Pesticide Transport Research Articles

Simulating event-based pesticide transport with runoff and erosion; OpenLISEM-pesticide v.1

This study presents a novel pesticide transport module for the OpenLISEM runoff and erosion model. During water erosion events, high amounts of pesticides can be transported alongside the runoff. Simulating this process helps to mitigate adverse effects of pesticides in the environment. We conceptualized pesticide uptake during runoff with a mixing-layer, including mass transfer of dissolved pesticides into the runoff water and detachment in combination with enrichment of sorbed pesticides. Lateral transport of pesticides is modelled with a kinematic wave based on the overland flow of water. The model simulations were in line with observations for two events in a small agricultural catchment in South-Limburg, the Netherlands. A sensitivity analysis showed that pesticide transport was mainly influenced by the mass transfer rate, the soil-water partitioning and the exponent for the enrichment ratio. The accurate simulation of runoff and erosion by OpenLISEM, enables OpenLISEM-pesticide to simulate transport and redistribution adequately.

A Mechanistic Model for Simulation of Carbendazim and Chlorothalonil Transport through a Two-Stage Vertical Flow Constructed Wetland

A mechanistic model was developed to simulate one-dimensional pesticide transport in two-stage vertical flow constructed wetland. The two pesticides taken under study were carbendazim and chlorothalonil. The water flow patterns within the constructed wetland were simulated using the Richards equation. Water content and vertical flux, which are the outputs of the substrate water flow model, were used to calculate the substrate moisture-related parameters and advection term in the solute transport model. The governing solute transport equation took into account a total of six processes: advection, molecular diffusion, dispersion, adsorption to the solid surface, degradation and volatilization. A total of 14 simulation cases, corresponding with available experimental data, were used to calibrate the model, followed by further simulations with standardized influent pesticide concentrations. The simulations indicated that the constructed wetland reached a steady state of pesticide removal after 7 days of operation. Two distinct water flow patterns emerged under saturated and unsaturated conditions. The patterns observed while varying the hydraulic loading rates were similar for each individual saturation condition. Two-factor ANOVA of the simulated data further revealed that the carbendazim and chlorothalonil removal was dependent on the hydraulic loading rates, but it was independent of the influent pesticide concentration. Analysis of the simulated pesticide removal showed that degradation emerged as the predominant removal process over time for both the pesticides. The model developed in this study can be an important tool for the design and construction of treatment wetlands for pesticide removal from wastewater.

Low-molecular-weight organic acids-mediated transport of neonicotinoid pesticides through saturated soil porous media: Combined effects of the molecular structures of organic acids and the chemical properties of contaminants

Empirical information about the transport properties of neonicotinoid pesticides through the soil as affected by the ubiquitous low molecular weight organic acids (LMWOAs) is lacking. Herein, the impacts of three LMWOAs with different molecular structures, including citric acid, acetic acid, and malic acid, on the mobility characteristics of two typical neonicotinoid pesticides (Dinotefuran (DTF) and Nitenpyram (NTP)) were explored. Interestingly, under acidic conditions, different mechanisms were involved in transporting DTF and NTP by adding exogenous LMWOAs. Concretely, acetic acid and malic acid inhibited DTF transport, ascribed to the enhanced electrostatic attraction between DTF and porous media and the additional binding sites provided by the deposited LMWOAs. However, citric acid slightly enhanced DTF mobility due to the fact that the inhibitory effect was weakened by the steric hindrance effect induced by the deposited citric acid with a large molecular size. In comparison, all three LMWOAs promoted NTP transport at pH 5.0. Because the interaction between NTP with soil organic matter (e.g., via π-π stacking interaction) was masked by the LMWOAs coating on soil surfaces. Nevertheless, LMWOAs could promote the mobility of both neonicotinoid pesticides at pH 7.0 due to the steric hindrance effect caused by the deposited organic acids and the competitive retention between LMWOAs and pesticides for effective surface deposition sites of soil particles. Furthermore, the extent of the promotion effects of LMWOAs generally followed the order of citric acid > malic acid > acetic acid. This pattern was highly related to their molecular structures (e.g., number and type of functional groups and molecular size). Additionally, when the background solutions contained Ca2+, the bridging effect of cations also contributed to the transport-enhancement effects of LMWOAs. The findings provide valuable information about the mobility behaviors of neonicotinoid pesticides co-existing with LMWOAs in soil-water systems.

Airborne Pesticides from Agricultural Practices: A Critical Review of Pathways, Influencing Factors, and Human Health Implications.

This critical review examines the release of pesticides from agricultural practices into the air, with a focus on volatilization, and the factors influencing their dispersion. The review delves into the effects of airborne pesticides on human health and their contribution to anthropogenic air pollution. It highlights the necessity of interdisciplinary research encompassing science, technology, public policy, and agricultural practices to effectively mitigate the risks associated with pesticide volatilization and spray dispersion. The text acknowledges the need for more research to understand the fate and transport of airborne pesticides, develop innovative application technologies, improve predictive modeling and risk assessment, and adopt sustainable pest management strategies. Robust policies and regulations, supported by education, training, research, and development, are crucial to ensuring the safe and sustainable use of pesticides for human health and the environment. By providing valuable insights, this review aids researchers and practitioners in devising effective and sustainable solutions for safeguarding human health and the environment from the hazards of airborne pesticides.

Exploration of a comprehensive versus a regulatory-oriented modeling framework for field pesticide transport assessment

Numerous computer models have been developed for simulating pesticide fate and transport. It is usually hard to choose which model is the best for a particular research or regulatory purpose. Currently, the PRZM (Pesticide Root Zone Model) model is widely used for regulatory purposes regarding runoff and erosion. However, it simplifies many hydrological processes and management practices which affect pesticide fate simulations. In this study, the APEX (Agricultural Policy / Environmental eXtender model) model, which is more comprehensive and may provide a more realistic representation of pesticide fate, was compared with the PRZM model regarding methods and capabilities of characterizing hydrology, management, and pesticide transport. Four case studies were used to compare the performances of the two models for simulating surface runoff, sediment yield, pesticide in runoff, and pesticide in sediment. Results showed that the APEX model performed better than the PRZM model for simulating surface runoff and sediment yield, and performed similarly to the PRZM model for simulating pesticide loads in runoff and erosion. Both models have limitations for capturing the runoff events caused by high intensity rainfall. APEX is superior to PRZM in simulating detailed management operations, considering more hydrological processes, and achieving spatially distributed simulation, but it requires a higher number of inputs and user-selected parameters compared to PRZM. With further validations of the capabilities of APEX in pesticide modeling and the development of web-based platforms to facilitate the set up and use of comprehensive models, a more accurate and reliable pesticide assessment scheme is anticipated by using comprehensive models like APEX.

Identification of representative sampling sites for the investigation of aerial longer distances transport of pesticides in Germany

Aerial transport of pesticides during and after their application both over medium range distances and long distance may lead to residues on plants and soil far away from agricultural treatments. Therefore, the Federal Office of Consumer Protection and Food Safety carried out a Germany-wide geographical analysis to identify monitoring sites which could be used for a representative German-wide monitoring. The identified sites reflect climate areas with different meteorological conditions, land coverage and pesticide use. By using a geographical information system, five different areas were identified representing the climatic and agricultural conditions of pesticide use in Germany. Since the required measuring technique needed a certain infrastructure, using already existing measuring sides was considered to be most efficient in order to use them for a German-wide monitoring. In a second step, agro-meteorological weather stations with distances of < 100 m, 100–1000 m and > 1 km in the main wind direction from treated fields were identified within these areas. The identified areas reflect the main different conditions for aerial pesticide transport along with suitable weather stations to monitor pesticide residues in the air and its deposition on plants and soil all over Germany.

Pesticide transport through the vadose zone under sugarcane in the Wet Tropics, Australia

Abstract. Photosystem II (PS II) pesticides, recognized as a threat to ecological health, were targeted for reduction in sugarcane farming in Great Barrier Reef (GBR) catchments. Alternative herbicides, the non-PS II herbicides (including glyphosate, paraquat, 2,4-D, imazapic, isoxaflutole, metolachlor, and S-metolachlor), continue to be used in these catchments. However, the potential ecological fate, transport, and off-site environmental effects of non-PS II herbicides, with respect to their usage scheme, local rainfall patterns, and infiltration dynamics, have not been investigated previously. A vadose zone monitoring system, instrumented beneath sugarcane land in a GBR catchment, was applied for real-time tracing of pesticide migration across the unsaturated zone, past the root zone during 2017–2019. The regularly applied pesticides (fluroxypyr and isoxaflutole) exhibited substantial migration through the unsaturated zone. Within 1 month of application of fluroxypyr, it leached to 2.87 m depth in the vadose zone, with declining concentrations with depth. Isoxaflutole, which was applied yearly, was found only once, in November 2018, at 3.28 m depth in the soil profile. Other pesticides (imazapic, metolachlor, glyphosate, and haloxyfop) applied during the same period were not detected in the vadose zone. However, imidacloprid, which was not applied at the site during the monitored period, was detected across the entire vadose zone, revealing substantial resistance to degradation. The results show no evidence of any regularly applied pesticides in the site bores at the end of the study, indicating their ultimate degradation within the vadose zone before reaching the groundwater.

Application of pesticide in paddy fields: a Southeast Asia case study review.

Pesticides are widely employed in rice crops since the ecosystem and surroundings of paddy promote insects, weeds, and fungal and bacterial pathogens. Each commonly utilised pesticide possesses different uses. For instance, fungicides control fungal issues, herbicides curb weed growth, and insecticides destroy and repel insects. Although several ways to categorise them exist, pesticides are typically classified according to their chemical compositions. Rice production remains one of the most dominant crops grown in most Southeast Asian countries as it is a staple food. Nonetheless, the crop is highly dependent on pesticides, leading to growing concerns over the potential adverse effects of pesticides on the environment and human health. Despite the availability of numerous studies on the subject, a comprehensive understanding of the specific effects of pesticides on paddy fields in Southeast Asia is still lacking. Consequently, reviewing existing knowledge is necessary for synthesising and identifying research gaps to better inform policymakers, farmers, and other stakeholders in the agricultural sector. The objectives of the present review paper were to review the interactions between pesticides and the environment by understanding the physical and chemical properties of the chemicals, compare pesticide transportation modes in air, water, and soil and how they affect the environment, and evaluate and discuss the effects of pesticides on non-targeted organisms. This study assessed pesticide innovation reported between 1945 and 2021 for a better understanding of the utilisation of the chemicals over time. The pesticides assessed in this study were classified based on their chemical compounds, such as organochlorines, organophosphates, carbamates, and pyrethroid. This review could provide a comprehensive understanding of the interactions between pesticides and the environment and their impacts on non-targeted organisms.

Modeling Environmental Fate, Transport, and Transformation of Pesticides: First-Order Kinetic Models for Regional and Global Applications

Predicting pesticide residue masses in environments requires time- and cost-efficient fate models, particularly for high-throughput simulations of hundreds of active ingredients registered for use in agriculture. Due to the adaptability of first-order kinetics-based models for simulating the fate of pesticides in environments of varying scales, we conduct a review of these models in the present investigation. We discuss the application of first-order kinetics-based fate models in different types of compartments, such as environmental media, plant tissues, and animal bodies, and at different levels, such as the product-oriented life cycle impact assessment and the chemical-oriented health risk assessment. In addition, the first-order kinetics-based rate constants of pesticides provide process- and scenario-specific information on the fate, transport, and transformation of pesticides, which is essential for predicting pesticide residue masses in different environmental compartments. By varying the level of model complexity and site-specific rate constants of pesticides, the first-order kinetics-based fate models can be used as either comparable or absolute tools for conducting the life cycle impact assessment or the health risk assessment of pesticides, respectively. Bioconcentration, bioaccumulation, and biomagnification of pesticides may be evaluated with the aid of an inventory database of rate constants based on first-order kinetics in future research. We suggest incorporating non-first-order kinetic processes into the first-order kinetics-based model to advance risk assessment, as well as approximating non-first-order kinetic processes using first-order kinetics to facilitate life cycle impact or screening-level risk assessments.

Assessment of exposure to pesticides and the knowledge, attitude and practice among farmers of western Bhutan.

An estimated 69% of the population of Bhutan is engaged in agriculture. Farmers are exposed to a wide variety of pesticides during the preparation, transport, storage, mixing and application of pesticides posing a significant health risk. A controlled cross-sectional study of farmers in selected sites of Bhutan was conducted to characterize the level of exposure to pesticides and assess their knowledge attitude and practice on the safe handling of pesticides. A total of 399 participants were enrolled in the study comprising of 295 exposed farmers and 104 healthy and unexposed controls. A structured investigator administered questionaries was used to assess their Knowledge, Attitude and practice, and their blood samples were taken for measuring Acetyl Cholinesterase enzyme activity level. There was a significant difference between the Acetyl Cholinesterase enzyme inhibition of exposed and non-exposed control groups observed in the study (P < 0.001). Of the total of 295 farmers, 62 (21.01%) had severe enzyme inhibition of >30% as compared to the unexposed group. Safety practices of handling pesticides were low. The most common symptoms self-reported were headache (OR 1.08, 0.60-1.93) and neurological problems like forgetfulness, lack of concentration (OR 1.12, 0.50-2.48) and increased tiredness (OR 1.075, 0.52-2.19) that were significantly associated with the enzyme inhibition. In addition, we record a very low level of knowledge (17.0%), a fair attitude (63.0%) and poor practice (35.0%) on the safe handling and management of pesticides. This pilot study provides indication of exposure to pesticides in the selected sites of the country. Furthermore, it provides evidence for public health interventions by identifying the exposure patterns and pathways of individuals most at risk in the farming communities of the country. Surveillance and bio-monitoring programs are deemed necessary.

In silico assessment of risks associated with pesticides exposure during pregnancy

Novel Quantitative Structure-Activity Relationship (QSAR) models of compounds' placenta (PL) permeability expressed as their log FM (fetus-to-mother blood concentration) values or binary PL1/0 (crossing/non-crossing) score were generated using a number of statistical tools: Multiple Linear Regression, Boosted Trees, Principal Component Analysis and Artificial Neural Networks, on the basis of molecular descriptors calculated by Mordred software and selected using Partial Least Squares (PLS) analysis. It was established that the most important predictor of both log FM and the binary PL1/0 score is Lipinski – a binary variable reflecting the compounds' ability to satisfy the criteria of drug-likeness according to the Lipinski's “Rule of 5”. The quantitative (log FM) and qualitative (PL1/0) models of PL permeability were applied to 345 pesticides from different chemical families (triazines, carbamates, pyrethroids, organochlorine, organophosphorus and miscellaneous compounds). The ability of studied pesticides to cross the placenta was assessed; the basic physico-chemical parameters responsible for good or poor placenta transport of pesticides were identified and the relationships between the pesticides' PL permeability, blood-brain barrier (BBB) transfer and gastro-intestinal (GI) absorption were investigated. It was found (on the basis of logistic regression analysis) that the probability of a compound crossing the placenta (PL1) is inversely correlated with its lipophilicity and molar refractivity and positively correlated with the total count of oxygen and nitrogen atoms.

Influence of exposure to pesticides on telomere length and pregnancy outcome: Diethylphosphates but not Dimethylphosphates are associated with accelerated telomere attrition in a Palestinian cohort

Exposure to environmental pesticides during pregnancy is associated with adverse health outcomes such as low birth weight and impaired neuro-development. In this study, we assessed maternal leukocyte telomere lengths (TL) in Palestinian pregnant women and compared the data with urinary organophosphate concentrations, demographic, lifestyle and dietary factors, birth weight, body length, gestational age, and head circumference. Women with high urine levels of creatinine adjusted diethylphosphate(DE)derived pesticide metabolites DEP, DETP or DEDTP had shorter telomeres (p = 0.05). Women living in proximity to agricultural fields had shorter telomeres compared to women not living in proximity to agricultural fields (p = 0.011). Regular consumption of organic food was associated with shorter telomeres (p = 0.01), whereas the consumption of other vegetables such as artichokes was rather associated with longer telomeres. By contrast, urine levels of dimethylphosphate(DM)-derived pesticide metabolites DMTP and DMDTP were associated with lower birth weight (p = 0.05) but not with shrter telomeres. In conclusion organophosphate pesticides and living in proximity to agriculture are associated with shorter TL, likely due to higher consumption of contaminated fruits and vegetables and/or the transport of pesticides to non-treatment sites. DE and DM substituted pesticides seem to have different effects on telomeres and development.

Improved physiologically based kinetic (PBK) matrix for biotransfer modeling of pesticides in birds: The role of feather dynamics

Pesticides can transportvia food webs and bioaccumulate in birds. Feathers can be used as a biomarker to investigate the bird's pesticide exposure, but there are no modeling methodologies that can link the bird's daily intake of pesticides to their amounts in feathers. To fill this gap, we propose a physiologically based kinetic modeling approach that takes into account the feather compartment and feather growth dynamics to estimate pesticide biotransfer potentials in the bird's body. In comparison with the non-feather model, the feather compartment acted as an additional elimination pathway for pesticides from the bird's body, resulting in a decrease in the overall simulated pesticide concentrations in the bird's body. High-lipophilic or high-volatile pesticides had exceptionally poor biotransfer potentials in feathers due to thermodynamics (e.g., partitioning potentials) or kinetics (e.g., elimination rates). As a result, legacy pesticides (such as persistent organic pollutants) will have limited biotransfer potentials in feathers, and the presence of legacy pesticides in feathers could imply relatively high daily pesticide consumption rates, which could affect bird reproductive health. The sensitivity and variability tests revealed that the metabolic (or biotransformation) kinetics of pesticides in avian livers influenced the biotransfer potential of pesticides in feathers significantly. Given the lack of information on pesticide metabolic kinetics in avian livers, we strongly suggest that future research (e.g., in vivo or in vitro studies) determine the metabolic or biotransformation rates of pesticides in avian livers in order to improve the performance of models. Furthermore, the use of additional biomarkers such as blood and uric acid could be valuable in assessing birds' exposure to pesticides. Hopefully, this study will help ecologists comprehend the fate, transport, and biotransfer of pesticides in bird feathers from a modeling point of view.

Challenges of spatially extrapolating aquatic pesticide pollution for policy evaluation

Aquatic pesticide pollution is an important issue worldwide. Countries rely on monitoring programs to observe water bodies quality and on models to evaluate pesticide risks for entire stream networks. Measurements are typically sparse and discontinuous which lead to issues in quantifying pesticide transport at the catchment scale. Therefore, it is essential to assess the performance of extrapolation approaches and provide guidance on how to extend monitoring programs to improve predictions. Here we present a feasibility study to predict pesticide levels in a spatially explicit manner in the Swiss stream network based on the national monitoring program quantifying organic micropollutants at 33 sites and spatially distributed explanatory variables. Firstly, we focused on a limited set of herbicides used on corn crops. We observed a significant relationship between herbicide concentrations and the areal fraction of hydrologically connected cornfields. Neglecting connectivity revealed no influence of areal corn coverage on the herbicide levels. Considering chemical properties of the compounds slightly improved the correlation. Secondly, we analysed a set of 18 pesticides widely used on different crops and monitored across the country. In this case, the areal fractions of arable or crop lands showed significant correlations with average pesticide concentrations. Similar results were found with average annual discharge or precipitation if two outlier sites were neglected. The correlations found in this paper explained only about 30 % of the observed variance leaving most of the variability unexplained. Accordingly, extrapolating the results from the existing monitoring sites to the Swiss river network comes with substantial uncertainty. Our study highlights possible reasons for weak matches, such as missing pesticide application data, limited set of compounds in the monitoring program, or a limited understanding of factors differentiating the loss rates from different catchments. Improving the data on pesticide applications will be essential to progress in this regard.

Modeling fate and transport of pesticides from dryland agriculture using SWAT model

The aim of this study was to understand pesticide fate and transport from dryland agriculture in a major drinking water basin using SWAT and to identify critical source areas in the basin. Hydrological calibration results indicated satisfactory simulation of hydrologic processes within the catchment. Long term average observed sediment values (0.16 ton/ha) were compared with the annual average simulated SWAT outputs (0.22 ton/ha). Generally, the simulated concentrations were higher than the observed values, but the distribution pattern and trends were similar among the months. Average concentrations in water were 0.036 μg/L and 0.006 μg/L for fenpropimorph and chlorpyrifos, respectively. Transfer rates of pesticides from landscape to rivers showed that 0.36% of fenpropimorph and 0.19% of the applied amount of chlorpyrifos were exported to the river. Higher amount of fenpropimorph transport from land to the reach was attributed to its lower Koc (soil adsorption coefficient) value compared to chlorpyrifos. Higher amounts from HRUs were observed in the application month (April) and following month (May) for fenpropimorph, while the months after September showed higher amounts for chlorpyrifos. The specific HRUs (Hydrological Response Units) located in sub-basins 3, 5, 9 and 11 presented highest dissolved pesticide amounts, while HRUs in sub-basins 4 and 11 exhibited highest concentrations for adsorbed pesticides. Best management practices (BMPs) were recommended in critical subbasins to protect the watershed. Despite the limitations, the results demonstrate the potential contributions of modeling in terms of assessing pesticide loadings, critical zones and application timing.

Genetic instability in farmers using pesticides: A study in Brazil with analysis combining alkaline comet and micronucleus assays.

The use of pesticides to prevent and control pests also increases food production. Pesticides are widely used by contemporary farmers, especially in Brazil, where the economy is based on agriculture. The objective of this study was to evaluate the genotoxic potential of pesticide use in rural workers in Maringá, Paraná, Brazil. DNA damage in whole blood cells was measured by the comet assay, while the frequency of cell types, abnormalities, and nuclear damage was estimated using the buccal micronucleus cytome assay. Samples of buccal mucosa were collected from 50 male volunteers (27 not exposed to pesticides and 23 occupationally exposed to pesticides). Among them, 44 volunteered for blood sampling (24 unexposed and 20 exposed). In the comet assay, the exposed farmers had a higher damage index than non-exposed ones. There were also statistically significant differences between the groups in the buccal micronucleus cytome assay. Farmers exhibited an increase in basal cell numbers, and cytogenetic alterations, represented by condensed chromatin and karyolitic cells. Comparisons between cell morphologies and epidemiological factors indicated an increased number of condensed chromatin and karyolitic cells in individuals who were responsible for preparation and transportation of pesticides to agricultural machines. Thus, the participants in this study who were exposed to pesticides were more sensitive to genetic damage, and thereby, more susceptible to diseases resulting from such damage. These results demonstrated that health policies should be developed for pesticide-exposed farmers to better mitigate risks and damage to their health.

CalBMP, a web-based modeling tool for evaluating pesticide offsite movement and best management practice scenarios in California agricultural land

Quantitative evaluation of best management practice (BMP) effectiveness can help stakeholders to make better watershed management decisions. However, such evaluations are always challenging as they require complex algorithms to simulate the relevant hydrological processes, crop growth and the corresponding pollutant transport pathways in order to evaluate potential BMPs and select the best one for the specific field conditions. In this study, a web-based interface (CalBMP) was developed to predict BMP effectiveness in California, focusing on pesticide modeling at the field scale. With built-in databases for soil, weather, crop, pesticides, and BMPs, users can run simulations for baseline and BMP scenarios using their site-specific field conditions by simply providing the field information, such as zip code, soil, crop management, and pesticide application data. CalBMP uses PRZM5 + , a USEPA model, to simulate pesticide transport and fate at the field edge. The CalBMP simulations were validated based on measurements from an alfalfa field study. The results indicated that the CalBMP interface could reasonably simulate the runoff and adsorbed pesticide loss leaving the field with default parameters from previously known field parameters or public databases. CalBMP underestimated sediment erosion, possibly due to uncertainties in field measurements or inaccurate simulation of the temporal distribution of flood irrigation. CalBMP is likely to underestimate pesticides with greater solubility, such as diuron, because PRZM5 + uses the simplified instantaneous equilibrium sorption model. In addition, a strawberry field study was adopted to demonstrate the capability of the CalBMP interface for simulating BMP effectiveness (pesticide reduction percentage in the main pathways) with easy-to-understand graphs and tables. The results indicated that users can easily compare and review the results from multiple scenarios, which could facilitate the decision-making process for mitigating the amount of active ingredient bifenthrin leaving the field. The CalBMP tool provides useful information on pesticide runoff potential and BMP selection at the field scale. With increasingly stringent regulations for water quality protection, CalBMP will add to the growers’ toolbox for minimizing the environmental impacts from their inevitable pesticide usage.

Pesticide contamination in agro-ecosystems: toxicity, impacts, and bio-based management strategies.

Continuous rise in application of pesticides in the agro-ecosystems in order to ensure food supply to the ever-growing population is of greater concern to the human health and the environment. Once entered into the agro-ecosystem, the fate and transport of pesticides is determined largely by the nature of pesticides and the soil attributes, in addition to the soil-inhabiting microbes, fauna, and flora. Changes in the soil microbiological actions, soil properties, and enzymatic activities resulting from pesticide applications are the important factors substantially affecting the soil productivity. Disturbances in the microbial community composition may lead to the considerable perturbations in cycling of major nutrients, metals, and subsequent uptake by plants. Indiscriminate applications are linked with the accumulation of pesticides in plant-based foods, feeds, and animal products. Furthermore, rapid increase in the application of pesticides having long half-life has also been reported to contaminate the nearby aquatic environments and accumulation in the plants, animals, and microbes surviving there. To circumvent the negative consequences of pesticide application, multitude of techniques falling in physical, chemical, and biological categories are presented by different investigators. In the present study, important findings pertaining to the pesticide contamination in cultivated agricultural soils; toxicity on soil microbes, plants, invertebrates, and vertebrates; effects on soil characteristics; and alleviation of toxicity by bio-based management approaches have been thoroughly reviewed. With the help of bibliometric analysis, thematic evolution and research trends on the bioremediation of pesticides in the agro-ecosystems have also been highlighted.

Occurrence, vertical distribution and transport of organic amine pesticides in the seawater from the East China Sea and the South China Sea

Organic amine pesticides (OAPs) are widely used as insecticides, fungicides and herbicides in agricultural production. China is a large agricultural country, and the sprayed pesticides may impact the fragile marine environment through surface runoff. This study revealed the pollution characteristics of thirty-three OAPs in the East China Sea (ECS) and the South China Sea (SCS) and investigated their vertical variations in water columns. The ∑OAPs ranged from below method detection limits to 3.4 ng/ L, with an average value of 0.93 ng/ L. Diphenylamine and beflubutamid were the two most abundant compounds, contributing 64 % and 14 % of the ∑OAPs, respectively. The ∑OAPs in the ECS were significantly (M−W U test, p < 0.01) higher than that in the SCS, and OAPs exhibited different composition profiles. Diphenylamine was the most abundant compound in the ECS, while beflubutamid was dominant in the SCS, which may be related to industrial production (such as rubber synthesis) and agricultural activities. In the water columns, OAPs concentrations were higher in deep layers compared to that in surface seawater, which may be due to weak light and low temperature reducing the degradation of pesticides, indicating the deep ocean is a sink for OAPs. Under the dilution of seawater, the concentrations of OAPs decreased from the Pearl River Estuary to the open sea, and the South China Sea Warm Current also caused the decrease of OAPs from south to north. A preliminary risk assessment indicated that OAPs in the water pose no significant risk to aquatic organisms.

Effects of soil redistribution by tillage on subsequent transport of pesticide to subsurface drains.

Tillage operations will change the distribution in soil for any pesticide residues still present from earlier applications. This redistributive effect of tillage has been neglected in the study of pesticide leaching behavior. This study reviews the literature to characterize this redistributive effect for different tillage operations and uses a pesticide leaching model to investigate the impact of redistribution on pesticide transport to subsurface drains which is a significant input route to surface water bodies. Inversion ploughing moves the majority of any residues of pesticide present at or near the soil surface into the bottom two-thirds of the plough layer, whereas non-inversion ploughing has only a limited redistributive effect. Incorporating this redistributive effect into model simulations resulted in large changes (typically 5-10-fold difference) in both the maximum concentration and total mass of pesticide transported to drains over the winter following cultivation. More intense cultivation decreased subsequent leaching for relatively mobile compounds (Koc ≤1000 mL g-1 ), but increased it for strongly sorbed pesticides (Koc ≥2000 mL g-1 ). The redistributive effect of soil tillage on pesticide residues can have a large effect on subsequent transport to subsurface drains. This effect has been neglected in the literature. Field research is required to validate the model simulations presented here, and consideration should be given as to whether the effect needs to be included within risk assessment procedures. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.