A national-scale distribution of organochlorine pesticides (OCPs) in cropland soils and major types of food crops in China: Co-occurrence and associated risks

Insights on common fungicides: A national survey on farmland soils from Mainland China

Fungicides are a growing concern owing to their ecological and human health threats. In China, which is a large fungicide-consuming country, only a few provincial studies have reported several fungicide residues in agricultural soils. Additionally, terrestrial ecological risk assessments of pesticides are limited to the single species. This study showed that fungicides were commonly found in agricultural soils in mainland China, and the Σ13fungicides concentrations ranged from 0.0548 to 3183 μg/kg, with the major contributing component being difenoconazole. Spatial variation in fungicide concentrations was significant, with the highest concentrations observed in Southern China. The Σ13fungicides concentration was higher in soils covered with plastic films compared to uncovered soils, possibly because microplastics from agro-film sources promote fungicide retention in the soil. Among the crop types, the highest fungicide residues were found in soils planted with fruits. In addition, this study was the first to use the probabilistic species sensitivity distribution (pSSD) approach to deduce the predicted no-effect concentrations of major fungicides as terrestrial safety thresholds. Particularly, soil texture conditions may influence the hazard assessment of fungicides. Finally, from the species taxa perspective, the proportions of ecological risks of carbendazim and tebuconazole in agricultural soils in China were 4.3 % and 5.9 %, respectively.

Deriving exposure route-specific cancer slope factors of carcinogenic chemicals via PBK modeling

Carcinogenic chemicals entering the body via different exposure routes result in varying internal doses and thus influence the tumors development. The internal doses can be quantified using biotransfer factors (BTF) simulated by the physiologically based kinetic (PBK) model. This study proposed a modeling method to analyze the quantitative relationships between BTF and cancer slope factors (CSFs). When the CSF for one exposure route is known, the CSF values for the other two routes can be derived using the relationships. A total of 45 carcinogenic chemicals were selected, and their oral CSF (CSForal) and BTF values were collected for analysis. The results demonstrated that route-specific CSFs of chemicals can be different due to their physicochemical properties. In addition, the derived route-specific CSFs are further utilized to conduct a comprehensive cancer risk assessment. The results revealed that cancer risk caused by most environmental chemical exposure exceeded 1 × 10-6, suggesting that long-term exposure to chemicals would pose certain human cancer risks. These findings highlight the importance of exposure route-specific CSFs for accurate cancer risk assessment and provide a scientific reference for environmental agencies to refine the risk assessment system.

Fate and ecological risk of legacy and emerging POPs in coastal waters in China

Short-chain chlorinated paraffins (SCCPs) and dechlorane plus (DPs) are persistent organic pollutants of emerging concern, however, little is known of their fate and ecological risks in coastal waters compared to legacy contaminants in marine environment. Here, we analyzed SCCPs, 2 DP isomers as well as legacy contaminants including 24 organochlorine pesticides and polychlorinated biphenyls (PCBs) in seawater from Hangzhou Bay (HZB) and Liaodong Bay (LDB) for comparison using GC-Orbitrap MS. The total contaminant load in seawater was dominated by SCCPs with the highest detection frequency, in concentrations ranging from 25.38 to 388.23 ng/L in HZB and 7.45 to 144.48 ng/L in LDB, respectively. The congener patterns of SCCPs differed significantly, where HZB was predominated by C11-13-CPs (accounted for 83 %) and C10-CPs (40.4 %) was the most abundant in LDB. SCCPs were positively correlated with legacy contaminants in HZB, indicating similar sources. In terms of legacy contaminants, HZB exhibited higher levels of hexachlorobenzene, whereas LDB showed a prevalence of hexachlorocyclohexane. The ocean current in HZB and direct terrestrial input with the impact of intensive human activities around LDB were suggested to attribute to their spatial distribution characteristics, respectively. The contaminants were identified to have medium risks to aquatic organisms by using the risk quotient method. SCCPs contributed most with proportions of 45 % and 80 % for HZB and LDB, the monitoring of which needs to be strengthened in the future.

Long-range atmospheric transport of organochlorine pesticides from China to South Korea: Evidence from Deokjeok Island

The influence of transboundary air pollutants originating from the Asian continent on South Korea has been a major concern. Although organochlorine pesticides (OCPs) have been banned for several decades, they continue to be detected in the Korean environment. However, studies on the long-range atmospheric transport (LRAT) of OCPs in South Korea, particularly in background areas, remain limited. This study investigated the atmospheric levels, sources, and behavior of OCPs at Deokjeok Island, a background site near the west coast of the Korean Peninsula. Total concentrations of 24 OCPs ranged from 53.6 to 325 pg/m3, which are lower than those reported by the national POPs monitoring network of South Korea and similar to levels found in other background regions in Northeast Asia. HCB (62.7 pg/m3, 45%) and PeCB (46.6 pg/m3, 33%) were the most dominant OCPs in the gaseous phase, whereas DDTs were predominant (1.65 pg/m3, 44%) in the particulate phase. Gaseous OCPs were strongly influenced by past use and re-emissions, while ongoing emissions and LRAT were the major sources of particulate OCPs. The consistent detection of mirex provides strong evidence of LRAT. In addition, correlation analysis and the Clausius-Clapeyron equation indicated that DDTs were significantly influenced by LRAT. Concentration-weighted trajectory maps identified East, North, and Northeast China as the major source regions for gaseous OCPs, driven by re-emissions, while the primary source areas for particulate OCPs were Beijing, Hebei, Tianjin, and Shandong. Air/soil fugacity fractions showed equilibrium or net deposition for most OCPs (except PeCB), indicating the dynamic environmental behavior of OCPs influenced by past use and LRAT. This study provides evidence of LRAT of OCPs to South Korea, demonstrating the significant impact of transboundary pollution. These results highlight the importance of ongoing monitoring of both historically and currently used pesticides at receptor sites in Northeast Asia.

Effect of soil-groundwater system on migration and transformation of organochlorine pesticides: A review

Soil is the place where human beings, plants, and animals depend on for their survival and the link between the various ecological layers. Groundwater is an important component of water resources and is one of the most important sources of water for irrigated agriculture, industry, mining and cities because of its stable quantity and quality. Soil and groundwater are important strategic resources highly valued by countries around the world. However, in recent years, the deterioration of the ecological environment of soil-groundwater caused by industrial, domestic, and agricultural pollution sources has continued to threaten human health and ecological security. Among them, organochlorine pesticides (OCPs), as typical organic pollutants, cause very serious pollution of soil and groundwater environment. However, most studies on the pollution of OCPs have focused on the aboveground or surface water environment, and little consideration has been given to the pollution and hazards of OCPs to the deep soil and groundwater environment, especially the effects of different environmental factors on the transport and transformation of OCPs in soil-groundwater. Moreover, in addition to the influence of a single factor on it, the interactions that arise between different factors cannot be ignored. This paper focuses on two major sources of OCPs in soil and groundwater environments, compiles and summarizes the effects of environmental factors such as pH, microbial communities and enzyme activities on the transport and transformation of OCPs in soil and groundwater systems, discusses the synergistic effects of individual environmental factors and others, and comprehensively analyses the effects of synergistic effects of various environmental factors on the transport and transformation of OCPs. In the context of ecological civilization construction, it provides the scientific basis and theoretical foundation for the prevention and treatment of OCPs-contaminated soil and groundwater, and puts forward new ideas and suggestions for the research and development of green, eco-friendly remediation and treatment technologies for OCPs-contaminated sites.

Spatial pattern and compositional distribution of organochlorine pesticides in the black soil region of Shenyang

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) prevalent in soils with carcinogenic, teratogenic and mutagenic hazards that are commonly found in soils and remain in the environment even though they have been banned. In order to fill the gap of fewer studies after the ban, soil samples were collected from 308 agricultural fields of cash crops and grain crops in the black soil area of Shenyang City (Liaozhong District, Faku County, Xinmin City and Kangping County) in this study. The aim was to determine, the use and distribution characteristics of OCPs in agricultural soils in the black soil region of Shenyang City. Compositional analysis showed that the detection rate of banned OCPs in agricultural soils was 71.75%, including contaminants such as technical dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB), which were widely distributed in Liaozhong District, Faku County, Xinmin City and Kangping County, with 45.25% of the fields having compounded contamination of OCPs, and several areas were involved in the fresh inputs of contaminants such as technical DDT. Among them, Kangping County and Faku County are more seriously polluted, with 66.29% and 60.71% of OCPs exceeding the standard. Soil OCPs is more serious in cabbage and rice farmland among cash and food crop farmland. Based on Chinese policy on control, prevention and other pesticide management measures, it was concluded that the framework should be strengthened to prevent further illegal use of banned OCPs.

Basal levels of biochemical biomarkers in the freshwater prawn Palaemon argentinus and their alterations due to the exposure of both insecticides cypermethrin and spirotetramat

The aim of this study was to evaluate the sensitivity of the prawn Palaemon argentinus to the pyrethroid cypermethrin (CYP) and the tetramic acid spirotetramat (STM). These treatments were compared with prawns collected at a reference site to define their basal physiological state. Initially, physicochemical parameters and several pollutants at the selected site were analyzed. The LC50-96 h was determined in adult prawns. Then, prawns were exposed for 96 h to sublethal concentrations of CYP (0.0005 μg/l) and STM (0.44 mg/l) to evaluate the effects on some biochemical endpoints. A treatment combining both pesticides was also added at 5 % of these values. Controls with and without solvent (acetone) were included. The LC50-96 h values were 0.005 μg/l and 4.43 mg/l for CYP and STM, respectively. Moreover, some biomarkers linked to oxidative and energy metabolism were analyzed in the hepatopancreas and muscle of both essayed prawns and those at the basal state. The STM caused a significant decrease in total protein content (32 %) in contrast to the increase of protein carbonyl content (71 %) (p < 0.05). Also, glutathione S-transferase (52 %) and catalase (61 %) activities in the hepatopancreas of exposed prawns were higher compared to both the control and state basal groups (p < 0.05). In muscle, only a significant decrease in the lactate content (69 %) was caused by STM (p < 0.05). In addition, CYP caused a significant increase in the lactate dehydrogenase activity (110 %) in muscle and triacylglycerol content (73 %) in the hepatopancreas (p < 0.05). The integrated biomarker index (IBRv2) analysis showed that STM caused greater damage than CYP. Besides, the combined treatment showed an antagonistic interaction between both insecticides. The differential response of biomarkers to both CYP and STM exposure with respect to their basal levels shows a high sensitivity of P. argentinus demonstrating its potential role as a bioindicator organism.

Residue changes, degradation, processing factors and their relation between physicochemical properties of pesticides in peanuts during multiproduct processing

This study systematically investigates the residue changes, processing factors (PFs), and relation between the physicochemical properties of pesticides during peanut processing. Results revealed that peeling, washing, and boiling treatments removed partial or substantial pesticide residues from peanuts with PFs of 0.29-1.10 (most <1). By contrast, pesticides appeared to be partially concentrated during roasting, stir-frying, and deep-frying peanuts with PFs of 0.16-1.25. During oil pressing, 13 of the 28 pesticides were concentrated in the peanut oil (PF range: 1.06-2.01) and 25 of the pesticides were concentrated in the peanut meal (1.07-1.46). Physicochemical parameters such as octanol-water partition coefficient, degradation point, molecular weight, and melting point showed significant correlations with PFs during processing. Notably, log Kow exhibited strong positive correlations with the PFs of boiling, roasting, and oil pressing. Overall, this study describes the fate of pesticides during multiproduct processing, providing guidance to promote the healthy consumption of peanuts for human health.

Persistent Organic Pollutants in Tagus Estuary Salt Marshes: Patterns of Contamination and Plant Uptake

The presence of anthropogenic compounds, including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), was studied in three salt marshes within the Tagus estuary, Portugal, along an anthropogenic pressure gradient. Results revealed differences in OCPs and PCBs among the marshes, with differing concentration levels. Specifically, one marsh, with surrounding agricultural activity, showed the highest OCP concentrations, while another, with a historical industrial past, exhibited elevated PCB levels. In contrast, a third marsh, part of a natural reserve, displayed comparatively lower concentrations of both substances. Sediment concentrations, likely influenced by agricultural practices, were found to be comparable to or higher than those observed in other Portuguese estuaries. The halophyte Spartina maritima was found to absorb OCPs, particularly in its aboveground tissues, suggesting bioaccumulation within the plant. Additionally, PCB levels appeared to be influenced by industrial history, with one marsh displaying notably higher concentrations. In conclusion, the persistence of organochlorine compounds in the salt marsh ecosystems notwithstanding the regulatory prohibitions implemented in the 1990s highlights the need for continuous monitoring and study of such sites and the necessity of remediation practices, which are imperative to mitigate ecological and health risks in these polluted salt marshes.

A nationwide characterization of organochlorine pesticides (OCPs) in livestock and poultry food products across China: Residual levels, origin and the associated health risks

Organochlorine pesticides (OCPs) are still occurring in various foodstuffs after the ban on their use. However, it remains unclear concerning the contamination source of OCPs in livestock and poultry food products and associated health risks. To fill this gap, we characterized the residual levels of 19 OCPs in multiple types of meats and eggs, which were sampled across China within the same period. Dichlorodiphenyltrichloroethanes (DDTs) were dominant in eggs, with the mean levels being 0.76 and 2.03 μg/kg for chicken eggs and duck eggs, respectively. By contrast, hexachlorocyclohexanes (HCHs) were the top one OCP in beef and lamb, with its mean levels being 0.51 and 0.65 μg/kg, respectively. Hexachlorobenzene (HCB) was rather detected in the poultry products. The componential ratio analysis implicated recent inputs of several banned OCPs including technical HCH and DDT, HCB and aldrin in multiple regions, which may origin from local industrial activities or possible illegal use. Risk assessment based on the risk quotient method suggested that daily consumption of cooked meats and eggs contaminated by dieldrin may pose a carcinogenic risk in adult residents of Jiangsu province. We concluded that OCPs remain present in meats and eggs at levels of health concern regionally in China.

Isomer, enantiomer and compound-specific stable isotope evidences for the transformation of dichlorodiphenyltrichloroethanes (DDTs) in soils from three typical paddy fields in China

Chlorinated pollutants may follow distinct degradation pathways in anaerobic environments compared to aerobic settings. However, the understanding of the behaviors and fate of dichlorodiphenyltrichloroethanes (DDTs) under anaerobic conditions remains limited. To address this knowledge gap, we conducted a study on flooded soil samples collected from three typical paddy fields in China using an integrated approach of enantiomer-specific analysis and compound-specific stable carbon isotope analysis. It is unexpected that the dichlorodiphenyldichloroethane /dichlorodiphenyldichloroethylene ratios (DDD/DDE=(o,p'-DDD+p,p'-DDD)/(o,p'-DDE+p,p'-DDE)) were below 1 in over 90 % of the samples. This might be attributed to the higher recalcitrance of p,p'-DDE, which concentrations were found to be 36 times higher than p,p'-DDD on average. There were 71.7 % of the samples showing enantiomeric fractions (EFs) of o,p'-DDT below 0.5, indicating a preferential accumulation of the (-)-enantiomer. The δ13C values of the anaerobic metabolite o,p'-DDD (-24.76 ± 1.35 ‰ to -34.39 ± 0.20 ‰) all deviated negatively from the initial product, while those of the aerobic metabolite o,p'-DDE (-23.61 ± 0.48 ‰ to -38.95 ± 0.81 ‰) displayed either negative or positive deviations. This demonstrates that o,p'-DDD is the primary metabolite of o,p'-DDT under anaerobic conditions. However, no clear correlations were observed between the δ13C and EF of o,p'-DDT. This study underscores the importance of such an integrated methodology in unraveling the fate and behaviors of DDTs in complex environmental systems.

Analysis of nationwide soil pesticide pollution: Insights from China

China is a typical agricultural country that heavily relies on pesticides. Some pesticides can remain in the soil after application and thus pose a significant threat to human health. In order to characterize the status and hazards of nationwide soil contamination, this study extracted concentration data from published literature and analyzed them by a scoring approach, standard comparison and health risk assessment. For the soil pollution score, northern regions got the highest values, such as Henan (0.63), Liaoning (0.55), Heilongjiang (0.54) and Jilin (0.53), which implies high soil pesticide residues in these provinces. In contrast, Qinghai (-0.77), Guizhou (-0.64) and Tibet (-0.63) had lower scores. China's soil pesticide standards cover only 16 pesticides, and these pesticide concentrations were all below the corresponding standards. Direct exposure to soil pesticides in this study generally posed a negligible risk to children. Furthermore, pesticide dissipation and usage intensity in each province were analyzed as they were possible influences on pollution. The result showed that soil in the northern regions could accumulate more pesticides than those in the southern regions, and this geographic pattern was basically consistent with the distribution of soil pollution. However, the relationship between agricultural activities and soil pollution was less well characterized. It is recommended to establish a long-term monitoring database for pesticides and include more pesticides in regulatory frameworks. Additionally, efforts to accelerate pesticide degradation and shift the planting structure to reduce pesticide usage can help alleviate the pressure on soil from pesticides. This study can serve as a critical reference for policymakers and stakeholders in the field of agriculture.

Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), the sum of dicofol and 4,4'-dichlorobenzophenone (p,p'-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, β-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and β-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p'-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p'-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p'-DDNU→p,p'-DBP, whereas the amount of p,p'-DDMU converted from p,p'-DDD and p,p'-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

Cross-regional scale studies of organochlorine pesticides in air in China: Pollution characteristic, seasonal variation, and gas/particle partitioning

Few simultaneous studies of organochlorine pesticides (OCPs) in the atmosphere have been conducted across Southeast and Northeast China, and no data on the gas/particle (G/P) partitioning behaviors of several current-use OCPs are available. In this study, a one-year synchronous monitoring program was conducted for OCPs in Chinese atmosphere spanning 30° latitude and 60 °C temperature. A total of 111 pairs of gas and particle samples were collected from Mohe and Harbin in Northeast China and from Shenzhen in Southeast China. The detection frequency for 66.7 % of the OCPs exceeded 80 %, indicating their prevalence in the atmosphere. The concentrations of individual OCPs spanned six orders of magnitude, indicating different pollution levels. Highest levels of hexachlorobenzene were observed at all sites. Banned OCPs were found predominantly in secondary distribution patterns, whereas current-use OCPs were dominated by primary distribution patterns. In Harbin and Mohe, the concentrations of OCPs were highest in summer, followed by autumn and winter. No obvious seasonal variation was observed in Shenzhen associated with different cultivation types. At all three sites, OCPs were predominantly found in the gas phase, and higher percentages of particle-phase OCPs were observed in Harbin and Mohe than in Shenzhen. In this study, G/P partitioning models were used to study the G/P partitioning mechanism of OCPs. The Li-Ma-Yang model provided the most accurate prediction of the G/P partitioning behavior of OCPs with high molecular weights and low vapor pressures, particularly at low temperatures. However, OCPs with lower molecular weights and higher vapor pressures were predominantly in the equilibrium state, for which the Junge-Pankow model was suitable. This systematic cross-scale study provides new insights into pollution, G/P partitioning, and the environmental behavior of OCPs in the atmosphere.

Spatio-temporal distribution of organochlorine pesticides in agricultural soils of southeast China during 2014-2019

Organochlorine pesticides (OCPs) are organic pollutants that are persistent and undegradable in the environment. To investigate their residual concentrations, spatial and temporal distributions, and the relationship with the crops planted, 12 individual OCPs in 687 soil samples from Jiangsu, Zhejiang and Jiangxi provinces of southeast China were examined. The detection frequencies of OCPs in the studied areas were 1.89%-64.9%. The concentrations of dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfans ranged from 0.01 to 5659 μg/kg, 0.03-3.58 μg/kg, and 0.05-3235 μg/kg, respectively. Jiangsu was mainly contaminated by p,p'-DDT, p,p'-DDD and endosulfan sulfate, Zhejiang was more polluted by OCPs except δ-HCH, and Jiangxi was more vulnerable to the contamination of OCPs except o,p'-DDE. The partial least-squares discrimination analysis (PLS-DA) model with RX2 36.3-36.8% revealed that compounds with similar chemical properties tended to appear in the same year and month. All crop lands were polluted by DDTs and Endosulfans. The highest concentrations of DDTs and Endosulfans were found in citrus and vegetable fields, respectively. This study offers new insight into the layout and partitioning of OCPs in agricultural land and into insecticide management on public health and ecological safety.