Endosulfan in China 2-emissions and residues

Atmospheric Hydroxyl Radical Reaction Rate Coefficient and Total Environmental Lifetime of α-Endosulfan

Endosulfan is a persistent organochlorine pesticide that was globally distributed before it was banned and continues to cycle in the Earth system. The chemical kinetics of the gas-phase reaction of α-endosulfan with the hydroxyl radical (OH) was studied by means of pulsed vacuum UV flash photolysis and time-resolved resonance fluorescence (FP-RF) as a function of temperature in the range of 348-395 K and led to a second-order rate coefficient kOH = 5.8 × 10-11 exp(-1960K/T) cm3 s-1 with an uncertainty range of 7 × 10-12 exp(-1210K/T) to 4 × 10-10 exp(-2710K/T) cm3 s-1. This corresponds to an estimated photochemical atmospheric half-life in the range of 3-12 months, which is much longer than previously assumed (days to weeks). Comparing the atmospheric concentrations observed after the global ban of endosulfan with environmental multimedia model predictions, we find that photochemical degradation in the atmosphere is slower than the model-estimated biodegradation in soil or water and that the latter limits the total environmental lifetime of endosulfan. We conclude that the lifetimes typically assumed for soil and aquatic systems are likely underestimated and should be revisited, in particular, for temperate and warm climates.

Signatures of Indian endosulfan usage in China's environment

Endosulfan, as an organochlorine pesticide (OCPs), was widely used in agriculture. As the largest endosulfan user country in the world and adjacent to China, it is interesting to know to what extent the endosulfan usage of India could affect the environment in China. In this study, we established gridded endosulfan usage, atmospheric emission, and soil residue inventories in 2010 based on its application in different crops in China and India. We employed an atmospheric transport model CanMETOP to simulate atmospheric and soil concentrations, as well as dry and wet deposition flux of α- and β-endosulfan. Results were used to assess the signatures of Indian endosulfan usage in the China's environment. In 2010, endosulfan usage, atmospheric emissions, and highest soil residue in China were 3083.9, 1312.7, and 587.5 tonnes, and 3204.8, 1441.4, and 463.7 tonnes in India, respectively. The spatial distribution of modeled atmospheric and soil concentrations, and dry deposition fluxes of endosulfan were in line with its usage but wet deposition fluxes were mainly identified in Southern China and Sichuan basin with heavy rainfall, especially for α-endosulfan. Endosulfan tended to transport from India to Tibetan plateau, Yunnan-Kweichow Plateau, and some provinces in southern China under the Indian Summer Monsoon regime. Due to its stronger volatility, α-endosulfan posed a more significant impact on China's environment via the atmospheric transport from India compared to β-endosulfan. Although rainfall during Indian Summer Monsoon reduced endosulfan levels in the air during its journey from India to China, it was observed that Indian endosulfan usage in 2010 contributed more than 50% of atmospheric concentrations and 30% of soil concentrations of α-endosulfan in some regions in Tibetan plateau.

Concentrations, distribution, and risk assessment of endosulfan residues in the cotton fields of northern Xinjiang, China

In the current study, surface soil samples were collected from cotton fields in Shawan and Shihezi areas in northern Xinjiang and tested for endosulfan residues using gas chromatography-mass spectrometry. Results showed endosulfan sulfate was the predominant compound in the surface soil studied, followed by β-endosulfan and α-endosulfan with detection rates of 86.9%, 55.7%, and 49.2%, respectively, for the 61 soil samples collected. The average concentrations of endosulfan sulfate, α-endosulfan, and β-endosulfan were 0.743, 0.166, and 0.073 µg/kg, respectively. The ratios of α-/β-endosulfan were below 2.33 in all samples tested, suggesting no new endosulfan was added to the soil and the presence of endosulfan residues in this region was due to historical application in the past. According to the health risk assessment model recommended by the USA Environmental Protection Agency, the health risk of endosulfan residues in the studied area was low, and the maximum values of noncarcinogenic risks for children and adults were 2.30 × 10^-5 and 2.70 × 10^-6, respectively. Folsomia candida was the most sensitive organism to total endosulfan residues, with 38% of the total sampling sites classified as high risk. For earthworms, the proportion of high risk site was 13%. Lactuca sativa was the most tolerant organism to ∑ESs, with all sampling sites identified as negligible risk. This study provided current status of endosulfan residues and related risk in cotton fields, which could be used to support decision makers to prepare relevant regulations.

A nationwide survey on the endosulfan residues in Chinese cotton field soil: Occurrence, trend, and ecological risk

The nationwide occurrence of endosulfan residues in cotton fields has not yet been investigated. Therefore, in this study, 202 surface soil samples from 27 cities were collected from cotton fields in 8 major cotton-planting provinces of China, covering more than 97% of the national cotton sown area. The results showed that endosulfan residues were detected in cotton fields throughout the country. The main type of residue found was endosulfan sulfate (ES-sulfate), followed by β-endosulfan and α-endosulfan, with average concentrations of 0.475, 0.129, and 0.048 μg/kg, respectively. Significant spatial variations in the endosulfan residues was noted, and the highest concentration of endosulfan residues was observed in the northwest inland cotton-growing area, followed by that in the Yellow River basin and Yangtze River basin cotton-growing areas. The endosulfan residues showed significant positive correlations with soil organic matter and soil clay contents. The α/β endosulfan ratio was determined to be in the range of 0.02-1.20, indicating that endosulfan residues originated from the endosulfan application performed in historical cotton cultivation efforts. Together with the literature data, the concentrations of α-endosulfan and β-endosulfan residues peaked in 2015 and 2017, respectively, and showed an overall decreasing trend from 2002 to 2021. The results of the ecological risk assessment suggested that Folsomia candida was most sensitive to endosulfan residues, with 20.8% of the sites presenting a high risk. However, in general, the soil ecological risk of cotton fields across the country was low. Our study demonstrated that China has achieved promising results in controlling the use and pollution of endosulfan, especially after 2014.

Status of arsenic accumulation in agricultural soils across China (1985-2016)

Based on 1677 published studies, 1648 sites across China collected from 1985 to 2016 were used to research the concentrations of arsenic in agricultural soils. In order to understand the status of arsenic pollution in agricultural soils in China over the past three decades, and to learn about the arsenic stocks in agricultural soils in various regions, and compared the relationship with annual arsenic emissions in China, and finally evaluated the potential ecological risks and human health risks. The median arsenic concentration in the surface agricultural soils of China was 10.40 mg Kg^-1, and it ranged from 0.4 mg Kg^-1 to 175.8 mg Kg^-1. The inventory of arsenic in Chinese agricultural surface soils was estimated to be 3.71 × 10⁶ t. In this study, the arsenic concentrations were found to be higher in Central, South, and Southwest China than those in other regions. The trend of arsenic pollution in agricultural soils has gradually increased over the past three decades. However, the growth rate of arsenic concentrations pollution in farmlands agricultural in China slowed during 2012-2016. The ecological risk index and geoaccumulation index revealed that arsenic in Chinese agricultural soil poses a low risk to the ecosystem. For human health assessment, the dietary pathway was the main pathway of exposure to arsenic in farmland soil of China. However, children's soil intake also contributed 34.48% to the exposure to arsenic, owing to their behavior. This study can provide a reference for the management of arsenic agricultural pollution in farmland soils in China.

Status of mercury accumulation in agricultural soil across China: Spatial distribution, temporal trend, influencing factor and risk assessment

Given its wide distribution in the natural environment and global transport potential, mercury (Hg) is regarded as a ubiquitous pollutant. In this study, we carried out nation-wide sampling campaigns across China to investigate the distribution of Hg in agricultural soils. Concentrations of Hg in the soils collected in 2011 and 2016 ranged from 0.04 to 0.69 and 0.06-0.78 mg kg^-1, respectively. Based on the data from 2016, the reserve of Hg in the surface arable soils (0-20 cm) in China was 4.1 × 10⁴ metric tons and Chinese cultivated soils accounted for 63.4-364 metric tons of Hg released to the global atmosphere. The soil Hg concentrations were significantly higher than the reference background level, highlighting the impacts of anthropogenic activities. The vertical distribution pattern showed a clear enrichment at the surface and a decrease with depth of the soils. Comparison of calculated geo-accumulation indexes among individual provinces showed that Northwest China had higher levels of Hg contamination than other regions of China, likely due to long-term energy related combustions in the area. Soil Hg level showed strong positive correlations with organic matter contents of soil, as well as the mean annual precipitation and temperature of the sampling locations. The non-carcinogenic human health risks of soil Hg were below the threshold level, but the general risk to the ecosystem was considerable. The increases in Hg accumulation from 2011 to 2016 at provincial level were found to relate to coal combustion, power generation and per capita GDP. This examination of energy consumption and socioeconomic drivers for China's soil Hg reserve increase is critical for direct Hg control by guiding policy-making and targets of technology development in era of rapid economic growth.

Arsenic in agricultural soils across China: Distribution pattern, accumulation trend, influencing factors, and risk assessment

Arsenic (As) in the environment is of concern due to its strong toxicity and high risks to the ecosystems and humans. In this study, soil samples across China collected in 2011 and 2016 were used to determine the concentrations of arsenic in arable soils. The median concentration of arsenic in surface soils was 9.7mg/kg. The inventory of arsenic in the Chinese agricultural surface soils was estimated to be 3.7×10⁶tons. In general, arsenic contamination was found higher in South and Northeast China than in other regions, with means of 18.7 and 15.8mg/kg, respectively. Vertically, arsenic concentrations were higher in top layer (0-15cm) soils (median of 9.8mg/kg) and decreased with soil depth (medians of 8.9mg/kg at 15-30cm and 8.0mg/kg at 30-45cm). By comparing with published data, an increasing accumulation trend over the past decades was found and this enhancement was positively related with the long-term application of fertilizers in agricultural practice, especially phosphate fertilizers. Soil pH was found to affect the movement of arsenic in soil, and high-pH conditions enhanced the pool of arsenic. The ecological risk assessment revealed that arsenic in Chinese agricultural soil posed a low risk to the ecosystem. Regarding human health, the mean hazard indices (HIs) of arsenic were below 1, suggesting an absence of non-carcinogenic risks. In addition, the cancer risks of arsenic in all soil samples were within the acceptable range (below 1×10^-4), indicating low to very low risks to the exposed population. Findings from this study are valuable to provide effective management options for risk avoidance and to control the persistent accumulation of arsenic in the agriculture sector across the world.

miR-22 contributes to endosulfan-induced endothelial dysfunction by targeting SRF in HUVECs

microRNAs (miRNAs) function in the posttranscriptional gene regulation, providing new insights into the epigenetic mechanism of toxicity induced by environmental pollutants. miR-22 was discovered to regulate cell proliferation and apoptosis in response to environmental toxicants. We have reported that endosulfan can cause endothelial toxicity in human umbilical vein endothelial cells (HUVECs). In the present study, we investigated the involvement of miR-22 in endosulfan-induced endothelial dysfunction. The expression level of miR-22 was increased in a dose-dependent manner by endosulfan exposure. Overexpression of miR-22 induced apoptosis and inflammation in HUVECs. Anti-miR-22 transfection significantly attenuated the increase in the percentage of apoptotic cells, caspase-3 activity and Interleukin (IL)-6, 8 mRNA levels in endosulfan-exposed HUVECs. Luciferase reporter assay confirmed that SRF and STAG2 were novel direct targets of miR-22. Endosulfan decreased mRNA expression of both SRF and STAG2, but only suppressed protein expression of SRF. Knockdown of SRF via siRNAs resulted in apoptosis and inflammation whereas STAG2 siRNAs only caused abnormal mitosis in HUVECs. Taken together, these findings will shed light on the role and mechanism of miR-22 in endosulfan-induced endothelial dysfunction via SRF in HUVECs.

Inhibition of cell growth and induction of inflammation by endosulfan in HUVEC-C cells

Endosulfan is one of the organochlorine pesticides. It has been associated with a wide range of adverse health effects. However, it is unknown whether endosulfan causes endothelial dysfunction. In the present study, we investigated the effects of endosulfan on human vascular endothelial cells. We exposed human umbilical vein endothelial cells (HUVEC-C) to varying concentrations of endosulfan for 48 h. The results showed that endosulfan lowered cell viability and inhibited cell proliferation in a dose-dependent manner. Flow cytometric analysis showed that endosulfan at 60 μM induced G1 cell cycle arrest, a response attributed to down-regulation of CDK6 and pRb dephosphorylation. We observed that endosulfan at 40 and 60 μM induced a considerable percentage of cells to undergo apoptosis, as detected by Annexin-V binding assays. Endosulfan reduced mitochondrial transmembrane potential, leading to the release of cytochrome c into the cytoplasm; meanwhile, endosulfan also inhibited the mRNA expression level of survivin, which resulted in the activation of caspase-3. These results indicated that the intrinsic mitochondria-mediated pathway was involved in apoptotic process. Exposure to endosulfan increased the secretion and mRNA expression levels of inflammation factors interleukin (IL)-6 and IL-8, suggesting that endosulfan could cause inflammation. Overall, these findings suggested that endosulfan is toxic to HUVEC-C cells, resulting in endothelial dysfunction. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1785-1795, 2016.

Research on persistent organic pollutants in China on a national scale: 10 years after the enforcement of the Stockholm Convention

As a signatory of the Stockholm Convention and the largest developing country, China plays a very important role in implementation of the convention to reduce and finally eliminate persistent organic pollutants (POPs) in the world. In the past ten years after the enforcement in 2004, Chinese Government and scientists have made great progress on the study of POPs. The present work aims to provide an overview on recent studies on POPs in China, with particular focus on usage/emission inventory, residue inventory, and pollution status of POPs on national scale. Several legend (old) and new target POPs were comprehensively summarized with progress on inventory. Furthermore, several national scale monitoring programs have been selected for the occurrence, spatial and temporal trends of POPs in China, which are compared with Asian data and Global data. Based on the observed results, some important scientific issues, such as the primary and secondary distribution patterns, the primary and secondary fractionations, and air-soil exchange of POPs, are also discussed. It is proposed that more studies should be carried out for the new targeted POPs in future for both the national and global interests.

Spatial distribution, transport dynamics, and health risks of endosulfan at a contaminated site

We analyzed concentrations, distribution characteristics, and health risks of endosulfan (α and β isomers, and endosulfan sulfate) in soils (top soils and soil profiles) and air, at and around a typical endosulfan production site in Jiangsu, China. The air-soil surface exchange flux is calculated to investigate transport dynamics of endosulfan. Concentrations at the production site ranged from 0.01 to 114 mg/kg d.w. in soil and 4.81-289 ng/m(3) in air, with very high concentrations occurring at the location of endosulfan emulsion workshop. In the surrounding area, endosulfan was detected in all samples, with concentrations ranging from 1.37-415 ng/g d.w. in soil and 0.89-10.4 ng/m(3) in air. In the contaminated site, endosulfan concentrations fluctuated with depth in the upper soil layers, then decreased below 120 cm. Soil and air within a distance of 2.0 km appear to be affected by endosulfan originating from the site. Even the health risk at the location of the endosulfan emulsifiable solution workshop was over seven times the acceptable value, the risk to nearby adults and children was low.

A preliminary compilation and evaluation of a comprehensive emission inventory for polychlorinated biphenyls in China

Emission inventories for polychlorinated biphenyls (PCBs) are crucial input data for atmospheric transport modeling and for the study of source-receptor relationships and the environmental behavior of these chemicals. Three types of primary PCB sources are considered in this study: intentionally produced PCBs (IP-PCBs), unintentionally produced PCBs (UP-PCBs), and PCB emissions from two e-waste sites (EW-PCBs). This study presents the historical emissions of all IP-, UP- and EW-PCBs into the air in China and the gridded Chinese emission inventories at a resolution of 1/6° latitude×1/4° longitude from 1950 to 2010. The UP-TPCB emissions from 1950 to 2010 were re-estimated to be 8.56t from eight emission sources comprising 96.3% of the Chinese UP-TPCB emissions. The EW-TPCB emissions from 1990 to 2010 were estimated to be 103.5 t, of which 7.1t and 12.3t were EW-PCB28 and EW-7PCB congeners (i.e., indicator-PCB28, 52, 101, 118, 138, 153, 180), respectively. The IP-PCB28 and IP-7PCB congener emissions from 1965 to 2010 were estimated to be 57.4 t and 130.1t, respectively. A significant correlation was found between congener PCB28 and 7PCBs (R(2)=0.988 and P=0.000), which suggests that PCB28 is a good marker congener for describing the emission trends of all 7PCB emission sources. The gridded emission data were compared with published measured atmospheric concentrations for 2004 and 2008, and a significant correlation was found between the modeled emissions and monitoring data. To our knowledge, this study presents the first comprehensive gridded emission inventories that include all IP-, UP-, and EW-PCBs on a national scale.

Exposure to Endosulfan can result in male infertility due to testicular atrophy and reduced sperm count

Endosulfan (ES) is a widely used organochlorine pesticide and is speculated to be detrimental to human health. However, very little is known about mechanism of its genotoxicity. Using mouse model system, we show that exposure to ES affected physiology and cellular architecture of organs and tissues. Among all organs, damage to testes was extensive and it resulted in death of different testicular-cell populations. We find that the damage in testes resulted in qualitative and quantitative defects during spermatogenesis in a time-dependent manner, increasing epididymal reactive oxygen species levels, affecting sperm chromatin integrity. This further culminated in reduced number of epididymal sperms and actively motile sperms. Finally, we show that ES exposure affected fertility in male but not in female mice. Therefore, we demonstrate that ES exerts pathophysiological changes in mice, induces testicular atrophy, affects spermatogenesis, reduces quantity and vigour of epididymal sperm and leads to infertility in males.

Persistent endosulfan sulfate is found with highest abundance among endosulfan I, II, and sulfate in German forest soils

Endosulfan - an agricultural insecticide and banned by Stockholm Convention - is produced as a 2:1 to 7:3 mixture of isomers endosulfan I (ESI) and endosulfan II (ESII). Endosulfan is transformed under aerobic conditions into endosulfan sulfate (ESS). The study shows for 76 sampling locations in German forests that endosulfan is abundant in all samples with an opposite ratio between the ESI and ESII than the technical product, where the main metabolite ESS is found with even higher abundance. The ratio between ESI/ESII and ESS show clear dependence on the type of stands (coniferous vs. deciduous) and humus type and increases from deciduous via mixed to coniferous forest stands. The study argues for a systematic monitoring of ESI, ESII, and ESS and underlines the need for further research, specifically on the fate of endosulfan including biomagnifications and bioaccumulation in soil.

Biodegradation of endosulfan isomers and its metabolite endosulfate by two biosurfactant producing bacterial strains of Bordetella petrii

The main objective of the investigation was to study the biodegradation of endosulfan isomers and its major metabolite endosulfate by two biosurfactant producing bacterial strains of Bordetella petrii. The significance of the study is to evaluate the capability of biosurfactant producing bacterial strains in enhancing the bioavailability of endosulfan. Sixty bacterial strains were isolated from the endosulfan degrading bacterial consortium and were screened for endosulfan degradation and biosurfactant production. Among those, two strains Bordetella petrii I GV 34 (Gene bank Accession No KJ02262) and Bordetella petrii II GV 36 (Gene bank Accession No KJ022625) were capable of degrading endosulfan with simultaneous biosurfactant production. Bordetella petrii I degraded 89% of α and 84% of β isomers of endosulfan whereas Bordetella petrii II degraded 82% of both the isomers. Both the strains were able to reduce the surface tension up to 19.6% and 21.4% with a minimum observed surface tension of 45 Dynes/cm and 44 Dynes/cm, respectively. The study revealed that the strains have the potential to enhance the degradation endosulfan residues in contaminated sites and water by biosurfactant production.

Organochlorine pesticides in the dust fall around Lake Chaohu, the fifth largest lake in China

The residual levels of organochlorine pesticides (OCPs) in the dust fall around Lake Chaohu were measured using gas chromatography mass spectrometry from April 2010 to March 2011. The fluxes, components, temporal-spatial variations, and sources of OCPs were also analyzed. Twenty-one types of OCPs were detected in the dust fall samples around Lake Chaohu, with a total concentration of 51.54 ± 36.31 ng/g and a total flux of 10.01 ± 13.69 ng/(m(2) day). Aldrin (35.3 %), endosulfan (39.1 %), dichlorodiphenyltrichloroethanes (DDTs) (49.8 %), and isodrin (37.1 %) were the major OCPs in the spring, summer, autumn, and winter, respectively. Both the residual level and the flux were higher in the spring than in other seasons and higher at the outer lake sampling sites than inner lake sampling site. The potential source of the hexachlorcyclohexanes in the dust fall may be recent lindane usage. The DDTs mainly came from historical dicofol usage, and a significant input of DDT was found during April and June. The presence of endosulfan may be due to the present use of technical endosulfan. The aldrin in the dust might be due to its occasional usage, and isodrin may be a result of long-distance transport from other countries.

Historical contamination and ecological risk of organochlorine pesticides in sediment core in northeastern Chinese river

Twenty-eight surface sediment samples and one sediment core were analyzed for 21 organochlorine pesticides (OCPs), in order to provide extensive information of distribution, sources, pollution history and ecological risk of these OCP compounds in Daling River area, China. The results showed that hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected contaminants in the surface sediment samples with concentrations (in ngg(-1) dry weight (dw)) from 1.1 to 30 and from 2.2 to 45, respectively. Analysis of variance showed significant (P<0.05) differences between HCHs and DDTs residues in surface sediment sampled from the various locations. Residues of HCHs and DDTs in sediment core (in ngg(-1)dw) ranged from 2.1 to 18 and 9.1 to 53, respectively. The temporal trends of HCHs and DDTs concentrations in the sediment core were affected by application history, emission and soil residues. Compositional analysis of HCHs and DDTs indicated that new sources were lindane and dicofol mainly due to agricultural activities. Additionally, based on the available sediment quality guidelines, slight potential health risks of DDTs may exist to benthic organisms in Daling River and Bohai Sea.

Organochlorine pesticide (OCP) residues in mountain soils from Tajikistan

The concentrations and spatial distribution of organochlorine pesticides (OCPs) in surface soils of different altitudes (570–4656 m) from Tajikistan were determined. OCPs were detected in all samples with concentrations in the range 52.83–247.98 ng g(-1) dry weight (ng g(-1) dw). Aldrins were the most predominant compounds followed by chlordanes, hexachlorocyclohexanes (HCHs) and endosulfans, while dichlorodiphenyltrichloroethanes (DDTs) and methoxychlor were detected at much lower concentrations. Composition analysis indicated that OCPs mainly came from the atmospheric transport of historically used pesticides. OCP residues in the west and northwest parts of Tajikistan were higher than the east and the southeast due to the proximity to the potential sources and anthropogenic activity intensities around. Additionally, correlation analysis between OCPs and altitudes indicated that the more volatile pollutants, such as HCH isomers, seemed to become enriched more easily in regions with higher altitudes relative to the less volatile ones, such as DDTs.

Levels, temporal-spatial variations, and sources of organochlorine pesticides in ambient air of Lake Chaohu, China

The residual levels of OCPs in the gas phase and particle phase in Lake Chaohu, China, were measured using GC-MS from March 2010 to February 2011. The temporal-spatial variations and sources of OCPs were also analyzed. Twenty types of OCPs were detected in the gas phase with a total concentration of 484.8 ± 550.4 pg/m³. Endosulfan, DDTs and chlordane were the primary OCPs in the gas phase. The mean concentration of OCPs in the gas phase was significantly higher in the summer than in the winter. Seventeen types of OCPs were detected in the particle phase with a total concentration of 18.3 ± 26.1 pg/m³. DDTs were major OCPs in the particle phase. The mean concentration of OCPs in the particle phase decreased at first and then increased during the period. The potential source of the HCHs in ambient air of Lake Chaohu might come from recent lindane usage. DDTs mainly came from historical dicofol usage, and an input of DDT was observed in the spring, which may result from the present use of marine paint that contains technical DDT. Endosulfan and chlordane in the air may be due to the present use of technical endosulfan and chlordane.

Residues of currently and never used organochlorine pesticides in agricultural soils from Zhejiang Province, China

Studies on residues of currently and never used organochlorine pesticides (OCPs) facilitate the assessment of the contamination level, distribution, sources, transportation, and trend of these selected OCPs in China. In this work we investigated the concentration levels of endosulfans and chlordane, which are currently used, and the never used aldrin and dieldrin in the province of Zhejiang, a rainy, and hilly tea-growing province in eastern China. The average/mean residue levels of OCPs was in the order ∑endosulfan > ∑chlordane > aldrin > dieldrin. The residue level was in good agreement with the usage of OCPs in Zhejiang. The spatial distribution showed that the residues of OCPs in soils from the mountain area were always higher than those in soils from the plains. The distribution characteristics were related to usage for current-use OCPs and temperature for never used OCPs. The isomeric ratios and enantiomeric fractions are useful tools to identify the degradation preference of contaminants. The wide range of ratios between trans-chlordane (TC) and cis-chlordane (CC) indicated that the degradation of the two isomers of chlordane was different at different sites. Nonracemic residues of TC and CC were observed in most soils; this is significant since the enantiomers have different toxicities.

Emission inventory for PFOS in China: review of past methodologies and suggestions

Perfluorooctane sulfonate (PFOS) is a persistent, bioaccumulative, and toxic chemical that has the potential for long-range transport in the environment. Its use in a wide variety of consumer products and industrial processes makes a detailed characterization of its emissions sources very challenging. These varied emissions sources all contribute to PFOS' existence within nearly all environmental media. Currently, China is the only country documented to still be producing PFOS, though there is no China PFOS emission inventory available. This study reviews the inventory methodologies for PFOS in other countries to suggest a China-specific methodology framework for a PFOS emission inventory. The suggested framework combines unknowns for PFOS-containing product penetration into the Chinese market with product lifecycle assumptions, centralizing these diverse sources into municipal sewage treatment plants. Releases from industrial sources can be quantified separately using another set of emission factors. Industrial sources likely to be relevant to the Chinese environment are identified.

Spatial distribution of hexachlorocyclohexanes in agricultural soils in Zhejiang province, China, and correlations with elevation and temperature

Large quantities of hexachlorocyclohexanes (HCHs) were historically applied to soils in Zhejiang, a hilly province of eastern China, yet very limited information is publicly available for the present levels and residue characteristics of HCHs in the region. In this work, concentrations of HCHs and enantiomeric fractions (EFs) of α-isomer were analyzed in 58 agricultural soil samples (0-20 cm) collected in Zhejiang province. On the basis of the ratio of α-HCH/β-HCH and the fact that HCHs were banned in 1983 for agricultural use in China, fresh application of technical HCHs in a large quantity was unlikely in this province. Significant correlation was found between soil concentrations and elevation (R = 0.52, P < 0.001) and temperature (R = -0.55, P < 0.0001), but not between soil concentrations and total technical usage (R = -0.24, P = 0.1), suggesting a typical secondary distribution pattern. The soil residue inventories of HCHs derived from the relationship between concentration and elevation indicated 14.2 tons of HCHs left in agricultural soils in plain areas with the average elevation less than 100 m, and 61.6 tons of HCHs left in mountain soils with the average elevation higher than 100 m. It was also found that EFs of α-HCH were significantly negatively correlated with carbon biomass (C(bio)) in soils. This implies that C(bio) might have important impact on orientation and extent of enantioselective degradation of α-HCH in the region, which is, according to our knowledge, the first report of this kind.

Monitoring and modeling endosulfan in Chinese surface soil

Endosulfan is a currently used organochlorine pesticide in China, with annual usage of 2300 t between 1994 and 2004. Concentrations of endosulfan (including α- and β-isomers and their metabolite endosulfan sulfate) were reported for surface soil collected in 2005 at 141 sites (6 background, 95 rural, and 40 urban) across China. The concentrations of total endosulfan (sum of α-endosulfan, β-endosulfan, and endosulfan sulfate) at all sites ranged from BDL (below detection limit) to 19000 pg/g dry weight (dw), with geometric mean (GM) 120 pg/g dw. Rural soils had the highest total endosulfan concentrations, with GM 160 pg/g dw, followed by urban soils (GM = 83 pg/g dw) and background soils (GM = 38 pg/g dw). The observed soil concentrations of α-endosulfan (GM = 6.5 pg/g dw) were much lower than those of β-endosulfan (GM = 49 pg/g dw) and endosulfan sulfate (GM = 47 pg/g dw). The fractional abundance of α-endosulfan F(α-endo) [α-endosulfan/(α-endosulfan + β-endosulfan)] for all soils ranged from 0.00040 to 0.91, with GM 0.10, much lower than those in technical products (ranged from 0.67 to 0.7), which most likely reflects that α-endosulfan is more volatile and degrades faster than β-endosulfan in soil. Consequently, half-life of β-endosulfan in soil is expected longer than α-endosulfan. Significant correlation between endosulfan sulfate and its parent isomers suggested that the presence of endosulfan sulfate originated from its parent isomers. Based on multiple linear regression model, inventories of endosulfan sulfate in Chinese agricultural soil in 2004 with a 1/4° longitude × 1/6° latitude resolution are established. Comparison between field measurements and modeling results showed significant correlations between the modeled and measured endosulfan concentrations, and 89%, 83%, and 70% of monitoring data fell between the lowest and the highest modeled concentrations for α- and β-endosulfan and endosulfan sulfate, respectively. The good agreement lends credibility to modeled soil concentrations of endosulfan. To our knowledge, this is the first soil concentration inventory for endosulfan sulfate, which paves the way for further study on its environmental behavior.

Levels, distributions, and source identification of organochlorine pesticides in the topsoils in Northeastern China

Seventeen topsoil samples (9 urban, 4 suburban, 3 rural and 1 background) were collected in/around Harbin, a typical city in northeast of China, to measure concentration levels of organocholrine pesticides (OCPs) in topsoil of Northeastern China in 2006. Hexachlorohexanes (HCH), dichlorodiphenyltrichloroethane (DDT), and hexachlorobenzene (HCB) were detected in soil samples with mean concentrations (in pg/g dry weight (dw)) of 7120, 5425, and 1039, respectively. The mean concentrations for other OCPs were very low, 4.8 pg/g dw for chlordane and 3.3 pg/g dw for endosulfan. Source identification analysis reveals that all OCPs found in soil samples were due to historical use of these chemicals or from other source regions through long- and short-range atmospheric transport. DDT was mainly used in the rural sites, whereas the sources of HCB, chlordane and endosulfan were mainly in the urban area. HCH was found almost equally in both urban and rural area. Soil concentrations of all detected OCPs, except HCHs, in and around Harbin were much lower than those in the southeast of China, which is expected since the use of these OCPs in the former was much lower than that in the latter, however higher HCH concentrations in and around Harbin than those found in most places of the Southeast China is not expected. It is suggested that high HCH concentration in soil of Northeast China was most likely due to long-range atmospheric transport (LRAT) from Southeast China and the cold condensation process.