Factors controlling spatial and temporal patterns of multiple pesticide compounds in groundwater (Hesbaye chalk aquifer, Belgium)

Impacts of Fulvic Acid on the Toxicity of the Herbicide Atrazine to Lemna minor

Fulvic acids (FA) are environmentally prevalent components of dissolved organic carbon. Little research has evaluated their potential influence on the bioavailability of herbicides to non-target aquatic plants. This study evaluated the potential impacts of FA on the bioavailability of atrazine (ATZ) to the aquatic plant Lemna minor. Plants were exposed to 0, 15, 30, 60, 125, and 750 µg/L ATZ in media containing three FA concentrations (0, 5, and 15 mg/L) in a factorial study under static conditions. Fronds were counted after 7- and 14-days exposure and intrinsic growth rates (IGR) and total frond yields were calculated for analysis. Atrazine NOAECs and LOAECs within each FA treatment series (0, 5, or 15 mg/L) were identified and EC50s were estimated. NOAEC/LOAECs for yield and IGR were 60/125 µg/L except for yield in the 0 mg/L-FA series (30/60) and IGR in the 5 mg/L-FA series (30/60). NOAEC/LOAECs were 30/60 µg/L for all treatments and both endpoints after 14 days exposure. EC50s ranged from 88.2 to 106.1 µg/L (frond production 7 DAT), 158.0-186.0 µg/L (IGR, 7 DAT), 74.7-86.3 µg/L (frond production, 14 DAT), and 144.1-151.3 µg/L (IGR, 14 DAT). FA concentrations did not influence the toxicity of ATZ.

Analysing agricultural plant protection product concentrations in groundwater in Germany: Nationwide database with site and compound insights

Pesticides from agricultural practices are among the most pressing reasons why groundwater sources do not reach the good chemical status standards as required by the European Water Framework directive. Complementary to previous federal pesticide reports, we analysed groundwater-monitoring data from 13 German Länder assembled in a database consisting of 26.192 groundwater measuring sites sampled between 1973 and 2021 of in total 521 parent compounds and metabolites. This study focuses on agricultural plant protection products. The monitored substance spectrum and site density developed over time and differs between Länder. More than 95 % of all samples lie below the respective (multiple) limits of quantification (LOQ). We thus report the frequency of exceedance above concentration thresholds, which allows to compare measurements temporally and spatially. Pesticide detections were found in all aquifer types, land uses and well screen depths. Most detections of higher concentrations were found in agricultural areas, at shallow screen depth in porous aquifers. Karst aquifers showed also a higher percentage of samples in higher concentration classes. Metabolites with high mobility and persistence were found in higher concentration ranges. Herbicides and metabolites thereof dominate the top 20 of pesticides that most frequently exceed 0.1 μg L-1. The ranking for 2010-2019 includes both authorised and banned compounds and their occurrence is discussed in the context of their mobility, persistence and underlying monitoring density. Yearly exceedance frequencies above 0.05, 0.1 μg L-1 and higher thresholds of metazachlor and its esa-metabolite, and national sales data of the parent compound did not show a temporal correlation in subsequent years. This study stresses the need for the harmonisation of heterogeneous pesticide data. Further, a characterisation of the groundwater data used to analyse pesticide occurrence in selected concentration ranges for relevant site factors and compound properties and provides a pesticide ranking based on exceedance frequencies is provided.

Concealed by darkness: Combination of NMR and HRMS reveal the molecular nature of dissolved organic matter in fractured-rock groundwater and connected surface waters

Detailed molecular composition of solid phase extracted dissolved organic matter (SPEDOM) collected from fractured-rock groundwater was compared to connected surface river water at two different watersheds in the unconfined chalk aquifer of Champagne in France using full scan ultrahigh resolution electrospray and photoionization Fourier transform ion cyclotron mass spectrometry (FT-ICR MS), Orbitrap tandem MS (MS/MS) and 1H magnetic resonance spectroscopy (NMR). 1H NMR spectroscopy indicated that groundwater SPEDOM carried a higher contribution of aliphatic compounds while surface river waters SPEDOM were enriched in carboxyl-rich alicyclic molecules (CRAM), acetate derivatives and oxygenated units. Furthermore, we show here that use of photoionization (APPI(+)) in aquifer studies is key, ionizing about eight times more compounds than ESI in surface river water samples, specifically targeting the dissolved organic nitrogen pool, accounting for more than 50% of the total molecular space, as well as a non-polar, more aromatic fraction; with little overlap with compounds detected by ESI(-) FT-ICR MS. On the other hand, groundwater SPEDOM samples did not show similar selectivity as less molecular diversity was observed in APPI compared to ESI. Mass-difference transformation networks (MDiNs) applied to ESI(-) and APPI(+) FT-ICR MS datasets provided an overview of the biogeochemical relationships within the aquifer, revealing chemical diversity and microbial/abiotic reactions. Finally, the combination of ESI(-) FT-ICR MS and detailed Orbitrap MS/MS analysis revealed a pool of polar, anthropogenic sulfur-containing surfactants in the groundwaters, likely originating from agricultural runoff. Overall, our study shows that in this aquifer, groundwater SPEDOM contains a significantly reduced pool of organic compounds compared to surface river waters, possibly related to a combination of lack of sunlight and adsorption of high O/C formulas to mineral surfaces.

Impact of historical legacy pesticides on achieving legislative goals in Europe

Pesticides are widely used in agriculture to optimise food production. However, the movement of pesticides into water bodies negatively impacts aquatic environments. The European Union (EU) aims to make food systems fair, healthy and environmentally friendly through its current Farm to Fork strategy. As part of this strategy, the EU plans to reduce the overall use and risk of chemical pesticides by 50 % by 2030. The attainment of this target may be compromised by the prevalence of legacy pesticides arising from historical applications to land, which can persist in the environment for several decades. The current EU Farm to Fork policy overlooks the potential challenges of legacy pesticides and requirements for their remediation. In this review, the current knowledge regarding pesticide use in Europe, as well as pathways of pesticide movement to waterways, are investigated. The issues of legacy pesticides, including exceedances, are examined, and existing and emerging methods of pesticide remediation, particularly of legacy pesticides, are discussed. The fact that some legacy pesticides can be detected in water samples, more than twenty-five years after they were prohibited, highlights the need for improved EU strategies and policies aimed at targeting legacy pesticides in order to meet future targets.

Temporal evolution of organochlorine and organophosphate pesticide residues in wells in the Akkar Region (Lebanon)

The Akkar plain is the second largest agricultural area in Lebanon. This region produces huge amount of regular crops such as maize, fruits, and vegetables. In order to protect the crops, farmers use large quantities of many pesticides (including authorized and prohibited molecules) without respecting the recommended doses. In this work, we wanted to study the evolution of OCP and OPP residues at 3-year intervals in water wells in the Akkar region. Twenty OCPs and 8 OPPs were monitored in eight wells in different villages in the plain and mountains of Akkar. Solid phase extraction (SPE) method was used for pesticide extraction, followed by gas chromatography-mass spectrometry (GC-MS) analysis. The results revealed an increasing concentration of OCPs and OPPs in groundwater over the last 3 years (between 2017 and 2019-2020). This increase in contamination is due to the uncontrolled and still unregulated (by the authorities) use of pesticides, and also to the introduction of new crops. The concentrations found in groundwater confirm that some banned pesticides are still widely used. The calculation of the theoretical pesticide intake suggests that pesticide concentrations in Akkar represent a greater health risk for the population consuming well water during the rainy season.

National Assessment of Long-Term Groundwater Response to Pesticide Regulation

Quantitative assessments of long-term, national-scale responses of groundwater quality to pesticide applications are essential to evaluate the effectiveness of pesticide regulations. Retardation time in the unsaturated zone (R_u) was estimated for selected herbicides (atrazine, simazine, and bentazon) and degradation products (desethylatrazine (DEA), desisopropylatrazine (DIA), desethyldesisopropylatrazine (DEIA), and BAM) using a multidecadal time series of groundwater solute chemistry (∼30 years) and herbicide sales (∼60 years). The sampling year was converted to recharge year using groundwater age. Then, R_u was estimated using a cross-correlation analysis of the sales and the frequencies of detection and exceedance of the drinking water standard (0.1 μg/L) of each selected compound. The results showed no retardation of the highly polar, thus mobile, parent compounds (i.e., bentazon), while R_u of the moderately polar compounds (i.e., simazine) was about a decade, and their degradation products showed even longer R_u. The temporal trends of the degradation products did not mirror those of the sale data, which were attributed to the various sale periods of the parent compounds, sorption of the parent compounds, and complex degradation pathways. The longer R_u in clayey/organic sediments than in sandy sediments further confirmed the role of soil-specific retardation as an important factor to consider in groundwater protection.

Occurrence and point-of-use treatment of contaminants of emerging concern in groundwater of the Nzoia River basin, Kenya

Groundwater constitutes a major source of fresh water globally. However, it faces serious quality challenges from both conventional pollutants and contaminants of emerging concern (CECs) such as pharmaceutically active compounds (PhACs), personal care products (PCPs) and pesticides. There exists a significant knowledge gap regarding the occurrence of CECs in groundwater, especially in Africa. This study presents unique data on the concentration of fourteen PhACs, five PCPs and nine pesticides in groundwater wells in Nzoia River basin, Kenya. Generally, PCPs were the most dominant class with concentrations up to 10 μg/L (methylparaben). Anti(retro)virals, being important in the treatment of HIV/AIDS, were more prevalent among the PhACs as compared to the developed world, with concentrations up to 700 ng/L (nevirapine). In contrast, pesticides were measured at lower concentrations, the maximum being 42 ng/L (metolachlor). A basic risk assessment shows that - among the detected CECs - carbamazepine may pose medium human health risk and requires further investigation among infants and children. Point-of-use (POU) technologies are being increasingly promoted especially in the developing nations to provide drinking water solutions at the household level, but very little data is available on their performance towards CECs removal. Therefore, besides measuring CECs in groundwater, we investigated ceramic filters and solar disinfection (SODIS) as possible POU treatment options. Both techniques show potential to treat CECs in groundwater, with removal efficiencies higher than 90% obtained for 41 and 22 compounds in ceramic filters and SODIS, respectively. Moreover, for the more recalcitrant compounds (e.g. sulfadoxin), the performance is improved by up to three orders of magnitude when using TiO₂ as a photocatalyst in SODIS.

Occurrence and spatial-temporal distribution of atrazine and its metabolites in the aquatic environment of the Volturno River estuary, southern Italy

The present study assesses the spatial distribution and temporal trends of the water dissolved phase (WDP), suspended particulate matter (SPM) and sediment partitioning of atrazine (ATR) and its metabolites in the Volturno River estuary. The load contribution of ATR and its metabolites in this river to the Central Mediterranean Sea was estimated. Samples were collected in 10 sampling sites during the four seasons. The total concentrations of ATR and DPs detected ranged from 18.1 to 105.5 ng L^-1 in WDP, from 4.5 to 63.2 ng L^-1 in SPM, and from 4.6 to 18.6 ng g^-1 in sediment samples, indicating high levels of these pollutants. Structural equation model and the ratio study indicated that the relationship between sediment and WDP pollutants occurred through the SPM. The pollutants load at the Volturno River in its mouth was evaluated in about 30.4 kg year^-1, showing that this river is an important source of these analytes through discharge into Central Mediterranean Sea. Principal component analysis indicated that ATR and its metabolites pollution moves from Volturno River mouth southward and increased in the rainy season. The desethylatrazine-to-atrazine ratio was higher than 0.5 for all samples analyzed, indicating an historical discharge and a long residence time of ATR in sediment about two decades after its ban, and classifying ATR as a nonpoint source contaminant. This study makes up the first record of ATR and its metabolites in superficial water of Southern Italy and provides helpful data as starting point for future studies.

Pesticides in groundwater at a national scale (France): Impact of regulations, molecular properties, uses, hydrogeology and climatic conditions

Contaminants in groundwater are a major issue worldwide. Temporal trends of such occurrences in French groundwaters were evaluated for several active substances of pesticides belonging to different chemical classes, to identify key factors explaining groundwater contamination. Our study relied on exploitation of a French national database (ADES, created in the mid-1990s and remarkable for the available data, including over 88 million analyses). Temporal changes in the frequency of exceeding a reference value of 0.1 μg/L for several substances were determined at yearly and monthly scales. Such trends were examined by distinguishing different periods according to changes in regulations (new approval, withdrawal, or dose reduction), and were combined with data on effective rainfall as a proxy for groundwater recharge, on aquifer lithology, and on sales of active substances as a proxy for actual applications. A review of monthly data shows that a rapid transfer of pesticides with contrasting physico-chemical properties can occur after application in many aquifers, regardless of their lithology. For substances such as metolachlor, showing a sharp increase in sales, a clear relationship exists between quantities sold and frequency of exceeding the reference value. For other active substances, such as isoproturon or chlortoluron, frequencies of exceedance are governed by both sales and effective rainfall. Finally, the occurrence of active substances in groundwater several years after their withdrawal from the market is explained by at least three major mechanisms: the transfer time from soil into groundwater, processes of remobilization from soil and/or unsaturated zone, and no or low degradation in the saturated zone. While these processes are well documented for atrazine and different types of aquifers, they can be virtually unknown for other active substances.

Remediation of bentazone contaminated water by Trametes versicolor: Characterization, identification of transformation products, and implementation in a trickle-bed reactor under non-sterile conditions

Bentazone, an herbicide widely applied in rice and cereal crops, is widespread in the aquatic environment. This study evaluated the capacity of Trametes versicolor to remove bentazone from water. The fungus was able to completely remove bentazone after three days at Erlenmeyer-scale incubation. Both laccase and cytochrome P450 enzymatic systems were involved in bentazone degradation. A total of 19 transformation products (TPs) were identified to be formed during the process. The reactions involved in their formation included hydroxylations, oxidations, methylations, N-nitrosation, and dimerization. A laccase mediated radical mechanism was proposed for TP formation. In light of the results obtained at the Erlenmeyer scale, a trickle-bed reactor with T. versicolor immobilized on pine wood chips was set up to evaluate its stability during bentazone removal under non-sterile conditions. After 30 days of sequencing batch operation, an average bentazone removal of 48% was obtained, with a considerable contribution of adsorption onto the lignocellulosic support material. Bacterial contamination, which is the bottleneck in the implementation of fungal bioreactors, was successfully addressed by this particular system according to its maintained performance. This research is a pioneering step forward to the implementation of fungal bioremediation on a real scale.

Thirty-year monitoring of s-triazine herbicide contamination in the aquifer north of Vicenza (north-east Italy)

The aquifer north of Vicenza, Italy, is one of the main and most studied drinking water reservoirs within the Veneto region. The area is an intensive cropland, and monitoring of s-triazine herbicides and metabolites has been carried out since the late eighties. This study analysed the trends of atrazine (ATR), terbuthylazine (TBZ), deethyl-atrazine (DEA), and deethyl-terbuthylazine (DET) concentrations from 1987 to 2016 and related the variations of agricultural land use, herbicide load, and pesticide regulations to the residence time of pollutants in the aquifer. In total, 785 water samples collected from 82 selected check wells were analysed with high-resolution gas chromatography combined with mass spectrometry. Non-detects were substituted by one-half the limit of detection. Over the 30 years of monitoring, concentrations of all of the pollutants decreased at all sampling sites. Since the beginning, TBZ and DET residues have been systematically lower than ATR and DEA, respectively, with more than 70% of the data below the limit of detection and never exceeding the European Maximum Acceptable Concentration (MAC) for a single pesticide (0.1 μg/L). The highest concentrations of ATR and DEA showed a spatial shift along the flow direction, suggesting an increase in groundwater residence time from the recharge zone to the accumulation zone of the aquifer. The last residues of ATR were found 27 years after its ban. Although all of the concentrations were lower than those found elsewhere in Europe, the sum of s-triazines overcame the MAC in 20% of the samples. Considering the structural and toxicological similarities of s-triazines, these findings confirm the necessity of better characterisation of the toxicological risk posed by mixtures.

In situ groundwater remediation with bioelectrochemical systems: A critical review and future perspectives

Groundwater contamination is an ever-growing environmental issue that has attracted much and undiminished attention for the past half century. Groundwater contamination may originate from both anthropogenic (e.g., hydrocarbons) and natural compounds (e.g., nitrate and arsenic); to tackle the removal of these contaminants, different technologies have been developed and implemented. Recently, bioelectrochemical systems (BES) have emerged as a potential treatment for groundwater contamination, with reported in situ applications that showed promising results. Nitrate and hydrocarbons (toluene, phenanthrene, benzene, BTEX and light PAHs) have been successfully removed, due to the interaction of microbial metabolism with poised electrodes, in addition to physical migration due to the electric field generated in a BES. The selection of proper BESs relies on several factors and problems, such as the complexity of groundwater and subsoil environment, scale-up issues, and energy requirements that need to be accounted for. Modeling efforts could help predict case scenarios and select a proper design and approach, while BES-based biosensing could help monitoring remediation processes. In this review, we critically analyze in situ BES applications for groundwater remediation, focusing in particular on different proposed setups, and we identify and discuss the existing research gaps in the field.

Transfer and degradation of the common pesticide atrazine through the unsaturated zone of the Chalk aquifer (Northern France)

Groundwater in the Chalk aquifer is an important water resource whose quality has degraded due to fertilizer and pesticide use. Atrazine, classified as a priority substance, has been one of the most applied pesticides and also one of the most frequently detected pesticides in groundwater. The present study investigated the transfer and degradation of atrazine in the unsaturated zone of the Chalk aquifer in Northern France. The study was conducted in an underground quarry (Saint-Martin-le-Noeud), which provides a direct access to the water table and intercepts the unsaturated zone at different depths. The lake and the ceiling percolation of 16 sites throughout the quarry were followed. For 16 sites, the percolating flow rate and lake level were measured and the lake water was sampled for nitrate, atrazine and deethylatrazine (DEA, main degradation product of atrazine) analysis over 2.5 years. High spatial variations in hydrodynamics (percolating flow rate and lake level) and in lake water quality (atrazine between 55±11 and 202±40 ng L^-1 and DEA between 269±53 and 1727±345 ng L^-1) indicate that the properties of the unsaturated zone influence the transfer and the degradation of atrazine. A counterclockwise hysteresis characterizes the relationship between the lake level and atrazine concentration. Temporal variation shows that the atrazine is transferred through the matrix and fractures with a delay caused by the sorption process that differs in atrazine and DEA. The layer of clay-with-flints is shown to favor the degradation of atrazine near the surface. Preferential pathways may be created below clay-with-flints, through which the transfer of atrazine is quicker.

A review of threats to groundwater quality in the anthropocene

Awareness concerning sustainable groundwater consumption under the context of land use and climate change is gaining traction, raising the bar for adequate understanding of the complexities of natural and anthropogenic processes and how they affect groundwater quality. The heterogeneous characteristics of aquifers have hampered comprehensive source, transport and contaminant identification. As questions remain about the behavior and prediction of well-known groundwater contaminants, new concerns around emerging contaminants are on the increase. This review highlights some of the key contaminants that originate from anthropogenic activities, organized based on land use categories namely agricultural, urban and industrial. It further highlights the extensive overlap, in terms of both provenance as well as contaminant type, between the different land use sectors. A selection of case studies from literature that describe the continued concern of established contaminants, as well as new and emerging compounds, are presented to illustrate the many qualitative threats to global groundwater resources. In some cases, the risk of groundwater contamination lacks adequate gravity, while in others the underlying physical and societal processes are not fully understood and activities may commence without adequately considering potential impacts. In the agricultural context, the historic and current application of fertilizers and plant protectants, use of veterinary pharmaceuticals and hormones, strives to safeguard the growing food demands. In the context of a sprawling urban environment, waste, human pharmaceuticals, and urban pesticide outputs are increasing, with adequate runoff and sanitation infrastructure often lagging. Finally, industrial activities are associated with accidental leaks and spills, while the large-scale storage of industrial byproducts has led to legacy contaminants such as those stemming from raw mineral extraction. With this review paper, we aim to underscore the need for transdisciplinary research, along with transboundary communication, using sound science and adaptive policy and management practice in order to procure sustainable groundwater quality.

Atrazine hinders PMA-induced neutrophil extracellular traps in carp via the promotion of apoptosis and inhibition of ROS burst, autophagy and glycolysis

Atrazine (ATR), a selective herbicide, is consistently used worldwide and has been confirmed to be harmful to the health of aquatic organisms. The release of neutrophil extracellular traps (NETs) is one of the newly discovered antimicrobial mechanisms. Although several immune functions have been analyzed under ATR exposure, the effect of ATR on NETs remains mainly unexplored. In the present study, we treated carp neutrophils using 5 μg/ml ATR and 5 μg/ml ATR combined with 100 nM rapamycin to elucidate the underlying mechanisms and to clarify the effect of ATR on phorbol myristate acetate (PMA)-induced NETs. The results of the morphological observation and quantitative analysis of extracellular DNA and myeloperoxidase (MPO) showed that NETs formation were significantly inhibited by ATR exposure. Moreover, we found that in the NETs process, ATR downregulated the expression of the anti-apoptosis gene B-cell lymphoma-2 (Bcl-2), increased the expression of the pro-apoptosis factors Bcl-2-Associated X (BAX), cysteinyl aspartate specific proteinases (Caspase3, 9), and anti-autophagy factor mammalian target of rapamycin (mTOR), decreased the expression of autophagy-related protein light chain 3B (LC3B) and glucose transport proteins (GLUT1, 4), disturbed the activities of phosphofructokinase (PFK), pyruvate kinase (PKM), and hexokinase (HK) and limited reactive oxygen species (ROS) levels, indicating that the reduced NETs release was a consequence of increased apoptosis and diminished ROS burst, autophagy and down-regulated glycolysis under ATR treatment. Meanwhile, rapamycin restored the inhibited autophagy and glycolysis and thus resisted the ATR-suppressed NETs. The present study perfects the mechanism theory of ATR immunotoxicity to fish and has a certain value for human health risk assessment.

Occurrence of greenhouse gases in the aquifers of the Walloon Region (Belgium)

This work aims to (1) identify the most conductive conditions for the generation of greenhouses gases (GHGs) in groundwater (e.g., hydrogeological contexts and geochemical processes) and (2) evaluate the indirect emissions of GHGs from groundwater at a regional scale in Wallonia (Belgium). To this end, nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) concentrations and the stable isotopes of nitrate (NO₃^-) and sulphate were monitored in 12 aquifers of the Walloon Region (Belgium). The concentrations of GHGs range from 0.05μg/L to 1631.2μg/L for N₂O, 0μg/L to 17.1μg/L for CH₄, and 1769 to 100,514ppm for the partial pressure of CO₂ (pCO₂). The highest average concentrations of N₂O and pCO₂ are found in a chalky aquifer. The coupled use of statistical techniques and stable isotopes is a useful approach to identify the geochemical conditions that control the occurrence of GHGs in the aquifers of the Walloon Region. The accumulation of N₂O is most likely due to nitrification (high concentrations of dissolved oxygen and NO₃^- and null concentrations of ammonium) and, to a lesser extent, initial denitrification in a few sampling locations (medium concentrations of dissolved oxygen and NO₃^-). The oxic character found in groundwater is not prone to the accumulation of CH₄ in Walloon aquifers. Nevertheless, groundwater is oversaturated with GHGs with respect to atmospheric equilibrium (especially for N₂O and pCO₂); the fluxes of N₂O (0.32kgN₂O-NHa^-1y^-1) and CO₂ (27kgCO₂Ha^-1y^-1) from groundwater are much lower than the direct emissions of N₂O from agricultural soils and fossil-fuel-related CO₂ emissions. Thus, indirect GHG emissions from the aquifers of the Walloon Region are likely to be a minor contributor to atmospheric GHG emissions, but their quantification would help to better constrain the nitrogen and carbon budgets.

Lignin and ethylcellulose in controlled release formulations to reduce leaching of chloridazon and metribuzin in light-textured soils

In this research, controlled release formulations (CRFs) of the herbicides chloridazon and metribuzin, identified as potential leachers, have been evaluated in soils with different texture. To prepare the CRFs, ethylcellulose (EC) and dibutylsebacate (DBS) have been used as coating agents in lignin-polyethylene glycol based formulations. Mobility experiments have been carried out in two light textured soils (sandy and sandy-loam). Breakthrough curves have shown that the use of CRFs reduces the presence of chloridazon and metribuzin in the leachate compared to technical and commercial products, being the lignin CRF coated with EC and DBS the most efficient to diminish the herbicide leaching. Mass balance study has shown a higher amount of chloridazon and metribuzin recovered in soils when these herbicides were tested as CRFs compared to technical and commercial products. The gradual release of herbicides from the CRFs resulting in a rather available levels of chloridazon and metribuzin in soil for a longer time. A good correlation between percentages of herbicide recovered in leachates and T₅₀ values (time corresponding to 50% release of herbicide in water) was obtained, which allows to select the most appropriate CRF in each agro-environmental practice to reduce the potential pollution of groundwater by chloridazon and metribuzin.

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

We report a data-set of CO₂, CH₄, and N₂O concentrations in the surface waters of the Meuse river network in Belgium, obtained during four surveys covering 50 stations (summer 2013 and late winter 2013, 2014 and 2015), from yearly cycles in four rivers of variable size and catchment land cover, and from 111 groundwater samples. Surface waters of the Meuse river network were over-saturated in CO₂, CH₄, N₂O with respect to atmospheric equilibrium, acting as sources of these greenhouse gases to the atmosphere, although the dissolved gases also showed marked seasonal and spatial variations. Seasonal variations were related to changes in freshwater discharge following the hydrological cycle, with highest concentrations of CO₂, CH₄, N₂O during low water owing to a longer water residence time and lower currents (i.e. lower gas transfer velocities), both contributing to the accumulation of gases in the water column, combined with higher temperatures favourable to microbial processes. Inter-annual differences of discharge also led to differences in CH₄ and N₂O that were higher in years with prolonged low water periods. Spatial variations were mostly due to differences in land cover over the catchments, with systems dominated by agriculture (croplands and pastures) having higher CO₂, CH₄, N₂O levels than forested systems. This seemed to be related to higher levels of dissolved and particulate organic matter, as well as dissolved inorganic nitrogen in agriculture dominated systems compared to forested ones. Groundwater had very low CH₄ concentrations in the shallow and unconfined aquifers (mostly fractured limestones) of the Meuse basin, hence, should not contribute significantly to the high CH₄ levels in surface riverine waters. Owing to high dissolved concentrations, groundwater could potentially transfer important quantities of CO₂ and N₂O to surface waters of the Meuse basin, although this hypothesis remains to be tested.

Evaluation of the Interaction between Pesticides and a Cell Membrane Model by Surface Plasmon Resonance Spectroscopy Analysis

A surface plasmon resonance (SPR) spectroscopy analysis was used for the characterization of the interaction between pesticides and a cell membrane model. A liposome was immobilized onto the surface of the SPR sensor chip (L1), and the lipid bilayer membrane formed on the sensor chip was regarded as the cell membrane model. The solution containing a pesticide was flowed onto the sensor chip, and an SPR sensorgram, which reflected the interaction between the pesticide and the lipid bilayer membrane, was obtained. As the results, the pattern and strength of the interaction of the pesticides with the cell membrane model were visualized and quantified. Triflumizole, hexythiazox, and pentachlorophenol showed a strong interaction with the lipid bilayer. It is well-known that triflumizole and pentachlorophenol interact with the membrane and reveal toxicities for cell membranes. In addition, there was a tendency for higher residual ratios to be observed when the no observable adverse effect level (NOAEL) values for chronic toxicity (1 year toxicity study in dogs) were lower. We suggest that a novel parameter for the evaluation or presumption of the behaviors and chronic toxicities of pesticides is obtained by the presented method.