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

Caging Gammarus roeseli to track pesticide contamination: How agricultural practices shape water quality in small waterbodies?

Contaminant monitoring in agroecosystems is increasingly revealing overlooked molecules, particularly within complex pesticide mixtures. This study assessed the effectiveness of chemical and ecotoxicological methods for evaluating contamination and biological responses in Gammarus roeseli exposed to pesticides and transformation products (TPs) in lentic small water bodies (LSWBs) near agricultural zones. We examined 7 LSWBs, finding variable contamination levels shaped by watershed composition differences. Analysis of 136 compounds identified key TPs, including chlorothalonil R471811, metazachlor ESA, and OXA, which collectively represented 86.2 % of the total quantified contaminants. These results underscore the persistence of both current and banned pesticides in the ponds studied. While G. roeseli showed favorable survival rates, significant reductions in locomotion and ventilation were observed at heavily contaminated sites, with biochemical analyses suggesting neurotoxic effects and activation of detoxification mechanisms in response to contaminants. Multivariate analyses revealed site-specific variations, highlighting the complex interactions between contamination levels and environmental conditions. Biomarker responses in gammarids served as sensitive indicators of residual toxicity in LSWBs, with frequent associations with historical contamination or current pesticide applications. This in situ caging approach across a contamination gradient demonstrates strong potential for biomonitoring and ecotoxicological assessments in agroecosystems. Extending exposure durations and including more heavily contaminated ponds could further enhance risk evaluation, thereby improving biomonitoring accuracy in headwater aquatic ecosystems. By integrating site-specific environmental conditions, contamination profiles, and biological responses, this study provides valuable insights into the influence of agricultural practices on LSWBs contamination and underscores the critical need to incorporate TPs into future risk assessment frameworks.

Multiyear and seasonal wide-scale indicators for French surface waters contamination by WFD substances

This study offers an unprecedented valuation of the French surface waters WFD chemical monitoring dataset, covering 101 substances (metals, industrial and persistent organic pollutants (POPs), plant protection product (PPP) and biocides active substances, combustion residues) measured monthly on 4000 sites of the 6 main continental river basins, during 12 years (2009-2020). The concentration data were first made comparable through an original process removing the bias induced by the space-and-time heterogeneity of the monitoring labs performance, to gather a reference workable set of monthly contamination indicators. These were then used to display the substances' seasonal and interannual timeseries, revealing, e.g. the succession of PPP active substances contamination peaking periods in the 6 basins, or the long-term trends of the concentrations of the various chemicals, sometimes evidencing insufficiencies in the monitoring performance. These environmental observations were put in regard of the knowledge of the substances ban, restriction or reduction measures, to assess how streams' chemical quality responds to them. Additionally, the observed contamination features and their variations over the years are discussed in terms of changes in their usages, product substitution, emission sources, and linked to environmental processes like runoff, river dilution and physicochemical conditions. Some original findings and interpretation are provided on glyphosate and AMPA wide-scale data inter-relation, and some light is cast on the efficacy of the recent national policies restricting pesticides use in populated areas. For PPPs, the developed water contamination indicators were compared to tonnage data. We assessed their degree of linear relationship, which we propose to quantitatively express through a substance specific basin-to-river contamination coefficient. The interannual variations of this coefficient appear to be related to the changes in the water contamination seasonal patterns. We were also able to describe and validate the dependency of this coefficient on the molecular properties of the substances, conferring some capabilities for predicting the relative environmental risk induced by non-yet monitored compounds. We finally discuss the relevance of the developed indicators to complement the national chemical pollutants management system currently in place.

Pesticide fate under varying cropping systems and soil depths: A study using leaching experiments and inverse modelling

Current pesticide leaching risk assessments overlook critical site-specific factors such as soil depth and agricultural practices. Relying on transport parameters from databases or manufacturer studies, often based on limited soil types, can lead to inaccurate contamination risk estimates and ineffective protection of groundwater resources. In this study, the fate of eight pesticides of concern for groundwater was investigated under three cropping systems and three soil depths. Leaching experiments were carried out in undisturbed columns from a loamy agricultural soil and mass balances were realized. Inverse dual-porosity modelling using Hydrus 1-D was then performed to adjust mobility parameters. The results reveal that different soil properties and structure between soil depths have a more substantial impact on pesticide leaching behaviour than the cropping systems. Significant differences in pesticide transport and retention are observed between soil horizons, illustrating the inadequacy of using surface parameters for the entire soil profile, which can lead to underestimation of groundwater contamination. Our analysis indicates that root architecture, soil properties and surface tillage can affect pesticide leaching dynamics. While short-term differences between cropping systems were limited, these factors could be important for long-term effects. The experimental transport parameters showed discrepancies with established databases, where higher adsorption and degradation could underestimate pesticide leaching and metabolites production. This study highlights the need to adapt transport parameter values for all pesticides of concern to site-specific conditions. In addition, accurate risk assessment requires advanced modelling techniques that take into account soil depth variability and local conditions to improve water protection decision-making. Future research should focus on long-term monitoring of the effects of sustainable agricultural practices on pesticide behaviour over several seasons and for a range of soil types. Special emphasis should be placed on the role of metabolites in environmental contamination.

A land use regression model to explain the spatial variation of nitrate concentration - A regional scale case study in the north-west of Ireland

Regional-scale groundwater contamination estimation is crucial for sustainable water management. The primary obstacles in evaluating groundwater include limited data availability, small sample sizes, and difficulties in linking concentration levels to land use patterns. Linear regression identifies the relationship between measured concentrations and both natural and human-influenced factors. However, the primary difficulty with this method lies in choosing a group of regressors that meet all necessary criteria for the model when multiple potential regressors exist. This study introduces a buffer-based land-use linear regression method to develop a catchment-scale model for predicting nitrate concentrations in groundwater. The model successfully captures 85 % of the spatial variability in nitrate across the study area, as indicated by the validation results from 32 training sites. The model's prediction capability and ability to capture the spatial variability of nitrate concentration were found to be good in the model development (R2 = 0.89) and validation (R2 = 0.80) steps. The model performed well in the accuracy assessment and error estimation processes (RMSE = 0.025 and MAE = 0.020). In future, this LUR model can be reparameterised with the latest available time series datasets to capture climate change scenarios. While this study focused on a small sub-catchment of the Bonet River, the methodology has the potential to be applied in a border study area. Future studies with a more robust methodology and more accurate predictor variables to explain the influence of the contamination sources, transport and attenuation processes can improve the buffer-based LUR technique for better model adaptation and applicability to other study areas.

Pesticide transformation products: a potential new source of interest for drinking water

Pesticide transformation products (TPs) are frequently quantified in aquatic systems, including surface and groundwater. They often present higher polarity than parent compounds, are less volatile and less biodegradable and are therefore more mobile and persistent. These properties make them compounds of main interest in water resources and drinking water. With more than 600 samples collected over two years and nearly 100,000 results available, this study was carried out to evaluate the occurrence of 157 pesticide TPs and certain active substances in raw and drinking water in France. Our study made it possible to assess the potential exposure of the population to pesticides and their metabolites through drinking water consumption and finally to put forward new TPs of interest for the monitoring of drinking water. Among TPs, chlorothalonil R471811 and metolachlor ESA were the most frequently quantified compounds, with quantification in more than 50% of raw and drinking water. TPs dimethachlor CGA369873, chlorothalonil R471811 and R417888, terbuthylazine LM2 and LM6, desphenyl chloridazon (DPC) and methyldesphenyl chloridazon (MeDPC) were monitored for the first time in drinking water in France. Concentrations exceeding the regulatory quality standard of 0.1 µg.L-1 were observed in more than 30% of drinking water samples for chlorothalonil R471811, and a maximum concentration was measured at 9.8 µg.L-1 for DPC in drinking water. The quantification frequencies were relatively similar in raw water and tap water, which appears to indicate poor efficiency of the majority of the currently used drinking water treatment plants. This research confirmed the benefit of focusing on TPs and parent compounds, and also to continue monitoring TPs that originate from compounds already withdrawn from the market for several years that appear to be highly persistent.

Mixed pesticide sources identified by using wastewater tracers in rivers of South African agricultural catchments

The agriculturally dominated region of the Western Cape, South Africa is vulnerable to pesticide pollution. A 2017-2019 pesticide monitoring campaign in the agricultural catchments of Grabouw, Piketberg and Hex River Valley identified year-round detections despite few agricultural applications, making pesticide pollution sources unclear. To better trace pesticide sources in these catchments, our study measured 19 pharmaceutical compounds and one industrial chemical as an indicator for wastewater treatment plant (WWTP) effluent - in addition to 44 pesticides. Passive samplers were deployed monthly in rivers from February 2022 to March 2023 in Grabouw, Hex River Valley, and Piketberg, and one control sample in Jonkershoek Nature Reserve (May 2022). Some pesticides without year-round agricultural applications had high detection frequencies and Groundwater Ubiquity Scores, suggesting leaching of pesticides into groundwater connected to rivers. Cumulative pharmaceutical concentrations correlated strongly with cumulative pesticide concentrations only in the Piketberg catchment, suggesting WWTPs as a possible pesticide source. Herbicide detections in Jonkershoek Nature Reserve (e.g., atrazine) suggest contamination from atmospheric transport, invasive plant control or trail maintenance. The Environmental Quality Standard (EQS) for imidacloprid, chlorpyrifos, terbuthylazine and spiroxamine was exceeded at least once during the 1-year monitoring period, mostly related to expected agricultural applications, indicating high persistence and continuous exposure risk to aquatic organisms. Our study is the first to describe the relevance of WWTPs as a pesticide source in South African agricultural catchments. Drivers of pesticide contamination were area dependent, emphasizing the need for catchment-specific understanding. Future research requires sampling of groundwater and wastewater influent and effluent to improve our understanding of pesticide transport pathways and sources.

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.

Spatiotemporal assessment of groundwater quality and quantity using geostatistical and ensemble artificial intelligence tools

The study investigated the spatiotemporal relationship between surface hydrological variables and groundwater quality/quantity using geostatistical and AI tools. AI models were developed to estimate groundwater quality from ground-based measurements and remote sensing images, reducing reliance on laboratory testing. Different Kriging techniques were employed to map ground-based measurements and fill data gaps. The methodology was applied to analyze the Maragheh aquifer in northwest Iran, revealing declining groundwater quality due to industrial. discharges and over-extraction. Spatiotemporal analysis indicated a relationship between groundwater depth/quality, precipitation, and temperature. The Root Mean Square Scaled Error (RMSSE) values for all variables ranged from 0.8508 to 1.1688, indicating acceptable performance of the semivariogram models in predicting the variables. Three AI models, namely Feed-Forward Neural Networks (FFNNs), Support Vector Regression (SVR), and Adaptive Neural Fuzzy Inference System (ANFIS), predicted groundwater quality for wet (June) and dry (October) months using input variables such as groundwater depth, temperature, precipitation, Normalized Difference Vegetation Index (NDVI), and Digital Elevation Model (DEM), with Groundwater Quality Index (GWQI) as the target variable. Ensemble methods were employed to combine the outputs of these models, enhancing performance. Results showed strong predictive capabilities, with coefficient of determination values of 0.88 and 0.84 for wet and dry seasons. Ensemble models improved performance by up to 6% and 12% for wet and dry seasons, respectively, potentially advancing groundwater quality modeling in the future.

Occurrence of contaminants of emerging concern and pesticides and relative risk assessment in Tunisian groundwater

Groundwater is an important source for drinking water supply, agricultural irrigation and industrial uses in the Middle East and North Africa region. Due to the growing need for groundwater use, groundwater quality studies on the presence of contaminants of emerging concern (CECs) and pesticides have gained attention. The Wadi El Bey is one of the most polluted areas in Tunisia. However, very limited data on CECs infiltration into aquifers has been described, in comparison to industrialized countries where groundwater contamination has been comprehensively addressed. To gain early insight into potential contamination, groundwater wells in northeast Tunisia, an area with high population density and intensive agricultural activity were sampled during two seasons and were analyzed with two high resolution mass spectrometry approaches: target and suspect screening. The latter was used for screening banned pesticides. A selection of 116 CECs of which 19 are transformation products (TPs) and 20 pesticides previously prioritized by suspect screening were screened in the groundwater samples. The results showed the presence of 69 CECs and 1 TP and 20 pesticides at concentrations per well, ranging between 43 and 7384 ng L-1 and 7.3 and 80 ng L-1, respectively. CECs concentrations in Tunisian groundwater do not differ from those in industrialized countries. WWTPs were considered the main source of pollution, where the main classes detected were analgesics, antihypertensives and artificial sweeteners and especially caffeine, salicylic acid and ibuprofen were found to be ubiquitous. Regarding pesticides, triazines herbicides and carbamates insecticides pose the highest concern due to their ubiquitous presence, high leachability potential for most of them and high toxicity. The environmental risk assessment (ERA) highlighted the high risk that caffeine, ibuprofen, and propoxur may pose to the environment, and consequently, to non-target organisms. This study provides occurrence and ERA analysis of CECs and pesticides in Tunisian groundwater.

Pesticides in aquifers from Latin America and the Caribbean

In Latin America and the Caribbean (LAC), agriculture is the primary consumer of water and the biggest user of pesticides worldwide. Given that groundwater is a crucial resource in this region, a systematic review was conducted to evaluate the current state of knowledge on the presence of pesticides in aquifers. The review examined 48 research papers published between 1998 and 2020, and found that only six countries in the region have information on pesticides in groundwater. A total of 70 agrochemicals were detected, encompassing legacy pesticides, herbicides, insecticides, fungicides, and metabolites. Herbicides, including the widely used atrazine and glyphosate, were the most commonly detected current-use pesticides. These herbicides are being gradually banned or restricted due to their potentially harmful effects on the environment. Factors that contribute to the presence of these contaminants in aquifers include preferential flows, seasonal variations in rainfall, aquifer type, unsaturated zone thickness, and land use and management practices. Researchers noted that analysis of these contaminants is often beyond the economic or methodological scope, and analytical capacity in the region is generally limited. Based on the findings of this review, there is a clear need for groundwater pesticide monitoring in the region to reduce health risks to humans and ecosystems.

Socio-hydrogeological survey and assessment of organic pollutants to highlight and trace back pollution fluxes threatening a coastal groundwater-dependent ecosystem

Despite being a vector of pollution towards connected ecosystems, groundwater is often underestimated or not taken into account in management frameworks. To fill this gap, we propose to add socio-economic data to hydrogeological investigations to identify past and present pollution sources linked to human activities at watershed scale in order to forecast threats towards groundwater-dependent ecosystems (GDEs). The aim of this paper is to demonstrate, by a cross-disciplinary approach, the added value of socio-hydrogeological investigations to tackle anthropogenic pollution fluxes towards a GDE and to contribute to more sustainable management of groundwater resources. A survey combining chemical compounds analysis, data compilation, land use analysis and field investigations with a questionnaire was carried out on the Biguglia lagoon plain (France). Results show a pollution with a two-fold source, both agricultural and domestic, in all water bodies of the plain. The pesticide analysis reveals the presence of 10 molecules, including domestic compounds, with concentrations exceeding European groundwater quality standards for individual pesticides, as well as pesticides already banned for twenty years. On the basis of both the field survey and the questionnaire, agricultural pollution has been identified as very local highlighting the storage capacity of the aquifer, whereas domestic pollution is diffuse over the plain and attributed to sewage network effluents and septic tanks. Domestic compounds present shorter residence time within the aquifer highlighting continuous inputs, related to consumption habits of the population. Under the Water Framework Directive (WFD), member states are required to preserve the good ecological status, quality and quantity of water bodies. However, for GDEs it is difficult to achieve the 'good status' required without considering the groundwater's pollutant storage capacity and pollution legacy. To help resolve this issue, socio-hydrogeology has proved to be an efficient tool as well as for implementing effective protection measures for Mediterranean GDEs.

An indicator to assess risks on water and air of pesticide spraying in crop fields

Stakeholders involved in actions to reduce the use and the impacts on the environment or human health of pesticides need operational tools to assess crop protection strategies in regard to these impacts. I-Phy3 brings together all improvements introduced since the first version of the indicator to better meet user's needs and requirements of integrating processes. I-Phy3 was deeply modified to ensure its predictive quality. I-Phy 3 is structured in three levels of aggregation in form of hierarchical fuzzy decision trees designed with the CONTRA method. At the 1st level, five basic subindicators assess the risk of contamination (RC) for the different transfer pathways involved in surface water, ground water and atmosphere contamination: leaching, runoff, drainage, drift, volatilization. At the 2nd level, RC subindicators are aggregated with a toxicity variable (human or aquatic) in a risk indicator. At the 3rd level, the global indicator I-Phy3 results from the aggregation of three risk indicators for groundwater, surface waters and air. I-Phy3 yielded better validation results than its previous versions. This effort to assess the predictive quality of the indicator should be pursued and completed by a feasibility and utility test by end-users. A subindicator on risk of soil contamination is a gap which remains to fill.

Reactive transport of micropollutants in laboratory aquifers undergoing transient exposure periods

Groundwater quality is of increasing concern due to the ubiquitous occurrence of micropollutant mixtures. Stream-groundwater interactions near agricultural and urban areas represent an important entry pathway of micropollutants into shallow aquifers. Here, we evaluated the biotransformation of a micropollutant mixture (i.e., caffeine, metformin, atrazine, terbutryn, S-metolachlor and metalaxyl) during lateral stream water flow to adjacent groundwater. We used an integrative approach combining concentrations and transformation products (TPs) of the micropollutants, compound-specific isotope analysis (δ¹³C and δ¹⁵N), sequencing of 16S rRNA gene amplicons and reactive transport modeling. Duplicate laboratory aquifers (160 cm × 80 cm × 7 cm) were fed with stream water and subjected over 140 d to three successive periods of micropollutant exposures as pulse-like (6000 μg L^-1) and constant (600 μg L^-1) injections under steady-state conditions. Atrazine, terbutryn, S-metolachlor and metalaxyl persisted in both aquifers during all periods (<10 % attenuation). Metformin attenuation (up to 14 %) was only observed from 90 d onwards, suggesting enhanced degradation over time. In contrast, caffeine dissipated during all injection periods (>90 %), agreeing with fast degradation rates (t_1/2 < 3 d) in parallel microcosm experiments and detection of TPs (theobromine and xanthine). Significant stable carbon isotope fractionation (Δδ¹³C ≥ 6.6 ‰) was observed for caffeine in both aquifers, whereas no enrichment in ¹⁵N occurred. A concentration dependence of caffeine biotransformation in the aquifers was further suggested by model simulations following Michaelis-Menten kinetics. Changes in bacterial community composition reflected long-term bacterial adaptation to micropollutant exposures. Altogether, the use of an integrative approach can help to understand the interplay of subsurface hydrochemistry, bacterial adaptations and micropollutants biotransformation during stream-groundwater interactions.

Atrazine pollution in groundwater and raw bovine milk: Water quality, bioaccumulation and human risk assessment

Atrazine herbicide can bioaccumulate over time and thus affect humans for generations to come. However, scarce studies have evaluated its bioaccumulation potential in bovine milk, a nutritional staple for children and the elderly both domestically and internationally. This study aimed to determine its concentration in groundwater and bovine milk, as well as the risks it is likely to pose for human health. Eighteen dairy farms in the Pampean plain of Argentina were analyzed. A strong correlation was found between the chemical composition and the geomorphological characteristics of the plain. In addition, increased salinity was observed in the groundwater at greater distances from the aquifer's recharge area. Atrazine was quantified in 50 % of the groundwater samples (at values ranging from 0.07 to 1.40 μg/L), and in 89 % of the bovine milk samples (from 2.51 to 20.97 μg/L). Moreover, atrazine levels in 44.4 % of the groundwater samples and 11.1 % of the bovine milk samples (n = 18) exceeded the limits internationally established as safe for human consumption. The hazard quotient (HQ) values of the compound were negligible for children and adults, both in groundwater (child = 9.7E-4, adult = 4.5E-4) and in milk (child = 1.0E-2, adult = 1.6E-3). The estimated cancer risk (CR) values need further evaluation (child = 7.8E-6, adult = 3.6E-6 in groundwater; child = 6.6E-5, adult = 1.3E-5 in milk). In both types of samples, the HQ and CR of residual atrazine were higher for children than for adults. Nevertheless, bioaccumulation factors suggest that dairy cows have a moderate capacity to incorporate atrazine from abiotic matrices. This is the first report on residual atrazine in bovine milk in Argentina. The results presented here indicate that the status of atrazine contamination in the area should continue to be monitored in order to assess its long-term impact on public health.

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.

Global groundwater vulnerability for Pharmaceutical and Personal care products (PPCPs): The scenario of second decade of 21st century

The global production of PPCPs have increased by multiple folds promoting excessive exposure of its metabolites to humans via different aquatic systems. The higher residence time of toxic precursors of these metabolites pose direct human health risk. Among the different aquatic systems, the contamination of groundwater by PPCPs is the most concerning threat. This threat is especially critical considering the lesser oxidizing potential of the groundwater as compared to freshwater/river water. A major challenge also arises due to excessive dependency of the world's population on groundwater, which is exponentially increasing with time. This makes the identification and characterization of spatial contamination hotspots highly probabilistic as compared to other freshwater systems. The situation is more vulnerable in developing countries where there is a reported inadequacy of wastewater treatment facilities, thereby forcing the groundwater to behave as the only available sequestrating sink for all these contaminants. With increased consumption of antibiotics and other pharmaceuticals compounds, these wastes have proven capability in terms of enhancing the resistance among the biotic community of the soil systems, which ultimately can become catastrophic and carcinogenic in near future. Recent studies are supporting the aforementioned concern where compounds like diclofenac (analgesic) have attained a concentration of 1.3 mgL^-1 in the aquifer systems of Delhi, India. The situation is far worse for developed nations where prolonged and indiscriminate usage of antidepressants and antibiotics have life threating consequences. It has been confirmed that certain compounds like ofloxacin (antibiotics) and bis-(2-ethylhexyl)phthalate are present in some of the most sensitive wells/springs of the United States and Mexico. The current trend of the situation has been demonstrated by integrating a comparative approach of the published literatures in last three years. This review provides first-hand information report for formulating a directive policy framework for tackling PPCPs issues in the groundwater system.

Pesticides and their metabolites in European groundwater: Comparing regulations and approaches to monitoring in France, Denmark, England and Switzerland

Pesticides, i.e. plant protection products (PPP), biocides and their metabolites, pose a serious threat to groundwater quality and groundwater dependent ecosystems. Across large parts of Europe these compounds are monitored in groundwater to ensure compliance with the European Water Framework Directive (WFD), the Groundwater Directive (GWD) and Drinking water Directive (DWD). European regulation concerning the placing of PPP on the market includes groundwater monitoring as a higher tier of the regulatory procedure. Nevertheless, the lists of compounds to be monitored vary from one directive to another and between countries. The implementation of monitoring strategies for these directives and other national drivers, differs across Europe. This is illustrated using case studies from France, Denmark (EU member states), England (part of the EU up to January 2020) and Switzerland (associated country). The collection of data (e.g. monitoring design and analytical approaches) and dissemination at national and European level and the scale of data reporting to EU is country-specific. Data generated by the implementation of WFD and DWD can be used for retrospective purposes in the context of PPP registration whereas the post-registration monitoring data generated by the product applicants are generally only directly available to the regulators. This lack of consistency and strategic coordination between thematic regulations is partly compensated by national regulations. This paper illustrates the benefits of a common framework for regulation in Europe but shows that divergent national approaches to monitoring and reporting on pesticides in groundwater makes the task of assessment across Europe challenging.

Restoring groundwater quality at the drinking water catchment scale: A multidisciplinary and participatory approach

Preserving or restoring the quality of groundwater resources with regard to nitrate is a major challenge. To date, useful and easily applicable tools to identify the best measures to implement at local scale are lacking. An innovative methodology is proposed to identify cost-effective restoration measures at the drinking water catchment scale. The methodology is based on the articulation of two tools: a model simulating nitrate groundwater contamination time series and an economic evaluation, within a participatory approach. It was applied to a representative drinking water catchment in Northwest France that has been affected by nitrate contamination for decades. Five scenarios of measures (changes in fertilization and intercropping practices, or in cropping patterns) were co-constructed with stakeholders, evaluated in terms of cost and impact on groundwater nitrate concentration, and discussed with stakeholders. Overall, two scenarios stand out. Introducing hemp in crop rotations is the only scenario generating an economic benefit, but for a very low impact on nitrate concentration (decrease of 4 mg/l by 2050 for 10% of hemp in crop rotations). Introducing alfalfa in crop rotations is the most effective measure to decrease nitrate concentration (decrease of 23 mg/l by 2050 for 20% of alfalfa in crop rotations), and for a moderate cost compared to the other scenarios (25-51 €/ha/year). Results show that substantial changes in cropping patterns - more important than those imagined initially by stakeholders (e.g. converting 40% of cropland to alfalfa) are needed to restore groundwater quality targets in the medium-long term. Measures deemed promising and achievable by the stakeholders proved to be insufficiently effective. The approach developed has been shown to provide valued and trusted information to stakeholders and to objectify debates. Stakeholders have shown interest in the evaluation of costs and further socio-economic information, in addition to the evaluation of the effectiveness of measures on groundwater quality, validating the multidisciplinary dimension of the approach. The approach has the advantage of being easy to implement, and is therefore applicable to other study sites where needed.

Managing groundwater resources using a national reference database: the French ADES concept

Abstract

Groundwater is an integral part of the water cycle and an essential human resource. Humans must protect this ever-changing heritage and preserve it in a sustainable way by understanding the physical and chemical properties of aquifers and monitoring their quantity and quality. Numerous studies have collected immense volumes of data that are difficult to access and not always comparable or of adequate quality. A pioneering national-scale database, ADES, was created in 1999 to store and make available quality data on French groundwater. This tool is freely accessible for/to water managers, scientists and the public. The data management system used in the database satisfies two important objectives: it is interoperable and based on a recognised groundwater reference system and provides high quality data to a large public. Data from different producers require normalisation and standardisation of system requirements to allow data integration and exchange. The database designers set up shared data models, and based the system on communal repositories of water points and hydrogeological entities. Nearly 102 million groundwater quality records and over 17 million water-level records are currently available, describing almost 61,800 stations. ADES makes it possible to visualise in “real-time" water level data for approximately 1500 stations equipped with GPRS (General Packet Radio Service) technology. ADES also provides, on a public website and via web services, public quantitative and qualitative data. ADES is an essential tool for developing groundwater services based on the FAIR guiding principles: Findable, Accessible, Interoperable and Reusable data (Wilkinson et al. in SD 3:160018, 2016)

Article highlights

Monoclonal Antibody-Based Immunosensor for the Electrochemical Detection of Chlortoluron Herbicide in Groundwaters

Chlortoluron (3-(3-chloro-p-tolyl)-1,1-dimethyl urea) is an herbicide widely used in substitution to isoproturon to control grass weed in wheat and barley crops. Chlortoluron has been detected in groundwaters for more than 20 years; and dramatic increases in concentrations are observed after intense rain outbreaks. In this context; we developed an immunosensor for the determination of chlortoluron based on competitive binding of specific monoclonal antibodies on chlortoluron and immobilized biotinylated chlortoluron; followed by electrochemical detection on screen-printed carbon electrodes. The optimized immunosensor exhibited a logarithmic response in the range 0.01-10 µg·L-1; with a calculated detection limit (LOD) of 22.4 ng·L-1; which is below the maximum levels allowed by the legislation (0.1 µg·L-1). The immunosensor was used for the determination of chlortoluron in natural groundwaters, showing the absence of matrix effects.