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In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements ( ∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76 % of the experimental sites with agricultural land use as the dominant type ( ∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it.

Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedo)transfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved. Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42). Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = −0.26) due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72). Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is probably more important than the estimation of water flow parameters. Overall, the results are encouraging for the use of this modelling set-up to estimate pesticide leaching risks at the regional-scale, especially where the objective is to identify vulnerable soils and "source" areas of contamination.

La réglementation et les attentes sociétales incitent aujourd'hui les aménageurs du territoire à évaluer les impacts environnementaux de leurs projets de construction, mais également à prévoir des mesures et des actions pour créer ou restaurer la biodiversité des espaces modifiés. Cependant, l'évaluation ex-post des projets de restauration ou de création d'habitats pose de nombreuses questions méthodologiques. L'étude de cas du Mont-aux-Liens, un aménagement paysager contigu à l'autoroute A19, montre que la diversité spécifique végétale est une composante pertinente de la performance écologique d'un tel aménagement. Le bilan quantitatif (richesse spécifique) est meilleur que celui projeté par l'aménageur, mais l'approche qualitative montre un échec des semis et une colonisation exogène forte. Les caractéristiques écologiques et les stratégies adaptatives expliquent ces bilans. Elles fournissent des informations utiles pour la redéfinition d'objectifs adaptés à l'amélioration de la performance écologique de l'aménagement, du point de vue de la biodiversité végétale

Among the release solutions for reducing the discharge of organic and persistent contaminants in the aquatic environment, the use of a tertiary treatment in addition to existing conventional wastewater treatment processes is considered. The use of micro-grain activated carbon in a fluidized bed is a promising technique investigated in this study. The effluents from a large-scale pilot system were analyzed by liquid chromatography coupled with high-resolution mass spectrometry (QToF). Several strategies were deployed, namely molecular fingerprint comparison, suspected and non-target analyses, identification of refractory compounds to treatment, and finally, quantification of identified compounds. The evaluation of the molecular fingerprints provided evidence of the overall effect of the tertiary treatment on the treated wastewater quality. The suspected approach highlighted the presence of 83 pharmaceuticals and pesticides as well as transformation products in the effluents. The non-target approaches also highlighted compounds refractory to tertiary treatment, such as illicit drugs or some pharmaceuticals. The identification and quantification of identified compounds underscored the suitability of micro-grain activated carbon in eliminating many classes of pharmaceuticals with various physicochemical properties, such as anti-hypertensive, analgesic, anti-viral, antidepressant and even various pesticides., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Among the solutions to reduce micropollutant discharges into the aquatic environment, activated carbon adsorption is a promising technique and a large scale pilot has been tested at the Seine Centre (240,000 m(3)/d - Paris, France) wastewater treatment plant (WWTP). While most of available works studied fixed bed or contact reactors with a separated separation step, this study assesses a new type of tertiary treatment based on a fluidized bed containing a high mass of activated carbon, continuously renewed. For the first time in the literature, micro-grain activated carbon (μGAC) was studied. The aims were (1) to determine the performances of fluidized bed operating with μCAG on both emerging micropollutants and conventional wastewater quality parameters, and (2) to compare its efficiency and applicability to wastewater to former results obtained with PAC. Thus, conventional wastewater quality parameters (n=11), pharmaceuticals and hormones (PPHs; n=62) and other emerging pollutants (n=57) have been monitored in μGAC configuration during 13 campaigns. A significant correlation has been established between dissolved organic carbon (DOC), PPHs and UV absorbance at 254 nm (UV-254) removals. This confirms that UV-254 could be used as a tertiary treatment performance indicator to monitor the process. This parameter allowed identifying that the removals of UV-254 and DOC reach a plateau from a μGAC retention time (SRT) of 90-100 days. The μGAC configuration substantially improves the overall quality of the WWTP discharges by reducing biological (38-45%) and chemical oxygen demands (21-48%), DOC (13-44%) and UV-254 (22-48%). In addition, total suspended solids (TSS) are retained by the μGAC bed and a biological activity (nitratation) leads to a total elimination of NO2(-). For micropollutants, PPHs have a good affinity for μGAC and high (>60%) or very high (>80%) removals are observed for most of the quantified compounds (n=22/32), i.e. atenolol (92-97%), carbamazepine (80-94%), ciprofloxacin (75-95%), diclofenac (71-97%), oxazepam (74-91%) or sulfamethoxazole (56-83%). In addition, alkylphenols, artificial sweeteners, benzotriazole, bisphenol A, personal care products (triclocarban and parabens) and pesticides have removals lying in the 50 ->90% range. Overall, the fluidized bed of μGAC allows obtaining performances comparable to PAC at the same activated carbon dose. Indeed, the average removal of the 13 PPHs found at a high occurrence (>75%) in WWTP discharges is similar at 20 g/m(3) of μGAC (78-89%) and PAC (85-93%). In addition, this recycled μGAC operation leads to several operational advantages (no FeCl3, reactivable, higher SRT, higher treated flow) and has a stronger impact on the overall wastewater quality compared to PAC., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The efficacy of a fluidized powdered activated carbon (PAC) pilot (CarboPlus(®)) was studied in both nominal (total nitrification + post denitrification) and degraded (partial nitrification + no denitrification) configuration of the Seine Centre WWTP (Colombes, France). In addition to conventional wastewater parameters 54 pharmaceuticals and hormones (PhPHs) and 59 other emerging pollutants were monitored in influents and effluents of the pilot. Thus, the impacts of the WWTP configuration, the process operation and the physico-chemical properties of the studied compounds were assessed in this article. Among the 26 PhPHs quantified in nominal WWTP configuration influents, 8 have high dissolved concentrations (>100 ng/L), 11 have an intermediary concentration (10-100 ng/L) and 7 are quantified below 10 ng/L. Sulfamethoxazole is predominant (about 30% of the sum of the PhPHs). Overall, 6 PhPHs are poorly to moderately removed (<60%), such as ibuprofen, paracetamol or estrone, while 9 are very well removed (>80%), i.e. beta blockers, carbamazepine or trimethoprim, and 11 are well eliminated (60-80%), i.e. diclofenac, naproxen or sulfamethoxazole. In degraded WWTP configuration, higher levels of organic matter and higher concentrations of most pollutants are observed. Consequently, most PhPHs are substantially less removed in percentages but the removed flux is higher. Thus, the PAC dose required to achieve a given removal percentage is higher in degraded WWTP configuration. For the other micropollutants (34 quantified), artificial sweeteners and phthalates are found at particularly high concentrations in degraded WWTP configuration influents, up to μg/L range. Only pesticides, bisphenol A and parabens are largely eliminated (50-95%), while perfluorinated acids, PAHs, triclosan and sweeteners are not or weakly removed (<50%). The remaining compounds exhibit a very variable fate from campaign to campaign. The fresh PAC dose was identified as the most influencing operation parameter and is strongly correlated to performances. Charge and hydrophobicity of compounds have been recognized as crucial for the micropollutant adsorption on PAC, as well as the molecular weight. Finally, a PAC dose of 10 mg/L allows an average removal of 72-80% of the sum of the PhPHs in nominal WWTP configuration. The comparaison of the results with those from the scarce other studies tends to indicate that an extrapolation of them to different PAC processes and to other WWTPs could be possible and relevant, taking into account the differences of water quality from WWTP to WWTP., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Transport processes in soils are strongly affected by heterogeneity of soil hydraulic properties. Tillage practices and compost amendments can modify soil structure and create heterogeneity at the local scale within agricultural fields. The long-term field experiment QualiAgro (INRA-Veolia partnership 1998-2013) explores the impact of heterogeneity in soil structure created by tillage practices and compost application on transport processes. A modeling study was performed to evaluate how the presence of heterogeneity due to soil tillage and compost application affects water flow and pesticide dynamics in soil during a long-term period. The study was done on a plot receiving a co-compost of green wastes and sewage sludge (SGW) applied once every 2 years since 1998. The plot was cultivated with a biannual rotation of winter wheat-maize (except 1 year of barley) and a four-furrow moldboard plow was used for tillage. In each plot, wick lysimeter outflow and TDR probe data were collected at different depths from 2004, while tensiometer measurements were also conducted during 2007/2008. Isoproturon concentration was measured in lysimeter outflow since 2004. Detailed profile description was used to locate different soil structures in the profile, which was then implemented in the HYDRUS-2D model. Four zones were identified in the plowed layer: compacted clods with no visible macropores (Δ), non-compacted soil with visible macroporosity (Γ), interfurrows created by moldboard plowing containing crop residues and applied compost (IF), and the plow pan (PP) created by plowing repeatedly to the same depth. Isoproturon retention and degradation parameters were estimated from laboratory batch sorption and incubation experiments, respectively, for each structure independently. Water retention parameters were estimated from pressure plate laboratory measurements and hydraulic conductivity parameters were obtained from field tension infiltrometer experiments. Soil hydraulic properties were optimized on one calibration year (2007/08) using pressure head, water content and lysimeter outflow data, and then tested on the whole 2004/2010 period. Lysimeter outflow and water content dynamics in the soil profile were correctly described for the whole period (model efficiency coefficient: 0.99) after some correction of LAI estimates for wheat (2005/06) and barley (2006/07). Using laboratory-measured degradation rates and assuming degradation only in the liquid phase caused large overestimation of simulated isoproturon losses in lysimeter outflow. A proper order of magnitude of isoproturon losses was obtained after considering that degradation occurred in solid (sorbed) phase at a rate 75% of that in liquid phase. Isoproturon concentrations were found to be highly sensitive to degradation rates. Neither the laboratory-measured isoproturon fate parameters nor the independently-derived soil hydraulic parameters could describe the actual multiannual field dynamics of water and isoproturon without calibration. However, once calibrated on a limited period of time (9 months), HYDRUS-2D was able to simulate the whole 6-year time series with good accuracy., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Pesticide pollution is a major threat to aquatic ecosystems that can be mitigated through complementary actions including buffer zones (BZs). This paper discusses the results of 3 yr of field-scale monitoring of the concentration and load transfer of 16 pesticides out of a tile-drained catchment (Bray, France) and their reduction through two BZ: an artificial wetland (AW) and a forest buffer (FB). Typically, the highest concentrations were measured in the first flows following pesticide applications or resuming after periods of low or no flow. An open/close water management strategy was implemented to operate the parallel BZ based on pesticide applications by the farmer. The strategy was efficient in intercepting molecules whose highest concentrations occurred during the first flows following application. Inlet vs. outlet pesticide load reductions ranged from 45% to 96% (AW) and from -32% to 100% (FB) depending on the pesticide molecule and the hydrological year. Partly reversible adsorption was a dominant process explaining pesticide removal; whereas, degradation occurred for sufficiently long water retention time. Apart from the least sorbing molecules (e.g., isoproturon), BZ can partially remove pesticide pollution., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Laboratory incubations were performed in order to evaluate the dissipation of the proherbicide isoxaflutole in seedbed layer soil samples from conventional and conservation tillage systems and in maize and oat residues left at the soil surface under conservation tillage. The effects of temperature and water pressure head on radiolabelled isoxaflutole degradation were studied for each sample for 21d. Mineralisation of isoxaflutole was low for all samples and ranged from 0.0% to 0.9% of applied (14)C in soil samples and from 0.0% to 2.4% of applied (14)C in residue samples. In soil samples, degradation half-life of isoxaflutole ranged from 9 to 26h, with significantly higher values under conservation tillage. In residue samples, degradation half-life ranged from 3 to 31h, with significantly higher values in maize residues, despite a higher mineralisation and bound residue formation than in oat residues. Whatever the sample, most of the applied (14)C remained extractable during the experiment and, after 21d, less than 15% of applied (14)C were unextractable. This extractable fraction was composed of diketonitrile, benzoic acid derivative and several unidentified metabolites, with one of them accounting for more than 17% of applied (14)C. This study showed that tillage system design, including crop residues management, could help reducing the environmental impacts of isoxaflutole., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Sorption largely controls pesticide fate in soils because it influences its availability for biodegradation or transport in the soil water. In this study, variability of sorption and desorption of isoxaflutole (IFT) and its active metabolite diketonitrile (DKN) was investigated under conventional and conservation tillage., Results: According to soil samples, IFT K(D) values ranged from 1.4 to 3.2 L kg(-1) and DKN K(D) values ranged from 0.02 to 0.17 L kg(-1) . Positive correlations were found between organic carbon content and IFT and DKN sorption. IFT and DKN sorption was higher under conservation than under conventional tillage owing to higher organic carbon content. Under conservation tillage, measurements on maize and oat residues collected from the soil surface showed a greater sorption of IFT on plant residues than on soil samples, with the highest sorbed quantities measured on maize residues (K(D) ≈ 45 L kg(-1) ). Desorption of IFT was hysteretic, and, after five consecutive desorptions, between 72 and 89% of the sorbed IFT was desorbed from soil samples. For maize residues, desorption was weak (<50% of the sorbed IFT), but, after two complementary desorptions allowing for IFT hydrolysis, DKN was released from maize residues., Conclusion: Owing to an increase in organic carbon in topsoil layers, sorption of IFT and DKN was enhanced under conservation tillage. Greater sorption capacities under conservation tillage could help in decreasing DKN leaching to groundwater., (Copyright © 2012 Society of Chemical Industry.)

Background: Sorption coefficients (the linear K(D) or the non-linear K(F) and N(F)) are critical parameters in models of pesticide transport to groundwater or surface water. In this work, a dataset of isoproturon sorption coefficients and corresponding soil properties (264 K(D) and 55 K(F)) was compiled, and pedotransfer functions were built for predicting isoproturon sorption in soils and vadose zone materials. These were benchmarked against various other prediction methods., Results: The results show that the organic carbon content (OC) and pH are the two main soil properties influencing isoproturon K(D) . The pedotransfer function is K(D) = 1.7822 + 0.0162 OC(1.5) - 0.1958 pH (K(D) in L kg(-1) and OC in g kg(-1)). For low-OC soils (OC < 6.15 g kg(-1)), clay and pH are most influential. The pedotransfer function is then K(D) = 0.9980 + 0.0002 clay - 0.0990 pH (clay in g kg(-1)). Benchmarking K(D) estimations showed that functions calibrated on more specific subsets of the data perform better on these subsets than functions calibrated on larger subsets., Conclusion: Predicting isoproturon sorption in soils in unsampled locations should rely, whenever possible, and by order of preference, on (a) site- or soil-specific pedotransfer functions, (b) pedotransfer functions calibrated on a large dataset, (c) K(OC) values calculated on a large dataset or (d) K(OC) values taken from existing pesticide properties databases., (Copyright © 2011 Society of Chemical Industry.)

Buffer zones such as artificial wetlands and forest buffers may help decrease non-point-source pesticide pollution from agricultural catchments. The present study focuses on understanding the role of the substrates mainly found in such buffer zones for pesticide adsorption and desorption. Radiolabeled [(14)C]isoproturon, [(14)C]metazachlor, and [(14)C]epoxiconazole were used to measure adsorption and desorption isotherms on wetland sediments and plants and forest soil and litter from two sites in France. Wetland sediments and forest soil exhibited the most important potential for pesticide adsorption. Wetland plants and forest litter also showed high adsorption coefficients and were associated with highly hysteretic desorption, particularly for the moderately mobile isoproturon and metazachlor. Adsorption of the highly hydrophobic epoxiconazole was strong and associated with weak desorption from all substrates. Calculated sorption coefficients were larger than those classically measured on soils. Isoproturon, metazachlor, and epoxiconazole K(OC) sorption coefficients ranged from 84 to 372, 131 to 255, and 1,356 to 3,939 L/kg, respectively. Therefore, specifically collecting buffer zone substrate sorption data is needed for modeling purposes. Results showed that forests and wetlands present potential for pesticide retention. This may be enhanced by planting vegetation and leaving dead vegetal material in buffer zone design., (Copyright © 2011 SETAC.)

Compost application tends to increase soil fertility and is likely to modify soil hydrodynamic properties by acting on soil structural porosity. Two composts, a municipal solid waste compost (MSW) and a co-compost of green wastes and sewage sludge (SGW), have been applied every other year for 6 yr to cultivated plots located on a silt loam soil in the Parisian Basin, France. Four soil zones were defined in the topsoil after plowing: the plowpan located at the base of the plowed layer, compacted (Delta) or noncompacted (Gamma) zones located within the plowed layer, and interfurrows created by plowing and containing a large quantity of crop residues together with the recently-applied compost. To assess the effect of compost application on the near-saturated soil hydraulic conductivity, infiltration rates were measured using a tension disc infiltrometer at three water pressure potentials -0.6, -0.2, and -0.05 kPa in the various zones of the soil profile. Compost addition decreased K((sat)) in the interfurrows after plowing by almost one order of magnitude with average values of 5.6 x 10(-5) m.s(-1) in the MSW plot and 4.1 x 10(-5) m.s(-1) in the SGW plot, against 2.2 x 10(-4) m.s(-1) in the control plot. This effect had disappeared 6 mo after plowing when the average K((sat)) in the control plot had decreased to 1.9 x 10(-5) m.s(-1) while that in the compost-amended plots remained stable.

Laboratory studies were conducted to evaluate the effects of temperature and water pressure head on the degradation of the diketonitrile metabolite (DKN) of isoxaflutole during 84d in samples collected in a loamy soil under conventional (CT) and conservation (MT) tillage systems. Soil temperature was the major factor controlling DKN degradation in the two tillage systems. The shortest half-lives (T(1/2)) were measured in the seedbed samples under MT at 25 degrees C and -33cm water pressure head. We found that mouldboard ploughing under CT was responsible for the spatial variability of herbicide degradation properties, whereas under MT herbicide degradation was associated to the vertical distribution of organic matter.

The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), is widely used to control pre- and post-emergence of grass and broad-leaved weeds in cereal crops. Its degradation in soils is a key process for assessing its leaching risk to groundwater resources. The degradation properties of various samples from surface and subsurface soil (down to 1m depth) of a heterogeneous agricultural field were studied using (14)C-IPU. Laboratory incubations were carried out at 22 and 10 degrees C and at water contents 90% and 50% of the estimated water holding capacity (eWHC) corresponding to water potentials between -56 kPa and -660 MPa. Degradation was found to be more sensitive to water content variations than to temperature variations in the ranges that we used. For surface layers, at 10 and 22 degrees C, the degradation half-life increased by a factor 10 and 15, respectively, when water content decreased from 90% to 50% eWHC. Under optimal degradation conditions (i.e. 22 degrees C and 90% eWHC), 3-(4-isopropylphenyl)-1-methylurea (MDIPU) was the main metabolite in surface samples. At subsurface depths, IPU half-lives were larger than 100 d, IPU was the main compound after 92 d of incubation and the main metabolite was an unidentified polar metabolite. These results suggest a metabolic pathway involving hydroxylations for subsurface materials. IPU degradation was largely affected by water availability in both surface and subsurface horizons. Clay content seemed to play a major role in degradation processes in subsurface soil by determining through sorption IPU availability in soil solution and/or by limiting water availability for microorganisms.

Two series of displacement experiments with isoproturon and metribuzin herbicides were performed on two undisturbed grassed filter strip soil cores, under unsaturated steady-state flow conditions. Several rainfall intensities (0.070, 0.147, 0.161, 0.308 and 0.326 cm h(-1)) were used. A water tracer (bromide) was simultaneously injected in each displacement experiment. A descriptive analysis of experimental breakthrough curves of bromide and herbicides combined with a modeling analysis showed an impact of rainfall intensity on the solute transport. Two contrasting physical non-equilibrium transport processes occurred. Multiple (three) porosity domains contributed to flow at the highest rainfall intensities, including preferential flow through macropore pathways. Macropores were not active any longer at intermediate and lowest velocities, and the observed preferential transport was described using dual-porosity-type models with a zero or low flow in the matrix domain. Chemical non-equilibrium transport of herbicides was found at all rainfall intensities. Significantly higher estimated values of degradation rate parameters as compared to batch data were correlated with the degree of non-equilibrium sorption. Experimental breakthrough curves were analyzed using different physical and chemical equilibrium and non-equilibrium transport models: convective-dispersive model (CDE), dual-porosity model (MIM), dual-permeability model (DP), triple-porosity, dual permeability model (DP-MIM); each combined with both chemical instantaneous and kinetic sorption.

The spatial variability in mineralization of atrazine, isoproturon and metamitron in soil and subsoil samples taken from a 135-ha catchment in north France was studied. Fifty-one samples from the top layer were taken to represent exhaustively the 31 agricultural fields and 21 soil types of the catchment. Sixteen additional samples were collected between depths of 0.7 and 10 m to represent the major geological materials encountered in the vadose zone of the catchment. All these samples were incubated with 14C-labelled atrazine under laboratory conditions at 28 degrees C. Fourteen selected surface samples which exhibited distinctly different behaviour for atrazine dissipation (including sorption and mineralization) were incubated with 14C-isoproturon and 14C-metamitron. Overall soil microbial activity and specific herbicide degradation activities were monitored during the incubations through measurements of total carbon dioxide and 14C-carbon dioxide respectively. At the end of the incubations, extractable and non-extractable (bound) residues remaining in soils were measured. Variability of herbicide dissipation half-life in soil surface samples was lower for atrazine and metamitron (CV < 12%) than for isoproturon (CV = 46%). The main contributor to the isoproturon dissipation variability was the variability of the extractable residues. For the other herbicides, spatial variability was mainly related to the variability of their mineralization. In all cases, herbicide mineralization half-lives showed higher variability than those of dissipation. Sorption or physicochemical soil properties could not explain atrazine and isoproturon degradation, whose main factors were probably directly related to the dynamics of the specific microbial degradation activity. In contrast, variability of metamitron degradation was significantly correlated to sorption coefficient (K(d)) through correlation with the sorptive soil components, organic matter and clay. Herbicide degradation decreased with depth as did the overall microbial activity. Atrazine mineralization activity was found down to a depth of 2.5 m; beyond that, it was negligible., (Copyright 2005 Society of Chemical Industry)

We present a set of adsorption coefficients measured on various Eocene and Quaternary materials sampled from the vadose zone of a catchment in Northern France for three herbicides, atrazine, isoproturon and metamitron. Some vadose zone materials were found to have higher adsorption coefficients than the topsoil. The adsorption coefficients were strongly dependent on the clay content of the material. From 83% to 97% of the variability in the adsorption coefficients could be explained by a linear relationship to the clay content. Adsorption coefficients normalized for clay content, Kclay, ranged between 1.6 and 17.6 litre kg(-1) for atrazine. Neglecting the adsorption properties of the vadose zone and relying exclusively on Koc values to predict mobility may bias regional or local risk assessment of groundwater contamination by pesticides. More information on the adsorption properties of geological materials should be collected to improve our ability to predict pesticide concentrations in groundwaters.

The variation of the sorption isotherm of pesticides has seldom been explored at the catchment scale. Such a study was conducted at the scale of a 187-ha agricultural catchment for three herbicides: atrazine, isoproturon and metamitron. Partition coefficient (Kd) values were measured in batch experiments on 51 topsoil samples, and showed moderate variability at the catchment scale (coefficient of variation CV approximately 30%). Values of Kd ranged from 0.47 to 1.70 litre kg(-1) for atrazine, 0.47 to 1.81 for isoproturon, and 0.55 to 2.21 for metamitron. A clustering method was used to reduce the number of samples on which to measure sorption isotherms to 14. Sorption isotherms agreed with the Freundlich rather than the linear model. Kf parameters had CV values similar to those for Kd, with values ranging from 0.78 to 2.13 mg(1 - Nf) litre(Nf) kg(-1) for atrazine, 0.61 to 1.82 for isoproturon, and 0.69 and 2.58 for metamitron. Nf exponents showed little variation (CV < 5%). Nf values were between 0.86 and 0.98 for atrazine, 0.85 and 0.90 for isoproturon, and 0.82 and 0.87 for metamitron. More than 97% of the Kf catchment-scale variations could be explained by the variations of the soil organic carbon content.