Pesticide Mitigation Research Articles

Eco-friendly copper nanoparticles for acetamiprid pesticide mitigation in water effluents

Water pollution by pesticides is a significant environmental concern, given their extensive use in agriculture to meet food production demands. This study focuses on evaluating the effectiveness of biosynthesized copper nanoparticles in removing the pesticide acetamiprid (AMP). The degradation process is tracked by measuring the absorbance at 245 nm (AMP λmax) while considering variables such as adsorbent dosage, pH, and time. It provides valuable insights into the design and preparation of CuO nano adsorbents and their efficiency in purifying and remediating aquatic environments. The research investigated the ability of CuO nanoparticles, with an average size of 60 nm, to eliminate acetamiprid at very low concentrations (0.0005–0.01 mg/ml). The results showed that the nanoparticles could remove up to 97.5 % of AMP (0.01 mg/ml GT-CuO) after 90 min of contact time. Additionally, the study used the Langmuir isotherm model (R2 = 0.99125) and the pseudo-second order kinetic model (R2 = 0.98303) to model the adsorption of AMP on CuO NPs. Overall, CuO NPs derived from Glochidium tomentosum (GT) could offer a promising approach for adsorbing AMP pesticides.

Multi-stage batch adsorption of acephate onto cauliflower like Fe3O4-MMT: Characterization and statistical optimization using response surface methodology

Globally acephate (an organophosphate pesticide) contaminates water bodies, and detriment to the biota is cancer-causing and neurotoxic which needs to be safely removed. This study presents the synthesis and characterization of magnetic montmorillonite (Fe3O4-MMT) as an adsorbent for the adsorption of acephate. The features and characteristics of the nanocomposite were traced by XRD, SEM-EDX, gas sorption analysis, FTIR, and XRF. RSM techniques were used to identify the optimal process variables that result in the highest removal. The numerical optimization of optimum variables corresponds to an initial acephate concentration of 2 mg/L, pH 6 and material adsorbent dose of 0.5 g/L. The uptake of acephate achieved 83.18 % under optimum environs. Dual factors i.e., concentration and dosage remarked as vital parameters that affected the response from ANOVA. Results revealed that equilibrium adsorption data were best fitted with Langmuir and kinetic data were well described by pseudo-first order kinetic model. Thermodynamic parameters such as enthalpy, entropy and Gibb’s energy were evaluated and the effect of temperature on acephate adsorption was studied. Greater acephate adsorption onto on Fe3O4 serves as an excellent material for pesticide mitigation.

Effects of dietary garlic (Allium sativum) oil on growth performance, haemato-biochemical and histopathology of cypermethrin-intoxicated Nile tilapia (Oreochromis niloticus).

When pesticides are introduced into wetlands by agriculture, fish quickly absorb them through their gills. Pesticides reduce hatchability, impede growth, and antioxidant response, killing fish. Therefore, it's crucial to find effective pesticide mitigation methods for fish. In this study, the effects of garlic (Allium sativum) oil on the growth, haematology, biochemistry and histopathology parameters of Nile tilapia (Oreochromis niloticus) exposed to cypermethrin toxicity were investigated. In the research, cypermethrin was added to the water of the experimental groups at a rate of 1:20 of the LC50 value, and 1.00% garlic oil was added to the fish feed. Fish with an initial weight of 30.26 ± 0.26g were fed for 45 days. At the end of feeding, the final weights were determined as 69.39 ± 0.41 (G1), 61.81 ± 0.65 (G2), 82.25 ± 0.36 (G3), and 75.04 ± 0.68 (G4) grams, respectively. Histopathological examinations revealed serious lesions in the gill, liver, brain, and muscle tissues in the cypermethrin group, whereas these lesions were minimal or absent in the garlic oil group. Garlic oil supplementation had positive effects on growth, haematology, blood biochemistry, hepatosomatic index and histopathological parameters. These findings suggest that garlic oil is a potential protective agent against cypermethrin toxicity.

Recent advancements in pesticide mitigation using engineered Escherichia coli strains

Pesticides have considerably increased agricultural output, but their overuse presents serious threats to human health, food safety, and the environment. Alarmingly, only around 1% of pesticides used reach their intended pests, with the remainder polluting soil, water, and air. This causes broad environmental contamination and negative consequences on non-target animals, including people. Top pesticide-consuming countries, including China, the United States, and Brazil, confront considerable issues due to residual pesticide buildup. Recent biotechnology developments provide intriguing pesticide mitigation strategies. Engineered Escherichia coli (E. coli) strains have developed as very efficient bioremediation agents. These genetically engineered microbes are intended to convert hazardous chemicals into harmless metabolites. E. coli strains are tailored for increased expression of pesticide-degrading genes using modern genetic and metabolic engineering, dramatically enhancing their ability to break down hazardous chemicals. Studies have shown that modified E. coli may degrade persistent pesticides such as Paraoxon and p-nitrophenol (PNP), turning them to harmless molecules. These bacteria may reach great densities, making them ideal for large-scale detoxifying operations. Furthermore, recombinant DNA technology enables the development of E. coli strains with several copies of degradation genes, which improves their bioremediation capacities. Despite these advances, obstacles persist, including biosafety issues and the need for regulatory supervision. Ongoing research is critical for addressing these concerns and developing safer, more sustainable agriculture techniques. Engineered E. coli strains represent a substantial advancement in pesticide mitigation, providing a feasible approach for reducing environmental pollution and protecting human health.

Mitigation of multiple pesticide residues in green bell pepper using natural extracts as an emerging trend in pesticide decontamination using GC–MS/MS

AbstractThe main objective of this work is to assess the effect of natural extracts and its characterization for the mitigation of multiple pesticide residues in green bell pepper. In this study, four plant extracts such as Acacia concinna, Albizia amara, Tamarindus indica, and Azadirachta indica have been used to mitigate the six pesticides present in green bell pepper and its phytochemical constituents were analyzed using gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC–MS/MS). In addition to that, the method for the quantification of six pesticide residues in green bell pepper using GC–MS/MS was validated according to SANTE/11312/2021 guidelines. The extracts of Acacia concinna, Albizia amara, Tamarindus indica, and Azadirachta indica were showed effective mitigation for selected pesticides. The phytochemical compounds present in plant extracts were correlated with its effect on the mitigation of multiple pesticide residues. The T. indica showed better pesticide mitigation efficiency when compared to A. indica, A. amara, and A. concinna, respectively. The plant extracts showed higher mitigation efficiency for organophosphorous pesticides than the synthetic pyrethroids. The nutritional and sensorial properties of green bell pepper were highly retained after pesticide decontamination using plant extracts. The results of this work indicated the application of plant extracts for the mitigation of multiple pesticides in green bell pepper by household and commercial processing units. This study addressed the balance between food safety and food quality.Practical ApplicationsPesticide contamination in vegetables is one of the major global food safety issues and it poses potent threat to human health. Pesticide decontamination is always a challenging task due to the unpredictability of types and levels of pesticides and the presences of multiple pesticides in contaminated vegetables. Washing of vegetables with water is the common procedure followed by both household and commercial units. However, washing of vegetables only with water is not enough to reduce the multiple pesticides residues to safe levels. The washing of vegetables with chemical solutions and other thermal and non‐thermal processing could result in toxic byproduct formation based on the types of pesticides present in contaminated sample. Hence, in this study, the plant extracts were characterized for its efficiency on the mitigation of multiple pesticide residues in vegetables has been analyzed by Gas Chromatography—Triple Quadrupole Tandem Mass Spectrometry and the method has been validated according to SANTE/11312/2021 guidelines. The phytochemical compounds of the plant extracts could be correlated with the effective multiple pesticide decontamination efficiency and the plant extracts were found to retain the physicochemical properties of vegetables during washing. The results of this study showed that the selected plant extracts could enhance the food safety without compromising food quality. The results of this study could be useful for the formulation of vegetables cleaning solutions for the effective mitigation of multiple pesticide residues.

Incorporating the benefits of vegetative filter strips into risk assessment and risk management of pesticides.

The pesticide registration process in North America, including the USA and Canada, involves conducting a risk assessment based on relatively conservative modeling to predict pesticide concentrations in receiving waterbodies. The modeling framework does not consider some commonly adopted best management practices that can reduce the amount of pesticide that may reach a waterbody, such as vegetative filter strips (VFS). Currently, VFS are being used by growers as an effective way to reduce off-site movement of pesticides, and they are being required or recommended on pesticide labels as a mitigation measure. Given the regulatory need, a pair of multistakeholder workshops were held in Raleigh, North Carolina, to discuss how to incorporate VFS into pesticide risk assessment and risk management procedures within the North American regulatory framework. Because the risk assessment process depends heavily on modeling, one key question was how to quantitatively incorporate VFS into the existing modeling approach. Key outcomes from the workshops include the following: VFS have proven effective in reducing pesticide runoff to surface waterbodies when properly located, designed, implemented, and maintained; Vegetative Filter Strip Modeling System (VFSMOD), a science-based and widely validated mechanistic model, is suitable for further vetting as a quantitative simulation approach to pesticide mitigation with VFS in current regulatory settings; and VFSMOD parametrization rules need to be developed for the North American aquatic exposure assessment. Integr Environ Assess Manag 2024;20:454-464. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Leveraging high spatiotemporal resolution data of pesticides applied to agricultural fields in California to identify toxicity reduction opportunities

Pesticides remain a leading environmental hazard, imperiling aquatic and terrestrial ecosystems. Reducing pesticide toxicity is hampered by the ability to evaluate toxicity over large extents, the spatiotemporal resolution of pesticide use data, the ability to assess cumulative toxicity, and the identification of health/economic contributions of different pesticide application sites. We introduce the Environmental Release Tool, a sub-tool of the Pesticide Mitigation Prioritization Model, to advance these four areas. Using daily pesticide use reports required for agricultural applicators in California, we quantify the applied toxicity of pesticides to fish as well as aquatic invertebrates, nonvascular plants, and vascular plants. With the tool’s ability to quantify applied toxicity for hundreds of pesticides and watersheds simultaneously, we explore the significance of accounting for cumulative applied pesticide toxicity for application sites and watersheds statewide. Our results show that 14 pesticides account for 99.9% of applied toxicity, and 16 of 432 application site types introduce 90% of toxicity for taxa investigated. We also find cumulative applied toxicity within watersheds was significantly greater (p <1.0 E-16) than the maximum impact pesticide for all taxonomic groups, with a mean-annual difference of 460–630%. While cumulative applied toxicity was significant, and sources varied in individual watersheds, the net applied toxicity can be approximated with a short list of active ingredients and site types.

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.

Weak evidence base for bee protective pesticide mitigation measures.

Pesticides help produce food for humanity's growing population, yet they have negative impacts on the environment. Limiting these impacts, while maintaining food supply, is a crucial challenge for modern agriculture. Mitigation measures are actions taken by pesticide users, which modify the risk of the application to nontarget organisms, such as bees. Through these, the impacts of pesticides can be reduced, with minimal impacts on the efficacy of the pesticide. Here we collate the scientific evidence behind mitigation measures designed to reduce pesticide impacts on bees using a systematic review methodology. We included all publications which tested the effects of any pesticide mitigation measure (using a very loose definition) on bees, at any scale (from individual through to population level), so long as they presented evidence on the efficacy of the measure. We found 34 publications with direct evidence on the topic, covering a range of available mitigation measures. No currently used mitigation measures were thoroughly tested, and some entirely lacked empirical support, showing a weak evidence base for current recommendations and policy. We found mitigation measure research predominantly focuses on managed bees, potentially failing to protect wild bees. We also found that label-recommended mitigation measures, which are the mitigation measures most often applied, specifically are seldom tested empirically. Ultimately, we recommend that more, and stronger, scientific evidence is required to justify existing mitigation measures to help reduce the impacts of pesticides on bees while maintaining crop protection.

Pond mitigation in dissolved and particulate pesticide transfers: Influence of storm events and seasonality (Auradé agricultural catchment, SW-France)

In agricultural headwater catchments, wetlands such as ponds are numerous and well known to partly dissipate contamination. Most of the pesticides are transferred from soils to the aquatic environment during flood events. This study reports the annual/seasonal behaviour of 6 pesticides (metolachlor, boscalid, epoxiconazole, tebuconazole, aclonifen and pendimethalin) in such an environment. Because it is rarely considered, the study focussed on the high frequency of the distribution of pesticides between dissolved and particulate phases, as well as the main controlling factors of their upstream-downstream transfer. The pond removal rate was calculated to evaluate the wetland efficiency in pesticide mitigation. We conducted a one-year high frequency hydrochemical survey, with particular emphasis on flood events, in the upper Auradé catchment (SW-France), an area of long-term conventional agriculture on highly erosive carbonated soils. The inlet and outlet of the pond were instrumented for water level measurements and water sampling.The highest concentrations were observed for tebuconazole and, in general, the presence of the molecules during the year depended on the season. The pond showed satisfactory efficiency in pesticide attenuation for the six molecules considered, although the removal rate depended on the molecule and the bearing phase (from 28.4% for boscalid to 89.4% for aclonifen in the dissolved phase and from 22.1% for pendimethalin to 96.8% for metolachlor in the particulate fraction). Interestingly, the more hydrophilic the molecule (low LogKOW), the more efficient the pesticide removal rate was for its particulate fraction, and the opposite for hydrophobic molecules (high LogKOW).Flood events carried a large amount of Total Suspended Solid (TSS) bearing hydrophobic molecules from a major legacy of upper catchment soils, although 52% of the pesticides were transported by the dissolved fraction. Significant resuspension of TSS from the pond was evidenced by the annual mass balance with four tons of TSS released, while the positive rate of pesticide removal involved other effective mechanisms such as exchange and complexation. Although these constructed wetlands may be beneficial for pesticide mitigation, the results highlighted the need for improved land management in the upstream catchment during the different seasons to avoid bare soils that pose a risk of high surface water contamination, especially due to the presence of hydrophobic molecules in combination with a high erosive context.

Behavioural Responses and Mortality of Mozambique Tilapia Oreochromis mossambicus to Three Commonly Used Macadamia Plantation Pesticides

The use of pesticides in agricultural systems may have deleterious effects on surrounding environments. Aquatic systems are no exception and are increasingly polluted through the leaching of pesticides from agricultural activities. However, the pesticide pollution effects on key aquatic species have not been studied in many regions. In southern Africa, increasing pesticide use associated with macadamia tree Macadamia integrifolia farming presents a growing risk to surrounding aquatic ecosystems. This study assessed behavioural responses of an important and widely-distributed freshwater fish, Mozambique tilapia Oreochromis mossambicus, following exposure to three commonly used macadamia pesticides (i.e., Karate Zeon 10 CS, Mulan 20 SP, Pyrinex 250 CS) at different concentrations (0.7–200 µL, 0.3–1000 mg, and 0.7–8750 µL, respectively) over 24 h. Behavioural responses, i.e., swimming erratically, surfacing, vertical positioning, loss of equilibrium, being motionless and mortality were observed after pesticides exposure. Lethal dose 50 (LD50) values of Karate Zeon 10 CS, Mulan 20 SP and Pyrinex 250 CS were 2.1 µL (per water litre dilution—WLD), 5.2 mg (WLD) and 21.5 µL (WLD), respectively. These concentrations are therefore expressed as a maximal threshold usage in the environment around macadamia farms and a minimum distance of the plantations to water systems should be considered. Further studies should examine effects on other fish species and aquatic invertebrates to inform on pesticide pollution threats and mitigation plans for the region.

Can Pesticides Dissolved in Runoff and Exposed to Maturing Rice (Oryza sativa) Plants be Transferred to Seeds?

Agriculture's global challenge to feed an estimated 7.7 billion people is further exacerbated by less available cropland for production and rapidly changing climate patterns. Pesticides are often utilized to minimize crop losses due to pest infestations; however, problems arise when these chemicals are transported off production acreage, either by storm or irrigation events, and into nearby water bodies. Innovative management practices are needed to not only reduce the volume of runoff, but also to mitigate various pollutants, such as pesticides, within the runoff. One such practice being evaluated involves using rice (Oryza sativa) as a pesticide mitigation tool. While rice plants may serve as a mechanism for phytoremediation, whether the seeds harvested from exposed plants could then be utilized as a human food source is an unanswered question. Thirty round mesocosms (55 L volume; 56cm diameter; six replicates per treatment) were established with rice and exposed to aqueous concentrations of the pesticides clomazone, propanil, or cyfluthrin, as well as a mixture of the three pesticides. Six replicates with rice and no pesticide exposure served as controls. Initial pesticide exposure took place 8weeks post-planting and continued once a week for 5weeks. Rice plants, unmilled seeds, and mesocosm sediment were collected from each mesocosm 2weeks after seed formation began and analyzed for pesticide concentrations using gas chromatography. Concentrations of pesticides in unmilled seed were below detection for individual exposures of clomazone, propanil, and cyfluthrin. When rice was exposed to the pesticide mixture, the mean ± SE unmilled seed cyfluthrin concentration was 14.8 ± 1.25µgkg-1. These small-scale, preliminary studies offer insight into the possibility of using immature rice plants as a phytoremediation tool, while harvesting its grain after plant maturation for human consumption. Further research is needed to address this question on a larger scale and with multiple pesticide mixtures.

Deconstructing Pesticide Toxic Burden Sources and Mitigation Opportunities with Globally Most Comprehensive Database

Deconstructing Pesticide Toxic Burden Sources and Mitigation Opportunities with Globally Most Comprehensive Database

Deconstructing Pesticide Hazard Sources and Mitigation Opportunities with Globally Most Comprehensive Database

Deconstructing Pesticide Hazard Sources and Mitigation Opportunities with Globally Most Comprehensive Database

Dynamic Prediction of Effective Runoff Sediment Particle Size for Improved Assessment of Pesticide Mitigation Efficiency with Vegetative Filter Strips

Dynamic Prediction of Effective Runoff Sediment Particle Size for Improved Assessment of Pesticide Mitigation Efficiency with Vegetative Filter Strips

Advancing Surface Water Pesticide Exposure Assessments for Ecosystem Protection

HighlightsCrop protection and pest management programs continue to be integral for modern food production.Potential ecological impacts of pesticides must be assessed, and key mitigation practices adopted.Efforts are needed to advance surface water pesticide exposure assessments from field to landscape scales.Ensuring effective pesticide mitigation practices requires quantifying dynamic site-specific characteristics.Ecological assessments must improve prediction of adverse population and community-level outcomes.Abstract. As the global food demand increases, the use of pesticides will continue to increase with significant growth in low- and middle-income countries. Agricultural systems in which pesticides are used are complex with significant and often unknown biological, human, and physical-chemical interactions. These interactions include climate and hydrology, soil type, selection and use of best management practices, chemical fate and transport, application technology, and land use socioeconomics. The objective of this review article is to highlight key research opportunities identified from recent special meetings and workshops on advancing pesticide exposure assessments and mitigation. Research is needed in using advanced analytics and forensics to better understand the distribution of pesticides in the environment through novel monitoring and detection. Higher-tier modeling approaches can help inform monitoring a priori to better characterize pesticide distributions in the environment. Current pesticide exposure assessments are largely focused on the field or watershed scale, but advancements are needed to move toward landscape-scale analyses capable of analyzing for interacting ecosystems. Assessing the effects of complex, low-dose chemical mixtures on non-target aquatic organisms must advance with new quantitative high-throughput experimental methods focused on identifying interactions and not just additive effects. Field mitigation measures are currently considered as part of the pesticide exposure and risk assessment process using qualitative, fixed-efficiency type approaches, but we specifically call for the use of existing quantitative tools moving forward. These mechanistic modeling and simulation tools can capture the inherent complexity within an agroecological system. There is a need for risk assessment to be more predictive of population and community-level impacts as part of environmentally relevant scenarios. Finally, it is imperative that professional societies take a more proactive role in promoting the transdisciplinary collaboration of biological and agricultural engineers with other disciplines contributing to advances in ecological risk assessment. Keywords: Ecosystem, Exposure assessment, Landscape scale, Mechanistic modeling, Mitigation, Pesticides, Surface water quality.

Multi-actor approach and engagement strategy to promote the adoption of best management practices and a sustainable use of pesticides for groundwater quality improvement in hilly vineyards

The adoption of pesticide mitigation measures and innovation at farm level, are seen as a drivers to reach the sustainable water policy objectives. With the aim to prevent the pesticide pressure of hilly vineyards on groundwater contamination, a stepwise approach in Tidone Valley was applied using different consultation mechanisms and involvement strategies throughout the overall process. Face to face meetings, direct surveys, participatory monitoring and planning of several activities aiming to inform, educate, improve skills, change of individual behaviour or raise awareness, or even initiatives to build institutional trust or support for new investment in innovation are some examples. These activities allowed us to involve key actors of water use and governance (such as farmers, advisors, representatives of drinking water management, farmer's associations, Winemaking cooperatives, local Health Authority), and to have a deeper knowledge of the context agricultural practices, of farmer's knowledge and skills concerning factors influencing water contamination and also to promote the most suitable Best Management Practices aimed at limiting the pesticide occurrence in groundwater. Indeed, the surveys results highlighted that the majority of the farms are small (64% of vineyards <10 ha), that most of the farmers (62%) are not aware of the current legislation on water, even if 64% of them declare to participate regularly to training courses for the prevention of water contamination and that there is a low to moderate level of adoption of Best Practices able to prevent contamination by pesticides. At the end of the overall process, it can be stated that the multi-actor approach and engagement strategy adopted were successful in improving attitudes to more sustainable practices. This is supported also by the monitoring data that show in 2019 a decrease by 44% of pesticides occurrences and a fall by 68% of values above EQSgw if compared with the period 2017–2018.

Metamodeling methods that incorporate qualitative variables for improved design of vegetative filter strips

Significant amounts of pollutant are measured in surface water, their presence due in part to the use of pesticides in agriculture. One solution to limit pesticide transfer by surface runoff is to implement vegetative filter strips. The sizing of VFSs is a major issue, with influencing factors that include local conditions (climate, soil, vegetation). The BUVARD modeling toolkit was developed to design VFSs throughout France according to these properties. This toolkit includes the numerical model VFSMOD, which quantifies dynamic effects of VFS on site-specific pesticide mitigation efficiency. In this paper, a metamodeling, or model dimension reduction, approach is proposed to ease the use of BUVARD and to help users design VFSs that are adapted to specific contexts. Three different reduced models, or surrogates, are compared: a linear model, GAM, and kriging. It is shown that kriging, implemented with a covariance kernel for a mixture of qualitative and quantitative inputs, outperforms the other metamodels. The metamodel is a way of providing a relevant first approximation to help design the pollution reduction device. In addition, it is a relevant tool to visualize the impact that lack of knowledge of some field parameters can have when performing pollution risk analysis and management.

Influence of hydrodynamics on the water pathway and spatial distribution of pesticide and metabolite concentrations in constructed wetlands

Constructed wetlands (CWs) are likely to reduce pesticide levels reaching surface water. However, the distribution of the water flow path between the main channel and isolated areas may influence global pesticide mitigation. Little information is known about the influence of water pathways on pesticide mitigation. Thus, we performed tracer experiments at low and high flow rates (0.5 L/s and 4–7 L/s) in a pond CW and ditch CW to determine the localization of various hydraulic zones and to understand their implication on pesticide mitigation. The hydraulic performance reflecting the fraction of water transported from inlet to outlet passing through the whole of CW, was greater for the pond CW than for the ditch CW regardless of the flow rate, and greater at mean flow rates (MF) than at low flow rates (LF) due to a lower proportion of isolated areas at a MF (11%–68%) than at LF (38%–89%). Dispersion governed the water transport inside the isolated areas and the water convection inside the main channel. Consequently, dissolved pesticide concentrations are heterogeneously distributed in the CWs, i.e., in the main channel and isolated area, for both flow rates. However, one month after a no-flow period, this heterogeneity disappears, and dissolved pesticide concentrations become similar in the water of the whole CW due to dispersion. Furthermore, sedimentation and storage in sediments were greater in the isolated area than in the main channel, which is possibly due to a lower speed flow rate and a higher hydraulic residence time (HRT) in the isolated area than in the main channel. Thus, isolated areas act as effective's zones to mitigate pesticides from dissolved and particulate phases inside the CW during a complete drainage season (i.e., succession of high/low/no-flow periods).

Occurrence and potential risk of organophosphorus pesticides in urbanised Linggi River, Negeri Sembilan, Malaysia.

The application of organophosphorus pesticides (OPPs) increased gradually because of the rise in global food demand that triggered the agriculture sector to increase the production, leading to OPP residues in the surface water. This study elucidated the presence of OPPs and estimated its ecological risk in the riverine ecosystem of the urbanised Linggi River, Negeri Sembilan, Malaysia. The OPP concentration in surface water was determined using solid-phase extraction method and high-performance liquid chromatography coupled with diode array detection. Further, the ecological risk was estimated by using the risk quotient (RQ) method. The three OPPs, i.e. chlorpyrifos, diazinon, and quinalphos were detected with mean concentrations of 0.0275µg/L, 0.0328µg/L, and 0.0362µg/L, respectively. The OPPs were at high risk (in general and worst cases) under acute exposure. The estimated risk of diazinon was observed as medium for general (RQm = 0.5857) and high for worst cases (RQex = 4.4678). Notably, the estimated risk for chlorpyrifos was high for both general and worst cases (RQm = 1.9643 and RQex = 11.5643) towards the aquatic ecosystem of the Linggi River. Chronic risk of quinalphos remains unknown because of the absence of toxicity endpoints. This study presented clear knowledge regarding OPP contamination and possible risk for aquatic ecosystems. Hence, OPPs should be listed as one of the main priority contaminants in pesticide mitigation management in the future.