Pesticide soil sorption parameters: theory, measurement, uses, limitations and reliability

Dissipation of pesticides and responses of bacterial, fungal and protistan communities in a multi-contaminated vineyard soil

The effect of pesticide residues on non-target microorganisms in multi-contaminated soils remains poorly understood. In this study, we examined the dissipation of commonly used pesticides in a multi-contaminated vineyard soil and its effect on bacterial, fungal, and protistan communities. We conducted laboratory soil microcosm experiments under varying temperature (20°C and 30°C) and water content (20 % and 40 %) conditions. Pesticide dissipation half-lives ranged from 27 to over 300 days, depending on the physicochemical properties of the pesticides and the soil conditions. In both autoclaved and non-autoclaved soil experiments, over 50 % of hydrophobic pesticides (dimethomorph > isoxaben > simazine = atrazine = carbendazim) dissipated within 200 days at 20°C and 30°C. However, the contribution of biodegradation to the overall dissipation of soluble pesticides (rac-metalaxyl > isoproturon = pyrimethanil > S-metolachlor) increased to over 75 % at 30°C and 40 % water content. This suggests that soluble pesticides became more bioavailable, with degradation activity increasing with higher temperature and soil water content. In contrast, the primary process contributing to the dissipation of hydrophobic pesticides was sequestration to soil. High-throughput amplicon sequencing analysis indicated that water content, temperature, and pesticides had domain-specific effects on the diversity and taxonomic composition of bacterial, fungal, and protistan communities. Soil physicochemical properties had a more significant effect than pesticides on the various microbial domains in the vineyard soil. However, pesticide exposure emerged as a secondary factor explaining the variations in microbial communities, with a more substantial effect on protists compared to bacterial and fungal communities. Overall, our results highlight the variability in the dissipation kinetics and processes of pesticides in a multi-contaminated vineyard soil, as well as their effects on bacterial, fungal, and protistan communities.

Comparing the abiotic removal of glyphosate by β-MnO2 and δ-MnO2 colloids: Insights into kinetics and mechanisms

Glyphosate as an effective broad-spectrum herbicide is frequently detected in various water and soil resources. Given the ubiquity of β-MnO2 and δ-MnO2 colloids in groundwater and soil, the abiotic removal of glyphosate by MnO2 colloids was investigated. β-MnO2 colloids exhibited superior glyphosate removal efficiency, up to 37%, compared to 21% for δ-MnO2 colloids at a pH of 4.0. Glyphosate removal involved simultaneous adsorption and oxidation process, identified by HRTEM, NH3-TPD, XPS, LC-MS, FTIR analyses and the occurrence of aminomethylphosphonic acid (AMPA) and Mn2+. Moreover, adsorption dominated the removal of glyphosate by two MnO2 colloids. The solution pH had a substantial effect on glyphosate removal. Co-existing ions in the solution, such as carbonate (CO32-), phosphate (Na2HPO4, NaH2PO4) and humic acid (HA), were also found to impede glyphosate removal. Phosphate, in particular, exhibited a strong competitive effect for adsorption sites on both MnO2 colloids. Of them, the removal of glyphosate by β-MnO2 colloids was more prone to occur due to its higher specific surface area, abundant oxygen vacancies, and moderate acid sites. However, δ-MnO2 colloids presented a stronger oxidation capacity than that of β-MnO2 colloids due to the quicker generation rate of Mn2+. Finally, AMPA was the same products by two MnO2 colloids in the oxidation process, revealing the degradation pathway based on the cleavage of C-N bond. Therefore, by comparing kinetics and mechanisms of glyphosate removal by β- and δ-MnO2 colloids, this study improves us better understanding for the behavior of glyphosate in the environment.

Sorption and degradation processes of imidacloprid in Florida soils

Imidacloprid (IDP) is an active ingredient of the Admire brand pesticide used to control the vector (Asian citrus psyllid) that transmits the causative organism Candidatus Liberibacter asiaticus (CLas) for citrus greening or huanglongbing disease. Imidacloprid products are applied via soil drench where citrus roots are mostly concentrated which is between 0 and 60 cm depth. These soil depths exhibit different characteristics that may affect IDP leaching beyond the rooting zone. Representative soil samples were collected from Entisols and Ultisols, which are the dominant soil orders under citrus production in central Florida, at 15 cm increments up to 60 cm to estimate and understand the batch sorption, kinetics, equilibria, and degradation of IDP. Results showed that the equilibrium time for IDP at 0-15 cm depth (10 hours) was 2 times faster than at 15-60 cm (20 hours) for the Entisol. Nevertheless, all depths reached equilibrium within 24 hours for the Entisol. The 0-30 cm depth adsorbed 2 times more IDP than the 30-60 cm depth for both soils. Nevertheless, the adsorption coefficient was approximately ≤ 1 mL g-1 for both soils. The half-life of IDP in both soils ranged from 10 to 17 days. The Entisol showed higher adsorption than the Ultisol at both depths, probably due to relatively lower organic carbon (OC) content in the Ultisol compared to the Entisol. Thus, the Ultisol showed high IDP leaching vulnerability compared to the Entisol. Movement of IDP is affected by the amount of OC in the citrus critical zone.

A web-based pesticide risk assessment tool for drinking water protection zones in Sweden

To protect human health, wildlife and the aquatic environment, "safe uses" of pesticides are determined at the EU level while product authorization and terms of use are established at the national level. In Sweden, extra precaution is taken to protect drinking water, and permits are therefore required for pesticide use within abstraction zones. This paper presents MACRO-DB, a tool for assessing pesticide contamination risks of groundwater and surface water, used by authorities to support their decision-making for issuing such permits. MACRO-DB is a meta-model based on 583,200 simulations of the physically-based MACRO model used for assessing pesticide leaching risks at EU and national level. MACRO-DB is simple to use and runs on widely available input data. In a qualitative comparative assessment for two counties in Sweden, MACRO-DB outputs were in general agreement with groundwater monitoring data and matched or were more protective than the national risk assessment procedure for groundwater.

Mechanistic modelling of amphibian body burdens after dermal uptake of pesticides from soil

Amphibians are currently considered to be covered by pesticide Environmental Risk Assessment schemes by surrogacy assumptions of exposure and susceptibility based on typical laboratory test species such as fish, mammals, and birds. While multiple reviews have shown for this approach to be adequate in the case of aquatic stages, the same cannot be definitively stated for terrestrial stages. Concerns have risen that exposure of amphibians is likely to be highly influenced by dermal absorption, primarily due to the high permeability of their skin and the lack of a protective layer, such as fur or feathers. It is thus hypothesized that dermal uptake could be a significant route of exposure. Consequently, it is necessary to determine the relative importance of different exposure routes that might affect the integrated toxicity outcome for terrestrial amphibian life-stages. Here, a one-compartment Toxicokinetic model was derived and tested using a publicly available dataset containing relevant exposure and uptake information for juvenile anurans exposed to 13 different pesticides. Modelled body burdens were then compared to measured burdens for a total of 815 individuals. Overall, a good concordance between modelled and measured values was observed, with the predicted and measured body burdens differing by a factor of 2 on average (overall R2 of 0.80 and correlation coefficient of 0.89), suggesting good predictivity of the model. Accordingly, the model predicts realistic body burdens for a variety of frog and toad species, and overall, for anurans. As the model includes rehydration (implicit in the evaluated studies) but currently does not account for metabolism, it can be seen as a worst-case assessment. We suggest toxicokinetic models, such as the one here presented, could be used to characterize dermal exposure in amphibians, screen for pesticides of concern, and prioritize risk assessment efforts, whilst reducing the need for de novo vertebrate testing.

Application of mid-infrared spectroscopy to the prediction and specification of pesticide sorption: A promising and cost-effective tool

The cocktail of pesticides sprayed to protect crops generates a miscellaneous and generalized contamination of water bodies. Sorption, especially on soils, regulates the spreading and persistence of these contaminants. Fine resolution sorption data and knowledge of its drivers are needed to manage this contamination. The aim of this study is to investigate the potential of Mid-Infrared spectroscopy (MIR) to predict and specify the adsorption and desorption of a diversity of pesticides. We constituted a set of 37 soils from French mainland and West Indies covering large ranges of texture, organic carbon, minerals and pH. We measured the adsorption and desorption coefficients of glyphosate, 2,4-dichlorophenoxyacetic acid (2,4-D) and difenoconazole and acquired MIR Lab spectra for these soils. We developed Partial Least Square Regression (PLSR) models for the prediction of the sorption coefficients from the MIR spectra. We further identified the most influencing spectral bands and related these to putative organic and mineral functional groups. The prediction performance of the PLSR models was generally high for the adsorption coefficients Kdads (0.4 < R2 < 0.9 & RPIQ >1.8). It was contrasted for the desorption coefficients and related to the magnitude of the desorption hysteresis. The most significant spectral bands in the PLSR differ according to the pesticides indicating contrasted interactions with mineral and organic functional groups. Glyphosate interacts primarily with polar mineral groups (OH) and difenoconazole with hydrophobic organic groups (CH2, CC, COO-, C-O, C-O-C). 2,4-D has both positive and negative interactions with these groups. Finally, this work suggests that MIR combined with PLSR is a promising and cost-effective tool. It allows both the prediction of adsorption and desorption parameters and the specification of these mechanisms for a diversity of pesticides including polar active ingredients.

Remediation of neonicotinoid-contaminated soils using peanut shell biochar and composted chicken manure: Transformation mechanisms of geochemical fractions

Soil remediation techniques are promising approaches to relieve the adverse environmental impacts in soils caused by neonicotinoids application. This study systematically investigated the remediation mechanisms for peanut shell biochar (PSB) and composted chicken manure (CCM) on neonicotinoid-contaminated soils from the perspective of transformation of geochemical fractions by combining a 3-step sequential extraction procedure and non-steady state model. The neonicotinoid geochemical fractions were divided into labile, moderate-adsorbed, stable-adsorbed, bound, and degradable fractions. The PSB and CCM addition stimulated the neonicotinoid transformation in soils from labile fraction to moderate-adsorbed and stable-adsorbed fractions. Compared with unamended soils, the labile fractions decreased from 47.6% ± 11.8% of the initial concentrations to 12.1 ± 9.3% in PSB-amended soils, and 7.1 ± 4.9% in PSB and CCM-amended soils, while the proportions of moderate-adsorbed and stable-adsorbed fractions correspondingly increased by 1.8-2.4 times and 2.3-4.8 times, respectively. A small proportion (<4.8%) in bound fractions suggested there were rather limited bound-residues after 48 days incubation. The PSB stimulated the -NO2-containing neonicotinoid-degraders, which promoted the degradable fractions of corresponding neonicotinoids by 8.2 ± 6.3%. Degradable fraction of neonicotinoids was the dominant fate in soils, which accounted for 58.3 ± 16.7%. The findings made beneficial theoretical supplements and provided valuable empirical evidence for the remediation of neonicotinoid-contaminated soils.

Environmental fate and metabolic transformation of two non-ionic pesticides in soil: Effect of biochar, moisture, and soil sterilization

Soil moisture, organic matter, and soil microbes are the key considering factors that control the persistence, degradation, and transformation of applied pesticides under varied soil conditions. In this study, underlying influence of these factors was assessed through the fates and metabolic transformation of two non-ionic pesticides (e.g., Phorate and Terbufos) in soils. Concisely, two distinct experiments including a customized batch equilibrium (sorption study), and a lab incubation trial (degradation study) were performed, following the OECD guidelines. As per study findings, biochar (BC) amendment was found to be the most influential factors during sorption study, particularly, 1% BC amendment contributed to achieve the best results. In addition, the non-linearity of sorption isotherm (1/n < 1.0) was revealed through Freundlich isotherm, indicating the strong adsorption of studied pesticides onto the soils. On the other hand, during degradation study, soil moisture initiates the enhanced degradation of parent pesticides and subsequent metabolism. In the presence of 40% water holding capacity (WHC), 1% BC amendment enhances the metabolic transformation, while H2O2 treatment could hinder the process. Additionally, the half-life degradation (t1/2) of phorate and terbufos was controlled by biochar amendment, moisture, and soil sterilization, respectively. Finally, BC can accelerate the metabolic transformation, whereas, phorate underwent a metabolic change into sulfoxide and sulfone while terbufos turned into solely sulfoxide. This pioneering study gathered crucial data for understanding the persistence and metabolic transition of non-ionic pesticides in soils and their patterns of degradation.

The Interaction of Pesticides with Humin Fractions and Their Potential Impact on Non-Extractable Residue Formation

The constant influx of pesticides into soils is a key environmental issue in terms of their potential retention in the soil, thus reducing their negative impact on the environment. Soil organic matter (SOM) is an important factor influencing the environmental fate of these substances. Therefore, the aim of this research was to assess the chemical behavior of pesticides (flufenacet, pendimethalin, α-cypermethrin, metazachlor, acetamiprid) toward stable soil humin fractions (HNs) as a main factor affecting the formation of non-extractable residues of agrochemicals in soil. This research was conducted as a batch experiment according to OECD Guideline 106. For this purpose, HNs were isolated from eight soils with different physicochemical properties (clay content = 16-47%, pHKCl = 5.6-7.7, TOC = 13.3-49.7 g·kg-1, TN = 1.06-2.90 g·kg-1, TOC/TN = 11.4-13.7) to reflect the various processes of their formation. The extraction was carried out through the sequential separation of humic acids with 0.1 M NaOH, and then the digestion of the remaining mineral fraction with 10% HF/HCl. The pesticide concentrations were detected using GC-MS/MS. The pesticides were characterized based on the different sorption rates to HNs, according to the overall trend: metazachlor (95% of absorbed compound) > acetamiprid (94% of absorbed compound) > cypermethrin (63% of partitioning compound) > flufenacet (39% of partitioning compound) > pendimethalin (28% of partitioning compound). Cypermethrin and metazachlor exhibited the highest saturation dynamic, while the other agrochemicals were much more slowly attracted by the HNs. The obtained sorption kinetic data were congruous to the pseudo-first-order and pseudo-second-order models related to the surface adsorption and interparticle diffusion isotherm. The conducted research showed that the processes of pesticide sorption, apart from physicochemical phenomena, are also affected by the properties of the pollutants themselves (polarity, KOC) and the soil properties (SOM content, clay content, and pHKCl).

A Pesticide Decision Support Tool to guide the selection of less environmentally harmful pesticides for the sugar cane industry

Pesticides applied to agricultural land have been shown to decrease the quality of water entering the Great Barrier Reef lagoon. This issue is addressed by the Reef 2050 Water Quality Improvement Plan which includes a pesticide reduction target. As part of a wider educational strategy, one method that could help meet the target is to provide stakeholders with information that assists in the selection and use of pesticide active ingredients (PAIs) that pose a lower risk to aquatic environments compared to those currently used. This study developed a Pesticide Decision Support Tool (PDST) in collaboration with stakeholders for the sugar cane industry. The PDST covers all PAIs registered and applied to sugar cane in Australia and four additional PAIs registered for use on crops grown in rotation with sugar cane. The PDST incorporates both the measure of mobility and persistence of a PAI and the measure of effect, which is based on the PAI application rate and ecotoxicity threshold value. The aquatic risk, which is the product of the measure of effect and the measure of mobility and persistence, is a measure of the likelihood that a PAI will reach the aquatic environment and cause harmful effects. Insecticide active ingredients (e.g., cadusafos, chlorpyrifos) posed the greatest aquatic risk, followed by herbicide active ingredients (e.g., MSMA, metolachlor), while fungicide AIs typically had a lower aquatic risk. An interactive spreadsheet allows characteristics, including application rate and tank mixes, to be considered when assessing the potential risk. While focusing on sugar cane, the results are equally appropriate to other crops that use the same PAIs provided the application rates are corrected to the new crop. In addition, the approach used in the PDST can be applied internationally and to any PAIs with sufficient toxicity, mobility, and persistence data.

Establishing the extent of pesticide contamination in Irish agricultural soils

To establish meaningful and sustainable policy directives for sustainable pesticide use in agriculture, baseline knowledge of pesticide levels in soils is required. To address this, five pesticides and one metabolite widely used in Irish agriculture and five neonicotinoid compounds pesticides were screened from soils from 25 fields. These sites represented a diversity of soil and land use types. Prothioconazole was detected in 16 of the 18 sites where it had been recently applied, with the highest maximum concentration quantified of 46 μg/kg. However, a week after application only four fields had prothioconazole concentrations above the limit of quantification (LOQ). Fluroxypyr was applied in 11 sites but was not detected above LOQ. Glyphosate and AMPA were not detected. Interestingly, neonicotinoids were detected in 96% of all sampling sites, even though they were not reported as recently applied. Excluding neonicotinoids, 60% of sites were found to contain pesticide residues of compounds that were not previously applied, with boscalid and azoxystrobin detected in 15 of the 25 sites sampled. The total number of pesticides detected in Irish soils were significantly negatively correlated with clay fraction, while average pesticide concentrations were significantly positively correlated with log Kow values. 17 fields were found to have total pesticide concentrations in excess of 0.5 μg/kg, even when recently applied pesticides were removed from calculations. Theoretical consideration of quantified pesticides determined that azoxystrobin has high leaching risk, while boscalid, which was detected but not applied, has an accumulation risk. This information provides insight into the current level of pesticide contamination in Irish agricultural soil and contributes to the European-level effort to understand potential impacts of pesticide contamination in soil.

Potential of fluorescent tracers to appraise biochar amendment strategies for pesticide mitigation - insights from comparative sorption

Mitigation of pesticide dispersion in soil and water is required to protect ecosystem health and the anthropic uses of water bodies. Biochar amendments have been suggested to reduce pesticide dispersion due to their high sorption potentials. Nevertheless, appraisals at different scales have been limited by the costs of pesticide analyses. The aim of this study was to evaluate the potential of two fluorescent tracers, uranine (UR) and sulforhodamine B (SRB), for use as pesticide proxies in the context of biochar amendments used for mitigation purposes. Therefore, we compared the sorption processes of both fluorescent tracers and those of three pesticides, glyphosate, 2,4-D, and difenoconazole for soils; three wood biochars (pine, oak, and beech/charm blend); and soil/biochar mixtures representing agricultural usages. The results showed that the sorption of glyphosate by soil was unaffected by amendment with the tested pine, oak, and wood blend biochars. In contrast, the sorption coefficients of UR, SRB, 2,4-D, and difenoconazole were significantly increased with these biochar amendments. SRB, in particular, exhibited sorption behavior similar to that of the hydrophobic fungicide difenoconazole. This indicates promise for the use of SRB as a proxy for hydrophobic pesticides, in testing biochar amendments.

Effect of salinity on the fate of pesticides in irrigated systems: a first overview

This review investigates the impact of salinity on the fate of the active compounds of pesticides in a cultivated environment. Due to the over-exploitation of water resources and intensification of agriculture, salinity outbreaks are being observed more often in cultivated fields under pesticide treatments. Nevertheless, there is a poor understanding of the incidence of varying water salt loads on the behavior of pesticides' active ingredients in soil and water bodies. The present review established that water salinity can affect the diffusion of pesticides' active ingredients through numerous processes. Firstly, by increasing the vapor pressure and decreasing the solubility of the compounds, which is known as the salting-out effect, salinity can change the colligative properties of water towards molecules and the modification of exchange capacity and sorption onto the chemicals. It has also been established that the osmotic stress induced by salinity could inhibit the biodegradation process by reducing the activity of sensitive microorganisms. Moreover, soil properties like dissolved organic matter, organic carbon, clay content, and soil texture control the fate and availability of chemicals in different processes of persistence in water and soil matrix. In the same line, salinity promotes the formation of different complexes, such as between humic acid and the studied active compounds. Furthermore, salinity can modify the water flux due to soil clogging because of the coagulation and dispersion of clay particle cycles, especially when the change in salinity ranges is severe.

Soil Organic Matter Composition and pH as Factors Affecting Retention of Carbaryl, Carbofuran and Metolachlor in Soil

The majority of studies concerning the environmental behavior of hydrophobic pollutants in soil consider soil organic matter (SOM) content as a main factor influencing chemical retention, whereas the composition of SOM and its individual fraction share are often neglected. In the present paper, carbaryl, carbofuran and metolachlor retention by loamy sand and loam topsoil materials is compared and referred to humic acids (CHA) and the residual carbon (CR) content of SOM. Additionally, the sorption-desorption behavior of agrochemicals in soils was tested at a pH of three to seven. Calculated isothermal parameters point to favorable, spontaneous and physical pesticide sorption. Groundwater ubiquity score (GUS) indexes confirmed the low leaching ability of metolachlor on soils and moderate of carbofuran. The high affinity of carbaryl to CR may explain its pronounced sorption in loam soil and the lowest percolation potential. Carbofuran retention in soils was associated with montmorillonite (Mt) and CR fractions. Meanwhile, metolachlor uptake was related to humic acid and Mt content of the soils. Lower pH enhanced retention of the agrochemicals, except for carbaryl sorption in sandy loam soil. Results of this study highlight that SOM composition and mutual share of individual organic carbon fractions alongside pH may play a crucial role in predicting non-ionic pesticide behavior in soil.

Soil metabolomics: A powerful tool for predicting and specifying pesticide sorption

Sorption regulates the dispersion of pesticides from cropped areas to surrounding water bodies as well as their persistence. Assessing the risk of water contamination and evaluating the efficiency of mitigation measures, requires fine-resolution sorption data and a good knowledge of its drivers. This study aimed to assess the potential of a new approach combining chemometric and soil metabolomics to estimate the adsorption and desorption coefficients of a range of pesticides. It also aims to identify and characterise key components of soil organic matter (SOM) driving the sorption of these pesticides. We constituted a dataset of 43 soils from Tunisia, France and Guadeloupe (West Indies), covering extensive ranges of texture, organic carbon and pH. We performed untargeted soil metabolomics by liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS). We measured the adsorption and desorption coefficients of three pesticides namely glyphosate, 2,4-D and difenoconazole for these soils. We developed Partial Least Square Regression (PLSR) models for the prediction of the sorption coefficients from the RT-m/z matrix and conducted further ANOVA analyses to identify, annotate and characterise the most significant constituents of SOM in the PLSR models. The curated metabolomics matrix yielded 1213 metabolic markers. The prediction performance of the PLSR models was generally high for the adsorption coefficients Kd_ads (0.3 < R² < 0.8) and for the desorption coefficients Kf_des (0.6 < R² < 0.8) but low for n_des (0.03 < R² < 0.3). The most significant features in the predictive models were annotated with a confidence level of 2 or 3. The molecular descriptors of these putative compounds suggest that the pool of SOM compounds driving glyphosate sorption is reduced compared to 2,4-D and difenoconazole, and these compounds are generally more polar. This approach can provide estimates of the adsorption and desorption coefficients of pesticides, including polar pesticide, for contrasted pedoclimates.

Multiresidue extraction of current-use pesticides from complex solid matrices using energized dispersive guided extraction with analysis by gas and liquid chromatography tandem mass spectroscopy

The development of sample processing techniques that recover a broad suite of pesticides from solid matrices, while mitigating coextracted matrix interferences, and reducing processing time is beneficial for high throughput analyses. The objective of this study was to evaluate the effectiveness of an automated extraction system for pesticide analyses in solid environmental samples. An Energized Dispersive Guided Extraction (EDGE) system was used to evaluate two different extraction solvents in optimizing the extraction of 210 pesticides and pesticide transformation products. A graphitized carbon cleanup step was implemented, and three elution solvents were evaluated separately for analyte recoveries. Recoveries between 70 and 130% were achieved for 167 compounds in a test soil using acetonitrile as an extraction solvent and carbon cleanup with acetonitrile and dichloromethane elutions. Nine field samples (soil, sediment, and biosolids) were extracted using the newly developed method and were compared with a previously validated pressurized liquid extraction (PLE) method using an Accelerated Solvent Extraction (ASE) system. Concentrations obtained from the two methods were comparable (linear R² > 0.999), suggesting similar performance between the EDGE and PLE extractions in complex matrices. The new method provided slightly better sensitivities in comparison to the PLE method, ranging from 0.09 to 2.56 ng g^-1. The method presented here significantly reduces extraction setup and runtimes while also minimizing the volume of carcinogenic solvents (e.g., dichloromethane) used in the laboratory and presents a sensitive multiresidue method for a wide range of pesticides in solid matrices.

Mobility in the context of exposure-based assessment of chemicals for drinking water resource protection

In order to protect European Union (EU) drinking water resources from chemical contamination, criteria for identifying persistent, mobile, and toxic (PMT) chemicals and very persistent and very mobile (vPvM) chemicals under the EU REACH Regulation were proposed by the German Environment Agency (Umweltbundesamt-UBA). Additionally, new hazard classes for PMT and vPvM substances in the revised EU classification, labeling, and packaging (CLP Regulation) are intended. Therefore, a reliable approach in the identification of potential drinking water resource contaminants is needed. The scientific basis of the property-based PMT/vPvM criteria, focusing on mobility, which dictates the migration of chemical drinking water sources, was evaluated, and a critical analysis of the deviation of sorption metrics from simple behavior was carried out. Based on our evaluation, a K_oc may be used for nonionic substances on a screening level only, requiring a higher tier assessment. It is considered inappropriate for hydrophilic and ionizable chemicals, particularly for soils with low organic carbon contents. The nonextractable residue formation is complex and not well understood but remains significant in limiting the mobility of chemicals through soils and sediments. In order to inform the EU commission's work on the introduction of new hazard classes for PMT and vPvM substances into the European legislation, the derivation of a tiered approach is proposed, which utilizes the weight of evidence available, with adoption of appropriate higher tier models commensurate with the nature of the substance and the data available. Integr Environ Assess Manag 2023;19:775-791. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

On the representability of soil water samples in space and time: Impact of heterogeneous solute transport pathways underneath a sandy field

In Europe, millions of water samples have been collected from sampling points, especially in the saturated zone to assess the water quality among others to fulfil EU water quality directives. Often water samples are collected from sampling points installed in the subsurface without knowing what the water collected represents in space and time. As such, without detailed knowledge of hydrogeological settings and fluctuations in groundwater levels, it is not possible to assess whether water collected represents a hydraulic active sediment setting or an adjacent isolated sediment body. Collecting water from the latter will hence not reveal by analysis potential contamination in the hydraulic active setting. Based on a detailed three-dimensional sedimentary facies model interpreted from geological and geophysical data combined with groundwater level measurements, this study focuses on delineating the impact of changing solute transport pathways underneath a sandy field (2 ha) exposed to bromide and pesticide applications. Hence, the analyses utilize detections in water samples of bromide, pesticides, and/or their degradation products collected through 19 years at 25 sampling points. A special focus is on the relatively high concentration, long-termed leaching of four degradation products (1,2,4-triazole, CGA108906, PPU, and desethyl-terbuthylazine) through the field. The results show that even for sand, knowledge of the hydrogeological setting and in-situ fate knowledge is imperative to assess the representability of water being sampled from both the variably-saturated and saturated zone of the soil-sediment system. Especially, the sub-horizontal layered sediments with numerous facies shifts facilitate horizontal solute transport, and fluctuations in the groundwater table seem to be decisive for, which solute transport pathways are dominating. Such detailed insights are crucial for accurately assessing sources of contaminants, leaching risk of contaminants through the variably-saturated zone, and improving monitoring procedures in the protection of the water resources and hereby the water quality of the future.

Degradation of Kresoxim-Methyl in Different Soils: Kinetics, Identification of Transformation Products, and Pathways Using High-Resolution-Mass-Spectrometry-Based Suspect and Non-Target Screening Approaches

This study investigated the degradation of strobilurin fungicide kresoxim-methyl (KM) in three typical agricultural soils from China by aerobic and anaerobic degradation experiments, focusing on degradation kinetics of KM, identification of transformation products (TPs), and prediction of toxicity end points via in silico approaches. KM showed a pronounced biphasic degradation in different soils and could rapidly degrade, with DT₅₀ of <3 days. Four TPs were identified by high-resolution mass spectrometry (HRMS), and three of them have never been reported before. Possible degradation pathways of KM in soil were proposed, including hydrolysis, oxidation, and reduction, and the main mechanism involved in the biodegradation of KM was the hydrolysis of methyl ester regardless of aerobic or anaerobic conditions. The results of toxicity evaluation indicated that some TPs are more toxic than KM and may have a developmental toxicity and mutagenicity, and further risk assessment should be carried out.

Behavior and fate of microcystin-LR in soils amended with biochar and peat

Activities such as irrigation with cyanobacteria-polluted water can lead to microcystins (MCs) migration from soil surface to the deeper layers, which could pose a potential risk to ground drinking water safety. The present study evaluated the sorption, degradation and leaching behavior of microcystin-LR (MC-LR) in two different soils amended with biochar and peat. Results showed that both biochar and peat could significantly increase MC-LR sorption in both soils. The Freundlich unit capacity coefficient (K_f) of 2% biochar treatment were 2-3 times higher than those of the control treatment. Amendment of 2% peat greatly boosted the biodegradation of MC-LR, whereas amendment of 2% biochar significantly reduced the biodegradation of MC-LR in both soils. The half-lives of MC-LR were 4.99 d (Control), 5.59 d (2% Biochar) and 3.50 d (2% Peat) in soil A and 6.66 d (Control), 6.93 d (2% Biochar) and 5.13 d (2% Peat) in soil B, respectively. All the amendments, except treatment 1% Peat, could significantly reduce the recovery rates of MC-LR in the leachate of columns with both soils. Amendment of 2% biochar and 2% peat reduced the recovery rates of MC-LR by 15.87% and 8.6% in soil A and 18.4% and 10.3% in soil B, compared with the controls. This work provides a better understanding of the environmental behavior of MC-LR in soils with different amendments, which is also meaningful for groundwater protection in cyanobacterial-polluted areas.

Regulation of Paraquat for wheat crop contamination

Paraquat is a highly toxic and persistent pesticide in soil but is still used for wheat crops in many countries. Paraquat can pose potential health hazards if it is translocated from soil into wheat grains, but no study is available for its possible translocation causing wheat grain contamination. The present study aimed at finding out Paraquat residue in wheat grains under field conditions for two crop seasons to explore the sustainability of this pesticide. The experiments were conducted scientifically under field conditions at agricultural fields Pusa, Delhi, India. The soil texture was classified as sandy loam. Paraquat dichloride 24% SL (herbicide) was applied on five fields except for control field. Paraquat in wheat grains was analyzed using HPLC equipped with a photodiode array (PDA) detector. The method of analysis was validated for the pesticide residue recovery. The results showed that there was an alarming concentration of Paraquat in wheat grains ranging between 21.6 and 49.02 mg kg^-1 against maximum residue level of 0.1 mg kg^-1. Paraquat was also found in control crop (3.1 mg kg^-1) due to background residue in soil even when no Paraquat was applied. Furthermore, wheat flour samples from market also gave alarming Paraquat residue (20.39, 25.88, and 27.68 mg kg^-1). Paraquat residue was primarily dependent on % clay in field soils. More the % clay lesser was Paraquat residue in wheat grain. Thus, Paraquat was translocated from soil into wheat grains and resulted in worrying concentration of Paraquat residue in wheat grains. Consequently, use of Paraquat for wheat crops needs to be regulated as it contaminated the soil and resulted in the wheat grain contamination posing severe health hazards for humans.

Emerging Contaminant Imidacloprid in Mediterranean Soils: The Risk of Accumulation Is Greater than the Risk of Leaching

Imidacloprid (IMI) is an extensively used neonicotinoid insecticide whose occurrence in the environment is a worldwide problem. Its sorption/transport properties are recognized as one of the key knowledge gaps hindering policymaking regarding its international routine monitoring in soils. Therefore, we studied IMI transport behaviour in Croatian Mediterranean soils using column experiments. Breakthrough curves were analysed using the two-site adsorption model and compared against dimethoate (DIM). Transport parameters were correlated to soil physicochemical properties. The results indicate that IMI shows a high degree of preference for soil organic matter over any other soil constituent. For IMI, the clay did not exhibit any sorption activity, while hematite did act as an active sorbent. Contrarily, hematite increased the leachability of DIM by blocking the active sorption sites on clay platelets. Both hematite and clay sorption acted as type-2 (i.e., rate-limiting) sites. In all soils, IMI exhibited lower short-term leachability than DIM. Combined with a body of data concerning other aspects of IMI environmental behaviour, the results indicate that the risk of accumulation of IMI in the soil is greater than the risk of contamination by leaching. Thus, continuous monitoring of IMI in soils should be incorporated into future soil health protection programs.

Field test of the TOXSWA pesticide fate model: Comparison of simulated and observed chlorpyrifos in water, sediment and macrophytes in four stagnant ditches

TOXSWA is a numerical model describing pesticide behavior in an edge-of-field waterbody. It is widely used to predict exposure in regulatory risk assessment for aquatic ecosystems. Exposure concentrations are predicted based upon pesticide process parameters obtained in standardized laboratory experiments. However, few tests of the model performance based on field data have been carried out. We compare simulated concentrations to observations from a field experiment with four shallow stagnant ditches over sprayed with chlorpyrifos, a moderately volatile pesticide with a significant sorption capacity. Input parameters describing the four ditches, such as dimensions, water depth, sediment and macrophyte characteristics were measured in detail. Additionally, laboratory experiments were carried out to determine site-specific values for parameters describing chlorpyrifos degradation in water and sediment, as well as sorption to the two dominant macrophyte species. Based upon these estimated parameters, the correspondence between simulated and measured concentrations in water, sediment and macrophytes is poor. We attribute this discrepancy to a lack of site-specific input for the processes of volatilization and sorption to sediment, which both are important processes for chlorpyrifos. Therefore, we calibrated TOXSWA using the optimization tool PEST. The transfer coefficient for volatilization and the coefficient for sorption to sediment were optimized based on the observed concentrations in water and sediment. This resulted in a substantial improvement of correspondence. Optimized values of the transfer coefficient for volatilization and the coefficient for sorption to sediment are substantially higher than their initial estimates (4-8-fold and 2-4-fold increase, respectively), but can be well explained. The optimized coefficients vary less than a factor 2 between the four ditches. We conclude that TOXSWA can adequately predict chlorpyrifos behavior in the four ditches, provided that reliable site-specific parameter estimates are available. Field tests for other pesticides, waterbodies and agro-environmental conditions are warranted.

Intra aquifer variations in pesticide sorption during a field injection experiment

A field injection experiment was performed in an anoxic sandy aquifer over 6 days to assess sorption characteristics of 7 commonly applied pesticides in agriculture and 2 frequently detected metabolites. Pesticide use changed considerably in the last decades, and there is insufficient knowledge of the fate of currently used pesticides in aquifers. Injected water arrival was monitored at 6 depth intervals of 1 m ranging from 11.4 to 32.2 m-below surface level with varying organic carbon contents (0.057-0.91%d.w.) to examine intra-aquifer variations in sorption. Observed pesticide concentrations were fit using a non-linear least squares routine to an advection-dispersion equation, from which retardation factors (R) were obtained. Pesticide degradation did not significantly influence the simulated R during the experiment. We observed that bentazon and cycloxydim were most mobile with R < 1.1 at all depths. Desphenyl chloridazon, methyl desphenyl chloridazon, and imidacloprid were, on average, less mobile, with maximum R of 1.5. Boscalid, chloridazon, fluopyram, and flutolanil showed a larger range of R, and R > 2.0 were observed in the shallowest part of the aquifer. Largest R were observed at the top of the aquifer and decreased with depth. K_oc values varied similarly, which indicates that sorption is not only influenced by sedimentary organic matter (SOM) content but also by its sorption reactivity. Obtained sorption parameters were substantially lower than reported in a widely used pesticide sorption database, which suggests that sorption parameters are influenced by methodological differences and variations in the sorption reactivity of SOM. The large intra-aquifer variations in pesticide sorption highlights that aquifer heterogeneity should be considered in groundwater risk assessments.

A fuzzy knowledge-based model for assessing risk of pesticides into the air in cropping systems

Pesticide use in current cropping systems has become a key input to improve productivity. However, their potential risk to nature demands tools for designing a sustainable use. In this work, a fuzzy knowledge-based model was developed for assessing risk of pesticides into the air. The model was based on fuzzy logic theory which provides a means for representing uncertainty by including knowledge about different processes related to pesticide dynamics using functions, control rules and logical inference systems. All these elements were built through a literature review. Results from the sensitivity analysis on the final model structure showed that the Henry's law constant was the most influential input variable related to the active ingredient identity, while the most influential management and environmental input variables on the pesticide air risk values were the droplet size together with the application method and the current wet bulb temperature depression value, respectively. Results from an independent model validation showed a significant goodness-of-fit between the simulated risk of drift and volatilization and the observed values under experimental conditions. Long-term simulations in a real soybean production system in Argentina showed results of drift reduction in post-emergence conditions of the crop under aerial application condition, and a significant effect of the identity of the active ingredient in the risk values. Simulated risk values from the developed model allow to identify ex ante the combination of agronomic decisions, together with environmental conditions that can reduce the risk of pesticides in the air in real production systems. Further combination with ecotoxicological classification tools should improve pesticide use assessment in agricultural systems.

Occurrence and distribution of organophosphate flame retardants in the typical soil profiles of the Tibetan Plateau, China

The urbanization and development of Tibetan Plateau (TP) probably results in a significant contamination of organic pollutants, such as organophosphate flame retardants (OPFRs). However, there is a lack of monitoring and evaluation of their occurrence and risks in the soil of TP. We investigated the concentrations, vertical distributions, potential sources, and ecological risks of OPFRs in soil profiles from four regions of TP, China. The total concentrations of OPFRs in all soil samples ranged from 1.35 to 126 ng/g with a median of 12.6 ng/g. Relatively high concentrations were discovered in the top soils from Lhasa, suggesting a rising contamination around cities of TP due to anthropogenic disturbance. Tri-n-butyl phosphate (TNBP) was the dominant OPFRs followed by tris(2-chloroethyl) phosphate (TCEP). Vertical distribution of ΣOPFRs was discovered, especially at site Lhasa. Source apportionment based on principle component analysis and correlation analysis suggests that OPFRs in the TP soil mainly originate from atmospheric transport, while some OPFRs in the top soil may be also influenced by nearby sources. The vertical distributions of OPFRs in soil may be influenced by both soil and chemical properties, as well as their use. The ecological risk quotients (RQs) of 6 OPFRs in the TP soil were calculated, and most of their ecological risks were relatively low or negligible. However, for the worst-case scenario calculated by the 95th percentile concentrations, TNBP and tris(2-chloro-isopropyl) phosphate (TCIPP) at site Lhasa and cresyl diphenyl phosphate (CDP) at site Nagri had moderate risks. More attentions should be paid to the Tibetan Plateau in the future due to the rising ecological risks of OPFRs, especially to the areas around cities.

Dynamics in imidacloprid sorption related to changes of soil organic matter content and quality along a 20-year cultivation chronosequence of citrus orchards

The on-going and extensive use of neonicotinoids occur in orchards. However, it is still unknown whether and how orchard management affects soil properties, especially the contents and structure of soil organic matter during orchard development, and their further influences on neonicotinoid persistence. Here, surface soil samples were collected from the citrus orchards with different cultivation ages (1, 10, 14, and 20 years), and their physicochemical properties were determined. Changes in the chemical structure of soil organic matter (SOM) were furtherly examined using solid-state CP/TOSS ¹³C NMR. Then, the sorption isotherms of imidacloprid in these soils were investigated. The sorption coefficient (K_d) of imidacloprid at C_e of 0.05 mg/L in the orchard soils increased by 19.4-23.3%, along a 20-year chronosequence of cultivation, which should be mainly ascribed to the increase of SOM. However, the organic carbon-normalized sorption coefficient (K_oc, sorption per unit mass of OM) of imidacloprid declined with increasing cultivation ages. Moreover, the polar and aliphatic domains of SOM had a significantly positive relation to the K_oc of imidacloprid, suggesting its key role in governing imidacloprid sorption. The results highlighted that reasonable management measures could be adopted to control the occurrence and fate of neonicotinoids in soils, mainly by affecting the content and quality of SOM.

From field to plate: Agricultural pesticide presence in the guayas estuary (Ecuador) and commercial mangrove crabs

Mangroves are unique coastal ecosystems, located in tropical and subtropical regions. Yet, the functioning of these essential ecosystems is threatened by the presence of pollutants, including pesticides originating from agricultural activities. We investigated pesticide residues in the Guayas estuarine environment, since agricultural activities rapidly increased in the Guayas river basin over the past decades. A multi-residue analysis involving a selection of 88 pesticides was performed on the white meat and the hepatopancreas of the red mangrove crab (Ucides Occidentalis) at 15 sampling sites within the Guayas estuary along with water, sediment, and leaves samples. We found that 35 active compounds were present in the Guayas estuary, of which pyrimethanil was most commonly detected and had the highest concentrations in almost all compartments. Also, cadusafos was present in all studied compartments of the Guayas mangrove system and several prohibited pesticides (including carbendazim, carbofuran, and parathion) were detected. An ecotoxicological and probabilistic consumer risk assessment pointed out that current butachlor, carbendazim, and fludioxonil concentrations can cause adverse effects in aquatic organisms in the long term. Moreover, high potential acute and chronic risks of cadusafos residues on aquatic invertebrates and of diuron on algae in the Guayas wetlands were observed. Still, the exposure results indicated that the health risk for the consumers of the commercial red mangrove crab is low concerning cadusafos, chlorpyrifos, diuron, linuron, and pyrimethanil residues in crab tissues. The findings presented in this research can provide a useful basis for local water managers and environmental conservation groups to act and reduce the usage of pesticides, to avoid threatening aquatic and human health.

The adsorption-desorption characteristics and degradation kinetics of ceftiofur in different agricultural soils

Cephalosporins are one of the most widely used antibiotics. When cephalosporins are discharged into the environment, they not only induce the production of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARBs) but also cause toxic effects on animals and plants. Due to their complicated environmental behavior and lack of relevant data, the environmental behavior remains unclear. In this study, the adsorption-desorption and degradation characteristics of the third-generation cephalosporin drug ceftiofur (CEF) were investigated in three agricultural soils (sandy loam, loam and clay). According to the relevant parameters of the Freundlich adsorption isotherm (the K_f range was 57.63-122.44 μg^1-1/n L^1/n kg^-1), CEF was adsorbed moderately in the soils and had the potential to migrate into groundwater. CEF exhibited low persistence in the soils and faster degradation than other antibiotics, such as tetracyclines and fluoroquinolones. The degradation half-lives (DT50) of CEF in soils ranged from 0.76 days to 4.31 days. Adding feces, increasing the water content, providing light and increasing the temperature significantly accelerated the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged when the soils were sterilized, indicating that both physical degradation and biodegradation played important roles in the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged at high concentrations, indicating that the degradability of CEF in soils was affected by the initial concentration. No significant differences were observed in the DT50 values for the different soil types (p > 0.05). This study provides useful information about the environmental behavior of CEF and improves the environmental risk assessment of CEF.

Recognition of human hemoglobin with macromolecularly imprinted polymeric nanoparticles using non-covalent interactions

Hemoglobin (Hb) is the most abundant protein in the blood. It is vital for the living as oxygen carriers. Some of the very pure Hb-containing biological fluids are currently under clinical trial. However, the removal and purification of Hb from the blood are quite difficult, especially when it is at a low concentration level. In this study, the molecularly imprinted polymeric nanoparticles (MIPNs) were prepared using N-methacryloyl-histidine methyl ester (MAH) by mini-emulsion polymerization technique for specific binding of human hemoglobin (HHb). MIPNs in monosize form have a size of 152 ± 4 nm. They also have a high binding capacity (32.33 mg/g) of HHb. MIPNs retain 84% of the re-binding capacity for HHb after 10 cycles. The nanoparticles have 16 and 5 times higher binding capacity of HHb, respectively, in the presence of bovine serum albumin and lysozyme. Thanks to their high binding capacity and selectivity, MIPNs will allow them to be detected selectively for different target molecules. According to molecular docking, the main binding forces depend on hydrogen bonds and Van der Waals forces in the interaction within 5 Å around MAH molecule are observed through the amino acid residues of HHb at β1 and β2 subunit. The statistical mechanical analysis of docking showed that the free energy (ΔG) is -2732.14 kcal/mol, which indicates the interaction between MAH and HHb is energetically favorable at 298.15°K.

The role of soils in regulation of freshwater and coastal water quality

Water quality regulation is an important ecosystem service function of soil. In this study, the mechanism by which soil regulates water quality was reviewed, and the effects of soil management on water quality were explored. A scientometrics analysis was also conducted to explore the research fields and hotspots of water quality regulation of soil in the past 5 years. This review found that the pollutants entering the soil can be mitigated by precipitation, adsorption and desorption, ion exchange, redox and metabolic decomposition. As an optimal substrate, soil in constructed wetlands has perfect performance in the adsorption and passivation of pollutants such as nitrogen, phosphorus and heavy metals in water, and degradation of pesticides and emerging contaminants. Mangrove wetlands play an important role in coastal zone protection and coastal water quality restoration. However, the excessive application of agricultural chemicals causes soil overload, which leads to the occurrence of agricultural non-point source pollution. Under the dual pressures of climate change and food insecurity in the future, developing environmentally friendly and economically feasible sustainable soil management measures is crucial for maintaining the water purification function of soil by relying on the accurate quantification of soil function based on big data and modelling. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Influence of Organic Matter in Sorption of the Saflufenacil in Ferralsols

The saflufenacil herbicide has been applied in the agricultural areas as an efficient alternative for the control of resistant weeds to glyphosate. However, the environmental risks from the use of saflufenacil, especially in tropical soil, is not yet clearly known. We evaluated if the organic matter addition into the soil influences the sorption of saflufenacil in samples of a sandy and clayey texture soils. The sugarbeet was used as a species indicating the presence of saflufenacil in the solution of the substrates. We estimated the required dose of saflufenacil responsible for causing 50% of sugarbeet intoxication (C₅₀) and the sorption ratio (SR) of this herbicide. The addition of organic matter increased the C₅₀ and SR of saflufenacil in both soils. Here it is demonstrated that the soil organic matter content increases saflufenacil sorption in tropical soils and, consequently influences the dose of this herbicide to be applied in pre-emergence of weeds.

Use of the Dynamic Technique DGT to Determine the Labile Pool Size and Kinetic Resupply of Pesticides in Soils and Sediments

The diffusive gradients in thin films (DGT) technique has been successfully and widely applied to investigate the labile fractions of inorganic contaminants in soils and sediments, but there have been almost no applications to organic contaminants. Here we developed and tested the approach for the pesticide Atrazine (ATR) in a controlled soil experiment and in situ in an intact lake sediment core. The soil study explored the relationships between soil solution, DGT measured labile ATR and solvent extractable ATR in dosed soils of different organic matter, pH status and incubation times. The results are further interpreted using the DIFS (DGT-induced fluxes in soils and sediments) model. Resupply of ATR to the soil solution was partially sustained by the solid phase in all the soils. This was due to small labile pool size and slow kinetics, with soil pH being an important controlling factor. The in situ sediment study successfully used a DGT probe to examine labile ATR distribution through the core on the subcm scale. It demonstrated-for the first time-an easy to use in situ technique to investigate the effects of redox on resupply kinetics and biogeochemical processes of trace organic contaminants in sediments.

Mobility of insecticide residues and main intermediates in a clay-loam soil, and impact of leachate components on their photocatalytic degradation

This work assesses the behavior (adsorption, degradation and leaching) of four insecticides (chlorantraniliprole, thiametoxam, imidacloprid and pirimicarb) and their main reaction intermediates in a clay-loam textured soil (1.6% OM). Following the batch equilibrium method, the K_OC (as log values) ranged from 1.2 to 3.9 (thiametoxam and pirimicarb, respectively). All the insecticides were moderately persistent (t_½ = 39-100 days) in the following order: thiametoxam > imidacloprid > pirimicarb > chlorantraniliprole. Two major transformation products, desmethyl-formamido pirimicarb and desmethyl pirimicarb, were formed as consequence of dealkylation of the parent compound. Using disturbed soil columns only thiametoxam (93% of the initial amount) and imidacloprid (42% of the initial amount) were recovered from leachates. In the case of pirimicarb and chlorantraniliprole, 74% and 30%, respectively, were recovered from the soil. Thiametoxam and imidacloprid can be catalogued as mobile compounds, while pirimicarb and chlorantraniliprole are classified as immobile according to the screening indices used (GUS and ELI). Leachates containing thiametoxam and imidacloprid were subjected to photocatalytic treatment for 240 min using TiO₂/Na₂S₂O₈ with the help of a photochemical reactor equipped with LED lamp. Both compounds had a very fast degradation rate (half-lives ≤ 0.5 min) in deionized water, while their half-lives were 112 min and 178 min, respectively, in leaching water. This implies a strong effect of the water matrix composition, mainly due to organic matter dissolved (quenching). Only traces of thiametoxam urea and hydroxy imidacloprid were detected during the photocatalytic experiment.

Amendments with pyrolyzed agrowastes change bromacil and diuron's sorption and persistence in a tropical soil without modifying their environmental risk

Knowledge of pesticides fate in tropical soils and how it could be affected by pyrolyzed biomass as amendment is limited. Combining conventional and radiotracer methods, as well as risk assessment tools, the effects of several charred agrowastes on the sorption, persistence, and ecological risk of the herbicides bromacil (BMC) and diuron (DRN) were evaluated in a tropical agricultural soil under laboratory conditions. Pineapple stubble (PS), palm oil fiber (PF), and coffee hull (CH) were charred at 300 (torrefied) and 600 °C (biochar) and applied to the soil at 10 and 20 t ha^-1 rates. The sorption coefficients (Koc) in unamended soil for BMC and DRN were 18.4 and 212.1 L kg^-1, respectively. The addition of torrefied PS and PF caused a 3 to 4-fold increment in BMC sorption and a 3 to 6-fold change in DRN's sorption. The only biochar that affected the sorption was PS that increased DRN's sorption 3.5 times. The application of coffee hull materials had no significant effect. In terms of degradation (half-life, DT50), for unamended soil BMC's degradation (300 days) was limited compared to DRN (73 days). Alternatively, biodegradation (mineralization half-life time, MT50) was 1278 d for BMC and 538 for DRN. While only PF and CH torrefied increased BMC's persistence, all the torrefied affected DRN's persistence. However, despite the observed effects, the predicted ecological risk was not mitigated. Our results highlight the need for scientific evidence on the use of pyrolyzed organic amendments to assess potential benefits and prevent unintended impacts in tropical agroecosystems.

Influence of chemical charge on the fate of organic chemicals in sediment particle size fractions

In order to investigate the influence of differently sized particle fractions on the fate of ionic chemicals in water-sediment systems, we performed simulation studies following OECD guideline 308. We used ¹⁴C-labelled anionic (4-n-dodecylbenzenesulfonic acid sodium salt, '¹⁴C-DS^-'), cationic (4-n-dodecylbenzyltrimethyl ammonium chloride, '¹⁴C-DA⁺') and non-ionic (4-n-dodecylphenol, '¹⁴C-DP') organic chemicals. The sediment was subjected to particle size fractionation. For each particle fraction and test compound, water-sediment systems were prepared and incubated for 14 days. Across all particle fractions, higher amounts of applied radioactivity (AR) of ¹⁴C-DS^- (in sand 60.1%, in silt 45.1%, in clay 57.0%) and of ¹⁴C-DP (sand: 31.8%, silt: 24.4%, clay: 29.2%) were mineralised compared to ¹⁴C-DA⁺ (sand: 5.1% AR, silt: 3.5% AR, clay: 2.4% AR). The highest bioavailability was observed for ¹⁴C-DS^- followed by ¹⁴C-DP and ¹⁴C-DA⁺ across all particle fractions. Formation of non-extractable residues (NER) of ¹⁴C-DS^- did not substantially differ between the particle fractions, whereas NER formation of ¹⁴C-DA⁺ was higher in the clay fraction (24.3% AR) than in silt (15.9% AR) and sand (8.4% AR). The same trend was observed for ¹⁴C-DP. We showed that differently sized particle fractions have an influence on the fate of ionic chemicals in water-sediment systems and conclude that this should be considered when simulation studies in soils and sediments with different textural compositions are performed. Since a positive charge of organic chemicals tends to form higher portions of NER in the clay fraction of sediments, these NER should be further investigated in terms of their nature and types of binding.

The quality of soil organic matter, accessed by 13C solid state nuclear magnetic resonance, is just as important as its content concerning pesticide sorption

The global increase of food production has been achieved mainly through the intensive use of inputs such as pesticides. Once released to the soil, sorption (which could be represented by Freundlich solid-water distribution coefficients - K_F) and degradation are two governing processes that determine the distribution and persistence of pesticides in the environment. In spite of the huge dataset, the only apparent generalisation is the high correlation between K_F and soil organic matter (SOM) content. However, in this work no correlation was observed between K_F and organic C content (OC) and so the obtained K_OC (K_F normalised by OC) spread out in a wide range: 1100 to 11,400 mL g^-1 for abamectin; and 30-150 mL g^-1 for atrazine, both ranges corroborate with data from literature. These high variabilities indicate that other soil components or SOM quality strongly interfere in the pesticide sorption in addition to SOM content. Seeking to estimate the influence of SOM quality in the abamectin and atrazine K_OC values, the humic acids, a fraction of the SOM, was analysed by ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) and Principal Component (PC) Regression. The first PC of ¹³C NMR spectra presented negative loadings for aliphatic compounds and positive loadings for aryl C, typical of partially oxidised pyrogenic C. Their scores showed strong correlation with the abamectin K_OC values (R² = 0.91, p < 5 10^-8) and weaker with atrazine K_OC (R² = 0.63, p < 0.0001), in addition to a smaller standardised slope: 1.01 for abamectin and 0.76 for atrazine. These results could be explained by the higher hydrophobicity of abamectin, being thus more prone to interact with the polycondensed aryl groups from the pyrogenic C. It is also important to highlight that humic acids are useful proxies for understanding the paramount interaction of SOM with pesticides.

Studies on the sorption behavior and plant uptake of pesticides in Japanese soils

To estimate pesticide residue levels in succeeding crops based on those in soils, the relationship between pesticide concentrations in komatsuna (Brassica rapa var. perviridis) and the concentrations extracted sequentially from soils using water and acetone was investigated. The concentrations of many pesticides in komatsuna shoots showed higher positive correlation with water-extractable concentrations (C _W) than total-extractable concentrations in soils, so that the C _W was available for evaluating the phytoavailability of pesticides in the soil. As a result of examining the dissipation behavior of the C _W, the dissipation of the C _W was able to be predicted by considering time-dependent soil sorption, which could be estimated using the sorption coefficients (K _d) measured by a standard batch method. Furthermore, the present study showed that the properties of soil organic carbon such as black carbon content and the molecular structure of pesticides were important for estimating the K _d values more accurately.

Towards a spatiotemporally explicit toxicokinetic-toxicodynamic model for earthworm toxicity

The aim of the environmental risk assessment of chemicals is the prevention of unacceptable adverse effects on the environment. Therefore, the risk assessment for in-soil organisms, such as earthworms, is based on two key elements: the exposure assessment and the effect assessment. In the current risk assessment scheme, these two elements are not linked. While for the exposure assessment, advanced exposure models can take the spatial and temporal scale of substances into account, the effect assessment in the lower tiers considers only a limited temporal and spatial variability. However, for soil organisms, such as earthworms, those scales play a significant role as species move through the soil in response to environmental factors. To overcome this gap, we propose a conceptual integration of pesticide exposure, ecology, and toxicological effects on earthworms using a modular modeling approach. An essential part of this modular approach is the environment module, which utilizes exposure models to provide spatially and temporally explicit information on environmental variables (e.g., temperature, moisture, organic matter content) and chemical concentrations. The behavior module uses this information and simulates the feeding and movement of different earthworm species using a trait-based approach. The resulting exposure can be processed by a toxicokinetic-toxicodynamic (TKTD) module. TKTD models are particularly suitable to make effect predictions for time-variable exposure situations as they include the processes of uptake, elimination, internal distribution, and biotransformation of chemicals and link the internal concentration to an effect at the organism level. The population module incorporates existing population models of different earthworm species. The modular approach is illustrated using a case study with an insecticide. Our results emphasize that using a modular model approach will facilitate the integration of exposure and effects and thus enhance the risk assessment of soil organisms.

Fate of the nonsteroidal, anti-inflammatory veterinary drug flunixin in agricultural soils and dairy manure

A large percentage of flunixin, a nonsteroidal anti-inflammatory drug widely used for treating livestock, is excreted in intact form and thus potentially available for environmental transport. As the fate of flunixin in the environment is unknown, our objective was to quantify sorption, desorption, and transformation in five agricultural soils and manure using batch equilibrium methods. Concentrations of flunixin and degradation products were determined by high performance liquid chromatography time of flight mass spectrometry. For all studied soils, sorption of flunixin exhibited linear character, with both linear and Freundlich models providing adequate fit. Linear sorption coefficients varied from 8 to 112 L kg^-1. The strongest Pearson correlations with sorption coefficients were for clay content (r = 0.8693), total nitrogen (r = 0.7998), and organic carbon (r = 0.6291). Desorption of the reversibly bound fraction (3-10% of total sorbed flunixin) from all five studied soils exhibited non-hysteretic character suggesting low affinity of this fraction of flunixin to soil. Flunixin degradation in soils was relatively slow, exhibiting half-lives of 39-203 days, thus providing time for off-site transport and environmental contamination. The biological impacts of flunixin at environmentally relevant concentrations must be determined given its environmental behavior and extensive use as a nonsteroidal anti-inflammatory drug in livestock. Graphical abstract.

Reactivity of vadose-zone solids to S-metolachlor and its two main metabolites: case of a glaciofluvial aquifer

The vulnerability of groundwater to pesticides is governed in part by sorption mechanisms in the vadose zone, commonly studied in soil but less well-known in the geological solids. To alleviate this lack of knowledge, adsorption of the herbicide S-metolachlor (SMOC) and of two of its metabolites-metolachlor ethane sulfonic acid (MESA) and metolachlor oxanilic acid (MOXA)-was studied with batch equilibrium method on seventeen surface soils and three geological solids of the vadose zone overlying a glaciofluvial aquifer. In grainsize terms, the latter three were sand for the first two samples and gravel for the third. Adsorption is ordered as follows: SMOC > > MESA > MOXA, except for one of the geological solids for which MESA adsorption was slightly higher than that of SMOC (K_d = 0.73 vs. 0.44 L kg^-1). The low MOXA adsorption could only be quantified for the gravel sample (K_d = 0.74 L kg^-1), which was also more reactive than all the other samples to MESA and SMOC (K_d = 2.08 and 28.8 L kg^-1, respectively). Statistical multivariate tests related the highest K_d values for SMOC with the soils and geological solids with the highest organic-carbon and clay-fraction contents. The highest K_d values for MESA were found in the samples containing high oxide concentrations. Our results shed a new light on the adsorption of SMOC, MESA and MOXA suggesting that during their transfer to groundwater, pesticides and metabolites can be adsorbed in the vadose zone on both soils and geological solids.

A review of the impact of wastewater on the fate of pesticides in soils: Effect of some soil and solution properties

Reuse of wastewater (WW) as an agricultural irrigation source is being considered with increasing interest, mainly in arid and semiarid zones. However, due to the complex nature of WW its reuse can have an impact on the fate of the pesticides added to the soils and crops for pest control. This review provides a detailed insight about the main processes involved in pesticide-soil-WW interactions (adsorption/desorption, degradation, transport, plant uptake and field assays) focusing on the role of dissolved organic matter and salt content in the mentioned processes. The influence of pesticide and soil properties in these processes is also discussed. The review explores current research gaps in the pesticide-soil-WW interactions and identifies areas that merit further research, providing a perspective for further scientific exploration.

A critical review of different factors governing the fate of pesticides in soil under biochar application

Pesticides are extensively used in the modern agricultural system. The inefficient and extensive use of pesticides during the last 5 to 6 decades inadvertently led to serious deterioration of environmental quality with health risk to living organisms, including humans. It is important to use some environmentally-friendly and sustainable approaches to remediate, restore and maintain soil quality. Biochar has gained considerable attention globally as a promising soil amendment because it has the ability to adsorb and as such minimize the bioavailability of pesticides in soils. This review emphasizes the recent trends and implications of biochar in pesticide-contaminated soils, as well as highlights need of the pesticides use and associated environmental issues in context of the biochar application. The overarching aim of this review is to signify the role of biochar on primary processes such as effect of biochar on the persistence, mineralization, leaching and efficacy of pesticides in soil. Notably, the effects of biochar on pesticide adsorption-desorption, degradation and bioavailability under various operating/production conditions are critically discussed. This review delineates the indirect impact of biochar on pesticides persistence in soils and proposes key recommendations for future research which are essential for the remediation and restoration of pesticides-impacted soils.

Use of Index-Based Screening Models to Evaluate the Leaching of Triclopyr and Fluroxypyr Through a Loam Soil Amended with Vermicompost

The effect of vermicompost added to a loam soil on the leaching behaviour of two herbicides (triclopyr and fluroxypyr) was examined. Mobility of the herbicides was assessed using disturbed soil columns under laboratory conditions. In both cases, the addition of vermicompost significantly increased the sorption of the compounds. For both, DT₅₀ values were slightly higher in the amended soil, due to the increased adsorption. Rate constants (k) calculated according to pseudo-first order model were significantly lower in the case of triclopyr (very persistent), which led to a much lower degradation rate compared to fluroxypyr (persistent) in both unamended and amended soils. Values calculated for the experimental leaching index (ELI) in unamended and amended soils showed medium and high leachability for fluroxypyr (0.31 and 0.29) and triclopyr (0.72 and 0.70), respectively. Other index-based screening models (GUS, RLPI, LIX) also catalogue both herbicides as potential leachers. Results confirm that triclopyr and fluroxypyr may contaminate groundwater resources.

Environmental risk assessment of the anionic surfactant sodium lauryl ether sulphate in site-specific conditions arising from mechanized tunnelling

Sodium lauryl ether sulphate (SLES) is the anionic surfactant commonly utilized as the main synthetic chemical component in most foaming agents used in mechanized tunnelling. This produces huge amounts of soil debris which can contain residual concentrations of SLES. The absence of environmental quality standards for soil and water and the limited information about SLES persistence in real excavated soils do not facilitate any re-use of soil debris as by-products. The environmental risk assessment (ERA) of foaming agents containing SLES can be a valid tool for this purpose. In this study, an ERA analysis of SLES in 12 commercial formulations (cf) used for tunnelling excavation was performed. Various soils from different tunnel excavation sites were conditioned with the selected foaming agents containing SLES. Predicted or measured environmental concentrations (PECs, MECs) were determined and then compared with the Predicted No Effect Concentrations (PNECs) for both the terrestrial and aquatic compartments. The results indicate a reduction of the potential risk over time for these ecosystems, with differences depending on both the commercial foaming formulation and the spoil material characteristics. However, because potential threats to the natural environment cannot be excluded, some risk management and mitigation actions are discussed.

Sensitivity analysis of the Pesticide in Water Calculator model for applications in the Pampa region of Argentina

Despite the widespread use of pesticides in the Pampa region of Argentina, mathematical models are rarely employed to predict pesticide fate due to the lack of regionally tested models and the absence of readily available databases to run such models. The objective of the current study was to perform a sensitivity analysis of the Pesticide in Water Calculator (PWC) model for the Pampa Region of Argentina. The sensitivity analysis was performed while simulating applications of 2,4-D (mobile, low Kd) and glyphosate (soil-binding, high Kd) in five localities of the Pampa region: Anguil, Paraná, Marcos Juárez, Pergamino and Tres Arroyos. The sensitivity of the various parameters involved in PWC modelling was evaluated though a two-steps sensitivity analysis which included a first screening of less sensitive parameters with Morris method, followed by a fully global sensitivity analysis of the remaining parameters using Sobol method. When ran under soil and climate conditions typical of the Pampa region of Argentina, PWC was most sensitive to 25% of the parameters evaluated. The sensitive parameters identified depended mainly on the nature of the pesticide molecule being modelled; the location and endpoint considered having much less influence on the sensitivity results. Sensitive parameters belonged to two main grand categories: (i) degradation rates of the pesticide in soil and water, and (ii) parameters descriptive of soil binding, runoff and erosion. The sensitivity analysis of the model PWC performed in the current study represents a crucial first step towards the development and expansion of probabilistic pesticide risk assessment in Argentina, and provides important parameterization criteria that will help obtaining more certain modelling results from PWC in Argentina and elsewhere.

Adsorption-Desorption Behavior of Polar Imidazolinone Herbicides in Tropical Paddy Fields Soils

Analysis of herbicides sorption behavior in soil is critical in predicting their fate and possible harmful side effects in the environment. Application of polar imidazolinone herbicides is growing in tropical agricultural fields. Imidazolinones have high leaching potential and are persistent. In this study, adsorption-desorption of imazapic and imazapyr herbicides were evaluated in different types of Malaysian agricultural soils. Effects of soil parameters were also investigated on the soils' sorption capacities. The adsorption data fitted best to Freundlich isotherm (R² > 0.991). The herbicides adsorptions were physical and spontaneous processes as ΔG values were negative and below 40 kJ/mol. The adsorption correlated positively with clay content, total organic carbon (TOC) content, and cation exchange capacity (CEC). There were strong negative correlations between hysteresis index and these factors indicating their importance in imidazolinones immobilization and, thus, their pollution reduction in the environment.

Pharmaceutical and Personal Care Products: From Wastewater Treatment into Agro-Food Systems

Irrigation with treated wastewater (TWW) and application of biosolids introduce numerous pharmaceutical and personal care products (PPCPs) into agro-food systems. While the use of TWW and biosolids has many societal benefits, introduction of PPCPs in production agriculture poses potential food safety and human health risks. A comprehensive risk assessment and management scheme of PPCPs in agro-food systems is limited by multiple factors, not least the sheer number of investigated compounds and their diverse structures. Here we follow the fate of PPCPs in the water-soil-produce continuum by considering processes and variables that influence PPCP transfer and accumulation. By analyzing the steps in the soil-plant-human diet nexus, we propose a tiered framework as a path forward to prioritize PPCPs that could have a high potential for plant accumulation and thus pose greatest risk. This article examines research progress to date and current research challenges, highlighting the potential value of leveraging existing knowledge from decades of research on other chemicals such as pesticides. A process-driven scheme is outlined to derive a short list that may be used to refocus our future research efforts on PPCPs and other analogous emerging contaminants in agro-food systems.

Pesticide Sorption to Soilless Media Components Used for Ornamental Plant Production and Aluminum Water Treatment Residuals

Commercial producers of containerized ornamental plants almost exclusively use soilless media as the substrate for growing the plants. Soilless media are composed primarily of organic materials as opposed to mineral soils. Significant amounts of pesticides can leach from pots containing soilless media to which pesticides have been added as drenches or top-dressings. One of the goals of this project was to identify whether individual components comprising soilless media have differing affinities for the pesticides acephate, imidacloprid, metalaxyl, and plant growth regulator paclobutrazol. One-point 24 h equilibrium sorption assays were conducted to characterize sorption of the pesticides to sand, perlite, vermiculite, coir, peat, pine bark, and aluminum-water treatment residuals (Al-WTRs). Five-point isotherms were then constructed for the more sorptive peat and pine bark substrate components, and for the Al-WTRs. Results indicated significant differences in pesticide behavior with each substrate. Sorption of acephate to most of the substrate components was relatively low, comprising 21-31% of the initial amounts for soilless media components and 63% in Al-WTRs. Al-WTRs were highly sorptive for imidacloprid as evidenced by a partition coefficient of K F = 3275.4 L kg-1. Pine bark was the most sorptive for metalaxyl-M with a measured K F = 195.0 L kg-1. Peat had the highest affinity for paclobutrazol (K F = 398.4 L kg-1). These results indicate that none of component of soilless media has a universally high attraction for all of the pesticides studied.