Degradation of four pesticides in five urban landscape soils: human and environmental health risk assessment

Advancing the Spatiotemporal Dimension of Wildlife-Pollution Interactions

Chemical pollution is one of the fastest-growing agents of global change. Numerous pollutants are known to disrupt animal behavior, alter ecological interactions, and shift evolutionary trajectories. Crucially, both chemical pollutants and individual organisms are nonrandomly distributed throughout the environment. Despite this fact, the current evidence for chemical-induced impacts on wildlife largely stems from tests that restrict organism movement and force homogeneous exposures. While such approaches have provided pivotal ecotoxicological insights, they overlook the dynamic spatiotemporal interactions that shape wildlife-pollution relationships in nature. Indeed, the seemingly simple notion that pollutants and animals move nonrandomly in the environment creates a complex of dynamic interactions, many of which have never been theoretically modeled or experimentally tested. Here, we conceptualize dynamic interactions between spatiotemporal variation in pollutants and organisms and highlight their ecological and evolutionary implications. We propose a three-pronged approach-integrating in silico modeling, laboratory experiments that allow movement, and field-based tracking of free-ranging animals-to bridge the gap between controlled ecotoxicological studies and real-world wildlife exposures. Advances in telemetry, remote sensing, and computational models provide the necessary tools to quantify these interactions, paving the way for a new era of ecotoxicology that accounts for spatiotemporal complexity.

Pesticide Residues, Glyphosate Adsorption and Degradation Characteristics in Ethiopian Agricultural Soils

Background

The decline in wheat output in Ethiopia is widely attributed to pests, which has led to a rise in the usage of pesticides to boost productivity. The degree of pesticides sorption and degradation which influence the likelihood of environmental contamination from pesticides seeping into water bodies from soil has not yet been published for Ethiopian soils. The study aimed at to quantify the levels of pesticide residues, assess glyphosate's adsorption capabilities and degradation rate in the soils.

Materials and methods

QuEChERS method of extraction was employed to determine the concentration of the respective pesticides. The adsorption capacities of glyphosate in agricultural soils of Cheha and Dinsho districts were measured using batch adsorption techniques.

Results

Six pesticide residues were found in 12 soil samples at varied quantities. Glyphosate (24.00-219.31 µg kg-1), s-metolachlor (23.67-220.67 µg kg-1), chlorpyrifos (27.74 202.67 µg kg-1), pyroxulam (14.67-50.65 µg kg-1), florasulam (78.00-250.67 µg kg-1), malathion (15.00-49.67 µg kg-1). The experimental results showed that glyphosate was slightly sorbed at SD10 soil (18.91 μg-1-n mLn g-1) in comparison to SC1 soil (114.66 μg-1-n mLn g-1). Organic matter and clay content proving to be the principal factors influencing the process. According to adsorption experimental data, chemisorption is the major process in glyphosate adsorption, with the pseudo-second order kinetic model providing the best fit (R 2 = .99). The soils in the study area exhibit notable variations in glyphosate rate of degradation (0.0076-0.0221 week-1). The findings show that the main soil variables affecting the half-life (glyphosate degradation) were clay concentrations (R 2 = .48; P = .013), pH (R 2 = .55; P = .0055), Organic matter (R 2 = .74; P = .00027), Feox (R 2 = .50; P = .0105), and Alox (R 2 = .73; P = .00046).

Conclusion

The weak glyphosate adsorption capabilities of soils can be a good indicator that the pesticide residues in the soil are poised to endanger soil organisms and contaminate nearby water bodies through runoff and leaching.

Pre-emergence herbicides used in urban and agricultural settings: dissipation and ecological implications

Herbicides are widely recognized as the most cost-effective solution for weed control, but their extensive use in both urban and agricultural settings raise serious concerns about nontarget effects. We assessed the possible hazards associated with pre-emergence herbicides such as dimethenamid-P, metazachlor, and pyroxasulfone, which are frequently applied in both urban and agricultural soils. The dissipation rate constant values (k day-1: 0.010-0.024) were positively linked to total organic carbon (TOC), silt, clay, soil pH, and Al and Fe oxides, but negatively correlated with sand content. In contrast, half-life values (DT50: 29-69 days) of the herbicides showed negative correlations with TOC, clay, silt, soil pH, and Fe and Al oxides, while sand content showed a positive impact. The selected herbicides showed minimal impact on soil dehydrogenase activity (DHA). Mostly, soils with higher organic matter (OM) content exhibited increased DHA levels, highlighting the role of OM in influencing this soil enzyme across different soils. Assessment of environmental indicators like groundwater ubiquity score (GUS:1.69-6.30) and leachability index (LIX: 0.23-0.97) suggested that the herbicides might reach groundwater, posing potential risks to nontarget biota and food safety. Human non-cancer risk evaluation, in terms of hazard quotient (HQ < 1) and hazard index (HI < 1), suggests minimal or no risks from exposure to soil containing herbicide residues at 50% of the initial concentrations. Our data thus help the stakeholders and regulatory agencies while applying these pre-emergence herbicides in soils and safeguarding human and environmental health.

Concurrent Analysis of Tiafenacil and Its Transformation Products in Soil by Using Newly Developed UHPLC-QTOF-MS/MS-Based Approaches

As new pesticides continue to emerge in agricultural systems, understanding their environmental behavior is crucial for effective risk assessment. Tiafenacil (TFA), a promising novel pyrimidinedione herbicide, was the focus of this study. We developed an efficient QuEChERS-UHPLC-QTOF-MS/MS method to measure TFA and its transformation products (TP1, TP2, TP3, TP4, and TP5) in soil. Our calibration curves exhibited strong linearity (R2 ≥ 0.9949) ranging from 0.015 to 2.0 mg/kg within a low limit of quantification (LOQ) of 2.0 µg/kg. Inter-day and intra-day recoveries (0.10 to 2.0 mg/kg, 80.59% to 110.05%, RSD from 0.28% to 12.93%) demonstrated high sensitivity and accuracy. Additionally, TFA dissipation under aerobic conditions followed first-order kinetics, mainly yielding TP1 and TP4. In contrast, TP1 and TP2 were mainly found under sterilized and anaerobic conditions, and TFA dissipation followed second-order kinetics. Moreover, we predicted the transformation pathways of TFA using density functional theory (DFT) and assessed the toxicity levels of TFA and its TPs to aquatic organisms using ECOSAR. Collectively, these findings hold significant implications for a better understanding of TFA fate in diversified soil, benefiting its risk assessment and rational utilization.

Enhanced removal of pesticide micropollutant and bacteria using solar light-assisted Ag-doped TiO2: prospects for environmental and health impacts

Pesticide micropollutants like 4-chlorophenol (4CP) and E. coli bacteria represent a substantial hazard, impacting both the environment and human health. This study delves into the effectiveness of Ag-doped TiO2 (Ag@TiO2) in removing both 4CP and E. coli. Ag@TiO2 has demonstrated remarkable effectiveness in removing 4CP under both solar and visible light conditions, earning degradation efficiencies of 91.3% and 72.8%, respectively. Additionally, it demonstrates outstanding photodegradation efficiency for 4CP (98.8%) at an initial concentration of 1 mg L-1. Moreover, Ag@TiO2 exhibited substantially higher removal performance for 4CP (81.6%) compared to TiO2 (27.6%) in wastewater. Analysis of the radicals present during the photodegradation process revealed that ·O2- primarily drives the decomposition of 4CP, with h+ and ·OH also playing significant roles in the oxidation reactions of the pollutant. Interestingly, even under dark conditions, Ag@TiO2 exhibited the capability to eliminate approximately 20% of E. coli, a percentage that increased to over 96% under solar light. In addition, the prospects for environmental and health impacts of utilizing Ag@TiO2 for pesticide micropollutant removal and bacteria were discussed.

Pre-emergence herbicides widely used in urban and farmland soils: fate, and potential human and environmental health risks

We determined the distribution, fate, and health hazards of dimethenamid-P, metazachlor, and pyroxasulfone, the effective pre-emergence herbicides widely used both in urban and agricultural settings globally. The rate-determining phase of sorption kinetics of these herbicides in five soils followed a pseudo-second-order model. Freundlich isotherm model indicated that the herbicides primarily partition into heterogeneous surface sites on clay minerals and organic matter (OM) and diffuse into soil micropores. Principal component analysis revealed that soil OM (R2, 0.47), sand (R2, 0.56), and Al oxides (R2, 0.33) positively correlated with the herbicide distribution coefficient (Kd), whereas clay (R2, ‒ 0.43), silt (R2, ‒ 0.51), Fe oxides (R2, ‒ 0.02), alkaline pH (R2, ‒ 0.57), and EC (R2, ‒ 0.03) showed a negative correlation with the Kd values. Decomposed OM rich in C=O and C-H functional groups enhanced herbicide sorption, while undecomposed/partially-decomposed OM facilitated desorption process. Also, the absence of hysteresis (H, 0.27‒0.88) indicated the enhanced propensity of herbicide desorption in soils. Leachability index (LIX, < 0.02-0.64) and groundwater ubiquity score (GUS, 0.02‒3.59) for the soils suggested low to moderate leaching potential of the herbicides to waterbodies, indicating their impact on water quality, nontarget organisms, and food safety. Hazard quotient and hazard index data for human adults and adolescents suggested that exposure to soils contaminated with herbicides via dermal contact, ingestion, and inhalation poses minimal to no non-carcinogenic risks. These insights can assist farmers in judicious use of herbicides and help the concerned regulatory authorities in monitoring the safety of human and environmental health.

Evaluation of health risk of glyphosate pesticide intake via surface and subsurface water consumption: A deterministic and probabilistic approach

As the usage of pesticides for both agricultural and non-agricultural uses increases, it is more important than ever to employ probabilistic methods rather than deterministic ones to calculate the danger to human health. The current work demonstrates the application of deterministic and probabilistic approaches to assess the human health risk related to glyphosate during the consumption of surface and groundwater by different population groups. To that aim, the concentration of glyphosate pesticide in the surface and groundwater was measured and human health risk for three population groups including children, teens, and adults was evaluated. Overall, the probabilistic approach via Monte Carlo simulation showed a valid result for the estimation of human health risk and determination of dominant input parameters.•The health risk of glyphosate exposure during water consumption for various population groups were evaluated using deterministic and probabilistic methods.•The modeling is performed by Crystal Ball (11.1.2.4) software, as open access software, and requires a limited number of inputs.•The probabilistic method could reliably assess the risks of glyphosate by considering the variability and uncertainty in input variables.