and solidarity

Most important aspects concerning solidarity processes that have fostered recovery are the following ones:

 Districts have offered free recycling of garbage for farms.  Most of solidarity was self organized in between the farmers. But, farmers' association contributed to networking for specific problems. For instance, difficulties to find straw and fodder have been encountered by farmers.  Some low cost workforce from unemployment agency could be employed thanks to a specific system existing in Germany (Arbeitsbeschaffungsmaßnahme, ABM) and helped the recovery of farms.

Vulnerability to other risks related to water

During the interviews, farm vulnerability to other risks related to water has been mentioned. Main ideas are in this section briefly presented.

Consequences of pre-summer droughts

These phenomena mostly occurs during the stem elongation for which wheat requires water and nutrients. The pre-summer drought not only influences water uptake but also the one of nutrients.

Even if the rest of the season is rainy, this loss of yield can never be recovered.

Irrigation

Some infrastructure to irrigate existed and was well developed in GDR times but now, few of these infrastructures have been maintained and are currently used mainly because of maintenance costs and questions of governance. However, it has been mentioned that it might become valuable again in the light of climate change.

Influence of energy policy on vulnerability

Due to the shift in energy policy, there is an increasing demand in crops used for bio-energy i.e. corn silage and rape. The increase of corn silage may have potential impacts on vulnerability to summer floods because the corn is harvested much later (September, October) than wheat. Concerning winter flood, in case of corn, there is no crop on the plot in winter. The increase in corn production may also lead to problem of water scarcity. Even more if considering that corn may need to be irrigated due to the increase of pre-summer drought.

Table 12. Crop damage Some crops were about or were in the process to be harvested. This means that a huge variability in crop loss can exist depending on local conditions of the plot. This was the case for:

 peas,  triticale,  winter wheat.

Some crops have been fully destroyed if exposed to flood. This is the case for:

 silage maize,  sugar beets.

Flood and heavy rain damage

The interviews we carried out were focused on flood damage. However, the flood which happened in August 2002 at the Mulde River was associated to heavy rains which happened in July and August 2002. For some interviews, it was not easy to really differentiate crop damage related to flood or heavy rain. The main difference between flood and heavy rain comes from soil damage. Heavy rains do not induce deposits but can erode soils. This is, in particular, the case for plots planted with hops.

In 2002, heavy rainfalls had also consequences on the wheat harvest. In fact, many fields where not yet harvested due to these rainfalls as it would usually be the case by the 13th of August.

Damage to buildings and contents

The total area of the farm buildings has been collected for two farms. These were about 20 ha and the buildings are usually located on different sites on the farm. Among the four farms interviewed, only one had its buildings severely impacted by the 2002 flood due to a breach in a dyke nearby (Table 13).

Few damage to building contents (machinery and inputs) have been noted during the interviews.

Table 13. Flood damage on farms' buildings

Animal fatalities and evacuation

None of the farms interviewed endured animal fatalities in 2002 but some animals had to be evacuated (Table 14).

Table 14. Animals evacuated due to 2002 ood

Soil damage

Five types of damage to soil resulted from the interviews:

1. deposit of sands, gravels and woods, 2.

deposit of litter, 3.

erosion, 4. compaction, 5.

contamination.

The problem of soil contamination due to flooding has been raised in some interviews. One farm manager said that the levels of heavy metals on grassland (arsenic) and arable land (cadmium) have increased after 2002 flood. Generally, when an important concentration of cadmium in wheat is detected, it cannot be sold for human consumption. However, this phenomenon cannot be clearly linked with the flood since wheat is quite frequently declared unfit for human consumption due to this reason (every 3 years in average).

Two types of actions were carried out to recover after flooding: the tasks properly related to soil recovery and the tasks necessary to clean plots from destroyed but remaining crops.

•

The first category mainly aims at removing deposits from the river flow. Removing sands, gravels and woods have been identified, in the interviews, as the most time demanding tasks that have to be carried out after flooding. Usually, deposit removal has begun just after the flooding (August 2002). The priority has been given to plots that had to be seeded with wheat for the next campaign. However, in some instance, those soil recovery tasks have lasted until September 2003. The second category of recovery tasks has to be done mainly because crops could not be harvested and plots must be cleaned to prepare the next crop. They are closed to some production tasks achieved on the farm and usually do not require specific machinery.

Achievement of farm recovery and solidarity processes

Most of the farms recovered by using their own internal resources, except if some specific machinery was necessary (Table 16). Only the farm that has been the most severely exposed to the 2002 flood needed to hire service providers for recovery tasks. The recovery has lasted until more than one year for some farms. Two farms benefited from low cost (ABM) or voluntary workforce. Farm managers did not mention having received help from other farms of the region except for forage for cattle which was organized by the regional farmers' association.

Table 16. Solidarity processes at farm level

Consequences on crop management sequences for the next years

In the case of sugar beets, direct damage on plot exposed was a loss of 100 %. Then, sugar beets needed to be drilled and incorporated in the soil. One farm manager explained that they tried to seed wheat on these plots (around November) but the wheat yield, the next year (2003) was less than 50 % of the average yield. Some plots were planned to be seeded with rape for the next year. This was not possible for all the plots that have been flooded since rape seeding has to take place between the 15th and the end of August. At this time, plots were not yet removed from discharge and litter.

Compensations after 2002 flood

Most of the farm's managers have established a paper file to describe precisely damage endured due to flooding and tasks that have been carried out. The compensations have been provided by the Free State of Saxony and it was an ad hoc system. Two farms out of four have benefited from these compensations.

We tried to collect this information with institutions. However, representatives of administration we interviewed did not participate in compensation process or could not give us information about a potential data base.

Insurance

We collected few information about insurance. Note that only one farm has contracted an insurance for the loss of yield after 2002. None of the other farms have this kind of insurance. One of the reasons which could explain this is the financial criteria. All farms are insured for the buildings except one.

Conclusion and further research

Two research questions were to be addressed in the MuldEVA project:

1.

Knowing that the EVA model is highly data demanding, which are the conditions and difficulties to transfer EVA model to a case study in Saxony? 2.

Can different patterns of vulnerability to flooding be identified between the farms on the Rhône River downstream and on the Mulde River?

In the next two sections, we proposed some conclusions about these research questions and perspectives for continuing this research.

Conditions and difficulties to transfer EVA model to a case study in Saxony

Concerning data collection, one of the results of the collaboration is already the production of a framework which precisely describes every data needed and the way it can be collected on a case study.

Two different methods were used in the Rhône River downstream and in the Mulde River area to collect data at farm level. On the Rhône River downstream, EVA model has been applied on typical farms whereas on the Mulde River, it has been applied on real farms. From a research point of view, it was interesting to test that data collection was possible on field with real farms. The next step of the collaboration could be to define typical farms in the Mulde River and vice-versa to apply EVA method on real farms in the Rhone River downstream.

Comparison of farm vulnerability patterns of the Rhône and Mulde case studies

The Table 17 proposes a comparison of the flood risk and farm vulnerability patterns on the two case studies.

As said earlier, with the definition of risk we adopted, three components have to be analysed: hazard, exposure and vulnerability.

As a reminder, hazard refers to the flood probability and characteristics and exposure refers to the value of assets in the hazard-prone area. Vulnerability can be distinguished into susceptibility (or sensitivity) and coping capacity as suggested by Gallopin (2006a). Susceptibility / sensitivity refers to the potential of elements at risk to suffer harm or loss while coping capacity describes their potential to cope with these losses and to recover afterwards. All these risk components can be altered by mitigation/adaptation measures (i.e. explicit risk management measures).

Concerning the analysis of the risk, it is clear that two different patterns exist on the two case studies. This is mainly due to a different distribution of flood period of occurrence and a different pattern of farm exposure which lead to a different damage distribution. This point could be deepen by simulating damage on typical farms for given flood scenarios and compare them on the Mulde and Rhône cases studies.

Concerning farm vulnerability patterns, given the fact that we did not find specific data on farm component (crop, buildings, machinery...) sensitivity, we assumed the same sensitivity for the two case studies. This assumption may need to be confirmed but is acceptable since we did not identified, during the interviews, specificities on the Mulde CS which would let us think that damage functions need to be adapted. However, the interviews revealed different patterns for coping capacities: different institutions in charge of solidarity organization, different needs of external resources, different compensation systems, different impacts on farm cash flow. These aspects require further field research to be analysed.

Figure 1 :

 1 Figure 1: Data needed to feed EVA model

Figure 2 :

 2 Figure 2: Localization of the Rhone River downstream case study

Figure 3 :

 3 Figure 3: Monthly probability of occurence

Figure 4 :

 4 Figure 4: Localization of the case study in Saxony

Figure 5 :

 5 Figure 5: Return period of the 2002 flood on the Mulde River watershed (LfULG, 2009b)

Figure 6 :

 6 Figure 6: Land use in the flood plain area

Figure 7 :

 7 Figure 7: Comparison of agricultural area in Saxony, Languedoc-Roussillon and Provence Alpes Cotes d'Azur (PACA) 2

Figure 8 :

 8 Figure 8: Proportion of crop type in Saxony, Languedoc-Roussillon and Provence Alpes Cotes d'Azur (PACA) 4

Figure 9 :

 9 Figure 9: Number of farm by crop type in the floodplain area of the Rhone River downstream

Table 1 :

 1 Past floods on the Mulde watershed(LfULG, 2009b)

	Date	Period of occurrence	Height (cm)
	1573	August	636
	1771	June/July	598
	1858	August	481
	1897	July	490
	1932	January	455
	1954	July	508
	1958	July	414
	1974	December	464
	2002	August	752

Table 2 :

 2 Distribution of flood damage after 2002(Staatregierung, 2002a)

		Million €	%
	Residential building	1 706	27,5
	Industry	1 420	22,9
	Municipal infrastructure	1 287	20,8
	National infrastructure	928	15,0
	Furniture	529	8,5
	Emergency costs	136	2,2
	Other infrastructure	111	1,8
	Agriculture and forestry	79	1,3
	Total	6 196	100
	2.2.3.2 Focus on agricultural damage from 2002 flood

Table 3 :

 3 Distribution of agricultural flood damage after 2002 (Staatregierung, 2002a) Analysis of the damage distribution for the 2002 flood

	Million	%

  The competencies of flood and water policy in Germany lie mostly with the German Federal States (Länder), whereas the central government is entitled to frame the legislation. In Saxony, the Saxon State Ministry of the Environment and Agriculture (Sächsisches Staatsministerium für Umwelt und Landwirtschaft, SMUL) is the main decision authority for flood management and is supported by the State Office for the Environment, Agriculture and Geology (Landesamt für Umwelt, Landwirtschaft und Geologie, LfULG).

	of agriculture 1
	2.2.4.1 Institutions and responsibilities

Table 4 :

 4 Employment in the agricultural sector

		Active population Agriculture (number) Agriculture (%)
	Saxony	2 000 000	40 000	2 %
	LR	932 000	41 400	4 %
	PACA	1 616 000	15 000	1 %

Table 5 :

 5 Distribution of farm legal form(SMUL, 2010b)

		Saxony	Germany
	Corporate bodies	610	5 000
	Registered co-operatives	197	1 100
	Ltd's and similar	289	2.800
	Natural persons	4 987	295 600
	Partnerships	372	21 000
	Individual farmers (total)	4 615	274 600

Table 6 :

 6 Overview on the interviews carried out with representatives of institutions

		Institution	Date
	Hening Stahl	LfULG Leipzig	09.05.12
	Ulrich Henk	SMUL	04.05.12
	Uwe Büttner	LHWZ	07.05.12
	Reinhard Eggert	Farmers' assocation	06.06.12
		(Delitszch)
	Frank Freiberg	Farmers' assocation	04.06.12
		(Muldental)
	Heike Weiß and Ondrej Kunze	Experimental farm	19.07.12
		LfULG

Figure 12: Local sections of the Regionalbauernverband

Table 7 :

 7 Interviews with farm managers

	Farm	Structure	Date
	Tilo Bishoff	Agrargenossenschaft eG	14.06.12
	Ulrich Kröber	Agrargenossenschaft eG	18.06.12
	Lutz Eilenberg	GmbH Co.KG	25.06.12
	Matthias Hofmann	GmbH Co.KG	25.06.12

Table 15 .

 15 Recovery tasks for soil damage •

Table 17 .

 17 Comparison of risk and vulnerability patterns on the two case studies (CS)

For a more detailed presentation of flood management in Saxony see the report of the project RISKMAP from which this section is derived RiskMap (2011a).

Eurostat 2007

Eurostat 2007

Qualitative analysis of interviews with farm managers

General description of farms

Farm size

Table 9 gives the size of the farms where interviews have been carried out. Note that all are cooperatives and belong to several stakeholders. The smallest farm is 1 100 ha and the biggest 4 230 ha.

On Figure 13, the proportions of arable land (AL) and grassland (GL) flooded for each farm are given. Most of the time the grassland has been flooded by more than 80 % in 2002. For arable land, even if the areas flooded are huge (2 000 ha in average), this generally represents less than 30 % of the total arable land except for farm K which arable land was flooded by 70 % and grassland by 100 %.

Table 9. Farm area in hectares and exposure to ood 10 shows the number and type of animals for each farm. As expected from interviews with representatives from the administration, the size of cattle is high. All farms have cow cattle for milk production.

Shareholders and workforce

All farms have stakeholders (between 41 and 62). Concerning workforce, the number of employees vary between 29 and 70. As showed in Table 11, the ratio, in terms of employee per ha, varies between 0.01 and 0.03 Annual Working Units (AWU).

Crop damage

Harvest period and consequences on damage

We distinguished, in the interviews with farm managers, the plots that have been flooded and the real crop damage suffered. Table 12 summarizes all crop types that have been cited during the interviews, if the plot where this crop was localized has been flooded in 2002, if the crop has been impacted by the flood which depends on the harvest time.

In fact, some plots have been flooded without suffering any damage if the crop were already harvested when the flood occurred (12th August). This is the case for  winter barley,  winter rape,  winter rye.


Yanxia Hou
email: yanxia.hou-broutin@cea.fr

An overview of biomimetic optoelectronic noses based on various biological sensing materials and surface plasmon resonance imaging

Keywords: electronic nose, biological sensing materials, peptide, volatile organic compounds, surface plasmon resonance imaging

Inspired by mammalian olfactory system, electronic noses (eNs) are promising alternatives for the reliable and rapid analysis of volatile organic compounds (VOCs). As for sensing materials, so far the materials most often used are inorganic or organic. Nevertheless, various biological materials are emerging in recent studies such as peptides, hairpin DNA, peptide nanostructures, etc. Concerning transduction system, surface plasmon resonance imaging (SPRi) is particularly interesting for eN development. Since this technique allows to monitoring binding events in label-free and real-time by providing temporal responses with kinetic information, with capacity for simultaneous detection on a multiplexed sensor array. Therefore, the combination of such a detection system with novel biological sensing materials could lead to the development of original biomimetic optoelectronic noses with improved performances in terms of sensitivity and selectivity.

I. INTRODUCTION

In the last decades, electronic noses (eNs) have been considered as promising alternatives for the reliable and rapid analysis of volatile organic compounds (VOCs) with potential applications in a wide range of domains. However, from an industrial point of view, the eN suffers from significant drawbacks related to their performance that forbade this technology the bright future that it was initially promised. Most existing eNs are based on a small number of non-specific sensors each functionalized with chemical layers. To date, conducting polymer composites (e.g. carbon black/insulating polymer matrix), conducting polymers (polypyrrole, polythiophene, polyaniline, etc.) and metal oxides (n-type including zinc oxide, tin dioxide, titanium dioxide and iron (III) oxide and p-type including nickel oxide, cobalt oxide, etc.) are the most commonly used sensing materials in the eNs [START_REF] Arshak | A review of gas sensors employed in electronic nose applications[END_REF]. In particular, almost all commercial eN systems are based on these sensing materials.

The initial hope was to approach the ability of human nose by increasing the number of individual sensors. However, the problem is that the information gained by adding additional sensors rapidly saturates. Since these sensing materials suffer from a general lack of selectivity for VOC analysis on the basis of simple physical adsorption. In fact, the unequalled performance of the human nose has turned out to be not only the great diversity of sensing receptors, about 400 different types of olfactory receptors (ORs) compared to 10 -50 sensors generally used in eNs, but their selectivity and their unsurpassed sensitivity for some odorant molecules. Consequently, an enhancement in selectivity and capabilities of the eNs by increasing the number of sensing receptors is possible only if these additional sensing receptors can deliver new and supplementary information.

In this context, new sensitive materials with good sensitivity and selectivity are under development, for instance, based on thin layers, synthetic receptors and molecularly imprinted polymers. One particularly interesting tendency is using small organic and biological molecules as building blocks with the help of surface chemistry and nanomaterials. The general idea is to use small, simple and easily-accessible molecules as building blocks; then to make them self-assembly onto sensor surfaces via appropriate surface engineering. This gives a nanometer-scale organic or biological thin film, such as self-assembled monolayers (SAMs). The composition, structure, and physicochemical properties of the monolayers can be varied and tuned rationally according to applications. Different laboratories in the world have adopted this strategy. For instance, Hossam Haick's group used monolayers of silane or thiol with various physicochemical properties as sensing materials [START_REF] Wang | Artificial sensing intelligence with silicon Nanowires for ultraselective detection in the gas phase[END_REF][START_REF] Nakhleh | Monolayer-capped gold nanoparticles for disease detection from breath[END_REF]. The group of Charlie Johnson used monolayers of single stranded DNA (ssDNA) as sensing materials for development of VOC sensors [START_REF] Kybert | Differentiation of complex vapor mixtures using versatile DNAcarbon nanotube chemical sensor arrays[END_REF][START_REF] Ping | Scalable Arrays of Chemical Vapor Sensors Based on DNA-Decorated Graphene[END_REF].

Another biomolecule family has great potential as sensing materials for the detection of VOCs is peptide. [START_REF] Brenet | Highly-Selective Optoelectronic Nose Based on Surface Plasmon Resonance Imaging for Sensing Volatile Organic Compounds[END_REF] The diverse physicochemical properties and chemical robustness make peptides particularly interesting for such applications. Thanks to recent advances in peptide synthesis, short peptides or polypeptides can be chemically synthesized, recombinantly made in cells or plants with little difficulty. Moreover, based on biomimetic approaches with the help of phage display and molecular simulation, it is possible to tune the binding properties of peptides for VOCs. [START_REF] Kim | Selective and sensitive TNT sensors using biomimetic polydiacetylene coated CNT-FETs[END_REF][START_REF] Gaggiotti | Development of an optoelectronic nose based on surface plasmon resonance imaging with peptide and hairpin DNA for sensing volatile organic compounds[END_REF] Finally, in a recent published work, it was shown that short peptides can selfassemble into nanostructures such as nanofibers, which could further increase sensor diversity. [START_REF] Weerakkody | A Surfactant-like Peptide Self-assembled into a Biohybrid Multi-sensor Array for an Electronic Nose[END_REF] In the last decade, we have focused on the development of biomimetic optoelectronic noses using biomolecules as sensing materials and an original optical system, surface plasmon resonance imaging (SPRi), as transduction system. Herein, an overview of their development will be given.

II. OVERVIEW OF BIOMIMETIC OPTOELECTRONIC NOSES

A. Surface plasmon resonance imaging for analysis of VOCs in gas phase

SPRi has been largely used for the development of biosensors and biochips for monitoring binding events in liquid phase. While we were the first to use SPRi for VOC analysis in gas phase and to explore its potential for eN development [START_REF] Brenet | Highly-Selective Optoelectronic Nose Based on Surface Plasmon Resonance Imaging for Sensing Volatile Organic Compounds[END_REF]. Indeed, SPRi is ideal for such application since it allows to monitoring binding events in label-free and real-time by providing temporal responses with kinetic information, with capacity for simultaneous detection on a multiplexed sensor array.

We have studied and optimized different optical parameters for the improvement of detection sensibility of SPRi for gas sensing. It was shown that the surface sensitivity of SPRi is dependent on the wavelength of the light source [START_REF] Brenet | Improvement of Sensitivity of Surface Plasmon Resonance Imaging for the Gas-Phase Detection of Volatile Organic Compounds[END_REF]. In the range of 530 nm to 740 nm, the SPRi sensitivity increases as the wavelength increases. For example, with the wavelength of 740 nm, the obtained optoelectronic nose was able to reliably detect 1-butanol at very low concentration (10 ppb). In another study, we have investigated the impact of the prism geometry on SPRi sensitivity [START_REF] Weerakkody | Optical Index Prism Sensitivity of Surface Plasmon Resonance Imaging in Gas Phase: Experiment vs. Theory[END_REF]. All these studies allow us to validate SPRi as an efficient system for gas sensing.

B. Biomimetic optoelectronic noses based on various biological sensing materials

In a previously reported study, short peptides with varied physicochemical properties (hydrophobic, hydrophilic, charged, neutral, etc.) were used as sensing materials. They were deposited on the gold surface of SPRi prism by a noncontact microspottor and formed self-assembled monolayers thanks to the thiol-gold chemistry. It was shown that the obtained biomimetic optoelectronic nose was very efficient and versatile for the analysis of VOCs from diverse chemical families. Thanks to SPRi, the generated temporal responses provided supplementary discriminatory information compared to a simple equilibrium response used by most existing eNs. Based on them, the good performance of the eN was exemplified by its ability to discriminate between VOCs differing by a single methylene group [START_REF] Brenet | Highly-Selective Optoelectronic Nose Based on Surface Plasmon Resonance Imaging for Sensing Volatile Organic Compounds[END_REF] and even between chiral molecules demonstrated in another study. [START_REF] Maho | Reliable chiral recognition with an optoelectronic nose[END_REF] Furthermore, the eN exhibited very good repeatability and stability upon repeated use and prolonged storage. It is important to mention that our SPRi technology has been valorized by a local company, which has succeeded in miniaturizing the system into a portable device for odor analysis.

As mentioned before, peptides can be further modeled and virtually screened in order to obtain better selectivity and specificity to VOCs of interest. Indeed, using virtual screening 'in silico' testing of VOC -peptide binding can be carried out in a fast and low-cost way. One of our collaborators has developed this approach to identify short peptides with good sensitivity and selectivity for VOCs. Besides, they have also designed and selected several hairpin DNA (hpDNA) for gas sensing by computational screening. The shape of these sequences was very interesting because it maximized the orientation of the binding element (via the stem) using the loop as a sensitive element. Both their short peptides and hpDNA were integrated into SPRi chips [START_REF] Gaggiotti | Development of an optoelectronic nose based on surface plasmon resonance imaging with peptide and hairpin DNA for sensing volatile organic compounds[END_REF]. Thanks to the complementarity of their binding properties, the obtained optoelectronic nose has very good selectivity, being able to discriminate not only between VOCs of different chemical families, but also VOCs of the same family with very similar structures.

In a very recent study, we developed a novel paradigm in order to diversify the structural heterogeneity of sensing elements using a single peptide as building block to obtain different binding properties for VOCs. [START_REF] Weerakkody | A Surfactant-like Peptide Self-assembled into a Biohybrid Multi-sensor Array for an Electronic Nose[END_REF] To do so, we have designed a surfactant-like peptide CG7-NH2, with a cysteine as head group and seven repetitive glycine residues as the tail group where the C-terminal is amidated. Such a peptide is able to self-assemble into various supramolecular nanostructures (nanofibers, globular aggregates, etc.) under certain experimental conditions. In this study, by tuning pH and water content of peptide solutions, we successfully fabricated a fiveelement biohybrid sensor array, containing morphologically and physicochemically heterogeneous "biohybrid" surfaces with immobilized hierarchical peptide nanostructures surrounded by self-assembled monolayers of the peptide. The obtained optoelectronic nose has excellent sensitivity, which was benchmarked for hexanoic acid and phenol, with a LOD of <1 and 6 ppb, respectively.

III. CONCLUSION AND PERSPECTIVES

Through this overview, we demonstrate that peptides have great potential as sensing materials for eNs thanks to their chemical robustness, diverse chemistry, capability to form nanostructures and their homology to natural ORs. Their integration into SPRi chip led to the development of original biomimetic optoelectronic noses with excellent performances in terms of sensitivity and selectivity.

Very promisingly, based on biomimetic approaches with the help of molecular simulation and phage display, peptides can offer promising alternatives for ORs with high sensitivity, selectivity and much better stability. In the future, we aim to develop a new methodology for eNs, by taking inspiration from human nose, which uses the combination of two types of recognition principles. Indeed, among about 400 different types of ORs, some ORs are "narrowly tuned" and thus specific to few odorants while the others are "broadly tuned" and crossreactive to many odorants. It is such a combination that gives the human nose extraordinary capacity of discriminating over 10,000 of different odors. In contrast, the existing eNs employ solely the cross-reactive principle, and never the combination of the two. Therefore, in the future we will combine these two recognition principles on the same chip for designing and developing a new generation of biomimetic eNs with greatly improved performances.


Marielle El Kazzy

Charlotte Hurot

Arnaud Buhot

Lucie Moitrier

Christine Belloir

Loïc Briand

Yanxia Hou

Odorant binding protein-based optoelectronic nose: Hydration and protein activity

Keywords: electronic nose, odorant binding protein, surface plasmon resonance imaging, volatile organic compounds

Over the past three decades, electronic nose devices have gained popularity in various fields due to their great potential for detecting volatile organic compounds (VOCs). To improve the performance of such devices, proteins from the olfactory system are very attractive sensing materials. Nevertheless, conserving their biological properties when exposed to gaseous VOCs is quite challenging. Indeed, the absence of an aqueous environment can largely affect the activity of the proteins. Water molecules play a crucial role in the stabilization of the protein structure. Consequently, the hydration degree of the working milieu has a large impact on the function of the biosensors. In this study we investigated the performance of an optoelectronic nose based on odorant binding proteins and emphasized the role of humidity on the activity of the system.

I. INTRODUCTION

Volatile organic compounds (VOCs) are small organic molecules (< 300 g/mol) that generally exhibit odorous properties. They have a high vapor pressure at ambient temperature and are often hydrophobic [START_REF] Genva | Is It Possible to Predict the Odor of a Molecule on the Basis of its Structure?[END_REF]. VOCs emanate from a wide range of biogenic and anthropogenic sources. The detection and analysis of these compounds has proven to be very useful for diverse applications such as quality control in the food and cosmetic industry, disease diagnosis, security checks, environmental monitoring, etc. Currently, the most effective and commonly employed analytical techniques are the trained human or canine nose and gas chromatography coupled with mass spectrometry (GC-MS). Although very sensitive and reliable, these techniques suffer from various drawbacks and are not suitable for large scale and industrial applications. Indeed, the biological nose is prone to fatigue, requires extensive training and can sometimes give biased results. On the other hand, GC-MS requires qualified personnel, is time consuming and often expensive. In this regard, electronic nose (eN) systems are an alternative that could address the need for an affordable, portable and highperformance device for VOC detection. By definition, an eN is a biomimetic system that consists of a set of VOC sensors having partial specificity (i.e. can interact with different classes of VOCs) combined with a transducer and a pattern recognition system. Over the past three decades, electronic nose systems have largely grown in popularity and their market size is expected to reach 34.78 M$ in 2026 [START_REF]Electronic Nose Market -Growth, Trends, COVID-19 Impact, and Forecasts[END_REF]. Many eNs and VOC sensors based on a broad variety of transduction techniques (e.g., chemiresistive, field effect transistor (FET), gravimetric, optical, electrochemical) and sensing materials (e.g., MOS, polymers, proteins) have been developed by the research and industrial communities. Nevertheless, the performances of these devices require further improvements in terms of sensitivity and selectivity.

Designed by nature to bind VOCs, two protein families of the olfactory system are very attractive sensing materials for eN development: olfactory receptors and odorant binding proteins (OBPs). OBPs are small proteins (about 20 kDa), particularly suitable for eN systems owning to their high stability. Indeed, they can withstand large variations in temperature and pH and are resistant to proteolytic degradation. They are also soluble proteins, which facilitate their production and have a large binding spectrum that can be tuned via site-directed mutagenesis [START_REF] Pelosi | Odorant-Binding Proteins as Sensing Elements for Odour Monitoring[END_REF]. In this context, several studies have attempted to exploit the capacities of these biomolecules and have proven their effectiveness as sensing materials for VOC biosensors and eN development. Several studies have been carried out in solution (in liquid phase) but also in gas phase despite the challenges that this environment can pose. Indeed, the absence of an aqueous environment can largely affect the biological properties of the proteins and consequently their activity. To our knowledge, the impact of humidity on the performance of OBP based sensors for the detection of gaseous VOCs has not been explored.

In this work, we investigated the potential of an OBP-based optoelectronic nose for the detection of gas-phase VOCs and highlighted the effect of humidity on protein activity.

For this purpose, rat OBP3 and two mutant forms of the protein, with genetically customized binding affinities, were designed, produced and used. The OBPs were deposited on the gold surface of a prism to form a sensor microarray. The biochip was then exposed to gaseous VOCs carried by either completely dry or humid air. The performance of the sensors, under both conditions was assessed by surface plasmon resonance imaging (SPRi) which is an optical transduction technique that allows real-time, label free and multiplexed monitoring [START_REF] Boozer | Looking towards label-free biomolecular interaction analysis in a high-throughput format: a review of new surface plasmon resonance technologies[END_REF].

II. MATERIALS AND METHODS

A. Production of the OBPs

Three different OBPs were used for the study: the wild type rat OBP3 (rOBP3-wt) and two mutant forms of this protein that we will call rOBP3-a and rOBP3-c. The wild type protein exhibits high affinity to cyclic compounds, rOBP3-a was tuned to have higher affinity to aldehydes and finally rOBP3-c was modified to not bind any VOC and so it was used as negative control. An His-tag and a cysteine were added to the N-terminal of the three OBPs to allow their purification and immobilization on the gold surface, respectively. The recombinant proteins were expressed in E. coli then purified by immobilized metal affinity chromatography. Their purity was checked by SDSPAGE and their binding properties characterized by isothermal titration calorimetry (ITC) [START_REF] Barou | Electrochemical detection of the 2-isobutyl-3-methoxypyrazine model odorant based on odorant-binding proteins: The proof of concept[END_REF].

B. Biochip fabrication

To fabricate the OBP chip, an N-BK7 right angle glass prism (Edmund optics) was used. The surface of the prism was first coated with 53 nm gold layer. Then, the prism was plasma-cleaned (Diener Electronic) for 3 minutes (75% oxygen, 25% argon, 0.6 mbar, 80 W) and left for 48h, in sealed environment, prior to OBP deposition. Subsequently, OBP solutions (10µM, 100 mM NaH2PO4, pH 7.5, 5% [v/v] glycerol) were prepared. Then, using an automated, non-contact spotting robot (SciFLEXARRAYER, Scienion), a 6 nL droplet of each solution was deposited on the prism surface forming a sensor microarray. Three replicates of each sensor were randomly distributed on the microarray. It should be noted that, the parameters of the protein solutions (concentration, proportion of glycerol) were chosen on the basis of substantial optimization work.

After OBP deposition, the biochip was placed in a humidcontrolled chamber (ca 96% RH) at 4°C for about 18h to allow the proteins to self-assemble. Finally, the chip was rinsed with HPLC-MS grade water to remove the unbound OBPs and installed in the SPRi measurement chamber.

Sodium dihydrogen phosphate and glycerol were purchased from Sigma Aldrich and water from Carlo-Erba.

C. Experimental Set-up and data processing

The experimental set-up consists of two parts: a VOC sampling fluidic system and an SPRi measurement part.

The first part allows to inject VOCs into the SPRi chamber at controlled flow rate (100 mL/min), pressure (50 mbar above ambient pressure), concentration and relative humidity level thanks to flow and pressure controllers (Bonkhorst). A zero-air generator (Umwelttechnik MCZ) was used to generate clean and dry (ca. 3% RH) compressed air. To perform VOC injection, the compressed carrier air was pushed through the fluidic system where it is first humidified (or not) then charged with VOCs thanks to a dynamic headspace before going into the SPRi analysis chamber. Finally, at the outlet of the chamber, the VOC concentration was measured by a photo ionization detector (PID). To perform "dry injections" a cylinder of compressed dry air (Air liquide) was used instead of the zero-air generator. A blank injection of clean air was systematically performed before each VOC analysis to make sure that the fluidic system is clean. All VOC solutions were purchased from Sigma Aldrich.

The second part (i.e., the measurement part) consists of a homemade SPRi set-up placed in an incubator at 25°C. An LED coupled to a bandpass filter was used to generate an excitation light beam at 632.8 nm wavelength. The excitation light was collimated and polarized before reaching the prism. A CCD camera was used to monitor the reflected light.

Modulation in the reflectivity (ΔR) of all the sensors on the chip, upon exposure to VOCs, was monitored simultaneously at a fixed working angle. A measurement was made every three seconds. Finally, the mean response of each sensor (i.e., ΔR) at equilibrium is calculated and normalized by the root mean square then processed by principal component analysis (PCA).

III. RESULTS AND DISCUSSION

To carry out the study, different sets of experiments were performed. For each experiment, two identical chips were prepared then exposed to the same VOCs under the same experimental conditions (concentration of VOC, air flow, pressure, temperature) but different relative humidity levels (0% and 30%).

As stated earlier, rOBP3-a has been genetically customized to have strong affinity for aldehydes, in this respect, octanal and hexanal were selected in order to test the performance of the sensors. Hexanol was used as a negative control because it has a similar molecular weight to the target VOCs, namely octanal and hexanal, and does not specifically bind any of the OBPs. It is important to mention that after the synthesis and purification of the recombinant proteins, their binding affinities and activity, in solution, were validated by ITC. Additionally, in a previous study, the performance of the OBPs after immobilization on prism was examined in liquid phase. The proteins were found to be highly sensitive and selective. More importantly, the study suggested that a conformational change of the OBPs occurs upon VOC binding.

The results presented above were obtained in aqueous solution, which is known to be a favorable milieu for protein activity. Indeed, it is commonly accepted that the presence of an aqueous environment is required in order to maintain the active conformation of proteins. Water molecules play many roles with respect to protein function and in particular surface "structural" water i.e., the water molecules that interact with the proteins surface [START_REF] Dunn | The use of gas-phase substrates to study enzyme catalysis at low hydration[END_REF]. Studies on enzymes have showed that there is an improvement of their activity with increasing hydration. When working in gas phase, the hydration degree of the proteins is correlated with the relative humidity level.

In this study, we provided evidence that the level of hydration obtained at a RH of 30%, which corresponds approximately to the ambient humidity, is sufficient to obtain active OBPs for the detection of VOCs in gas phase. Indeed, PCA of the OBPs response at equilibrium at 0% RH (Fig. 1a) shows very weak discrimination between the injected VOCs. On the contrary, at 30% RH (Fig. 1b), we observe a good separation between the two classes of VOCs namely alcohols and aldehydes and the sensors can even separate between hexanal from hexanol, which corresponds to a resolution of one hydrogen atom. Moreover, very satisfyingly, the loading plot indicates that the rOBP3-a sensors are the one that bind the aldehydes which is in agreement with the expected result.

Other experiments are underway to better understand the mechanisms of protein stabilization at low hydration levels. In particular, molecular docking simulations will be performed. IV. CONCLUSION Regardless of their good stability, maintaining the activity of OBPs, when immobilized on chips and exposed to a "water free" stream of gaseous odorants was found to be unachievable. However, we found that the proteins are active under ambient humidity (ca. 30%). These results confirmed that indeed water molecules plays an important role in the stabilization of protein structure and even low hydration level are sufficient to maintain protein activity. The results also showed that under the optimal conditions the OBP-based optoelectronic nose can discriminate alcohol from aldehydes with a resolution of one hydrogen atom.

  ANR and Labex LANEF du Programme d'Investissements d'Avenir: ANR-10-LABX-51-01, ANR and AID/DGA (ANR-18-CE42-0012).

  a. PCA at equilibrium with 0% RH, b. PCA at equilibrium with 30% RH.