Direct Phototransformation of Sulfamethoxazole Characterized by Four-Dimensional Element Compound Specific Isotope Analysis.

The antibiotic sulfamethoxazole (SMX) undergoes direct phototransformation by sunlight, constituting a notable dissipation process in the environment. SMX exists in both neutral and anionic forms, depending on the pH conditions. To discern the direct photodegradation of SMX at various pH levels and differentiate it from other transformation processes, we conducted phototransformation of SMX under simulated sunlight at pH 7 and 3, employing both transformation product (TP) and compound-specific stable isotope analyses. At pH 7, the primary TPs were sulfanilic acid and 3A5MI, followed by sulfanilamide and (5-methylisoxazol-3-yl)-sulfamate, whereas at pH 3, a photoisomer was the dominant product, followed by sulfanilic acid and 3A5MI. Isotope fractionation patterns revealed normal 13C, 34S, and inverse 15N isotope fractionation, which exhibited significant differences between pH 7 and 3. This indicates a pH-dependent transformation process in SMX direct phototransformation. The hydrogen isotopic composition of SMX remained stable during direct phototransformation at both pH levels. Moreover, there was no variation observed in 33S between the two pH levels, indicating that the 33S mass-independent process remains unaffected by changes in pH. The analysis of main TPs and single-element isotopic fractionation suggests varying combinations of bond cleavages at different pH values, resulting in distinct patterns of isotopic fractionation. Conversely, dual-element isotope values at different pH levels did not significantly differ, indicating cleavage of several bonds in parallel. Hence, prudent interpretation of dual-element isotope analysis in these systems is warranted. These findings highlight the potential of multielement compound-specific isotope analysis in characterizing pH-dependent direct phototransformation of SMX, thereby facilitating the evaluation of its natural attenuation through sunlight photolysis in the environment.

Emissions of the Urban Biocide Terbutryn from Facades: The Contribution of Transformation Products.

Biocides are added to facade paints and renders to prevent algal and fungal growth. The emissions of biocides and their transformation products from building facades during wind-driven rain can contaminate surface waters, soil, and groundwater. Although the emissions of biocide transformation products may be higher than those of the parent biocide, knowledge of the emissions of transformation products over time is scarce. Combining field- and lab-scale experiments, we showed that solar irradiation on facades controls the formation of transformation products and can be used with runoff volume to estimate the long-term emissions of terbutryn transformation products from facades. The slow (t1/2 > 90 d) photodegradation of terbutryn in paint under environmental conditions was associated with insignificant carbon isotope fractionation (Δδ13C < 2 ‰) and caused 20% higher emission of terbutryn-sulfoxide than terbutryn in leachates from facades. This indicated continuous terbutryn diffusion toward the paint surface, which favored terbutryn photodegradation and the concomitant formation of transformation products over time. The emissions of terbutryn transformation products (77 mg m-2) in facade leachates, modeled based on irradiation and facade runoff, were predicted to exceed those of terbutryn (42 mg m-2) by nearly 2-fold after eight years. Overall, this study provides a framework to estimate and account for the long-term emissions of biocide transformation products from building facades to improve the assessment of environmental risks.

Phase Transfer and Biodegradation of Pesticides in Water-Sediment Systems Explored by Compound-Specific Isotope Analysis and Conceptual Modeling.

Current approaches are often limited to evaluating the contribution of pesticide dissipation processes in water-sediment systems as both degradation and phase transfer, that is, sorption-desorption, contribute to the apparent decrease of pesticide concentration. Here, the dissipation of widely used herbicides acetochlor and S-metolachlor was examined in laboratory by water-sediment microcosm experiments under oxic and anoxic conditions. Compound-specific isotope analysis (CSIA) emphasized insignificant carbon isotope fractionation in the sediment, indicating prevailing pesticide degradation in the water phase. Conceptual modeling accounting for phase transfer and biodegradation indicated that biodegradation may be underestimated when phase transfer is not included. Phase transfer does not affect carbon isotope fractionation for a wide spectrum of molecules and environmental conditions, underscoring the potential of pesticide CSIA as a robust approach to evaluate degradation in water-sediment systems. CSIA coupled with the identification of transformation products by high-resolution tandem mass spectrometry suggests the degradation of acetochlor and S-metolachlor to occur via nucleophilic substitution and the predominance of oxalinic acids as transformation products under both anoxic and oxic conditions. Altogether, combining the pesticide CSIA, the identification of transformation products, and the use of conceptual phase-transfer models improves the interpretation of pesticide dissipation in water-sediment systems.

Copper Content and Export in European Vineyard Soils Influenced by Climate and Soil Properties.

Copper-based fungicides (Cuf) are used in European (EU) vineyards to prevent fungal diseases. Soil physicochemical properties locally govern the variation of the total copper content (Cut) in EU vineyards. However, variables controlling Cut distribution at a larger scale are poorly known. Here, machine learning techniques were used to identify governing variables and to predict the Cut distribution in EU vineyards. Precipitation, aridity and soil organic carbon are key variables explaining together 45% of Cut distribution across EU vineyards. This underlines the effect of both climate and soil properties on Cut distribution. The average net export of Cu at the EU scale is 0.29 kg Cu ha-1, which is 2 orders of magnitude less than the net accumulation of Cu (24.8 kg Cu ha-1). Four scenarios of Cuf application were compared. The current EU regulation with a maximum of 4 kg Cu ha-1 year-1 may increase by 2% of the EU vineyard area, exceeding the predicted no-effect concentration (PNEC) in soil in the next 100 years. Overall, our results highlight the vineyard areas requiring specific remediation measures and strategies of Cuf use to manage a trade-off between pest control and soil and water contamination.

Dissipation of S-metolachlor and butachlor in agricultural soils and responses of bacterial communities: Insights from compound-specific isotope and biomolecular analyses.

The soil dissipation of the widely used herbicides S-metolachlor (SM) and butachlor (BUT) was evaluated in laboratory microcosms at two environmentally relevant doses (15 and 150 µg/g) and for two agricultural soils (crop and paddy). Over 80% of SM and BUT were dissipated within 60 and 30 days, respectively, except in experiments with crop soil at 150 µg/g. Based on compound-specific isotope analysis (CSIA) and observed dissipation, biodegradation was the main process responsible for the observed decrease of SM and BUT in the paddy soil. For SM, biodegradation dominated over other dissipation processes, with changes of carbon isotope ratios (Δδ13C) of up to 6.5‰ after 60 days, and concomitant production of ethane sulfonic acid (ESA) and oxanilic acid (OXA) transformation products. In crop soil experiments, biodegradation of SM occurred to a lesser extent than in paddy soil, and sorption was the main driver of apparent BUT dissipation. Sequencing of the 16S rRNA gene showed that soil type and duration of herbicide exposure were the main determinants of bacterial community variation. In contrast, herbicide identity and spiking dose had no significant effect. In paddy soil experiments, a high (4:1, V/V) ESA to OXA ratio for SM was observed, and phylotypes assigned to anaerobic Clostridiales and sulfur reducers such as Desulfuromonadales and Syntrophobacterales were dominant for both herbicides. Crop soil microcosms, in contrast, were associated with a reverse, low (1:3, V/V) ratio of ESA to OXA for SM, and Alphaproteobacteria, Actinobacteria, and Bacillales dominated regardless of the herbicide. Our results emphasize the variability in the extent and modes of SM and BUT dissipation in agricultural soils, and in associated changes in bacterial communities.

Fungicides: An Overlooked Pesticide Class?

Fungicides are indispensable to global food security and their use is forecasted to intensify. Fungicides can reach aquatic ecosystems and occur in surface water bodies in agricultural catchments throughout the entire growing season due to their frequent, prophylactic application. However, in comparison to herbicides and insecticides, the exposure to and effects of fungicides have received less attention. We provide an overview of the risk of fungicides to aquatic ecosystems covering fungicide exposure (i.e., environmental fate, exposure modeling, and mitigation measures) as well as direct and indirect effects of fungicides on microorganisms, macrophytes, invertebrates, and vertebrates. We show that fungicides occur widely in aquatic systems, that the accuracy of predicted environmental concentrations is debatable, and that fungicide exposure can be effectively mitigated. We additionally demonstrate that fungicides can be highly toxic to a broad range of organisms and can pose a risk to aquatic biota. Finally, we outline central research gaps that currently challenge our ability to predict fungicide exposure and effects, promising research avenues, and shortcomings of the current environmental risk assessment for fungicides.

Natural Chlordecone Degradation Revealed by Numerous Transformation Products Characterized in Key French West Indies Environmental Compartments.

Production and use of the insecticide chlordecone has caused long-term environmental pollution in the James River area and the French West Indies (FWI) that has resulted in acute human-health problems and a social crisis. High levels of chlordecone in FWI soils, even after its ban decades ago, and the absence of detection of transformation products (TPs), have suggested that chlordecone is virtually nonbiodegradable in the environment. Here, we investigated laboratory biodegradation, consisting of bacterial liquid cultures and microcosms inoculated with FWI soils, using a dual nontargeted GC-MS and LC-HRMS approach. In addition to previously reported, partly characterized hydrochlordecones and polychloroindenes (families A and B), we discovered 14 new chlordecone TPs, assigned to four families (B, C, D, and E). Organic synthesis and NMR analyses allowed us to achieve the complete structural elucidation of 19 TPs. Members of TP families A, B, C, and E were detected in soil, sediment, and water samples from Martinique and include 17 TPs not initially found in commercial chlordecone formulations. 2,4,5,6,7-Pentachloroindene was the most prominent TP, with levels similar to those of chlordecone. Overall, our results clearly show that chlordecone pollution extends beyond the parent chlordecone molecule and includes a considerable number of previously undetected TPs. Structural diversity of the identified TPs illustrates the complexity of chlordecone degradation in the environment and raises the possibility of extensive worldwide pollution of soil and aquatic ecosystems by chlordecone TPs.

Pesticide mass budget in a stormwater wetland.

Wetlands are reactive landscape zones that provide ecosystem services, including the improvement of water quality. Field studies distinguishing pesticide degradation from retention to evaluate the sink and source functions of wetlands are scarce. This study evaluated based on a complete mass budget the partitioning, retention, and degradation of 12 pesticides in water, suspended solids, sediments, and organisms in a wetland receiving contaminated runoff. The mass budget showed the following: (i) dissolved pesticides accounted for 95% of the total load entering the wetland and the pesticide partitioning between the dissolved phase and the suspended solids varied according to the molecules, (ii) pesticides accumulated primarily in the <250 µm bed sediments during spring and late summer, and (iii) the hydrological regime or the incoming pesticide loads did not influence the pesticide dissipation, which varied according to the molecules and the wetland biogeochemical conditions. The vegetation enhanced the pesticide degradation during the vegetative phase and the pesticides were released during plant senescence. The dithiocarbamates were degraded under oxic conditions in spring, whereas glyphosate and aminomethylphosphonic acid (AMPA) degradation occurred under reducing conditions during the summer. The complete pesticide mass budget indicates the versatility of the pesticide sink and source functions of wetland systems.

Copper stable isotopes to trace copper behavior in wetland systems.

Wetlands are reactive zones of the landscape that can sequester metals released by industrial and agricultural activities. Copper (Cu) stable isotope ratios (δ(65)Cu) have recently been used as tracers of transport and transformation processes in polluted environments. Here, we used Cu stable isotopes to trace the behavior of Cu in a stormwater wetland receiving runoff from a vineyard catchment (Alsace, France). The Cu loads and stable isotope ratios were determined in the dissolved phase, suspended particulate matter (SPM), wetland sediments, and vegetation. The wetland retained >68% of the dissolved Cu and >92% of the SPM-bound Cu, which represented 84.4% of the total Cu in the runoff. The dissolved Cu became depleted in (65)Cu when passing through the wetland (Δ(65)Cuinlet-outlet from 0.03‰ to 0.77‰), which reflects Cu adsorption to aluminum minerals and organic matter. The δ(65)Cu values varied little in the wetland sediments (0.04 ± 0.10‰), which stored >96% of the total Cu mass within the wetland. During high-flow conditions, the Cu flowing out of the wetland became isotopically lighter, indicating the mobilization of reduced Cu(I) species from the sediments and Cu reduction within the sediments. Our results demonstrate that the Cu stable isotope ratios may help trace Cu behavior in redox-dynamic environments such as wetlands.

Stable isotope composition of pesticides in commercial formulations: The ISOTOPEST database.

By assessing the changes in stable isotope compositions within individual pesticide molecules, Compound Specific Isotope Analysis (CSIA) holds the potential to identify and differentiate sources and quantify pesticide degradation in the environment. However, the environmental application of pesticide CSIA is limited by the general lack of knowledge regarding the initial isotopic composition of active substances in commercially available formulations used by farmers. To address this limitation, we established a database aimed at cataloguing and disseminating isotopic signatures in commercial formulations to expand the use of pesticide CSIA. Our study involved the collection of 25 analytical standards and 120 commercial pesticide formulations from 23 manufacturers. Subsequently, 59 commercial formulations and 25 standards were extracted, and each of their active substance was analyzed for both δ13C (n = 84) and δ15N CSIA (n = 43). The extraction of pesticides did not cause significant isotope fractionation (Δ13C and Δ15N < 1‰). Incorporating existing literature data, stable carbon and nitrogen isotope signatures varied in a relatively narrow range among pesticide formulations for different pesticides (Δ13C and Δ15N < 10‰) and within different formulations for a single substance (Δ13C and Δ15N < 2‰). Overall, this suggests that pesticide CSIA is more suited for identifying pesticide transformation processes rather than differentiating pesticide sources. Moreover, an inter-laboratory comparison showed similar δ13C (Δ13C ≤ 1.2 ‰) for the targeted substances albeit varying GC-IRMS instruments. Insignificant carbon isotopic fractionation (Δ13C < 0.5‰) was observed after 4 years of storing the same pesticide formulations, confirming their viability for long-term storage at 4 °C and future inter-laboratory comparison exercises. Altogether, the ISOTOPEST database, in open access for public use and additional contributions, marks a significant advancement in establishing an environmentally relevant pesticide CSIA approach.

Novel extraction methods and compound-specific isotope analysis of methoxychlor in environmental water and aquifer slurry samples.

Multi-element compound-specific stable isotope analysis (ME-CSIA) allows monitoring the environmental behavior and transformation of most common and persistent contaminants. Recent advancements in analytical techniques have extended the applicability of ME-CSIA to organic micropollutants, including pesticides. Nevertheless, the application of this methodology remains unexplored concerning harmful insecticides such as methoxychlor, a polar organochlorine pesticide usually detected in soil and groundwater. This study introduces methods for dual carbon and chlorine compound-specific stable isotope analysis (δ13C-CSIA and δ37Cl-CSIA) of both methoxychlor and its metabolite, methoxychlor olefin, with a sensitivity down to 10 and 100 mg/L, and a precision lower than 0.3 and 0.5 ‰ for carbon and chlorine CSIA, respectively. Additionally, three extraction and preconcentration techniques suitable for ME-CSIA of the target pesticides at environmentally relevant concentrations were also developed. Solid-phase extraction (SPE) and liquid-solid extraction (LSE) effectively extracted methoxychlor (107 ± 27 % and 87 ± 13 %, respectively) and its metabolite (91 ± 27 % and 106 ± 14 %, respectively) from water and aquifer slurry samples, respectively, with high accuracy (Δδ13C and Δδ37Cl ≤ ± 1 ‰). Combining CSIA with polar organic chemical integrative samplers (POCISs) for the extraction of methoxychlor and methoxychlor olefin from water samples resulted in insignificant fractionation for POCIS-CSIA (Δδ13C ≤ ± 1 ‰). A relevant sorption of methoxychlor was detected within the polyethersulfones membranes of the POCISs resulting in temporary carbon isotope fractionation depending on the sorbed mass fraction during the first deployment days. This highlights the critical role of the interactions of polar analytes with POCIS sorbents and membranes in the performance of this method. Altogether, this study proposes a proof of concept for ME-CSIA of methoxychlor and its metabolites, opening the door for future investigations of their sources and transformation processes in contaminated sites.

Evaluating pesticide degradation in artificial wetlands with compound-specific isotope analysis: A case study with the fungicide dimethomorph.

Pesticide degradation in wetland systems intercepting agricultural runoff is often overlooked and mixed with other dissipation processes when assessing pesticide concentrations alone. This study focused on the potential of compound-specific isotope analysis (CSIA) to estimate pesticide degradation in a stormwater wetland receiving pesticide runoff from a vineyard catchment. The fungicide dimethomorph (DIM), with diastereoisomers E and Z, was the prevalent pesticide in the runoff entering the wetland from June to September 2020. DIM Z, the most commonly detected isomer, exhibited a significant change (Δ(13C) > 3 ‰) in its carbon isotopic composition in the wetland water compared to the runoff and commercial formulation, which indicated degradation. Laboratory DIM degradation assays, including photodegradation and biodegradation in oxic wetland water with and without aquatic plants and in anoxic sediments, indicated that DIM degradation mainly occurred in the wetland sediments. The rapid degradation of both DIM isomers (E:t1/2 = 1.2 ± 0.6, Z: t1/2 = 1.5 ± 0.8 days) in the wetland sediment led to significant carbon isotopic fractionation (εDIM-E = -3.0 ± 0.6 ‰, εDIM-Z = -2.0 ± 0.2 ‰). In contrast, no significant isotope fractionation occurred during DIM photodegradation, despite the rapid isomerization of the E isomer to the Z isomer and a half-life of 15.3 ± 2.2 days for both isomers. DIM degradation was slow (E: t1/2 = 56-62 days, Z: t1/2 = 82-103 days) in oxic water with plants, while DIM persisted (120 days) in water without plants. DIM CSIA was thus used to evaluate the in situ biodegradation of DIM Z in the wetland. The DIM Z degradation estimates based on a classical concentration mass balance (86-94 %) were slightly higher than estimates based on the isotopic mass balance (61-68 %). Altogether, this study shows the potential of CSIA to conservatively evaluate pesticide degradation in wetland systems, offering a reliable alternative to classical labor-intensive mass balance approaches.).

Dimethomorph degradation in vineyards examined by isomeric and isotopic fractionation.

Knowledge of the degradation extent and pathways of fungicides in the environment is scarce. Fungicides may have isomers with distinct fungal-control efficiency, toxicity and fate in the environment, requiring specific approaches to follow up the degradation of individual isomers. Here we examined the degradation of the widely used fungicide dimethomorph (DIM) in a vineyard catchment using ratios of carbon stable isotopes (δ13C) and E/Z isomer fractionation (IF(Z)). In a microcosm laboratory experiment, DIM degradation half-life in soil was 20 ± 3 days, and was associated with significant isomeric (ΔIF(Z) = +30%) and isotopic (Δδ13C up to 7‰) fractionation. This corresponds to an isomer enrichment factor of εIR = -54 ± 6%, suggesting isomer selectivity and similar carbon stable isotopic fractionation values of εDIM-(Z) = -1.6 ± 0.2‰ and εDIM-(E) = -1.5 ± 0.2‰. Isomeric and isotopic fractionation values were used to estimate DIM degradation in topsoil and transport in a vineyard catchment over two wine-growing seasons. DIM concentrations following DIM application were up to 3 µg g-1 in topsoil and 29 µg L-1 in runoff water at the catchment outlet. Accordingly, the IF(Z) and δ13C values of DIM in soil were similar to those observed in DIM commercial formulations. The gradual enrichments in DIM-(Z) and 13C of the residual DIM in soil indicated DIM biodegradation over time. DIM biodegradation estimated based on E/Z isomer and carbon stable isotope ratios in topsoil and runoff water ranged from 0% after DIM application up to 100% at the end of the wine-growing season. DIM biodegradation was overestimated compared to conventional approaches relying on DIM mass balance, field concentrations and half-lives. Altogether, our study highlights the usefulness of combining carbon stable isotopes, E/Z isomers and classical approaches to estimate fungicide degradation at the catchment scale, and uncovers difficulties in using laboratory-derived values in field studies.

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 (t1/2 < 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.

Is a dissipation half-life of 5 years for chlordecone in soils of the French West Indies relevant?

Recently, Comte et al. (2022) re-examined the natural degradation of chlordecone (CLD) in the soils of the French West Indies (FWI) by introducing an additional 'dissipation parameter' into the WISORCH model developed by Cabidoche et al. (2009). Recent data sets of CLD concentrations in FWI soils obtained by Comte et al. enabled them optimizing the model parameters, resulting in significantly shorter estimates of pollution persistence than in the original model. Their conclusions jeopardize the paradigm of a very limited degradation of CLD in FWI soils, which may lead to an entire revision of the management of CLD contamination. However, we believe that their study is questionable on several important aspects. This includes potential biases in the data sets and in the modeling approach. It results in an inconsistency between the estimated dissipation half-life time (DT50) of five years that the authors determined for CLD and the fate of CLD in soil from the application period 1972-1993 until nowadays. Most importantly, a rapid dissipation of CLD in the field as proposed by Comte et al. is not sufficiently supported by data and estimates. Hence, the paradigm of long-term persistence of CLD in FWI soils is still to be considered.

Seasonal changes of macroinvertebrate communities in a stormwater wetland collecting pesticide runoff from a vineyard catchment (Alsace, France).

Agricultural land use may influence macroinvertebrate communities by way of pesticide contamination associated with agricultural runoff. However, information about the relation between runoff-related pesticides and communities of benthic macroinvertebrates in stormwater wetland that receive agricultural runoff does not currently exist. Here we show changes in macroinvertebrates communities of a stormwater wetland that collects pesticide-contaminated runoff from a vineyard catchment. Sixteen runoff-associated pesticides, including the insecticide flufenoxuron, were continuously quantified at the inlet of the stormwater wetland from April to September (period of pesticide application). In parallel, benthic macroinvertebrate communities, pesticide concentrations, and physicochemical parameters in the wetland were assessed twice a month. Twenty-eight contaminated runoffs ranging from 1.1 to 114 m3 entered the wetland during the study period. Flufenoxuron concentrations in runoff-suspended solids ranged from 1.5 to 18.5 µg kg(-1) and reached 6 µg kg(-1) in the wetland sediments. However, flufenoxuron could not be detected in water. The density, diversity, and abundance of macroinvertebrates largely varied over time. Redundancy and formal concept analyses showed that concentrations of flufenoxuron, vegetation cover, and flow conditions significantly determine the community structures of stormwater wetland macroinvertebrates. This study shows that flow conditions, vegetation cover, and runoff-related pesticides jointly affect communities of benthic macroinvertebrates in stormwater wetlands.

Transformation and stable isotope fractionation of the urban biocide terbutryn during biodegradation, photodegradation and abiotic hydrolysis.

Terbutryn is a widely used biocide in construction materials like paint and render to prevent the growth of microorganisms, algae and fungi. Terbutryn is released from the facades into the environment during rainfall, contaminating surface waters, soil and groundwater. Knowledge of terbutryn dissipation from the facades to aquatic ecosystems is scarce. Here, we examined in laboratory microcosms degradation half-lives, formation of transformation products and carbon and nitrogen isotope fractionation during terbutryn direct (UV light with λ = 254 nm and simulated sunlight) and indirect (simulated sunlight with nitrate) photodegradation, abiotic hydrolysis (pH = 1, 7 and 13), and aerobic biodegradation (stormwater pond sediment, soil and activated sludge). Biodegradation half-lives of terbutryn were high (>80 d). Photodegradation under simulated sunlight and hydrolysis at extreme pH values indicated slow degradability and accumulation in the environment. Photodegradation resulted in a variety of transformation products, whereas abiotic hydrolysis lead solely to terbutryn-2-hydroxy in acidic and basic conditions. Biodegradation indicates degradation to terbutryn-2-hydroxy through terbutryn-sulfoxide. Compound-specific isotope analysis (CSIA) of terbutryn holds potential to differentiate degradation pathways. Carbon isotope fractionation values (εC) ranged from -3.4 ± 0.3‰ (hydrolysis pH 1) to +0.8 ± 0.1‰ (photodegradation under UV light), while nitrogen isotope fractionation values ranged from -1.0 ± 0.4‰ (simulated sunlight photodegradation with nitrate) to +3.4 ± 0.2‰ (hydrolysis at pH 1). In contrast, isotope fractionation during biodegradation was insignificant. ΛN/C values ranged from -1.0 ± 0.1 (hydrolysis at pH 1) to 2.8 ± 0.3 (photodegradation under UV light), allowing to differentiate degradation pathways. Combining the formation of transformation products and stable isotope fractionation enabled identifying distinct degradation pathways. Altogether, this study highlights the potential of CSIA to follow terbutryn degradation in situ and differentiate prevailing degradation pathways, which may help to monitor urban biocide remediation and mitigation strategies.

Ageing of copper, zinc and synthetic pesticides in particle-size and chemical fractions of agricultural soils.

The transformation and mobility of heavy metals and synthetic pesticides in soil depend on ageing, involving their chemical and physical distributions among soil fractions over time. Heavy metals and synthetic pesticides often co-occur in soil, although their ageing is usually evaluated separately and in bulk soil. Here, contrasting vineyard and crop soils were spiked with copper (Cu; 700 mg kg-1) and zinc (Zn; 200 mg kg-1) a and/or synthetic pesticides (5 mg kg-1), i.e., the fungicide metalaxyl (MTY) and herbicide S-metolachlor (SMET), to evaluate within 200 days their distribution among soil physical and chemical fractions. More than 90% of MTY and SMET in soil was released into the water phase, even 200 days after spiking. This emphasizes the potential mobilization of MTY and SMET from the soil following field application. MTY, SMET, Cu and Zn were associated mainly with the silt fraction and to a lesser extent (<30%) with the sand and clay fractions. Overall, the ageing of MTY, SMET, Cu and Zn in agricultural soil was affected mainly by the soil type and sterilization and only to a minor extent by their co-occurrence. Sorption controlled the dissipation of MTY and SMET in soil, while biodegradation contributed to less than 10%. A large fraction (37 ± 2%) of Cu was associated with Fe oxides after 200 days of ageing, while Zn was found (33 ± 2%) in the residual soil fraction. The silt fraction of the nonsterile vineyard soil became enriched in 65Cu over time (Δδ65Cu = 0.25 ± 0.07‰), whereas the clay fraction was depleted in 65Cu (Δδ65Cu = -0.20 ± 0.07‰). Cu isotope fractionation mirrored the Cu distribution in soil chemical fractions, suggesting that Cu stable isotopes may help to follow-up Cu ageing. In contrast, no significant Zn isotope fractionation was observed among soil experiments or over time. Overall, our study emphasizes the variability in ageing of synthetic pesticides and heavy metals co-occurring in agricultural soils and their interplay in physical and chemical fractions of the soil.

Simple extraction methods for pesticide compound-specific isotope analysis from environmental samples.

Compound-specific isotope analysis (CSIA) is a powerful approach to evaluate the transformation of organic pollutants in the environment. However, the application of CSIA to micropollutants, such as pesticides, remains limited because appropriate extraction methods are currently lacking. Such methods should address a wide range of pesticides and environmental matrices, while recovering sufficient mass for reliable CSIA without inducing stable isotope fractionation. Here, we present simple extraction methods for carbon and nitrogen CSIA for different environmental matrices and six commonly used herbicides, i.e., atrazine, terbutryn, acetochlor, alachlor, butachlor, and S-metolachlor, and three fungicides, i.e., dimethomorph, tebuconazole, and metalaxyl. We examined the potential of several extraction methods for four types of soils or sediments, three types of environmental waters and aerial and root plant samples for multielement (ME)-CSIA.•Pesticide extraction recoveries varied depending on the physical characteristics of the pesticides and matrix properties for environmental water (77 to 87%), soil and sediment (35 to 82%), and plant (40 to 59%) extraction.•The tested extraction methods did not significantly affect the carbon and nitrogen stable isotope signatures of pesticides (Δ(13C) <0.9‰ for Δ(15N) <1.0‰).