Pesticides are used worldwide with potential harmful effects on both fauna and flora. The Kibale National Park in Uganda, a site renowned for its biodiversity is surrounded by tea, banana and eucalyptus plantations as well as maize fields and small farms. We previously showed presence of pesticides with potential endocrine disruptive effects in the vicinity. To further investigate the water pollution linked to agricultural pressure in this protected area, we implemented a complementary monitoring strategy based on: analytical chemistry, effects based methods and the deployment of Polar Organic Chemical Integrative Samplers (POCIS). Chemical analysis of the POCIS extracts revealed the presence of 13 pesticides: carbofuran, DEET, 2.4-D amine, carbaryl, ametryn, isoproturon, metolachlor, terbutryn, dimethoate, imidacloprid, picaridin, thiamethoxam, carbendazim, with the first three being present in the largest quantities. Water samples collected at the POCIS sampling sites exhibited thyroid and estrogen axis disrupting activities in vivo, in addition to developmental and behaviour effects on Xenopus laevis tadpoles model. Based on our observations, for the health of local human and wildlife populations, further monitoring as well as actions to reduce agrochemical use should be considered in the Kibale National Park and in regions exposed to similar conditions.

Understanding the processes that regulate contaminant impacts in nature is an increasingly important challenge. For insecticides in surface waters, the ability of aquatic plants to sorb, or bind, hydrophobic compounds has been identified as a primary mechanism by which toxicity can be mitigated (i.e. the sorption-based model). However, recent research shows that submerged plants can also rapidly mitigate the toxicity of the less hydrophobic insecticide malathion via alkaline hydrolysis (i.e. the hydrolysis-based model) driven by increased water pH resulting from photosynthesis. However, it is still unknown how generalizable these mitigation mechanisms are across the wide variety of insecticides applied today, and whether any general rules can be ascertained about which types of chemicals may be mitigated by each mechanism. We quantified the degree to which the submerged plant Elodea canadensis mitigated acute (48-h) toxicity to Daphnia magna using nine commonly applied insecticides spanning three chemical classes (carbamates: aldicarb, carbaryl, carbofuran; organophosphates: malathion, diazinon, chlorpyrifos; pyrethroids: permethrin, bifenthrin, lambda-cyhalothrin). We found that insecticides possessing either high octanol-water partition coefficients (log Kow) values (i.e. pyrethroids) or high susceptibility to alkaline hydrolysis (i.e. carbamates and malathion) were all mitigated to some degree by E. canadensis, while the plant had no effect on insecticides possessing intermediate log Kow values and low susceptibility to hydrolysis (i.e. chlorpyrifos and diazinon). Our results provide the first general insights into which types of insecticides are likely to be mitigated by different mechanisms based on known chemical properties. We suggest that current models and mitigation strategies would be improved by the consideration of both mitigation models.

Polyethylene (PE) and polypropylene (PP) microplastics (MPs), as carriers, can bind with pesticides, which propose harmful impacts to aqueous ecosystems. Meanwhile, carbofuran and carbendazim (CBD), two widely used carbamate pesticides, are toxic to humans because of the inhibition of acetylcholinesterase activity. The interaction between two MPs and two pesticides could start in farmland and be maintained during transportation to the ocean. Herein, the adsorption behavior and mechanism of carbofuran and carbendazim (CBD) by PE and PP MPs were investigated via characterization and density functional theory (DFT) simulation. The adsorption kinetic and thermodynamic data were best described by pseudo-second-order kinetics and the Freundlich models. The adsorption behaviors of individual carbofuran/CBD on both MPs were very similar. The CBD adsorption rate and capacity of PE and PP MPs were higher than those of carbofuran. This phenomenon explained the lower negative effects of DOM (oxalic acid, glycine (Gly)) on CBD adsorption relative to those of carbofuran. The presence of oxalic acid and Gly decreased the PE adsorption by 20.40–48.02% and the PP adsorption by 19.27–42.11%, respectively. It indicated the significance of DOM in carbofuran cycling. The adsorption capacities were negatively correlated with MPs size, indicating the importance of specific surficial area. Fourier transformation infrared spectroscopy before and after adsorption suggested that the adsorption process did not produce any new covalent bond. Instead, intermolecular van der Waals forces were one of the primary adsorption mechanisms of carbofuran and CBD by MPs, as evidenced by DFT calculations. Based on the zeta potential, the electrostatic interaction explained the higher adsorption CBD by MPs than carbofuran.

This study investigated the ability of natural river biofilms from different seasons to degrade the carbamate pesticides methomyl, carbaryl and carbofuran in single and multiple pesticide systems, and the effects of these pesticides on algal and bacterial communities within biofilms. Spring biofilms had the lowest biomass of algae and bacteria but showed the highest methomyl degradation (>99%) and dissipation rates, suggesting that they might contain microorganisms with high methomyl degradation abilities. Degradation of carbofuran (54.1–59.5%) by biofilms in four seasons was similar, but low degradation of carbaryl (0–27.5%) was observed. The coexistence of other pesticides was found to cause certain effects on pesticide degradation and primarily resulted in lower diversity of diatoms and bacteria than when using a single pesticide. The tolerant diatoms and bacteria potentially having the ability to degrade test pesticides were identified. River biofilms could be suitable biomaterials or used to isolate degraders for bioremediating pesticide-contaminated water.

A new sampling system has been developed for the measurement of time-averaged concentrations (TWA) and diffusion coefficients of organic micropollutants in aquatic environments. The system is based on the diffusion of targeted organic compounds through a rate-limiting membrane and the subsequent accumulation of these species in a bound, hydrophobic solid-phase material. Two separate prototype systems are described. One is suitable for the sampling of carbamates such as carbaryl, carbofuran, 3-hydroxycarbofuran, baygon, propham, clorpropham, and the other one for s-triazines such as atrazine, prometryn, propazine, simazine, terbuthylazine, terbutryn, metribuzin, cyanazine, and metamitron pesticides. The systems use solid-phase material (47-mm C₁₈ Empore disk) as the receiving phase but are fitted with rate-limiting membranes of either polysulfone or polycarbonate. For the two designs investigated, the cumulative uptake of all target analytes was considered over exposure periods of 7 days. The determined sampling rates ranged from 0.1323 to 0.0465 L day⁻¹ with both membranes. The best system was the one with the polysulfone membrane allowing a better cumulative uptake.

A monitoring study was carried out in two micro-catchments in the Reventazón basin, in Northern Cartago, Costa Rica; pesticide occurrence and water quality were analyzed. Twelve pesticides were detected, five insecticides (chlorpyrifos, carbofuran, cypermethrin, imidacloprid, and oxamyl), four fungicides (carbendazim, imazalil, metalaxyl, and thiabendazole), and three herbicides (diuron, linuron, and terbutryn); eight of them presented risk quotients RQ >1, which implies a high risk for the environment. The water quality evaluation included fourteen physicochemical and microbiological parameters, out of which thermotolerant coliforms, nitrate, and total phosphorus exceeded a selected threshold value in every sample. Five metals were also included in the evaluation, Pb was the most frequent, followed by few detections of Cd, Cu, and Cr. Four water quality indexes (WQIs) were applied, two of them, the CCME WQI, based on physicochemical parameters, and the BMWP-CR WQI, based on benthic macroinvertebrate recount adapted to Costa Rican species, categorized all the sampling points as “bad” and “very bad” quality. This work of monitoring is important in the Latin American region, where there is a lack of information for regulation improvement and management decisions. These results showed poor management of the micro-catchments in this agricultural rural area.

In this study, a multi-residue method was used to analyze 13 pesticides and 1 degradation product in surface and groundwater in the region with the largest sugar cane production in the world. The potential effects of individual pesticides and their mixtures, for aquatic life and human consumption, were evaluated. For the surface water, 2-hydroxy atrazine, diuron, carbendazim, tebuthiuron, and hexazinone were the most frequently detected (100, 94, 93, 92, and 91%, respectively). Imidacloprid (2579 ng L⁻¹), carbendazim (1114 ng L⁻¹), ametryn (1101 ng L⁻¹), and tebuthiuron (1080 ng L⁻¹) were found at the highest concentrations. For groundwater, tebuthiuron was the only quantified pesticide (107 ng L⁻¹). Ametryn, atrazine, diuron, hexazinone, carbofuran, imidacloprid, malathion, carbendazim, and their mixtures presented risk for the aquatic life. No risk was observed for the pesticides analyzed in this work, alone or in their mixtures for human consumption.

This study aimed to evaluate histological changes in targeted tilapia organs exposed to sublethal concentrations of carbofuran. Fishes with an average weight of 67.5 ± 2.0 g were exposed to sublethal concentrations (0.0044, 0.0088, 0.0440, and 0.0880 mg L⁻¹) of carbofuran for 7 days. In the end of the experiment, the gill, the liver, and the kidney samples were collected for histological evaluation. In gills exposed to 0.0044 mg L⁻¹ of carbofuran, an increase in interlayer epithelium and disruption of the secondary lamella was observed, while in other concentrations (0.0088, 0.0440, and 0.0880 mg L⁻¹), only blood congestion in the secondary lamellae occurred. In the liver samples of exposed tilapias, all carbofuran concentrations caused hepatocyte hypertrophy with the nuclei displaced to the cell periphery, stasis within the sinusoid capillaries, and necrosis points. All sublethal concentrations tested caused detachment of the glomerular capsule, necrosis in the proximal and distal tubules, and absence of intercellular space in the kidney of exposed tilapia. The presence of carbofuran in aquatic environments at concentrations from 0.0044 mg L⁻¹ and exposure periods longer than 7 days alters the gill, the liver, and the kidney histology and consequently compromising the fish’s health.

Biomixtures comprise the active part of biopurification systems (BPS) for the removal of pesticide-containing wastewater from agricultural origin. Considering that biomixtures contain an important amount of lignocellulosic substrates, their bioaugmentation with degrading ligninolytic fungi represents a promising way to improve BPS. The fungus Trametes versicolor was employed for the bioaugmentation of rice husk-compost-soil (GCS) biomixtures in order to optimize the removal of the highly toxic insecticide/nematicide carbofuran (CFN). Composition of biomixtures has not been optimized before, and usually, a volumetric composition of 50:25:25 (lignocellulosic substrate:humic component:soil) is employed. Optimization of the biomixture composition was performed with a central composite design, using the volumetric content of rice husk (pre-colonized by the fungus) and the volumetric ratio compost/soil as design variables. Performance of biomixtures was comprehensively assayed considering CFN removal, the production of toxic transformation products (3-hydroxycarbofuran/3-ketocarbofuran), the ability to mineralize [¹⁴C]carbofuran, and the residual toxicity in the matrix. According to the models, the optimal volumetric composition of the GCS biomixture is 30:43:27, which maximizes removal and mineralization rate, and minimizes the accumulation of transformation products. Results support the value of assessing new biomixture formulations according to the target pesticide in order to obtain their optimal performance, before their use in BPS.