Application of agricultural pesticides in a peak period induces an abundance decline of metazoan zooplankton in a lake ecosystem

Field and Laboratory Evidence That Chlorpyrifos Exposure Reduced the Population Density of a Freshwater Snail by Increasing Juvenile Mortality

Pesticides have been frequently detected in global freshwater ecosystems, but attempts to document changes in population dynamics of organisms upon exposure to pesticides, establish a causal relationship between exposure and population effects, and identify the key toxic events within individuals under natural field conditions remain rare. Here, we used a field survey, a reciprocal cross-transplant experiment, and a laboratory toxicity experiment to build a compelling case that exposure to the insecticide chlorpyrifos was responsible for differences in snail (Bellamya aeruginosa) densities in eastern (ELL) and western basins of Liangzi Lake in China. Our field survey and reciprocal cross-transplant experiment revealed significant differences in snail densities, juvenile percentage, survival, and relative telomere length (RTL) in the two basins. The insecticide chlorpyrifos detected in snail tissues was negatively correlated with snail densities, the percentage of juvenile snails, and RTL and had an extremely high risk quotient in ELL. In the laboratory experiment, tissue concentrations of chlorpyrifos detected in ELL were associated with reduced RTL and increased juvenile mortality in B. aeruginosa. These results support the hypothesis that chlorpyrifos exposure in ELL reduced the density of snails by reducing juvenile survival and, consequently, recruitment to the adult population.

Application of machine learning models to improve the prediction of pesticide photodegradation in water by ZnO-based photocatalysts

Pesticide pollution has been posing a significant risk to human and ecosystems, and photocatalysis is widely applied for the degradation of pesticides. Machine learning (ML) emerges as a powerful method for modeling complex water treatment processes. For the first time, this study developed novel ML models that improved the estimation of the photocatalytic degradation of various pesticides using ZnO-based photocatalysts. The input parameters encompassed the source of light, mass proportion of dopants to Zn, initial pesticide concentration (C0), pH of the solution, catalyst dosage and irradiation time. Additionally, physicochemical properties such as the molecular weight of the dopants and pesticides, as well as the water solubility of both dopants and pesticides, were considered. Notably, the numerical data were extracted from the literature via relevant tables (directly) or graphs (indirectly) using the web-based tool WebPlotDigitizer. Four ML models including multi-layer perceptron artificial neural network (MLP-ANN), particle swarm optimization-adaptive neuro fuzzy inference system (PSO-ANFIS), radial basis function (RBF), and coupled simulated annealing-least squares support vector machine (CSA-LSSVM) were developed. In comparison, RBF showed the best accuracy of modeling among all models, with the highest determination coefficient (R2) of 0.978 and average absolute relative deviation (AARD) of 4.80%. RBF model was effective in estimating the photocatalytic degradation of pesticides except for 2-chlorophenol, triclopyr and lambda-cyhalothrin, where CSA-LSSVM model demonstrated superior performance. Dichlorvos was completely degraded by ZnO photocatalyst under visible light. The sensitivity analysis by relevancy factor exhibited that light irradiation time and initial pesticide concentration were the most important parameters influencing photocatalytic degradation of pesticides positively and negatively, respectively. The new ML models provide a powerful tool for predicting pesticide degradation in wastewater treatment, which will reduce photochemical experiments and promote sustainable development.

Theoretical explanation of direct photolysis and indirect photolysis of bendazone with •OH, •SO4-, and •CO3- in water: mechanism insights and ecotoxicity evaluation

Bendazone (BNTE) is an herbicide and a highly concerned pollutant in aquatic environments. Understanding the photochemical behavior of BNTE in water is crucial for evaluating its photochemical conversion process in aquatic environments. This study analyzed the direct photolysis and indirect photolysis pathways of two dissociated forms of BNTE in water through density functional theory and time-dependent density functional theory method. The results show that the reaction types of indirect photolysis of BNTE with free radicals (•OH, •SO4-, and •CO3-) are OH- addition, SO4- addition, and CO3- addition. In the process of indirect photolysis of BNTE and free radicals, the photolysis of •OH and BNTE was the easiest, followed by •SO4-. In addition, the active site of BNTE reacting with •OH is C8, and the active site of BNTE reacting with •SO4- is C10. However, the photolysis effect of •CO3- on BNTE is very small, indicating that •CO3- in water plays a secondary role in the indirect photolysis of BNTE. In the direct photolysis of BNTE, N1-C6 bond breaking is difficult to occur spontaneously in the environment due to its high endothermic property and energy barrier. The direct photolysis pathway of BNTE involves the break of the N1-S2/S2-N3/N3-C12 bond. In addition, the ecological toxicity evaluation showed that toxicity of most of the degradation products were reduced, but the toxicity level was still maintained at a harmful level. Our findings provide the photochemical fate of BNTE in aquatic environments and will help to more accurately understand their photochemical conversion mechanisms in the environment.

Development of a bioluminescence resonance energy transfer Quenchbody sensor for the detection of organophosphorus pesticides in water bodies

Rapid and precise quantification of organophosphorus pesticides (OPPs) in environmental water bodies is crucial for evaluating ecological risks and safeguarding human health. Traditional instrumental methods are complex, time-consuming, and expensive, while enzyme-based biosensors suffer from instability and require a constant supply of substrates. Hence, there is an urgent need for a fast, simple, and sensitive biosensor for OPPs. In this study, we developed a novel non-enzymatic biosensor for the detection of methyl parathion (MP) by employing the bioluminescence resonance energy transfer (BRET) Q-body strategy. Optimizing the spacer arm and screening fluorescent dyes identified the R6G BRET MP Q-body sensor with the best performance. Key parameters affecting the sensor's detection performance were optimized by using single-factor experiments. Under optimal conditions, the detection exhibited a detection limit of 5.09 ng·mL-1 and a linear range of 16.21-848.81 ng·mL-1. The sensor's accuracy was validated using standard recovery experiments, yielding a recovery rate of 84.47 %-102.08 % with a standard deviation of 1.93 %-9.25 %. The detection results of actual water samples demonstrate that this fast, simple, and highly sensitive BRET Q-body sensor holds great promise for practical water quality monitoring.

Determining the spatiotemporal variation, sources, and ecological processes of antibiotic resistance genes in a typical lake of the middle reaches of the Yangtze River

Antibiotic resistance genes (ARGs) are emerging environmental pollutants, influenced by complex regulatory factors. River-lake systems act as natural reservoirs for ARGs and provide an ideal model for studying their regulatory mechanisms. This study employed high-throughput quantitative PCR, high-throughput sequencing, correlation analyses, and model predictions to investigate the dynamics of ARGs and their influencing factors in Liangzi Lake, located in the mid-reaches of the Yangtze River. The research specifically centered on three environmental components: lake water, sediment, and river water. Results indicated that the ARGs from eight major antibiotic classes, displaying distinct seasonal distribution patterns. In comparison to the sediment, the water phase demonstrated a higher diversity of ARGs, with the highest level of ARGs sharing observed between lake and river waters (approximately 83.7 %). Furthermore, seasonal variations significantly influenced the distributions of both ARGs and bacterial communities. The diversity of ARGs was highest during the summer and autumn, and specific bacterial species exhibited robust correlations with ARGs (including matA/mel, aac (6')-Ib-03, and blaROB). It is worth noting that environmental attributes and bacterial diversity had the most substantial impact on the dynamic changes in ARGs. Lastly, source tracking analysis pinpointed that sediment as the primary source of ARGs in lake water, constituting 45 % to 48 % of the total ARGs. Our study provides a comprehensive analysis of ARGs and their influencing factors in the river-lake system of the middle reaches of the Yangtze River, with Liangzi Lake as a representative case.

Oxidative stress contributes to flumioxazin-induced cardiotoxicity in zebrafish embryos

Flumioxazin is a widely applied herbicide for the control of broadleaf weeds, including aquatic plants. Current evidence suggests that flumioxazin could induce cardiac defects (ventricular septal defects) in vertebrates, but the underlining mechanisms remain unclear. Because of the inhibitory effect of flumioxazin on polyphenol oxidase, the assumption is made that flumioxazin-induced cardiotoxicity is caused by oxidative stress. To verify whether oxidative stress plays an important role in flumioxazin-induced cardiotoxicity, we compared the differences in heart phenotype, oxidative stress level, apoptosis, and gene expression between flumioxazin exposure and a normal environment, and we also tested whether cardiotoxicity could be rescued with astaxanthin. The results showed that flumioxazin induced both cardiac malformations and the abnormal gene expression associated with cardiac development. Cardiac malformations included pericardial edema, cardiac linearization, elongated heart, cardiomegaly, cardiac wall hypocellularity, myocardial cell atrophy with a granular appearance, and a significant gap between the myocardial intima and the adventitia. An increase in oxidative stress and apoptosis was observed in the cardiac region of zebrafish after exposure to flumioxazin. The antioxidant astaxanthin reversed the cardiac malformations, excessive production of reactive oxygen species (ROS), and expression of genes for cardiac developmental and apoptosis regulation induced by flumioxazin. In addition, flumioxazin also activated aryl hydrocarbon receptor (AhR) signaling pathway genes (aryl hydrocarbon receptor 2 [ahr2], cytochrome p450 family subfamily a [cyp1a1], and b [cyp1b1]) and increased the concentration of porphyrins. The results suggest that excessive ROS production, which could be mediated through AhR, led to apoptosis, contributing to the cardiotoxicity of flumioxazin in zebrafish embryos. Environ Toxicol Chem 2023;42:2737-2746. © 2023 SETAC.

Highly efficient activation of peroxymonosulfate by cobalt ferrite anchored in P-doped activated carbon for degradation of 2,4-D: adsorption and electron transfer mechanism

The dispersing effect of carbon materials on nanoparticles can enhance the full exposure of their active sites. Herein, phosphorus (P)-doped activated carbon-supported trace cobalt ferrite composites (P-CoFe@BC_X) were achieved by two-step pyrolysis for efficient peroxymonosulfate (PMS) activation and water pollution remediation. The removal efficiency of 2,4-dichlorophenoxyacetic acid (2,4-D) was optimized by adjusting the coupling ratio of carbon substrate and cobalt ferrite. P-CoFe@BC₅/PMS oxidation system (0.10 g L^-1, 0.50 mM) eliminated 98.3% of 2,4-D (20.0 mg L^-1) within 60 min at unadjusted pH. The constructed adsorption enrichment and oxidative degradation pathways are highly efficient in utilizing reactive oxygen species (ROS), and the dual tracks of free and non-free radicals achieve the rapid degradation of 2,4-D. P-doped activated carbon acts as an electron shuttle to accelerate electron transfer between active sites and enhances the adsorption efficiency of 2,4-D and PMS onto the composites. In addition, the P-CoFe@BC₅/PMS oxidation system still exhibited strong 2,4-D removal performance at a wide pH range of 2.0-10.0. The inhibitory effect of environmental components was related to their concentration, such as chloride, bicarbonate, sulfate and humic acid. Density functional theory calculations show that ROS tends to attack the CO bond on the 2,4-D branch chain, and the degradation products show lower biological toxicity. Hence, the constructed cobalt ferrite anchored P-doped activated carbon activated PMS system has great potential in treating organic wastewater.

In situ boron-doped cellulose-based biochar for effective removal of neonicotinoids: Adsorption mechanism and safety evaluation

Biochar materials have been widely employed for adsorption of pollutants, which necessitates further consideration of their efficiency and safety in environmental remediation. In this study, a porous biochar (AC) was prepared through the combination of hydrothermal carbonization and in situ boron doping activation to effectively adsorb neonicotinoids. The adsorption process was shown to be a spontaneous endothermic physical adsorption process, where the predominant interaction forces between the acetamiprid and AC were electrostatic and hydrophobic interactions. The maximum adsorption capacity was 227.8 mg g^-1for acetamiprid and the safety of AC was verified by simulating the situation where the aquatic organism (D. magna) was exposed to the combined system (AC & neonicotinoids). Interestingly, AC was observed to reduce the acute toxicity of neonicotinoids owing to the reduced bioavailability of acetamiprid in D. magna and the newly generated expression of cytochrome p450. Thus, it enhanced the metabolism and detoxification response in D. magna, which reducing the biological toxicity of acetamiprid. This study not only demonstrates the potential application of AC from a safety perspective, but also provides insight into the combined toxicity caused by biochar after adsorption of pollutants at the genomic level, which fills the gap in related research.