Modeling actual water use under different irrigation regimes at district scale: Application to the FAO-56 dual crop coefficient method

The modeling of irrigation in land surface models are generally based on two soil moisture parameters SMthreshold and SMtarget at which irrigation automatically starts and stops, respectively. Typically, both parameters are usually set to optimal values allowing to fill the soil water reservoir with just the estimated right amount and to avoid crop water excess at all times. The point is that agricultural practices greatly vary according to many factors (climatological, crop, soil, technical, human, etc.). To fill the gap, we propose a new calibration method of SMthreshold and SMtarget to represent the irrigation water use in any (optimal, deficit or even over) irrigation regime. The approach is tested using the dual-crop coefficient FAO-56 model implemented at the field scale over an 8100 ha irrigation district in northeastern Spain where the irrigation water use is precisely monitored at the district scale. Both irrigation parameters are first retrieved at monthly scale from the irrigation observations of year 2019. The irrigation simulated by the FAO-56 model is then evaluated against observations at district and weekly scale over 5 years (2017–2021) separately. The performance of the newly calibrated irrigation module is also assessed by comparing it against three other modules with varying configurations including default estimates for SMthreshold and SMtarget. The proposed irrigation module obtains systematically the best performance for each of the 5 years with an overall correlation coefficient of 0.95 ± 0.02 and root-mean square error of 0.27 ± 0.07 hm3/week (0.64 ± 0.17 mm/day). Unlike the three irrigation modules used as benchmark, the new irrigation module is able to reproduce the farmers’ practices throughout the year, and especially, to simulate the actual water use in the deficit and excess irrigation regimes occurring in the study area in spring and summer, respectively.This study was supported by the IDEWA project ( ANR-19-P026-003 ) of the Partnership for research and innovation in the Mediterranean area ( PRIMA ) program and by the Horizon 2020 ACCWA project (grant agreement # 823965 ) in the context of Marie Sklodowska-Curie Research and Innovation Staff Exchange (RISE) program. The authors wish to acknowledge the "Comunitat de Regants Canal Algerri Balaguer" and the Ebro Hydrographic Confederation (SAIH Ebro) for providing the observation irrigation data used in this study

Search for biological signature of the degradation of chlordecone in soil of the French West Indies

L’utilisation du chlordécone (CLD) pour éradiquer les populations de charançon noir dans les bananeraies des Antilles françaises (Guadeloupe et Martinique) entre 1972 et 1993 a conduit à la contamination des sols et de l’environnement. Cet insecticide organochloré très hydrophobe persiste dans les sols d’où il transfère lentement vers les ressources en eau et vers les biotes terrestre et aquatique (plantes, animaux, poissons, crustacées). Réputé « indégradable », le CLD résiste à la photolyse, à l’hydrolyse et à la biodégradation. A ce jour, il n’existe pas de méthode pour remédier les 20 000 hectares de sols pollués avec cet insecticide. Compte-tenu de l’étendue de la pollution avec le CLD, les procédés biologiques de décontamination paraissent appropriés au contexte antillais. Les objectifs de mon travail de thèse étaient d’explorer les possibilités de transformation microbienne du CLD et l’impact écotoxicologique du CLD sur la communauté microbienne des sols. Mes travaux reposent sur l’hypothèse selon laquelle des populations microbiennes exposées de manière chronique au CLD se seraient adaptées à sa dégradation pour détoxifier leur environnement ou éventuellement pour l’utiliser comme source d’énergie pour leur croissance. Pour cela, j’ai développé une méthode d’analyse du CLD dans les sols et les cultures microbiennes basée sur l’isotopie stable. J’ai conduit des expériences d’enrichissement à partir de sols de Guadeloupe pollués avec le CLD. Une centaine de souches fongiques et près de 200 souches bactériennes ont été isolées. Aucunes souches bactériennes dégradantes n’ont pu être mises en évidence bien que certaines formaient un halo de dissolution du CLD sur milieu gélosé. Parmi les isolats fongiques, seul F. oxysporum sp. MIAE01197 se développait sur un milieu minéral contenant le CLD comme seul source de carbone et dissipait 40% du CLD. Cet isolat était deux fois plus tolérant au CLD qu’un isolat de référence jamais exposé au CLD. Cet isolat minéralisait très peu le 14C-CLD, formait très peu de 14C-métabolites, mais le 14C-CLD s’adsorbait sur les parois fongiques, suggérant que l’adsorption était le principal mécanisme impliqué dans la dissipation du CLD. L’analyse de trois autres isolats appartenant au genre Aspergillus a confirmé que l’exposition au CLD était un des paramètres améliorant la tolérance des souches fongiques au CLD et que la biomasse fongique était capable d’adsorber le CLD dans des proportions proches de celles obtenues avec du charbon actif utilisé pour traiter l’eau potable aux Antilles. L’évaluation de l’impact écotoxicologique du CLD sur la communauté microbienne et les fonctions qu’elle supporte a été menée sur deux sols aux propriétés physicochimiques contrastées n’ayant jamais été exposés au CLD. L’analyse de la structure globale (évaluée par RISA), de l’abondance et de l’activité de la communauté microbienne du sol argilo-limoneux n’étaient pas affectées par le CLD. En revanche, la composition taxonomique (qPCR) et l’activité respiratoire de la communauté microbienne étaient affectées par le CLD dans le sol sableux. Ces résultats montrent que la toxicité du CLD pour la communauté microbienne dépend des propriétés physicochimiques du sol qui conditionne sa biodisponibilité. Des études complémentaires devront être menées pour évaluer la toxicité possible du CLD sur des fonctions écosystémiques des sols des Antilles.The use of chlordecone (CLD) to eradicate the weevil populations in the banana plantations in the French West Indies (Guadeloupe and Martinique) between 1972 and 1993 led to the contamination of the soil and the environment. This very hydrophobic organochlorine insecticide persists in the soil where it slowly transfers not only to the water resources but also to terrestrial and aquatic biota (plants, animals, fishes, shellfishes). Deemed “non-degradable”, CLD is resistant to photolysis, hydrolysis and biodegradation. To date, there is no method to remediate the 20,000 hectares of polluted soil with this insecticide. Given the extent of CLD pollution, biological decontamination processes appear appropriate to the Caribbean context. The objectives of my thesis were to explore the possibilities of microbial transformation of CLD and to assess the ecotoxicological impact of CLD on the soil microbial community. My work is based on the hypothesis that microbial populations chronically exposed to CLD would be adapted to its degradation to detoxify their environment or possibly for use as an energy source for growth.To do so, I developed an analysis method in soils and microbial cultures based on the use of stable isotope to trace CLD. I conducted enrichment experiments with CLD polluted soils from Guadeloupe yielding in the isolation of one hundred fungal strains and nearly two hundred bacterial strains. No degrading bacterial strains have been identified although few of them formed dissolution halo of CLD on solid media. Among the fungal isolates, only F. oxysporum sp. MIAE01197 grew on a mineral medium containing CLD as sole carbon source and dissipated 40% of the CLD. This isolate was twice more tolerant than the reference isolate which had never been exposed to CLD. This isolate mineralizes 14C-CLD very lowly, formed very few 14C-metabolites, but the 14C-CLD was adsorbed on the fungal cell walls, suggesting that the adsorption was the main mechanism involved in the dissipation of the CLD. Analysis of three other isolates belonging to the genus Aspergillus confirmed that exposure to CLD was one of the parameters improving the tolerance of fungal strains to CLD and fungal biomass was capable of adsorbing the CLD in proportions close to those obtained with activated carbon used to treat drinking water in the French West Indies.The assessment of the CLD ecotoxicological impact on the microbial community and functions it supports was carried out on two soils never exposed to CLD showing contrasting physicochemical properties. The analysis of the overall structure (evaluated by RISA), the abundance and the activity of the microbial community of the silty-clay soil were not affected by the CLD. However, the taxonomic composition (evaluated by group specific qPCR) and respiratory activity of the microbial community were affected by the CLD in the sandy soil. These results showed that the toxicity of CLD for microbial community depends on the physicochemical properties of the soil which may determine its bioavailability. Further studies are needed to evaluate the possible toxicity of the CLD on Caribbean soil ecosystemic functions

Recherche de la signature biologique de la dégradation du chlordécone dans le sol des Antilles françaises

The use of chlordecone (CLD) to eradicate the weevil populations in the banana plantations in the French West Indies (Guadeloupe and Martinique) between 1972 and 1993 led to the contamination of the soil and the environment. This very hydrophobic organochlorine insecticide persists in the soil where it slowly transfers not only to the water resources but also to terrestrial and aquatic biota (plants, animals, fishes, shellfishes). Deemed “non-degradable”, CLD is resistant to photolysis, hydrolysis and biodegradation. To date, there is no method to remediate the 20,000 hectares of polluted soil with this insecticide. Given the extent of CLD pollution, biological decontamination processes appear appropriate to the Caribbean context. The objectives of my thesis were to explore the possibilities of microbial transformation of CLD and to assess the ecotoxicological impact of CLD on the soil microbial community. My work is based on the hypothesis that microbial populations chronically exposed to CLD would be adapted to its degradation to detoxify their environment or possibly for use as an energy source for growth.To do so, I developed an analysis method in soils and microbial cultures based on the use of stable isotope to trace CLD. I conducted enrichment experiments with CLD polluted soils from Guadeloupe yielding in the isolation of one hundred fungal strains and nearly two hundred bacterial strains. No degrading bacterial strains have been identified although few of them formed dissolution halo of CLD on solid media. Among the fungal isolates, only F. oxysporum sp. MIAE01197 grew on a mineral medium containing CLD as sole carbon source and dissipated 40% of the CLD. This isolate was twice more tolerant than the reference isolate which had never been exposed to CLD. This isolate mineralizes 14C-CLD very lowly, formed very few 14C-metabolites, but the 14C-CLD was adsorbed on the fungal cell walls, suggesting that the adsorption was the main mechanism involved in the dissipation of the CLD. Analysis of three other isolates belonging to the genus Aspergillus confirmed that exposure to CLD was one of the parameters improving the tolerance of fungal strains to CLD and fungal biomass was capable of adsorbing the CLD in proportions close to those obtained with activated carbon used to treat drinking water in the French West Indies.The assessment of the CLD ecotoxicological impact on the microbial community and functions it supports was carried out on two soils never exposed to CLD showing contrasting physicochemical properties. The analysis of the overall structure (evaluated by RISA), the abundance and the activity of the microbial community of the silty-clay soil were not affected by the CLD. However, the taxonomic composition (evaluated by group specific qPCR) and respiratory activity of the microbial community were affected by the CLD in the sandy soil. These results showed that the toxicity of CLD for microbial community depends on the physicochemical properties of the soil which may determine its bioavailability. Further studies are needed to evaluate the possible toxicity of the CLD on Caribbean soil ecosystemic functions.L’utilisation du chlordécone (CLD) pour éradiquer les populations de charançon noir dans les bananeraies des Antilles françaises (Guadeloupe et Martinique) entre 1972 et 1993 a conduit à la contamination des sols et de l’environnement. Cet insecticide organochloré très hydrophobe persiste dans les sols d’où il transfère lentement vers les ressources en eau et vers les biotes terrestre et aquatique (plantes, animaux, poissons, crustacées). Réputé « indégradable », le CLD résiste à la photolyse, à l’hydrolyse et à la biodégradation. A ce jour, il n’existe pas de méthode pour remédier les 20 000 hectares de sols pollués avec cet insecticide. Compte-tenu de l’étendue de la pollution avec le CLD, les procédés biologiques de décontamination paraissent appropriés au contexte antillais. Les objectifs de mon travail de thèse étaient d’explorer les possibilités de transformation microbienne du CLD et l’impact écotoxicologique du CLD sur la communauté microbienne des sols. Mes travaux reposent sur l’hypothèse selon laquelle des populations microbiennes exposées de manière chronique au CLD se seraient adaptées à sa dégradation pour détoxifier leur environnement ou éventuellement pour l’utiliser comme source d’énergie pour leur croissance. Pour cela, j’ai développé une méthode d’analyse du CLD dans les sols et les cultures microbiennes basée sur l’isotopie stable. J’ai conduit des expériences d’enrichissement à partir de sols de Guadeloupe pollués avec le CLD. Une centaine de souches fongiques et près de 200 souches bactériennes ont été isolées. Aucunes souches bactériennes dégradantes n’ont pu être mises en évidence bien que certaines formaient un halo de dissolution du CLD sur milieu gélosé. Parmi les isolats fongiques, seul F. oxysporum sp. MIAE01197 se développait sur un milieu minéral contenant le CLD comme seul source de carbone et dissipait 40% du CLD. Cet isolat était deux fois plus tolérant au CLD qu’un isolat de référence jamais exposé au CLD. Cet isolat minéralisait très peu le 14C-CLD, formait très peu de 14C-métabolites, mais le 14C-CLD s’adsorbait sur les parois fongiques, suggérant que l’adsorption était le principal mécanisme impliqué dans la dissipation du CLD. L’analyse de trois autres isolats appartenant au genre Aspergillus a confirmé que l’exposition au CLD était un des paramètres améliorant la tolérance des souches fongiques au CLD et que la biomasse fongique était capable d’adsorber le CLD dans des proportions proches de celles obtenues avec du charbon actif utilisé pour traiter l’eau potable aux Antilles. L’évaluation de l’impact écotoxicologique du CLD sur la communauté microbienne et les fonctions qu’elle supporte a été menée sur deux sols aux propriétés physicochimiques contrastées n’ayant jamais été exposés au CLD. L’analyse de la structure globale (évaluée par RISA), de l’abondance et de l’activité de la communauté microbienne du sol argilo-limoneux n’étaient pas affectées par le CLD. En revanche, la composition taxonomique (qPCR) et l’activité respiratoire de la communauté microbienne étaient affectées par le CLD dans le sol sableux. Ces résultats montrent que la toxicité du CLD pour la communauté microbienne dépend des propriétés physicochimiques du sol qui conditionne sa biodisponibilité. Des études complémentaires devront être menées pour évaluer la toxicité possible du CLD sur des fonctions écosystémiques des sols des Antilles

Caractérisation de populations microbiennes tolérantes au chlordécone à partir de sols contaminés des Antilles

Il n\u27existe que très peu d\u27évidence rapportant la biodégradation de la chlordécone, classée depuis 2009 comme polluant organique persistant (POP) par la convention de Stockholm. L\u27objectif de ce travail est de rechercher des éléments indiquant la biotransformation du CLD dans les sols contaminés des Antilles. Des cultures par enrichissement ont été établies à partir d\u27échantillons de sols contaminés pour isoler des populations microbiennes tolérantes au CLD et éventuellement capables de le dégrader

Caractérisation de populations microbiennes tolérantes au chlordécone à partir de sols contaminés des Antilles

National audienc

Diversité et dynamique des communautés microbiennes impliquées dans la dégradation des résidus de culture : influence du type de résidu et des pratiques agricoles

National audienc

Diversité et dynamique des communautés microbiennes impliquées dans la dégradation des résidus de culture : influence du type de résidu et des pratiques agricoles

National audienc

Isolement de champignons d’un andosol de Guadeloupe contaminé à la chlordécone : caractérisation de leurs tolérances

National audienc

Isolation of fungal isolates from french west indies soil contaminated with chlordecone: evidence for chlordecone tolerance and potential biodegrading ability

National audienceChlordecone (CLD), an organochloride insecticide used in French West Indies to control the banana weevil Cosmopolites sorditus, contaminates soils of banana plantations and water resources posing major environmental problem. Recently the link between CLD exposure and rate of prostate cancer was established (Multigner et al., 2010) highlighting a major public health concern. Being listed by the Stockholm convention as a persistent organic pollutant (POP), CLD is well known for its recalcitrance to biodegradation. Combined with a high soil organic matter, CLD is adsorbed to soils where Cabidoche et al. (2009) estimate that it will persist for several hundreds of years. Reports of CLD biodegradation being scarce, the aim of this work is to search for evidence for microbial transformation of this insecticide in West French Indies contaminated soils. The work consisted in performing enrichment cultures to isolate, characterize and test the tolerance of microorganisms from contaminated soils to CLD. Continuous culture enrichments carried out with activated charcoal (microbial communities’ sequestration) were conducted for several months on an Andosol heavily contaminated with CLD (i.e. 35 mg.kg-1). Starting from enriched soil and activated charcoal, successive enrichments were conducted in mineral salt medium added with CLD as sole carbon source in order to select CLD tolerant and/or degrading-microorganisms. Using this procedure, an important fungal diversity was retrieved from the Andosol. In total of 102 isolates gathered in 17 morphotypes were isolated. The intergenic region (ITS) between 18S and 28S genes of ribosomal operon of several representatives were sequenced. Three morphotypes namely Fusarium oxysporum (33 isolates), morphotype 1 yet unidentified (20) and Aspergillus flavus (13) co-dominate the cultivable fungal community. Fungal isolates are not known as degrading chlorinated compounds. Tolerance tests on glucose minimal medium supplemented or not with CLD have been performed on a representative of each dominant morphotype (i.e. Fusarium oxysporum strain CHL53, morphotype1 strain CHL22, Aspergillus flavus strain CHL48) and a reference strain which has never been in contact with CLD (Fusarium oxysporum MIAE00047). No statistically significant effect of CLD has been observed on the growth rate of the reference strain and isolate CHL48 (p<0.01, n=5). However, CLD increased significantly the growth rate of isolates CHL53 and CHL48 (p<0.01, n=5). These results indicate that on one hand, the tested strains are not sensitive to the CLD, and on the other hand, two isolates seem to grow on CLD. Growth tests of the three isolates and the reference strain were performed on minimal medium with CLD as the sole carbon source. Isolates CHL22, CHL48 and the reference strain did not grow, indicating that they cannot use CLD as carbon source. In contrast, strain CHL53 (F. oxysporum) grew on such a medium. These results corroborate the tolerance tests, suggesting that CHL53 is able use CLD for its growth. Radiorespirometry experiment performed with uniformly labeled 14C and GC-MS analyses of F. oxysporum CHL53 cultures are on going to evidence for CLD transformation

Detection and quantification of chlordecone in contaminated soils from the French West Indies by GC-MS using the C-13(10)-chlordecone stable isotope as a tracer

International audienceChlordecone is an organochlorine insecticide that has been widely used to control banana weevil in the French West Indies. As a result of this intense use, up to 20,000 ha are contaminated by this insecticide in the French West Indies, and this causes environmental damage and health problems. A scenario of exposure was drawn by French authorities, based on land usage records. Many efforts have been made to monitor the occurrence of chlordecone and its main metabolites using different analytical methods, including GC, GC/MS, LC/MS, and NIRS. Although these different methods allow for the detection and quantification of chlordecone from soils, none of them estimate the bottleneck caused by extraction of this organochlorine from soils with high adsorption ability. In this study, we used C-13(10)-chlordecone as a tracer to estimate chlordecone extraction yield and to quantify chlordecone in soil extracts based on the C-13/C-12 isotope dilution. We report the optimization of C-13(10)-chlordecone extraction from an Andosol. The method was found to be linear from 0.118 to 43 mg kg(-1) in the Andosol, with an instrumental detection limit estimated at 8.84 mu g kg(-1). This method showed that chlordecone ranged from 35.4 down to 0.18 mg kg(-1) in Andosol, Nitisol, Ferralsol, and Fluvisol soil types. Traces of the metabolite beta-monohydrochlordecone were detected in the Andosol, Nitisol, and Ferralsol soil samples. This last result indicates that this method could be useful to monitor the fate of chlordecone in soils of the French West Indies