Organochlorine pesticides in the lower reaches of Yangtze River: occurrence, ecological risk and temporal trends

Dissipation kinetics and the evaluation of dietary risks associated with deltamethrin, ethion, fenazaquin, and fenpropathrin on bell pepper (Solanum annuum L.)

Bell peppers, a globally significant crop, face infestations from various pests. In a study, bell peppers were treated with deltamethrin, ethion, fenazaquin, and fenpropathrin at recommended and double the doses, repeated twice with a 10-day interval. The QuEChERS method underwent validation for linearity, matrix match, accuracy, and precision in bell pepper matrices for residue analysis. The limit of detection for the tested pesticides on bell peppers was 0.01 mg/L, with a quantification limit of 0.05 mg/L. Recovery studies showed a range of 94.80% to 102.80%. Initial deposits of deltamethrin, ethion, fenazaquin, and fenpropathrin on bell peppers at recommended doses were 0.371, 1.237, 0.617, and 0.640 mg/L, respectively, and at double doses were 0.712, 1.945, 1.221, and 1.189 mg/L, respectively. Safe waiting periods of 10, 11, 10, and 8 days were suggested for deltamethrin, ethion, fenazaquin, and fenpropathrin, respectively. The corresponding half-lives for the pesticides were 1.96, 1.79, 2.06, and 1.69 days, all following first-order dissipation kinetics. Dietary risk assessment indicated Hazard Quotients (HQ) below 1 and Theoretical Maximum Daily Intake (TMDI) below Acceptable Daily Intake (ADI) and Maximum Permissible Intake (MPI) levels. Therefore, at their recommended doses, the pesticides were deemed safe for bell pepper cultivation.

Differentiated cognition of the effects of human activities on typical persistent organic pollutants and bacterioplankton community in drinking water source

Accelerated urbanization in developing countries led to a typical gradient of human activities (low, moderate and high human activities), which affected the pollution characteristics and ecological functions of aquatic environment. However, the occurrence characteristics of typical persistent organic pollutants, including organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), and bacterioplankton associated with the gradient of human activities in drinking water sources is still lacking. Our study focused on a representative case - the upper reaches of the Dongjiang River (Pearl River Basin, China), a drinking water source characterized by a gradient of human activities. A comprehensive analysis of PAHs, OCPs and bacterioplankton in the water phase was performed using gas chromatography-mass spectrometry (GC-MS) and the Illumina platform. Moderate human activity could increase the pollution of OCPs and PAHs due to local agricultural activities. The gradient of human activities obviously influenced the bacterioplankton community composition and interaction dynamics, and low human activity resulted in low bacterioplankton diversity. Co-occurrence network analysis indicated that moderate human activity could promote a more modular organization of the bacterioplankton community. Structural equation models showed that nutrients could exert a negative influence on the composition of bacterioplankton, and this phenomenon did not change with the gradient of human activities. OCPs played a negative role in shaping bacterioplankton composition under the low and high human activities, but had a positive effect under the moderate human activity. In contrast, PAHs showed a strong positive effect on bacterioplankton composition under low and high human activities and a weak negative effect under moderate human activity. Overall, these results shed light on the occurrence characteristics of OCPs, PAHs and their ecological effects on bacterioplankton in drinking water sources along the gradient of human activities.

Residue estimation and dietary risk assessment of fenvalerate, novaluron, and profenofos in bell pepper grown under protected and open field conditions

Residue studies were conducted in bell pepper crops (green and yellow bell pepper) to ensure the safe use of fenvalerate, profenofos, and novaluron (under open field and protected conditions) in randomized block design (RBD) following three applications at a 10-day interval over two consecutive years, 2021 and 2022. A robust analytical method was developed using quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and gas chromatography-tandem mass spectrometry (GC-MS/MS) for the determination of pesticide residues in bell pepper samples. The half-lives for fenvalerate were 2.47-2.87 and 2.50-3.03 days on bell pepper under open field conditions, whereas the corresponding values for bell pepper under protected conditions were 3.84-4.58 and 4.17-4.71 days, during 2021 and 2022, respectively. Profenofos displayed half-lives of 2.03-2.65 and 2.15-2.77 days in open field conditions and 3.05-3.89 and 3.16-3.78 days in protected conditions during 2021 and 2022, respectively. Similarly, novaluron had half-lives of 2.87-3.49 and 3.24-3.75 days under protected conditions in 2021 and 2022, respectively. The maximum residue limits (MRLs) were calculated to be 0.6 mg/kg for fenvalerate, while for profenofos it was 0.7 mg/kg on bell pepper under open field conditions at double doses, at the proposed pre-harvest interval (PHI) of 3 days. Likewise, for bell peppers grown under protected conditions, MRLs at the PHI of 3 days were determined to be 0.8 mg/kg for fenvalerate, 0.3 mg/kg for novaluron, and 1.5 mg/kg for profenofos. A dietary risk assessment study indicated that the percentage of acute hazard index (% aHI) was significantly lower than 100, and hazard quotient (HQ) values were below 1, signifying no acute or chronic risk to consumers. These findings underscore the safety of consuming bell peppers treated with fenvalerate, profenofos, and novaluron under the protected and open field conditions.

Ecological risk assessment of 50 emerging contaminants in surface water of the Greater Bay Area, China

Ecological risk assessment of emerging contaminants (ECs) is an international research hotspot and is also the focus of China's "14th Five-Year Plan". The Greater Bay Area (GBA) is one of the four major bay areas in the world and the most dynamic region in China. However, there are few studies on the risk assessment of ECs in the GBA, and there needs to be a systematic and comprehensive assessment of the ecological risk of ECs. We selectively collected environmental concentration and toxicity data reported in the literature before 2022 for 50 representative ECs. We use risk quotient (RQ), semi-probability, Margin of Safety (MOS), and joint Probability curve (JPC) methods for multiple-level risk assessment. The RQ results showed that there were primary ecological risks in 20 ECs. Nine ECs were screened by the semi-probability, MOS, and JPC methods. The total risk probability of nonylphenol (NP) to the GBA was 12.11 %, and the risk to the aquatic ecological environment was the highest, followed by α-endosulfan (α-END) and erythromycin (ERY). At the same time, a comprehensive assessment method was adopted to screen the list of medium and high-risk priority pollutants in the GBA. According to the comprehensive evaluation results, although the risk is low, perfluorooctanoic acid (PFOA) still deserves widespread attention. The results showed that NP, α-END, ERY, and PFOA may be the most concerned ECs in the GBA. This research fills the gap on the ECs ecological risk assessment of the GBA and can provide a theoretical reference for managers in the follow-up of ECs regulatory governance.

Sediment-water partitioning and risk assessment of organochlorine pesticides along the urban, peri-urban and rural transects of Krishna River Basin, Peninsular India

Organochlorine pesticides (OCPs) were widely used in the past for pest control in agricultural lands and vector control programs in India. Due to their persistence and toxic impacts, we have quantified twenty OCPs in surface water, groundwater, and surface sediment samples along the Krishna River Basin (KRB), flowing through Peninsular India. Samples were collected along the urban, peri-urban, and rural transects of the KRB to understand the relation between the occurrence of pesticidal organochlorine pollutants based on the land use and land cover (LULC) and asses potential risk. Diagnostic ratios revealed ongoing Lindane usage in rural and peri-urban transects. On the contrary, the urban transect of the Musi River (MR) showed fresh inputs of technical HCH. The ratios of (p,p'-DDE+ p,p'-DDD)/ΣDDT >0.5 and α/β-Endosulfan < 2.33 for most of the sites across the three transects for surface water, groundwater, and sediment indicate past DDT and Endosulfan usage across KRB. Excluding p,p'-DDE, and heptachlor in most of the sites, the logK_OC' was higher than logK_OC for other OCPs in the urban transect. However, for all the OCPs, the logK_OC' was lower than logK_OC in the peri-urban and rural transects of KRB thereby indicating that riverine sediment is acting as a sink for OCPs. The Krishna River annually transport about 0.24 tons HCH, 0.11 tons of DDT and 0.1 tons of Endosulfan. Despite having low water discharge, the compound-specific fluxes of the Wyra river are higher than the other two tributaries. Ecotoxicological risk assessment based on the Hazard Quotient suggested DDT pose higher risks to scud (zooplankton) and dinoflagellate and diatom (phytoplankton) whereas Endosulfan poses a threat to Bluegill (fish).

Coming ecological risks of organochlorine pesticides and novel brominated flame retardants in the Yellow River Basin

To conduct ecological risk assessment, food, water and soil samples were collected from five densely populated irrigation areas in the Yellow River Basin (YRB), and analyzed for organochlorine pesticides (OCPs) and novel brominated flame retardants (NBFRs). The results showed that the OCP residues (∑₁₄OCP were 0.748 ng L^-1, 13.1 ng g^-1 dw and 3.22 ng g^-1 dw in water, soil and maize) were generally within moderate levels in the YRB. Dichlorodiphenyltrichloroethane (DDT) residues dominated the OCPs, and potential ecological risks to aquatic and terrestrial organisms likely stemmed from dichlorodiphenyldichloroethylene (DDE) pollution in the upper reaches of the YRB in the Ningxia and Hetao Plain. The NBFR concentrations in the YRB were 90.9 pg L^-1 in water, 21.1 pg g^-1 dw in soil and 3.81 pg g^-1 dw in maize. Positive correlations were observed between soil and maize contamination in the five irrigated districts, indicating a potential threat to grain security and human health risks caused by OCPs and NBFRs. Pollutants detected in soil and maize primarily originated from historical use (36.3 %), while the sources in water were more complex (64.4 %) and new inputs could not be excluded. Integrated health risks of human exposure to agricultural products and water from the YRB were acceptable. However, the ecological risk of the Ningxia Plain would further deteriorate to the medium risk after 2032. The increasing ecological risk of DDT in water indicates that regular monitoring should strengthen to ensure grain and water safety in the YRB.

Bioaccumulation of organochlorine pesticide residues (OCPs) at different growth stages of pacific white leg shrimp (Penaeus vannamei): First report on ecotoxicological and human health risk assessment

Pesticide residues (PRs) in farmed shrimps are concerning food safety risks. Globally, India is a major exporter of pacific white leg shrimp (P. vannamei). This study was undertaken to analyze PRs in the water, sediments, shrimps, and feed at different growth stages to evaluate the ecotoxicological and human health risks. PRs in the seawater and sediments ranged from not detected (ND) to 0.027 μg/L and 0.006-12.39 μg/kg, and the concentrations were within the maximum residual limits (MRLs) and sediment quality guidelines prescribed by the World Health Organization and Canadian Environment Guidelines, respectively. PRs in shrimps at three growth stages viz. Postlarvae, juvenile, and adults, ranged from ND to 0.522 μg/kg, below the MRLs set by Codex Alimentarius Commission and European Commission. Most of the PRs in water, sediments, and shrimps did not vary significantly (p > 0.05) from days of culture (DOC-01) to DOC-90. The hazard quotient (HQ) and hazard ratio (HR) were found to be < 1, indicating that consumption of shrimps has no noncarcinogenic and carcinogenic risks. PRs in shrimp feed ranged from ND to 0.777 μg/kg and were found to be below the MRLs set by EC, which confirms that the feed fed is safe for aquaculture practices and does not biomagnify in animals. The risk quotient (RQ) and toxic unit (TU) ranged from insignificant level (ISL) to 0.509 and ISL to 0.022, indicating that PRs do not pose acute and chronic ecotoxicity to aquatic organisms. The study suggested no health risk due to PRs in shrimps cultured in India and exported to the USA, China, and Japan. However, regular monitoring of PRs is recommended to maintain a sustainable ecosystem.

Spatio-temporal variations and ecological risks of organochlorine pesticides in surface waters of a plateau lake in China

Qilu Lake is one of the 9 plateau lakes in Yunnan, China, with a lake surface altitude of 1796.62 m above sea level. In spite of the importance and agriculturally-intensive phenomenon in Qilu Lake Basin, few studies have provided a modern evaluation of pesticide residues and potential effects to local aquatic organisms. The primary goal of this study was to determine the spatio-temporal variations of organochlorine pesticides (OCPs) in this area, and to further assess the related ecological risks. Of the 25 OCPs analyzed, 14 were detected, and the concentrations of ∑₂₅OCPs were highest in the upstream of rivers, followed by regions close to the lake shore, and the lowest concentrations were found in Qilu Lake in every season except winter. The concentrations of ∑₂₅OCPs were the highest in summer, and the lowest in winter. OCP concentrations in spring and in autumn were similar. 4,4'-DDD, γ-HCH, HCB, trans-chlordane, and cis-chlordane were 5 OCPs with relatively high risk in Qilu Lake Basin. Interestingly, higher OCP concentrations do not necessarily correspond to higher ecological risk levels. Low predicted no-effect concentration (PNEC) values and relatively high toxicity of these OCPs led to their high risk quotient (RQ) values. This work further illustrated that although OCPs have been banned for many years, they were still frequently detected in surface waters, and caused risks to aquatic animals.

Organochlorine pesticides in riparian soils and sediments of the middle reach of the Huaihe River: A traditional agricultural area in China

Distributions, souces, ecological risks as well as environmental behaviors of 20 organochlorine pesticides (OCPs) in riparian soils and sediments of the middle reach of the Huaihe River, a traditional agricultural area of China, were investigated. ∑OCPs in riparian soils and sediments were 1.8-63 ng g^-1 (mean = 19 ± 12 ng g^-1) and 1.2-9.9 ng g^-1 (mean = 3.0 ± 1.8 ng g^-1), respectively. HCHs were the dominant OCPs in both soils and sediments, while high concentrations of ∑HEPTs and ∑DDTs were also detected in some soils and sediments. No correlations were found between concentrations of OCPs and organic matter contents in both soils and sediments. Based on the source analysis, most OCPs in the riparian soils were mainly from historical residues, such as historical usage of technical HCH, DDT, chlordane and endosulfan. OCPs in sediments were influenced not only by surface runoff by also by other factors, e.g. in-situ contamination (DDT-containing antifouling paints in ships) and/or hydraulic transport from some tributaries. Some never-used OCPs, such as heptachlor and aldrin, were widely detected in soils and sediments. This might be attributed to some unknown usages or long-range atmospheric transport of them from other source regions. Ecological risk analysis suggested that DDTs and HCHs in soils would not lead to an adverse effect on soil ecological environment as well as agricultural production, and OCP residues in sediments also would not pose a threat to the sediment-dwelling organisms.

Bioaccumulation and maternal transfer of two understudied DDT metabolites in wild fish species

While the secondary metabolites of DDT such as 2,2-bis(chlorophenyl)-1-chloroethylene (DDMU) and 2,2-bis(chlorophenyl)methane (DDM) have been detected in the environment for several decades, knowledge is extremely limited on their bioaccumulation characteristics. Here, we reported the bioaccumulation and maternal transfer of p,p'-DDMU and p,p'-DDM in two wild fishes, i.e., the northern snakehead (Channa argus) and crucian carp (Carassius auratus), from a DDT contaminated site in South China. The hepatic concentrations of p,p'-DDMU and p,p'-DDM in the fish were up to 549 and 893 ng/g lipid weight, contributing 5.3% and 3.2% in average to ΣDDXs (the sum concentrations of DDT and its 6 metabolites), respectively. The residues of p,p'-DDMU and p,p'-DDM in the fish exhibited interspecific and intraspecific variations, resulting from the differences in lipid content, sex, and body sizes (length and mass) between or within species. Both p,p'-DDMU and p,p'-DDM were consistently detected in the fish eggs, demonstrating their maternal transfer in female fish. The mean eggs to liver lipid-normalized concentration (E/L) ratios of p,p'-DDMU and p,p'-DDM were 0.98 and 1.77 in the northern snakehead, 0.35 and 0.01 in crucian carp, respectively; which were comparable to or even exceeded those of DDT and its major metabolites calculated in the same individual. Statistical analyses of the data showed that the E/L ratios were positively correlated with body sizes of the fish, but negatively correlated with the hepatic concentrations of p,p'-DDMU and p,p'-DDM in females; suggesting the influences of fish sizes and the mother body residues on their maternal transfer efficiencies.

Temporal Trends of Exposure to Organochlorine Pesticides in the United States: A Population Study from 2005 to 2016

The current study aimed to investigate temporal trends of serum organochlorine pesticide (OCP) concentrations in the general United States population, approximately 30 years after the prohibition of OCP usage, by using National Health and Nutrition Examination Survey data. The least square geometric means and percent change in OCP concentrations were calculated by a survey weighted multiple linear regression model. Over 2005–2016, OCP concentrations showed significant downward temporal trends. Females had substantially higher concentrations of β-Hexachlorocyclohexane (β-HCH), p,p′-DDE and p,p′-DDT, but lower concentrations of Hexachlorobenzene (HCB) and trans-nonachlor. In addition, females had a more rapid decrease in p,p′-DDT levels over time than males. The overall OCP concentrations increased with age, and the two oldest age groups (aged 40–59 and 60+ years) had substantially lower rates of decrease than the younger age groups (aged 12–39 years). Concentrations and declines in OCPs (except for trans-nonachlor) were higher in Mexican Americans than both non-Hispanic Whites and non-Hispanic Blacks. There is a particular need for the ongoing monitoring of these banned chemicals, and measures should be taken to mitigate the exposure of vulnerable populations, including adults aged over 60, Mexican Americans, females for β-HCH, p,p′-DDE and p,p′-DDT, and males for HCB and trans-nonachlor.

Dissipation pattern and dietary risk assessment of some commonly used insecticides on tomato (Solanum lycopersicum L.)

Pesticide residue in food commodities is a serious concern in relation to the consumer safety and also the most significant barrier in the trade of food commodities. The dissipation pattern of four insecticides viz., novaluron, λ-cyhalothrin, imidacloprid, and fenazaquin was evaluated on tomato fruits and cropped soil. The residues were extracted using the QuEChERS analytical method and quantized using GC-ECD, GC-MS, and HPLC-PDA. The analytical method was validated using parameters like recovery, linearity, accuracy, matrix effect, specificity with limit of detection and limit of quantitation established to be 0.01 and 0.05 mg kg-1, respectively for all the pesticides. The average initial deposits (samples collected after two hours of spray) at recommended dose of novaluron, λ-cyhalothrin, imidacloprid and fenazaquin were 0.593, 0.293, 0.227 and 0.431 mg kg-1 on tomato fruits, respectively and were below the limit of quantification in soil. The pre-harvest interval of 17, 8, 1 and 13 days were suggested for novaluron, λ-cyhalothrin, imidacloprid and fenazaquin on tomato, respectively. The risk assessment studies revealed that all pesticides under study are safe and did not pose any threat to humans as (TMDI) theoretical maximum dietary intake is less than maximum permissible intake (MPI) and acceptable daily intake (ADI).

The BODIPY-based chemosensor for the fluorometric determination of organochlorine pesticide dicofol

Dicofol is an organochlorine pesticide, which is widely used in fruits, tea and other crops, and is moderately toxic to humans. Therefore, the monitoring of organochlorine pesticide-dicofol is critical for food safety. In this work, a fluorometric chemosensor based on mercaptoethanol and boron dipyrromethene (BODIPY) was first constructed to detect the dicofol. The chemosensor displayed turn-off fluorescence behavior upon dicofol with a detection limit of 200 ppb. The nucleophilicity of the glutathione and other biological thiols was studied to evaluate the reactivity of thiols with dicofol. In practical applications, an obvious color difference was observed on a paper based microfluidic device modified by phenyltriethoxysilane (PTES). We designed an integrated device for pretreatment and paper-based detection, and successfully used for the detection of dicofol in tea. The applicability was demonstrated by detection of dicofol in real tea samples with good recovery ranging from 86% to 109%. The apparatus was convenient and could be used for on-site evaluation of dicofol.

Occurrence, sources, and ecological risks of three classes of insecticides in sediments of the Liaohe River basin, China

The frequent and extensive use of insecticides has caused serious aquatic pollution, thus posing a great threat to ecosystems and public health. In this study, three classes of insecticides including 20 organochlorine pesticides (OCPs), 6 organophosphorus pesticides (OPs), and 8 pyrethroids were analyzed in 24 sediments from the Liaohe River basin. The results showed that all sediment samples were contaminated with insecticides, with the total concentrations ranging from 7.3 ng/g dry weight (dw) to 242.8 ng/g dw. Among them, pyrethroids (2.2-102.5 ng/g dw) contributed 55% of the total insecticide concentration, followed by OCPs (1.3-94.8 ng/g dw) and OPs (2.6-45.5 ng/g dw), representing 24% and 21% of the total concentrations, respectively. For OCPs, hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) showed the highest concentrations of 0.37-37.5 ng/g dw and 0.05-23.2 ng/g dw, respectively. Historical inputs of lindane and technical DDT were the major sources of HCHs and DDTs, respectively, as indicated by isomer or metabolite ratios. Additionally, dichlorvos (0.26-17.1 ng/g dw) was the main OP, while cypermethrin dominated the pyrethroids with the concentrations of 1.6-32.6 ng/g dw. The spatial distribution revealed that significantly higher residues of insecticides were observed in sediments from the Daliao River system than those from the Liao River. This implied that these insecticides were most likely from the discharge of highly polluted sewage and industrial wastewater from adjacent industrial and populous cities as well as urban applications (e.g., landscape maintenance and household pest control). An ecological risk assessment based on risk quotients suggested that the three classes of insecticides analyzed here pose a low risk to aquatic organisms in the study area.

Twenty-year sediment contamination trends in some tributaries of Lake Maggiore (Northern Italy): relation with anthropogenic factors

Lake tributaries collect contaminants from the watershed, which may accumulate in lake sediments over time and may be removed through the outlets. DDx, PCB, PAH, PBDE, and trace element (Hg, As, Cd, Ni, Cu, Pb) contamination was analyzed over 2001-2018 period in sediments of the 5 main tributaries and of the outlet of Lake Maggiore (Northern Italy). Sediment cores were collected in two points of the lake, covering 1995-2017 period. Concentrations were compared to Sediment Quality Guidelines (PECs), potential sources and drivers (land use, population numbers, industrial activities, hydrology) were analyzed, and temporal trends were calculated (Mann-Kendall test). PCB, PBDE, Pb, Cd, and Hg contamination derives mainly from heavy urbanization and industry. Cu and Pb show a temporal decreasing trend in the basin, likely as result of improved wastewater treatments and change in use. A recent PAH increase in the whole lake may derive from a single point source. A legacy DDx and Hg industrial pollution is still present, due to high persistence in sediments. Values of DDx, Hg, Pb, and Cu above the PECs in lake sediments and/or in the outlet show potential risk for aquatic organisms. Results highlight the key role of tributaries in driving contamination from the watershed to the lake through sediment transport.

Occurrence, spatial distribution, source, and ecological risk assessment of organochlorine pesticides in Dongting Lake, China

The occurrence, distribution, sources, and ecological risks of organochlorine pesticides in Dongting Lake of China were investigated. The average concentrations of organochlorine pesticides (OCPs) in 22 surface water samples and 14 sediment samples were 90.07 ng/L and 80.65 ng/g dw, respectively. Sixteen types of OCPs, dominated by HCHs, DDTs and heptachlor, were detected in the Dongting Lake. The relationships of OCP residues between Dongting Lake and its tributary rivers have been discussed and the hydraulic connections with the Yangtze River and the Three Gorges Dam (TGD) were also considered. Results showed that the shortage of runoff, earlier dry season, and reduction of sediment deposition extremely deteriorated the hydraulic conditions, magnified the water cycle, and restrained the self-purification of OCPs. The ∑OCPs in surface water were concentrated in the inlets of Yangtze River, Lishui River, Zishui River, Yuanshui River, and Xiangjiang River. Moreover, the ∑OCPs in the outlet of the Yangtze River also maintained a high level, indicating that OCPs posed adverse effects on the Yangtze River. Risk assessments of OCPs in the surface water of Dongting Lake were estimated according to available water quality guidelines and health risk assessment models. The results indicated that OCPs in the surface water of Dongting Lake were safe for aquatic organisms and human health. In addition, sediment quality guidelines (SQGs) were also applied to evaluate the potential ecotoxicological risks of OCPs in sediments. The results presented that contaminants of γ-HCH; o,p'-DDD; and dieldrin in sediment had adverse effects on benthic organisms, indicating that fundamental solutions should be proposed to control OCP contamination in Dongting Lake.

Effect of Organic Residues on Pesticide Behavior in Soils: A Review of Laboratory Research

The management of large volumes of organic residues generated in different livestock, urban, agricultural and industrial activities is a topic of environmental and social interest. The high organic matter content of these residues means that their application as soil organic amendments in agriculture is considered one of the more sustainable options, as it could solve the problem of the accumulation of uncontrolled wastes while improving soil quality and avoiding its irreversible degradation. However, the behavior of pesticides applied to increase crop yields could be modified in the presence of these amendments in the soil. This review article addresses how the adsorption–desorption, dissipation and leaching of pesticides in soils is affected by different organic residues usually applied as organic amendments. Based on the results reported from laboratory studies, the influence on these processes has been evaluated of multiple factors related to organic residues (e.g., origin, nature, composition, rates, and incubation time of the amended soils), pesticides (e.g., with different use, structure, characteristics, and application method), and soils with different physicochemical properties. Future perspectives on this topic are also included for highlighting the need to extend these laboratory studies to field and modelling scale to better assess and predict pesticide fate in amended soil scenarios.

A critical review of different factors governing the fate of pesticides in soil under biochar application

Pesticides are extensively used in the modern agricultural system. The inefficient and extensive use of pesticides during the last 5 to 6 decades inadvertently led to serious deterioration of environmental quality with health risk to living organisms, including humans. It is important to use some environmentally-friendly and sustainable approaches to remediate, restore and maintain soil quality. Biochar has gained considerable attention globally as a promising soil amendment because it has the ability to adsorb and as such minimize the bioavailability of pesticides in soils. This review emphasizes the recent trends and implications of biochar in pesticide-contaminated soils, as well as highlights need of the pesticides use and associated environmental issues in context of the biochar application. The overarching aim of this review is to signify the role of biochar on primary processes such as effect of biochar on the persistence, mineralization, leaching and efficacy of pesticides in soil. Notably, the effects of biochar on pesticide adsorption-desorption, degradation and bioavailability under various operating/production conditions are critically discussed. This review delineates the indirect impact of biochar on pesticides persistence in soils and proposes key recommendations for future research which are essential for the remediation and restoration of pesticides-impacted soils.

Risk assessment of organochlorine pesticides in drinking water source of the Yangtze River

Organochlorine pesticides have been banned for many years, but the residual trace amount of organochlorine in water may still pose ecotoxicological risk. Meanwhile, the potential risk of organochlorine pesticides released from sediments, especially into drinking water sources, is receiving increasing attention. The present study assessed the pollution and potential risk of drinking water sources along the midstream and downstream Yangtze River. Residues of organochlorine pesticides (OCPs) in water, suspended particle matter (SPM), and sediment were evaluated with isotope dilution HRGC/HRMS. The results indicated that OCPs in water, SPM, and sediment ranged in 0.52-92.97 ng/L, 0.10-4.10 ng/L, and 0.038-11.36 ng/g, respectively. The predominant OCPs in water, SPM, and sediment were β-HCH, p,p'-DDE and PeCB. At site Y1, 8, 13, 18, β-HCH has a higher proportion in sediment samples, while, α-HCH has a higher proportion in SPM samples. The industrial use of HCHs in the history was the main HCHs source for most water and sediment samples, which indicated an absence of fresh inputs of industrial HCHs. Meanwhile, the abundance of p,p'-DDE in water, sediment and SPM samples could be attributed to long-term aerobic degradation of DDTs. The values of ffsw of HCHs, DDTs and PeCB indicate the transfer from water to sediment. Risk assessment showed that HCHs and DDTs posed low ecotoxicological risk to the Yangtze River.

Occurrence and Human Health Risk of Dichlorodiphenyltrichloroethane (DDT) and Hexachlorocyclohexane (HCH) Pesticide Residues in Commonly Consumed Vegetables in Southwestern Nigeria

BACKGROUND

Fluted pumpkin (Telfairia occidentalis) and amaranth (Amaranthus spp.) are common leafy vegetables produced and consumed in southwestern Nigeria. These vegetables attract insect pests which are controlled by pesticides that may have adverse impacts on human health.

OBJECTIVES

To determine the levels of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) pesticide residues in the two vegetables and evaluate the potential health risks associated with their consumption.

METHODS

The pesticide residue levels were quantitatively and qualitatively determined using a gas chromatograph coupled with electron capture detector. Health risk assessment were performed using estimated average daily intake and hazard indices for two weight categories: children (16.7 kg) and adults (60 kg).

RESULTS

The results showed that delta-HCH, DDT and methoxychlor were predominantly detected in the two vegetables from both farms and markets. In amaranth, the mean concentration of methoxychlor, DDT and delta-HCH were 4.590 ± 2.774 mg/kg (dry weight (dw)), 0.757 ± 0.457 mg/kg (dw) and 0.577 ± 0.390 mg/kg (dw), respectively, while fluted pumpkin levels were 6.223 ± 2.489 mg/kg dw (methoxychlor), 0.504 ± 0.056 mg/kg dw (delta-HCH) and 0.486 ± 0.123 mg/kg dw (DDT). The levels of HCH and DDT residues were generally above the United Kingdom/European Commission maximum residue limit. The analysis of health risk estimates for non-carcinogenic risk revealed that for both vegetables, the hazard quotient for p, p' DDT and methoxychlor was >1 for both children and adults. The health risk estimates for carcinogenic risk revealed that hazard indices values were >1 for children for both vegetables and alpha-HCH had a hazard index >1 for adults for amaranth. This means the residue exceeds acceptable standard and present potential risk to consumers of these vegetables.

CONCLUSIONS

The results obtained from the present study indicate that consumption of amaranth contaminated with alpha-HCH could pose a carcinogenic risk for adult consumers. The consumption of the two vegetables could pose both non-carcinogenic and carcinogenic health risks to children and adults. Therefore, there is need for strict enforcement of regulations on pesticide usage to minimize human health risks.

COMPETING INTERESTS

The authors declare no competing financial interests.

Spatial distribution, source identification, and potential risk assessment of toxic contaminants in surface waters from Yulin, China

The Yulin Energy and Chemical Industry Base is widely known for its rich mineral resources and multiple types of fossil-fuel-based chemical industries; nevertheless, information regarding the level of toxic contaminants in the surface waters is lacking in this area. Therefore, this study investigates the distributions, sources, and risks of various toxic contaminants, including heavy metals, organochlorine pesticides (OCPs), and polycyclic aromatic hydrocarbons (PAHs), from 35 sampling sites in eight rivers. The ΣHCH concentration ranged from 1.28 to 6.64 ng/L with predominant β-HCH, and the ΣDDT concentration was less than 0.35 ng/L. The OCPs were derived from the recent input of lindane, residual technical-grade HCHs, and DDTs. The soil type can affect the environmental fate of DDT, and p,p'-DDE was widespread in the sandy land and loess areas. p,p'-DDD was rarely detected in the Mu Us Sandy Land area. The calculated ratios of isomers indicated that petroleum was the major source of PAHs. OCP and PAH contamination in the surface waters posed potential risks at several sampling sites. Due to the impacts by industrial emissions, agricultural sources, and vehicular traffic, the distribution of contaminant concentrations in the surface waters exhibited a significant spatial relationship with the land use pattern in the study region according to the results of principal component analysis and cluster analysis.

Determination of Occurrences, Distribution, Health Impacts of Organochlorine Pesticides in Soils of Central China

Organochlorine pesticides are groups of chemicals applied to prevent pest and insect infestation. This study was aimed at investigating the concentration, potential sources, cancer risk and ecological toxicity of organochlorine pesticides (OCPs) in Huangpi district, Wuhan, China. Eight OCPs in soil samples collected from four land-use types at depths of 0–10 and 10–20 cm were examined. Sample extraction was carried out by solid phase matrix extraction method and analyzed using Agilent gas chromatograph 7890B equipped with electron capture detectors (ECD). The total concentration of OCPs ranged from 0.00–32.7 ng g⁻¹ in the surface and 0.01–100.45 ng g⁻¹ in the subsurface soil layer. Beta hexachlorocyclohexanes (β-HCH) with 2.20 and 7.71 ng g⁻¹ in the surface and subsurface soil layers, respectively, was the dominant compound. The mean concentrations of OCPs in all samples were less than the threshold values for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in China soil. Concentration of OCPs in the four land-use types were in the order of: paddy field > barren land > farmland > plastic greenhouse. Results of composition analysis revealed recent application of lindane as a major and historical use of new technical HCHs as a minor source of HCHs. On the other hand, application of new technical p,p’-DDT is the main source of DDTs in the study area. The estimated lifetime average daily dose, incremental lifetime cancer risks and hazard quotient values revealed that there is less likelihood of carcinogenic and noncarcinogenic health risks on the local residents.

Occurrence, distribution and risk assessment of pesticides in a river-reservoir system

The water environment from river to reservoir has been considered as a hybrid river-reservoir system due to pronounced environmental properties. This study investigated the distribution and potential environmental behavior of pesticides in river-reservoir system, examining 31 target pesticides in water phase from a key drinking water source (Dongjiang River). The concentrations of ∑₈OCPs, ∑₁₆OPPs and ∑₇SPs with the corresponding occurrence were in the range of 107.57-340.35 ng/L (moderate level), 232.65-1197.95 ng/L (moderate level) and 125.23-245.09 ng/L (low level), respectively. Ecological risk assessments indicated that most of the pesticides posed a high level of risk to the aquatic organisms. Moreover, seasonal agricultural application, rainfall and temperature could influence the levels and compositions of ∑₈OCPs, ∑₁₆OPPs and ∑₇SPs in the river system, while seasonal hydrological processes could only influence their compositions in the reservoir system. In the wet season, the levels of ∑₈OCPs and ∑₇SPs decreased from the river system to reservoir system probably via biogeochemical processes, while the level of ∑₁₆OPPs decreased along the environmental gradient probably via dilution process. Additionally, longer hydraulic retention time of the reservoir system could contribute to the biogeochemical processes for OPPs and SPs exported from the river system, but it might fail to facilitate this process for OCPs. Taken together, this study highlighted that the distributions and environmental behavior of pesticides in river-reservoir system varied seasonally from river system to reservoir system.

Occurrence, distribution and ecological risk of ultraviolet absorbents in water and sediment from Lake Chaohu and its inflowing rivers, China

The available information is insufficient to enable a reliable understanding of the global distribution and effect of organic ultraviolet absorbents (UVAs) on ecosystems. Little is known about the pollution of China's lakes by these chemicals. We conducted a survey of UVAs in water and sediment from Lake Chaohu and its inflowing rivers. The UVAs were widely present in this area and the concentrations of total 12 UVAs (Σ₁₂ UVAs) ranged between 162 and 587 ng/L in water and 9.70-178 ng/g in sediment. Benzophenone and benzophenone-3 were dominant in water, and benzophenone and octocrylene dominated in sediment. Higher concentrations of benzophenone were detected in the investigated water samples, although the contamination levels of UVAs in this study were comparable to those investigated in other areas. In addition to the inputs from the UVAs used as filters in cosmetics, the discharge from industries using UVAs as stabilizers also contributed much to the pollution in the study waters. Generally, the risk to aquatic organisms from exposure to UVAs in this area was low, but further research is needed to elucidate the fate of UVAs and to understand bioaccumulation and associated risks.

Spatial distributions, source apportionment and ecological risk of SVOCs in water and sediment from Xijiang River, Pearl River Delta

Xijiang River is an important drinking water source in Guangxi Province, China. Along the Xijiang River and surrounding tributary, the pollution profile of three important groups of semi-volatile organic compounds, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and phthalate esters (PAEs), was analyzed. Relatively low levels of PAHs (64-3.7 × 10² ng L^-1) and OCPs (16-70 ng L^-1), but high levels of PAEs (7.9 × 10²-6.8 × 10³ ng L^-1) occurred in the water. Comparatively, low levels of OCPs (39-1.8 × 10² ng g^-1) and PAEs (21-81 ng g^-1), but high levels of PAHs (41-1.1 × 10³ ng g^-1) were found in sediment. Principal component analyses for source identification indicated petroleum-derived residues or coal and biomass combustion, and vehicular emission was the main sources for PAHs. The OCPs sources of each category were almost independent, whereas the new input of HCHs and p,p'-DDTs probably existed in some areas. PAEs were mainly originated from personal care products of urban sewage, plastic and other industrial sources. Ecological risk through the risk quotient analysis indicated a small or significant potential adverse effect on fish, daphnia and green algae. Nevertheless, the integrated risk of all pollutants should be taken into account in future study.

Polycyclic aromatic hydrocarbons and organochlorine pesticides in surface water from the Yongding River basin, China: Seasonal distribution, source apportionment, and potential risk assessment

The presence of 17 polycyclic aromatic hydrocarbons (PAHs) and 15 persistent organochlorine pesticides (OCPs) in surface water of the Yongding River Basin was analyzed through GC/MS/MS during the spring and summer at 46 sampling sites. The goal was to investigate their seasonal distribution, possible sources, and potential risk. Our results showed that the total PAH concentration in surface water of Yongding River Basin ranged from 41.60 to 1482.60ng/L with a mean value of 137.85ng/L in the spring, and from 53.53 to 506.53ng/L with a mean value of 124.43ng/L in the summer. The total OCP concentration ranged from <0.08 to 197.71ng/L with a mean value of 7.69ng/L in the spring, and from <0.08 to 93.58ng/L with a mean value of 7.92ng/L in the summer. Moreover, the total PAH concentration was slightly lower in the spring than in the summer, whereas the total OCP concentration was similar between seasons. Source analysis indicated that combustion sources and petroleum sources both contributed to the presence of PAHs. Historical environmental residues and long range atmospheric transport were the major sources of HCH and DDT contamination. The concentrations of total PAHs and single PAHs including benz(a)anthracene, benzo(a)pyrene, benz(b)fluoranthene, and benz(k)fluoranthene in surface water at some sampling sites exceeded the water environmental quality standards of China and several other countries or organizations. This indicated a potential threat to human health from the consumption of aquatic organisms due to PAH bioaccumulation. The concentrations of α-HCH, p,p'-DDE, and p,p'-DDD at several sampling sites exceeded the limit for human health specified in the ambient water quality criteria developed by the US Environmental Protection Agency, which indicated that these pollutants provide potential hazards to the residents around the sampling sites.

Occurrence, enantiomeric signature and ecotoxicological risk assessment of HCH isomers and DDT metabolites in the sediments of Kabul River, Pakistan

Hexachlorocyclohexane (HCH) isomers and dichlorodiphenyltrichloroethane (DDT) metabolites were analyzed in sediments of three different depths (0-10, 10-20 and 20-30 cm) collected from Kabul River, Pakistan, in February 2014. The occurrence levels, enantiomer fractions and potential ecological risk of these organochlorine pesticides (OCPs) were evaluated. The total concentrations of ∑HCHs and ∑DDTs in surface sediments ranged from 4.9-23.9 ng g^-1 and from 6.4-18.8 ng g^-1 (dry weight basis), respectively. The vertical contamination profile of DDTs was found in order of 20-30 cm >10-20 cm >0-10 cm, indicated that the residue levels of DDTs gradually decreased after it was banned. The ratios of β-HCH/HCHs ranged from 0.04 to 0.73 (69 % of samples below 0.5) suggesting the fresh input of HCHs, while isomeric ratios of α-HCH/γ-HCH (ranged from 0.02 to 7.94), with 76 % of samples less than 3, indicating the cocktail use of technical grade HCH and lindane in the study area. The ratio of (DDE + DDD)/DDTs (ranged from 0.42 to 0.90) indicated long-term biodegradation of parent DDT. The enantiomer of α-HCH was generally racemic or close to racemic for most of the samples, with enantiomeric fraction (EF) value <0.5 for some of the samples indicated the preferential biodegradation of (+)-α-HCH enantiomer, while for o,p'-DDT the EF values >0.5 indicated the depletion of (-)-o,p'-DDT enantiomer in most of the samples. According to sediment quality guidelines (SQGs), HCH contamination is the main concern for ecotoxicological risk in Kabul River.

Levels and Sources of Organochlorine Pesticides in Surface Sediment from Anhui Reach of Huaihe River, China

Twenty-two organochlorine pesticides (OCPs) were investigated in Anhui reach of Huaihe river, China. Seventeen out of 22 OCPs were detected by GC-MS. The mean concentrations of OCPs followed the order: HCHs > DDTs > HCB > chlordanes > endosulfans. Levels of total HCHs and total DDTs ranged from 2.54 to 13.91 ng g^-1 (mean = 7.52 ng g^-1) and 0.016 to 2.54 ng g^-1 (mean = 0.45 ng g^-1), respectively. The concentrations of DDTs were lower than those of HCHs. Compared with the other rivers in China, DDTs and HCHs were relatively lower or similar. Statistical analysis indicated that the OCPs concentration differences were not insignificant between upstream, midstream and downstream. The compound compositions suggested that historical usage of lindane and fresh DDT were the main sources. The regression analysis indicated that TOC has influence on the levels of HCHs and little influence on the levels of DDTs in the sediments.

Recent strategies for removal and degradation of persistent & toxic organochlorine pesticides using nanoparticles: A review

Organochlorines (OCs) are the most hazardous class of pesticides, therefore, banned or restricted in several countries. The major sources of OCs include food industries, agriculture and sewage wastes. Their effluents discharged into the water bodies contain extremely high concentration of OCs which ultimately causes environmental concern. Because of their high persistence, toxicity and potential to bioaccumulation, their removal from wastewater is imperative. The degradation techniques are now advanced using nanomaterials of various kinds. During the last few years, nanoparticles such as TiO₂ and Fe are found to be excellent adsorbents and efficient photocatalysts for degrading more or less whole OCs as well as their toxic metabolites, which opens the opportunities for exploring various other nanoparticles as well. It is noteworthy that such methodologies are economic, fast and very efficient. In this review, the detailed information on different types of OC pesticides, their metabolites, environmental concern and present status on degradation methods using nanoparticles have been reviewed. An attempt has also been made to highlight the research gaps prevailing in the current research area.

Polybrominated diphenyl ethers, organochlorine pesticides, and polycyclic aromatic hydrocarbons in water from the Jiulong River Estuary, China: levels, distributions, influencing factors, and risk assessment

Estuarine systems play an important role in the transportation and transformation of organic pollutants from rivers. Polybrominated diphenyl ether (PBDE), organochlorine pesticide (OCP), and polycyclic aromatic hydrocarbon (PAH) concentrations in water of the Jiulong River Estuary (JRE), China, were investigated to characterize their distribution, possible source, and potential ecological risk as well as the influencing factors. The total concentrations of PBDEs, OCPs, and PAHs varied from 5.2 to 12.3 pg L^-1, from 29.1 to 96.4 ng L^-1, and from 28.6 to 48.5 ng L^-1, respectively. Their compositions were all consistent at different stations; even the input pathways were multifarious. A source analysis showed that PBDEs may come from the flame retardant usages of penta-BDE and deca-BDE; hexachlorocyclohexane isomers (HCHs) were from the use of technical HCHs, while DDTs were attributed to early residuals of industrial sources, and PAHs were mainly from pyrolytic sources. The spatial distributions of PBDEs and OCPs were quite similar with their concentrations, decreasing along the estuary and then increasing when passing the Xiamen Harbor. PAH concentrations were similar along the whole estuary, suggesting that local sources and hydrological conditions might be the influencing factors. The concentrations of these pollutants changed with tidal conditions and were positively correlated with SPM, DOC, and chlorophyll a but negatively correlated with salinity. The ecological risk assessment revealed that OCPs and PAHs posed slightly higher potential risks to aquatic organism in the study area.

Organochlorine pesticides and polychlorinated biphenyls in surface water around Beijing

Contaminant concentrations, sources, seasonal variation, and eco-toxicological risk of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in surface water around Beijing from summer to winter in 2015 and 2016 were investigated. The concentrations of ∑OCPs and ∑PCBs ranged from 9.81 to 32.1 ng L^-1 (average 15.1 ± 7.78 ng L^-1) and from 7.41 to 54.5 ng L^-1 (average 21.3 ± 1.87 ng L^-1), respectively. Hexachlorocyclohexane (HCHs) were the dominated contamination both in aqueous and particulate phase. For PCBs, lower chlorinated PCBs were the major contaminants. Compositions of HCHs, dichlorodiphenyltrichloroethane (DDTs), and PCBs indicated that the sources of OCPs and PCBs in water were due to historical usage in the study areas. For OCPs, there was an obvious variation among three seasons, while insignificant change was shown for PCBs. Water quality standards for China's surface water were not exceeded in this study. Concentrations at Miyun Reservoir, the primary source of drinking water to Beijing, when compared to the USEPA's criterion for cancer risk was below the level of risk.

Combination effects of pyrethroids and neonicotinoids on development and survival of Chironomus riparius

Standard ecotoxicological risk assessments are conducted on individual substances, however monitoring of streams in agricultural areas has shown that pesticides are rarely present alone. In fact, brief but intense pulse events such as storm water runoff and spray drift during application subject freshwater environments to complex mixtures of pesticides at high concentrations. This study investigates the potential risks to non-target aquatic organisms exposed to a brief but intense mixture of the neonicotinoid pesticides imidacloprid and thiacloprid and the pyrethroid pesticides deltamethrin and esfenvalerate, compared to single substance exposure. All four of these pesticides have been detected in surface waters at concentrations higher than benchmark values and both classes of pesticides are known to exert adverse effects on non-target aquatic organisms under single substance exposure scenarios. First instar midge larvae of the non-target aquatic organism, Chironomus riparius, were exposed to combinations of these four pesticides at 50% of their LC50 (96 h) values in a 1h pulse. They were then reared to adulthood in uncontaminated conditions and assessed for survival, development time and fecundity. Our results show that the risk of disruption to survival and development of non-target aquatic organisms under this scenario is not negligible on account of the significant increases in mortality of C. riparius found in the majority of the pesticide exposures and the delays in development after pyrethroid exposure. While none of the deleterious effects appear to be amplified by combination of the pesticides, there is some evidence for antagonism. No effects on fecundity by any of the pesticide treatments were observed.

The potential effects of phytoplankton on the occurrence of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in water from Lake Taihu, China

Seasonal distribution of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) and their possible interactions with phytoplankton species in water from Lake Taihu were investigated. OCP concentrations ranged from 69.95 to 223.08 ng L(-1) in winter and from 80.95 to 376.03 ng L(-1) in summer, while PAHs ranged from 45.40 to 232.74 ng L(-1) in winter and 49.53 to 197.72 ng L(-1) in summer. Such physicochemical and biological parameters as the larger amounts of pollutants taken up by phytoplankton, the increased atmospheric wet deposition, the discharge of wastewater, and the resuspension of polluted sediments in summer time were responsible for the higher residues of both OCPs and PAHs than in winter. Canonical correspondence analysis (CCA) between phytoplankton biomass and micropollutants indicated high affinity of OCPs to Bacillariophyta and Cryptophyta and PAHs to Cyanophyta and Chlorophyta, documenting the ecological effects of phytoplankton on the biogeochemical processes of OCPs and PAHs and thus should be further investigated especially in hyper-eutrophic lakes.

Air-Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River

Gaseous exchange fluxes of organochlorine pesticides (OCPs) across the air-water interface of the coastal East China Sea were determined in order to assess whether the contaminated plume of the Yangtze River could be an important regional source of OCPs to the atmosphere. Hexachlorocyclohexanes (HCHs), chlordane compounds (CHLs), and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected OCPs in air and water. Air-water exchange was mainly characterized by net volatilization for all measured OCPs. The net gaseous exchange flux ranged 10-240 ng/(m2·day) for γ-HCH, 60-370 ng/(m2·day) for trans-CHL, 97-410 ng/(m2·day) for cis-CHL, and ∼0 (e.g., equilibrium) to 490 ng/(m2·day) for p,p'-DDE. We found that the plume of the large contaminated river can serve as a significant regional secondary atmospheric source of legacy contaminants released in the catchment. In particular, the sediment plume represented the relevant source of DDT compounds (especially p,p'-DDE) sustaining net degassing when clean air masses from the open ocean reached the plume area. In contrast, a mass balance showed that, for HCHs, contaminated river discharge (water and sediment) plumes were capable of sustaining volatilization throughout the year. These results demonstrate the inconsistencies in the fate of HCHs and DDTs in this large estuarine system with declining primary sources.

Concentrations and distributions of 18 organochlorine pesticides listed in the Stockholm Convention in surface sediments from the Liaohe River basin, China

Organochlorine pesticides (OCPs) were analyzed in 26 surface sediment samples from the Liaohe River basin, and the distributions of and potential environmental risks posed by OCPs in the basin were evaluated. Eighteen OCPs listed in the Stockholm Convention were determined using isotope-dilution gas chromatography-high resolution mass spectrometry. This is the first study of hexachlorobenzene (HCB) in the Liaohe River basin sediments. The total OCP concentrations were 0.39-68.06 ng g(-1) dry weight. The total α-, β-, γ-, and δ-hexachlorocyclohexane (HCH), the total dichlorodiphenyltrichloroethane (DDT - p,p'-dichlorodiphenyldichloroethane (DDD), p,p'-dichlorodiphenyldichloroethylene (DDE), o,p(')-DDT, and p,p'-DDT), and the HCB concentrations in the sediment samples were 0.1-28.48 ng g(-1) (mean 4.01 ng g(-1)), 0.08-6.52 ng g(-1) (mean 3.07 ng g(-1)), and 0.18-24.8 ng g(-1) (mean 4.38 ng g(-1)), respectively. The HCB concentrations were higher than the concentrations of the other OCPs, and the HCHs and HCB together were the dominant OCPs. β-HCH was the most abundant HCH isomer. The concentrations of DDTs and other OCPs were relatively low, and the (DDE+DDD)/DDT ratios (>0.5) and DDD/DDE ratios (<1) indicated that no recent DDT inputs had occurred in the Liaohe River system. The main sources of HCHs were probably the historical production and agricultural use of HCH in the study area. The DDT and HCH concentrations were generally below or similar to the concentrations that have been found in other parts of the world. An ecotoxicological evaluation indicated that HCHs in surface sediments pose slight risks to human and ecological health in the Liaohe River basin.

Residues and potential health risks of DDTs and HCHs in commercial seafoods from two coastal cities near Yangtze River Estuary

Five species of commercial seafoods collected from the local markets in two coastal cities near Yangtze River Estuary (Ningbo and Zhoushan) in 2010 were analyzed to study the residues, potential sources, and health risks of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) in these areas. The total levels of DDTs and HCHs in the samples ranged from 1.13-20.2 ng g(-1) and 1.23-3.05 ng g(-1) wet weight, respectively, and were at a middle level compared with those from other marine systems. Results from one-way analysis of variance (ANOVA) indicated species-specific distributions of DDTs and HCHs in the seafoods of the studied area, which may be related to their different lipid contents and ecological characteristics. Compositional analysis suggested that historical usage dominates in this area, and fresh inputs of lindane and dicofol may also have part contributions. With respect to DDTs, it can be metabolized into both DDD and DDE simultaneously in seafoods tested. Assessment based on maximum residue levels, acceptable or tolerable daily intakes, and hazard ratios for non-carcinogens suggested no obvious adverse health effects, while the lifetime cancer risks may be increased from dietary exposure to DDTs and HCHs.

Spatial and seasonal distribution of organochlorine pesticides in the sediments of the Yangtze Estuary

The spatial and seasonal distribution of organochlorine pesticides (OCPs) in the sediments of the Yangtze Estuary was investigated. The total concentration of 19 OCPs (∑OCPs), including α-HCH, β-HCH, γ-HCH, δ-HCH, o, p'-DDE, p, p'-DDE, o, p'-DDD, p, p'-DDD, o, p'-DDT, p, p'-DDT, heptachlor, aldrin, heptachlor epoxide (Isomer B, Isomer A), endosulfan I, dieldrin, endrin, endosulfan II and methoxychlor, in the surface sediments ranged from 0.4 to 82.1 ng g(-1) d.w. The mean values of the ∑OCPs were 8.5 ± 8.3 ng g(-1) d.w., 26.7 ± 12.1 ng g(-1) d.w., 40.5 ± 18.2 ng g(-1) d.w., and 13.0 ± 11.2 ng g(-1) d.w. for August 2010, November 2010, February 2011 and May 2011, respectively. The highest concentration of OCPs was detected at the river-sea boundary because of the intense resuspension and redeposition of sediments in this area. The OCPs preferred to accumulate in the inner estuary, rather than in the offshore area in the dry season, whereas the opposite occurred in the flood season. This phenomenon was related to the seasonal changes of the Changjiang diluted water (CDW). OCPs in the offshore area were controlled by the ocean currents and the monsoon. There was a southward increase for the OCP deposition in the offshore area in the winter. This increase resulted from the influences of the southward Yellow Sea coastal current and the East China Sea coastal current, as well as the northwest wind in winter. The Three Gorges Dam had an impact on HCH composition by changing the sediment redistribution during the deposition process.

Distribution and accumulation of hexachlorobutadiene in soils and terrestrial organisms from an agricultural area, East China

Hexachlorobutadiene (HCBD) is a potential persistent organic pollutant that has been found in abiotic environments and organisms. However, information on HCBD in soils and its accumulation in terrestrial food chains is scarce. This study investigated the accumulation of HCBD in soils, plants, and terrestrial fauna in a typical agricultural area in Eastern China, and drew comparisons with organochlorine pesticides (OCPs). The HCBD concentrations in soils were <0.02-3.1ng/g dry weight, which were similar to α-endosulfan concentrations but much lower than the concentrations of some other OCPs. The HCBD soil-plant accumulation factors, 8.5-38.1, were similar to those of o,p'-DDT and higher than those of HCHs and p,p'-DDT, indicating that HCBD is strongly bioaccumulated by rice and vegetables. HCBD concentrations of 1.3-8.2ng/g lipid weight were found in herbivorous insects, earthworms, and Chinese toads. The biomagnification factor, the ratio between the lipid-normalized concentrations in the predator and the prey, was found to be 0.16-0.64 for different food chains of Chinese toads, so HCBD was found not to biomagnify, which is in contrast with OCPs. Further research into whether HCBD is biomagnified in high trophic level organisms or through the entire terrestrial food web is required.

Distribution and ecological risk assessment of organochlorine pesticides in surface sediments from the East Lake, China

Organochlorine pesticides (OCPs) are ubiquitous pollutants, and their presence in urban lakes is a concern for human and ecological health. Surface sediments in the East Lake, China, were collected in winter 2012 and summer 2013 to investigate concentrations, distribution patterns, possible sources, and potential ecological risks of OCPs in this area. The total concentrations of 14 OCPs ranged from 6.3 to 400 ng g(-1) dry weight (dw) with an average concentration of 79 ng g(-1) dw. The mean values of hexachlorocyclohexanes (HCHs) (α-, β-, γ-, and δ-HCH) and dichlorodiphenyltrichloroethanes (DDTs) (p,p'-DDE, p,p'-DDD, and p,p'-DDT) were 36 and 7.6 ng g(-1) dw, accounting for 45 and 10 % of the total OCPs, respectively. The concentrations of OCPs in sediment samples collected in winter were significantly higher than those in summer, especially the HCHs, of which in winter were two times greater than summer. Composition analyses indicated that DDTs and endosulfan were mainly from historical contribution. Historical use of technical HCH and new input of lindane were probably the source of HCHs in the East Lake. Most sampling sites of HCHs and DDTs were found to have the potential ecological risk based on levels specified in the sediment quality standards.

Distribution, sources and potential risk of HCH and DDT in soils from a typical alluvial plain of the Yangtze River Delta region, China

Spatial distribution, sources and potential health risks of organochlorine pesticides (OCPs), including hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), in surface soils (n = 544) collected from a typical alluvial plain of the Yangtze River Delta region, China, were elucidated. Concentrations of ΣHCH and ΣDDT in soils ranged from less than the limit of detection (<LOD) to 99.0 ng g(-1), dry weight (dw) (mean 3.23 ng g(-1) dw) and <LOD to 600 ng g(-1) dw (mean 88.8 ng g(-1) dw), respectively. Historical applications of HCH and DDT were the major sources of the residue in soils. HCH was mainly distributed in Anthrosols in the southern part of the watershed, while DDT was mainly distributed in Cambosols in the northern part. The 95 % cumulative probability incremental lifetime cancer risks (ILCRs) of different age groups such as children, youths, and adults all exceeded the acceptable risk level of 10(-6) recommended by USEPA for carcinogenic chemicals. The spatial distributions of ∑ILCRs were consistent with concentrations of OCPs in soils, while they were slight different for the different age groups. Adult females had the greatest risk of OCPs in soils, followed by children, while youths had the least risk. The ingestion of OCPs in soils was the more important route of exposure compared with dermal and inhalation exposures. The concentration of OCPs in soils, the particulate emission factor, the fraction of dermal exposure ratio, and the soil ingestion rate were the major contributing variables to total ILCRs according to sensitivity analyses.

Occurrence, possible sources, and temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans in water and sediment from the lower Yangtze River basin, Jiangsu and Shanghai areas of Eastern China

The concentrations, compositional profiles, and possible sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in water column and surface sediment samples from the lower reaches of the Yangtze River were investigated, and the potential risks posed by these chemicals were evaluated. Concentrations of the 17 2,3,7,8-substituted PCDD/PCDF in the water and sediment samples ranged from 0.45 to 10.0 pg TEQ/L (mean 2.34 pg TEQ/L) and from 0.31 to 51 pg TEQ/g dw (mean 5.25 pg TEQ/g dw), respectively. Water and sediments from the Nanjing-Nantong sections of the Yangtze River were found to have elevated PCDD/PCDF levels, and the PCDD/PCDF TEQ concentrations in 13 sediment samples exceeded the probable effect levels (PEL), above which adverse biological effects are likely. Multivariate statistical analysis indicated that the principal PCDD/PCDF contamination source for the water and sediment was the production and use of pentachlorophenol (PCP) or sodium pentachlorophenate (PCP-Na). PCDD/PCDF concentrations were stable over time near the Yangtze River Estuary but had increased sharply in recent decades in the Nanjing-Nantong section, which will have been related to the growth in industrial activities and other anthropogenic PCDD/PCDF sources. Total organic carbon (TOC) and PCDD/PCDF concentrations correlated significantly (R=0.474, P<0.01), suggesting that TOC plays an important role in the transport and re-distribution of PCDD/PCDF in the Yangtze River basin.

Distribution and sources of organochlorine pesticides in agricultural soils from central China

There is little information on the organochlorine pesticides (OCPs) residues in agricultural soils of Wuhan, the largest city in central China. Surface soil samples were collected from agricultural soils in Wuhan and analyzed to determine twenty-one OCPs. According to the measured concentrations and detection frequencies, dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), heptachlor (HEPT), hexachlorobenzene (HCB) and aldrin were the predominant compounds in soil. DDTs accounted for 77.10% of total OCPs, followed by HCHs (7.83%), aldrin (4.21%), HEPTs (2.82%) and HCB (1.53%). The total DDT concentrations ranged from nd to 1198.0ngg(-1) and the main contaminated areas were distributed in Hannan and Xinzhou districts of Wuhan. The total HCH concentrations ranged from nd to 100.58ngg(-1) in soil and relatively higher levels were observed in soil samples from Huangpi and Hannan districts. Source analysis showed that OCPs residues except heptachlor originated mainly from historical application, besides slight recent introduction at some sites. Based on the China National Soil Quality Standard, DDT pollution in most samples of Wuhan agricultural soils could be considered as no and low contamination, while the level of HCHs was classified as no pollution. Our study indicated that there existed potential exposure risk of OCPs in Wuhan agricultural soils although the use of OCPs has been banned.

Organochlorine Pesticide Residues in Sediments and Waters from Cocoa Producing Areas of Ondo State, Southwestern Nigeria

This study investigated levels of organochlorine pesticide (OCP) residues in water and sediment samples from eleven rivers serving as drinking water sources and receiving runoff from nearby cocoa plantations in Ondo State, Nigeria. Twenty-two composite samples of surface water and sediments (0–3 cm) were collected randomly using grab technique and replicated thrice per season. The efficiency of the two techniques [supercritical fluid extraction (SFE) and liquid/liquid extraction (LLE)] was evaluated with percentage analyte recoveries to for SFE and to 1 for LLE. Determination of OCPs by gas chromatography with electron capture detection gave higher concentrations for sediments compared to the equivalent water samples. The commonly occurring pesticide residues in the sediments were (range, μg g−1) cis-chlordane 0.03–6.99; α-endosulfan 0.03–6.99; p,p′-DDE 0.08–19.04; and dieldrin 0.01–7.62; in the sediments and dieldrin (not detected-1.51 μg L−1) in water samples, during the dry season. OCP levels were significantly higher in dry season than wet season among the rivers. The study concluded that most of the rivers in cocoa growing areas were contaminated with OCPs associated with agricultural activities.