Neonicotinoids in draining micro-watersheds dominated by rice-vegetable rotations in tropical China: Multimedia occurrence, influencing factors, transport, and associated ecological risks

Occurrence and transport of neonicotinoid insecticides in soils from an agriculture-dominated area in Henan Province, Northern China: Insights from agricultural management practices

Neonicotinoid insecticides (NNIs) are among the most widely used pesticides and have garnered significant attention recently because of their high toxicity to non-target organisms and potential risks to human health. In this study, vertical soil profiles were collected from the Zhoukou reach of the Shaying River Basin, China, where pesticides are heavily used, to investigate the pollution characteristics and ecological risks of NNIs, with a focus on the impact of agricultural management practices on NNI residues in farmland soils. NNIs were widely detected in the soils, with a detection frequency of 100 % and a mean concentration of 73.8 ± 167 ng/g. NNI levels were higher in farmland soil than in urban areas, which were 89.5 ± 182 ng/g and 4.8 ± 6.6 ng/g, respectively. NNI levels varied considerably among farmlands growing different crops, and higher NNI residues were found in soils growing vegetables and peanuts (Veg & Pn) than in those growing corn and fruit. Vertically, NNI levels in the soil significantly decreased from the surface layer (0-15 cm) to the intermediate (15-30 cm) and bottom layers (30-50 cm) (p < 0.05), with concentrations in the intermediate and bottom layers being 49.8 % and 22.4 % of those in the surface layer, respectively. The cultivation of Veg & Pn significantly increased NNI levels in farmland soils. Conversely, using river water for irrigation, having the correct knowledge of pesticide toxicity (higher toxicity does not necessarily lead to better pest control effectiveness), and long application intervals can significantly reduce NNI residues in the soil. Although the health risks of NNI exposure are relatively low, the ecological risk to non-target organisms in the soil requires attention, particularly in farmland areas.

Transport mechanisms and fate of neonicotinoids in the soil-water systems under the effects of wetting-drying cycles and rice cultivation

Neonicotinoids (NEOs), the most widely used class of insecticides in global agriculture, pose environmental risks due to their persistence and mobility. Despite their extensive application, the transport mechanisms and fate of NEOs in agroecosystem remain unclear. This study investigated the spatial-temporal dynamics mechanisms of six typical NEOs (i.e., clothianidin (CLO), imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (THM), dinotefuran (DIN), and nitenpyram (NIT)) under the effects of different water managements and rice cultivation in soil-water systems. After 61 days incubation, the dissipation in the soil-water systems were the dominated fate of NEOs (accounting for 96.3 ± 3.1 %), followed by storage in soils (2.6 ± 1.2 %), dissolution in interstitial water (0.7 ± 0.5 %) and overlying water (0.1 ± 0.1 %), and leakage in leakage water (0.3 ± 0.3 %). Both wetting-drying cycles and rice cultivation accelerated the NEOs dissipation. The possible reasons for this phenomenon were the wetting-drying cycles and rice cultivation stimulated NEO-degrader (i.e., Pseudomonas) growth in topsoil. Compared to flooding no rice treatment (half-life = 15.5 ± 4.4 days), the severe wetting-drying cycle with rice cultivation reduced NEO half-lives to 10.5 ± 3.1 days. The residual amounts of NEOs in each treatment were negatively (p < 0.05) correlated with the water solubility (CLO > IMI > ACE > THM > DIN > NIT), with the topsoil acting as the primary NEOs sink (41.6 % of total residues). The concentration of NEOs in the water phase decreased by 74.5 % from overlying water to leakage water, which due to the filtering effect of soils. The findings provide a scientific theoretical basis for the further prevention, control, and remediation of NEO pollution in agroecosystem.

Neonicotinoid and bisamide insecticides in wild freshwater fish from the Wanquan River, Hainan, China: Factors affecting tissue distribution and a risk assessment

A growing number of studies have reported that neonicotinoid (NEO) and bisamide (BIS) insecticides are widespread in multimedium; however, limited information is available on their occurrence in wild freshwater fish. Therefore, in the Wanquan River with national aquatic germplasm resource reserves in Hainan, China, 502 fish containing 22 species were collected to investigate the occurrence of twelve NEOs and six BISs. The results showed that six NEOs and three BISs were detected in liver (ND-26.1515 ng/g wet weight (ww), whereas five NEOs and three BISs were detected in muscle (ND-1.6067 ng/g ww). Clothianidin had the highest detection frequency in liver (35.26 %) and muscle (53.39 %); however, imidacloprid (0.2106 ng/g ww) and dinotefuran (0.0353 ng/g ww) had the highest mean concentrations. Furthermore, the results indicated significant differences in insecticide concentrations between fish with different feeding habits, habitats, and spatial distributions. Benthic fish tend to accumulate BISs in liver and carnivorous fish have highest NEOs concentration in muscle. In addition, fish in the midstream and downstream regions had higher NEOs and total concentrations than those in the upstream region. Spearman's correlation analysis revealed significant weak negative correlations between the concentration of almost all insecticides with body length and weight. Health risk assessments indicated that the hazard quotient for all insecticides was below 1, suggesting no immediate health risk to humans from consuming freshwater fish. These findings reveal previously unrecognized contamination of BISs in wild freshwater fish and expand the dataset on NEOs occurrence in fish from different sources, establishing a critical foundation for toxicologic research, insecticide pollution control, and human health protection.

Neonicotinoid metabolites in farmland surface soils in China based on multiple agricultural influencing factors: A national survey

Certain neonicotinoid metabolites (mNEOs) are causing widespread concern because they are equally or even more toxic than the parent NEOs. Currently, there is limited information on the distribution of mNEOs in soil. Especially, it is unknown that the effects of agricultural factors, such as plastic filming, plowing, irrigation, and fertilization, on mNEOs. This study is the first to reveal that mNEOs were commonly found in agricultural topsoil in China, with a geometric mean concentration of ΣmNEOs of 0.298 μg/kg. Among 31 provinces in Mainland China, Fujian had the highest mNEO residues, whereas Shanghai had the lowest. Among topsoil of various crop types, that of fruits and vegetables were found the highest mNEO residues. Furthermore, higher levels of film cover were associated with higher mNEO residues. Microplastics (MPs, serving as contaminant carriers) were positively correlated with mNEOs under field conditions, which was related to the adsorption capacity of microplastics and its influence on the soil conditions and the years of film cover. Alternatively, this study shows for the first time that irrigation water and manure might be sources of mNEO input into the soil, and that the plowing frequency might also influence on mNEOs.

Pollution characteristics, environmental issues, and green development of neonicotinoid insecticides in China: Insights from Imidacloprid

Imidacloprid (IMI), a leading neonicotinoid insecticide, is widely used in China. Nevertheless, owing to its high toxicity to pollinators, regulatory scrutiny of its usage has increased in recent years. Despite this, no relevant issues have been announced in China, and its usage continues to rise. In this study, we systematically reviewed the development history, pollution characteristics, and environmental problems associated with IMI in China, which is imperative to promote its green development. The results show that most IMI products (97.1%) in China are registered for agricultural use. Owing to its extensive use and strong migration ability in different environmental matrices, IMI has been broadly detected in multiple environmental media. The average detection rate (DR) of IMI in soils, ambient water, and sediments were 90.7%, 81.3% and 84.5%, respectively, and the corresponding concentrations were 54.6 ± 83.8 ng/g dry weight (dw), 32.8 ± 103 ng/L, and 1.7 ± 2.9 ng/g dw, respectively, indicating high IMI abundance in multiple environmental media in China. The spatiotemporal distribution of IMI was generally determined by its application modes, transport, and degradation rates. IMI is commonly overused in China, leading to the development of high IMI resistance in many pests, and a high DR of IMI in food, drinking water, and human bodies. To alleviate IMI pollution in China, the joint efforts of the government, farmers, and scientists are necessary, including but not limited to formulating laws and regulations, strengthening governmental supervision, improving farmers' knowledge of IMI use, and promoting technological innovation in IMI and application methods.

Invisible hazards: Exploring neonicotinoid contamination and its environmental risks in urban parks across China

Neonicotinoids (NEOs) are commonly used pesticides in agriculture. Urban parks containing numerous green plants and flowers also require NEOs for pest control. However, information on the distribution patterns and environmental risks of NEOs and their metabolites in urban park soils has yet to be discovered, which seriously limits the comprehensive evaluation of the potential hazards of NEOs. Our study explored the occurrence and distribution patterns of ten NEOs and five major metabolites in park soils from Guangzhou, Shijiazhuang, and Urumqi of China. At least three NEOs were detected in 95 % of soil samples, with the sum of all NEOs (∑10NEOs) ranging from 2.21 to 204 ng/g. Guangzhou has the highest levels of ∑10NEOs (median: 52.1 ng/g), followed by Urumqi (49.3 ng/g) and Shijiazhuang (21.7 ng/g). The top three most common NEOs in all three cities are imidacloprid, acetamiprid, and thiacloprid, which together account for 67 % to 70 % of ∑10NEOs. The levels of the metabolites of NEOs show a significant positive correlation with their corresponding parent NEOs. These NEOs pose detrimental effects to non-targeted invertebrates in the soil. Our findings raise concern about the environmental risks posed by NEO exposure to humans and other organisms in urban parks.

Neonicotinoids as emerging contaminants in China's environment: a review of current data

Neonicotinoids (NEOs), the most widely used class of insecticides, are pervasive in the environment, eliciting concerns due to their hydrophilicity, persistence, and potential ecological risks. As the leading pesticide consumer, China shows significant regional disparities in NEO contamination. This review explores NEO distribution, sources, and toxic risks across China. The primary NEO pollutants identified in environmental samples include imidacloprid, thiamethoxam, and acetamiprid. In the north, corn cultivation represents the principal source of NEOs during wet seasons, while rice dominates in the south year-round. The high concentration levels of NEOs have been detected in the aquatic environment in the southern regions (130.25 ng/L), the urban river Sects. (157.66 ng/L), and the downstream sections of the Yangtze River (58.9 ng/L), indicating that climate conditions and urban pollution emissions are important drivers of water pollution. Neonicotinoids were detected at higher levels in agricultural soils compared to other soil types, with southern agricultural areas showing higher concentrations (average 27.21 ng/g) than northern regions (average 12.77 ng/g). Atmospheric NEO levels were lower, with the highest concentration at 1560 pg/m3. The levels of total neonicotinoid pesticides in aquatic environments across China predominantly exceed the chronic toxicity ecological threshold of 35 ng/L, particularly in the regions of Beijing and the Qilu Lake Basin, where they likely exceed the acute toxicity ecological threshold of 200 ng/L. In the future, efforts should focus on neonicotinoid distribution in agriculturally developed regions of Southwest China, while also emphasizing their usage in urban greening and household settings.

A comprehensive evaluation of influencing factors of neonicotinoid insecticides (NEOs) in farmland soils across China: First focus on film mulching

Neonicotinoid insecticide (NEO) residues in agricultural soils have concerning and adverse effects on agroecosystems. Previous studies on the effects of farmland type on NEOs are limited to comparing greenhouses with open fields. On the other hand, both NEOs and microplastics (MPs) are commonly found in agricultural fields, but their co-occurrence characteristics under realistic fields have not been reported. This study grouped farmlands into three types according to the covering degree of the film, collected 391 soil samples in mainland China, and found significant differences in NEO residues in the soils of the three different farmlands, with greenhouse having the highest NEO residue, followed by farmland with film mulching and farmland without film mulching (both open fields). Furthermore, this study found that MPs were significantly and positively correlated with NEOs. As far as we know this is the first report to disclose the association of film mulching and MPs with NEOs under realistic fields. Moreover, multiple linear regression and random forest models were used to comprehensively evaluate the factors influencing NEOs (including climatic, soil, and agricultural indicators). The results indicated that the random forest model was more reliable, with MPs, farmland type, and total nitrogen having higher relative contributions.

Remediation of neonicotinoid-contaminated soils using peanut shell biochar and composted chicken manure: Transformation mechanisms of geochemical fractions

Soil remediation techniques are promising approaches to relieve the adverse environmental impacts in soils caused by neonicotinoids application. This study systematically investigated the remediation mechanisms for peanut shell biochar (PSB) and composted chicken manure (CCM) on neonicotinoid-contaminated soils from the perspective of transformation of geochemical fractions by combining a 3-step sequential extraction procedure and non-steady state model. The neonicotinoid geochemical fractions were divided into labile, moderate-adsorbed, stable-adsorbed, bound, and degradable fractions. The PSB and CCM addition stimulated the neonicotinoid transformation in soils from labile fraction to moderate-adsorbed and stable-adsorbed fractions. Compared with unamended soils, the labile fractions decreased from 47.6% ± 11.8% of the initial concentrations to 12.1 ± 9.3% in PSB-amended soils, and 7.1 ± 4.9% in PSB and CCM-amended soils, while the proportions of moderate-adsorbed and stable-adsorbed fractions correspondingly increased by 1.8-2.4 times and 2.3-4.8 times, respectively. A small proportion (<4.8%) in bound fractions suggested there were rather limited bound-residues after 48 days incubation. The PSB stimulated the -NO2-containing neonicotinoid-degraders, which promoted the degradable fractions of corresponding neonicotinoids by 8.2 ± 6.3%. Degradable fraction of neonicotinoids was the dominant fate in soils, which accounted for 58.3 ± 16.7%. The findings made beneficial theoretical supplements and provided valuable empirical evidence for the remediation of neonicotinoid-contaminated soils.

Occurrence, multiphase partitioning, drivers, and ecological risks of current-use herbicides in a river basin dominated by rice-vegetable rotations in tropical China

Rice-vegetable rotation practices prevail in subtropical and tropical agriculture worldwide, with applications of current-use herbicides (CUHs) vital for nontarget plant control. After application, CUHs migrate to environmental compartments, where the occurrence, fate, and ecological risks have not been well characterized. To further understand the occurrence and multiphase partitioning, as well as to evaluate potential drivers and mixture risks in environmental compartments, we analyzed 11 CUHs in 576 samples from 36 rice-vegetable rotations in Nandu River basin, Hainan, China. Samples included soil, water, suspended particulate matter, and sediment collected during both rice and vegetable planting periods. The CUH concentrations varied across environmental compartments, but with high levels of glyphosate and aminomethylphosphonic acid organophosphorus herbicides (OPHs) frequently detected, accounting for 82.3 % to 99.0 % in environmental compartments. Phenoxy acid (PAA) and chloroacetanilide (ANH) herbicides were detected at lower frequencies. Spatiotemporal variation was significantly different among OPHs, ANHs, and PAAs, with geographic and crop-related patterns most evident for CUHs rather than OPHs. Structural equation model, redundancy, and boosted regression tree analyses indicated environmental compartment properties (pH, organic matter, and Fe/Al oxides), crop type, and wet/dry climate were important drivers of spatiotemporal patterns. Fugacity ratios indicated multiphase partitioning and transport of CUHs differed in rice and vegetable planting periods. A new assessment framework based on species-sensitive distributions and environmental compartment weight index indicated unacceptable risks of CUHs (risk quotient >1 in >50 % of sites), with most risks from OPHs (10.5 % to 98.0 %) and butachlor, acetochlor, and 2,4-dichlorophenoxyacetic acid. Risk hot spots were identified as the soil, the central region, and the vegetable planting period, potentially threatening nontarget organisms (e.g., Lemna minor, Glomus intraradices, and Apis mellifera). This study provides a new risk assessment framework and demonstrates the domination of OPHs in CUH contamination and risks in the tropics, thus helping guide policymakers and stakeholders on herbicide management.

Distribution characteristics and risk assessment of neonicotinoid insecticides in planting soils of mainland China

Neonicotinoid insecticides (NEOs) are generally used in crop production. Their widespread use on agricultural soil has raised concerns regarding their health and ecological risks. Previous studies have reported the contamination of the farmland soils with NEOs from the coastal provinces of China. Information about NEOs at the national scale as well as the residues of their metabolites are relatively unknown. In this study, 391 soil samples were collected from 31 provinces in nine agricultural regions across mainland China, and the concentrations of ten parent NEOs and three metabolites were determined. At least one NEO was detected in all soil samples, with the sum of the NEOs (ΣNEOs) ranging from 0.04 to 702 μg/kg. The most common parent NEO and metabolite are imidacloprid and imidacloprid-urea, respectively. The concentrations of NEOs in coastal regions at the same latitude were higher than those in inland regions. The NEOs were further compared in the soils of seven types of monocrops and three types of multiple crops (multicrops) (i.e., two types of crops were produced in succession or simultaneously within the decade of this study). The results showed that the highest NEO residues were found in soils planted with vegetables (VE), fruits (FR), and cotton (CO) monocrops and VE & FR multicrops. Differences in NEO concentrations were observed between soils planted with monocrops and multicrops. For example, VE & FR > VE > vegetables and grains (VE & GR) > GR. Moreover, the health risks posed by NEOs in agricultural soils in China are extremely low, and the ecological risks require urgent attention. Particularly, individual NEOs in > 45% of agricultural soils in mainland China may have sublethal effects on two non-target species (HQnon-target > 0.01).

Enhanced persulfate activation by ethylene glycol-mediated bimetallic sulfide for imidacloprid degradation

CuFeS2 is regarded as a promising catalyst for heterogeneous activation to remove organic contaminants in wastewater. However, effects of solvents in regulating material synthesis and catalytic activity are still not clear. Herein, we reported the role of water, ethanol, ethylene glycol (EG), glycerol, and polyethylene glycol 200 on the synthesis of CuFeS2 micro-flowers and their performance in activating persulfate (PS) to remove imidacloprid (IMI) pesticide. The results showed that the solvent had an effect on the morphology, crystallinity, yields, specific surface areas and unpaired electrons of CuFeS2 micro-flowers. The degradation experiments revealed the efficient catalytic activity of EG-mediated CuFeS2 for heterogeneous PS activation. SO4•- and •OH were identified in EG-CuFeS2/PS system and •OH (90.4%) was the dominant reactive species. Meanwhile, stable 20% of η[PMSO2] (the molar ratio of PMSO2 generation to PMSO consumption) was achieved and demonstrated that Fe(IV) was also involved in the degradation process. Moreover, S2- promoted the cycling of Fe3+/Fe2+ and Cu2+/Cu+, enhancing the synergistic activation and reusability of the catalyst. Density functional theory (DFT) calculations verified that PS was adsorbed by Fe atom and electron transfer occurred on the catalyst surface. Three possible degradation pathways of IMI were proposed by analysis of the degradation intermediates and their toxicities were evaluated by ECOSAR. This study not only provides a theoretical foundation for catalyst design, but also promotes the industrial application of bimetallic sulfide Fenton-like catalysts for water management.