Organochlorine pesticide residues in archived UK soil

In ovo o,p'-DDT exposure induces malformation of reproductive organs and alters the expression of genes controlling sexual differentiation in Japanese quail embryo

In ovo exposure to o,p'-dichloro-diphenyl-trichloroethane (o,p'-DDT) impairs reproduction by inducing malformation of the reproductive organs in birds, although the mechanism remains unclear. Here, we examined the effects of o,p'-DDT on the development of the reproductive organs, the expression of genes controlling sexual differentiation, and the plasma concentrations of testosterone and estradiol in Japanese quail embryos. o,p'-DDT-containing sesame oil was injected into the yolk sac on Embryonic Day (E) 3 at a dose of 500, 2,000, or 8,000 μg per egg. On E15, the reproductive organs were observed; the gonads and Müllerian ducts (MDs) were sampled to measure the mRNA of steroidogenic enzymes, sex steroid receptors, anti-Müllerian hormone (AMH), and AMH receptor 2 (AMHR2); blood samples were collected to assay plasma testosterone and estradiol levels; and the gonads were used for histological analysis. o,p'-DDT dose-dependently increased the prevalence of hypertrophic MDs in females and residual MDs in males. In female MDs, o,p'-DDT dose-dependently decreased estrogen receptor (ER) α, ERβ, and AMHR2 mRNA expression. o,p'-DDT dose-dependently induced left-biased asymmetry of testis size, and ovary-like tissue was found in the left testis after exposure to 8,000 μg per egg o,p'-DDT, although asymmetric gene expression did not occur. o,p'-DDT did not affect ovarian tissue but did decrease 17α-hydroxylase/C17-20 lyase mRNA expression and dose-dependently increased ERβ mRNA expression. o,p'-DDT decreased plasma testosterone concentrations in females. These findings suggest that o,p'-DDT induces hypertrophy of the MDs and ovarian tissue formation in the left testis. Abnormal MD development may be linked to altered gene expression for sensing estrogens and AMH signals.

Distribution, sources and health risk assessment of DDT and its metabolites in agricultural soils in Zhejiang Province, China

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been officially banned as a pesticide around the world. However, DDT pollution still exists in natural environments in China because DDT degrade very slowly. In this study, 60 soil samples were collected from Cixi, Zhejiang Province, and the levels of DDTs and its metabolites in soil and health risks were investigated. The results showed that the detection rate of DDT in soil samples were 100%, and the total DDTs residue in soil ranged from 0.007 to 1.208 mg/kg, with an average of 0. 113±0. 035 mg/kg, which exceeded the second-level Chinese soil environmental quality standard for farmland soil. The average residuals of p,p'-DDT, p,p'-DDE (dichlorodiphenyldichloroethylene), p,p'-DDD (dichlorodiphenyldichloroethane) and o,p'-DDT accounted for 34.8%, 50.9%, 8.0% and 6.3% of the total DDTs, respectively. The DDD/DDE ratios indicated a dehydrochlorination of DDT to DDE under aerobic conditions at most sampling sites. The ratios of (p,p'-DDE+p,p'-DDD)/p,p'-DDT and o,p'-DDT/p,p'-DDT indicating the DDT in the field were mainly introduced via industrial DDT and dicofol, including historical residue and fresh input. The health risk assessment showed that DDT-contaminated sites do not pose a non-carcinogenic risk to humans, and pose a very low risk of cancer to children and a low risk of cancer to adults. Overall, this study helps to understand the distribution, sources and health risks of DDT in typical soils.

Developmental exposure to the Parkinson's disease-associated organochlorine pesticide dieldrin alters dopamine neurotransmission in α-synuclein pre-formed fibril (PFF)-injected mice

Parkinson's disease (PD) is the fastest-growing neurological disease worldwide, with increases outpacing aging and occurring most rapidly in recently industrialized areas, suggesting a role of environmental factors. Epidemiological, post-mortem, and mechanistic studies suggest that persistent organic pollutants, including the organochlorine pesticide dieldrin, increase PD risk. In mice, developmental dieldrin exposure causes male-specific exacerbation of neuronal susceptibility to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and synucleinopathy. Specifically, in the α-synuclein (α-syn) pre-formed fibril (PFF) model, exposure leads to increased deficits in striatal dopamine (DA) turnover and motor deficits on the challenging beam. Here, we hypothesized that alterations in DA handling contribute to the observed changes and assessed vesicular monoamine transporter 2 (VMAT2) function and DA release in this dieldrin/PFF 2-hit model. Female C57BL/6 mice were exposed to 0.3 mg/kg dieldrin or vehicle every 3 days by feeding, starting at 8 weeks of age and continuing throughout breeding, gestation, and lactation. Male offspring from independent litters underwent unilateral, intrastriatal injections of α-syn PFFs at 12 weeks of age, and vesicular 3H-DA uptake assays and fast-scan cyclic voltammetry were performed 4 months post-PFF injection. Dieldrin-induced an increase in DA release in striatal slices in PFF-injected animals, but no change in VMAT2 activity. These results suggest that developmental dieldrin exposure increases a compensatory response to synucleinopathy-triggered striatal DA loss. These findings are consistent with silent neurotoxicity, where developmental exposure to dieldrin primes the nigrostriatal striatal system to have an exacerbated response to synucleinopathy in the absence of observable changes in typical markers of nigrostriatal dysfunction and degeneration.

Spatial redistribution and enantiomeric signatures of hexachlorocyclohexanes in Chinese forest soils: Implications to environmental behavior and influencing factors

Hexachlorocyclohexanes (HCHs) are a group of highly persistent pesticides. The concentrations of HCHs and the enantiomeric fractions of α-HCH in the O- and A-horizons from 30 mountains across China were analyzed in this study. The concentrations of total HCHs ranged from 0.061 to 46.9 ng/g (mean 2.12 ng/g) and 0.046 to 16.1 ng/g (mean 0.792 ng/g) in the O- and A-horizons, respectively. The HCH residues were mainly derived from the historical applications of technical HCH and lindane. Higher concentrations of HCHs were typically found in northern China, and no significant correlations were found between historical technical HCH usage and HCH isomer concentrations in either the O- or A-horizons (p > 0.05). Conversely, the concentrations of HCH isomers were significantly correlated with the environmental parameters (temperature and precipitation), thus indicating a typical secondary distribution pattern. Some HCH isomers tended to be transported northward under the long-term effect of monsoon. Chiral α-HCH was non-racemic in soils and showed preferential degradation of (-) α-HCH in both the O- and A-horizons. The transformation from γ-HCH to α-HCH might alter the enantiomeric signatures of α-HCH in soils. Moreover, the deviation from racemic of α-HCH was positively correlated with the C/N ratio in the A-horizon (p < 0.01), thus suggesting that the C/N ratio could alter the microbial activity and significantly affect the enantioselective degradation extent of α-HCH in soils.

The influence of pesticides on the corrosion of a Roman bowl excavated in Kent, UK

We analysed corrosion from a copper bowl dating from the Roman period (43–410 AD) found in a farm in Kent, UK. Despite its relatively good condition, the interior and exterior surface of the object had areas of deterioration containing green and brown-coloured corrosion which were sampled for characterization by a multi-analytical protocol. Basic copper chlorides atacamite and paratacamite were identified in the context of mineral phases along with chlorobenzenes in the green corrosion. Chlorobenzenes are common soil contaminants in rural areas from the use of pesticides, many of which were banned more than 50 years ago. Here we show that their presence is associated with accelerated corrosion, and this provides a threat to the preservation of archaeological metal objects in the ground.

Status of Dieldrin in vegetable growing soils across a peri-urban agricultural area according to an adapted sampling strategy

Since the fifties, organochlorine pesticides (OCPs) had been used in agriculture to protect vegetables. Two decades after their ban by the Stockholm convention in 2001, OCPs are still present in agricultural soils inducing vegetable contamination with concentrations above Maximum Residue Level (MRL). This is a major concern for a 5 km² peri-urban vegetable growing valley located in the south west of France. In the present work, the sampling method was developed to clarify the spatial distribution of one OCP, Dieldrin, and its relationship with soil properties at the scale of study area. A total of 99 soil samples was collected for physicochemical analyses and Dieldrin concentrations. Results show Dieldrin concentrations in soils up to 204 μg kg^-1. The horizontal distribution of this pesticide is heterogeneous at the study area scale but homogeneous in each reference plot studied. About 85% of the contamination was located in the top soil layers (0-40 cm depth), but Dieldrin may still be quantified at a depth of 80 cm. Among all soil physicochemical parameters analysed, SOM was the most significantly related (P < 10^-4) with Dieldrin concentrations, once different grain size fractions were considered. Moreover, results indicate a 33 times higher Dieldrin concentration and/or extractability for coarse sand than for other grain size fractions. These results show that the developed sampling method is adapted for the study area scale as it helps understanding the factors influencing the spatial distribution of Dieldrin. Historical amendments are the predominant factor for the horizontal contamination and deep ploughing for the vertical contamination. Also, the variations of coarse sand repartition in soils prevents identification of relationships between SOM and Dieldrin contamination in bulk soil. Further investigation is required to explain these relationships but these results highlight why no clear relationship between OCPs and SOM was previously identified.

Environmental neurotoxicants and inflammasome activation in Parkinson's disease - A focus on the gut-brain axis

Inflammasomes are multi-protein complexes expressed in immune cells that function as intracellular sensors of environmental, metabolic and cellular stress. Inflammasome activation in the brain, has been shown to drive neuropathology and disease progression by multiple mechanisms, making it one of the most attractive therapeutic targets for disease modification in Parkinson's Disease (PD). Extensive inflammasome activation is evident in the brains of people with PD at the sites of dopaminergic degeneration and synuclein aggregation. While substantial progress has been made on validating inflammasome activation as a therapeutic target for PD, the mechanisms by which inflammasome activation is triggered and sustained over the disease course remain poorly understood. A growing body of evidence point to environmental and occupational chemical exposures as possible triggers of inflammasome activation in PD. The involvement of the gastrointestinal system and gut microbiota in PD pathophysiology is beginning to be elucidated, especially the profound link between gut dysbiosis and immune activation. While large cohort studies confirmed specific changes in the gut microbiota in PD patients compared to age-matched healthy controls, recent research suggest that synuclein pathology could be initiated in the gastrointestinal tract. In this review, we present a summarized perspective on current understanding on inflammasome activation and the gut-brain-axis link during PD pathophysiology. We discuss multiple environmental toxicants that are implicated as the etiological agents in causing idiopathic PD and their mechanistic underpinnings during neuroinflammatory events. We additionally present future directions that needs to address the research questions related to the gut-microbiome-brain mechanisms in PD.

Organochlorine Pesticide Dieldrin Suppresses Cellular Interferon-Related Antiviral Gene Expression

Organochlorine pesticides (OCPs) are persistent pollutants linked to diverse adverse health outcomes. Environmental exposure to OCPs has been suggested to negatively impact the immune system but their effects on cellular antiviral responses remain unknown. Transcriptomic analysis of N27 rat dopaminergic neuronal cells unexpectedly detected high level expression of genes in the interferon (IFN)-related antiviral response pathways including the IFN-induced protein with tetratricopeptide repeats 1 and 2 (Ifit1/2) and the MX Dynamin Like GTPases Mx1 and Mx2. Interestingly, treatment of N27 cells with dieldrin markedly downregulated the expression of many of these genes. Dieldrin exterted a similar effect in inhibiting IFIT2 and MX1 gene expression in human SH-SY5Y neuronal cells induced by an RNA viral mimic, polyinosinic: polycytidylic acid (poly I:C) and IFIT2/3 gene expression in human pulmonary epithelial cells exposed to human influenza H1N1 virus. Mechanistically, dieldrin induced a rapid rise in levels of intracellular reactive oxygen species (iROS) and a decrease in intracellular glutathione (GSH) levels in SH-SY5Y cells. Treatment with N-acetylcysteine, an antioxidant and GSH biosynthesis precursor, effectively blocked both dieldrin-induced increases in iROS and its inhibition of poly I:C-induced upregulation of IFIT and MX gene expression, suggesting a role for intracellular oxidative status in dieldrin's modulation of antiviral gene expression. This study demonstrates that dieldrin modulates key genes of the cellular innate immune responses that are normally involved in the host's cellular defense against viral infections. Our findings have potential relevance to understanding the organismal effects of environmentally persistent organochlorine contaminants on the mammalian cellular immune system.

Do dissipation and transformation of γ-HCH and p,p'-DDT in soil respond to a proxy for climate change? Insights from a field study on the eastern Tibetan Plateau

While the influence of climate change on the fate of persistent organic pollutants (POPs) is becoming a topic of global concern, it has yet to be demonstrated how POPs and their transformation products in soil respond to a changing climate at the local scale. We conducted a year-long field experiment with spiked soils to investigate the impact of climate on the dissipation of γ-hexachlorocyclohexane (γ-HCH) and p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT) as well as the formation of their products. Four sites along an elevational gradient on the eastern Tibetan Plateau were selected to represent four scenarios ranging from a dry and cold to a warm and humid climate. Based on the measured concentrations of the two pesticides and their transformation products, we calculated the dissipation rates of γ-HCH and p,p'-DDT in soil using two biphasic kinetic models, and the formation rates of transformation products using a mid-point rectangular approximation method. The spiked γ-HCH generally showed the expected decrease in dissipation from soils with increasing altitudes, and therefore decreasing temperature and precipitation, whereas dissipation of p,p'-DDT was influenced more by photolysis and sequestration in soil. The formation rates of the primary products of γ-HCH (i.e. γ-HCH→PeCCH and γ-HCH→TeCCH) and p,p'-DDT (i.e. p,p'-DDT→p,p'-DDE and p,p'-DDT→p,p'-DDD) indicate that a warmer and wetter climate favors dechloroelimination (anaerobic biodegradation) over dehydrochlorination (aerobic biodegradation). The significantly longer dissipation half-lives of γ-HCH at the coldest site suggests that the fate of POPs in frozen regions (e.g. polar regions) needs more attention. Overall, the fate of more volatile chemicals (e.g. γ-HCH) might be more responsive to the climate change.

Organochlorine pesticides and polychlorinated biphenyls in common kestrel eggs from the Canary Islands: Spatiotemporal variations and effects on eggshell and reproduction

Organochlorine (OC) pesticides were widely used on the Canary Islands (Spain) for intensive crop production and against plagues of African locust. A previous study performed in 1988-1994 showed a high concentration of p,p'-DDE in the eggs of common kestrels (Falco tinnunculus) from the island of Tenerife. The present study shows OC pesticide and polychlorinated biphenyl (PCBs) levels in 40 unhatched common kestrel eggs collected from southern Tenerife between 2009 and 2016. The protoporphyrin IX in eggshells has also been analysed in order to explore the use of this pigment as a biomarker. Egg biometry, status of embryo development, eggshell thickness and mass of extractable lipids of each egg were recorded. Surrounding land use and reproductive parameters (hatching and fledging rates) were obtained for each nest. The most abundant compound was p,p'-DDE (15.0 μg/g d.w), followed by PCBs (0.46 μg/g d.w.). The decline in p,p'-DDE levels in southern Tenerife (with 23.6 μg/g d.w. in 1988-1994) was 36.4%. p,p'-DDE levels were positively associated with the surface of active and abandoned cropland in a 200 m-radius around the nest and with proximity to urban areas. PCB levels were associated with proximity to roads. Shell thickness was negatively affected by the p,p'-DDE concentration. The concentration of protoporphyrin IX in the eggshell was negatively associated with the concentration of hexachlorobenzene in the egg content. Despite the total ban on the use of p,p'-DDT in Spain since 1986, p,p'-DDE levels remain elevated in those areas in which that use was formerly intensive.

Developmental exposure to the organochlorine pesticide dieldrin causes male-specific exacerbation of α-synuclein-preformed fibril-induced toxicity and motor deficits

Human and animal studies have shown that exposure to the organochlorine pesticide dieldrin is associated with increased risk of Parkinson's disease (PD). Previous work showed that developmental dieldrin exposure increased neuronal susceptibility to MPTP toxicity in male C57BL/6 mice, possibly via changes in dopamine (DA) packaging and turnover. However, the relevance of the MPTP model to PD pathophysiology has been questioned. We therefore studied dieldrin-induced neurotoxicity in the α-synuclein (α-syn)-preformed fibril (PFF) model, which better reflects the α-syn pathology and toxicity observed in PD pathogenesis. Specifically, we used a "two-hit" model to determine whether developmental dieldrin exposure increases susceptibility to α-syn PFF-induced synucleinopathy. Dams were fed either dieldrin (0.3 mg/kg, every 3-4 days) or vehicle corn oil starting 1 month prior to breeding and continuing through weaning of pups at postnatal day 22. At 12 weeks of age, male and female offspring received intrastriatal α-syn PFF or control saline injections. Consistent with the male-specific increased susceptibility to MPTP, our results demonstrate that developmental dieldrin exposure exacerbates PFF-induced toxicity in male mice only. Specifically, in male offspring, dieldrin exacerbated PFF-induced motor deficits on the challenging beam and increased DA turnover in the striatum 6 months after PFF injection. However, male offspring showed neither exacerbation of phosphorylated α-syn aggregation (pSyn) in the substantia nigra (SN) at 1 or 2 months post-PFF injection, nor exacerbation of PFF-induced TH and NeuN loss in the SN 6 months post-PFF injection. Collectively, these data indicate that developmental dieldrin exposure produces a male-specific exacerbation of synucleinopathy-induced behavioral and biochemical deficits. This sex-specific result is consistent with both previous work in the MPTP model, our previously reported sex-specific effects of this exposure paradigm on the male and female epigenome, and the higher prevalence and more severe course of PD in males. The novel two-hit environmental toxicant/PFF exposure paradigm established in this project can be used to explore the mechanisms by which other PD-related exposures alter neuronal vulnerability to synucleinopathy in sporadic PD.

Levels and enantiomeric signatures of organochlorine pesticides in Chinese forest soils: Implications for sources and environmental behavior

We investigated the levels and distributions of organochlorine pesticides (OCPs) in 159 background soil samples collected from 30 forested mountain sites across China. The sum of DDT was the most abundant OCP, with the concentrations of 0.197-207 ng/g and 0.033-122 ng/g in the O-horizon and A-horizon, respectively. High concentrations of OCPs usually occur near agricultural regions or high consumption areas. The spatial distribution was mainly influenced by the emission sources and soil total organic contents (TOC). The chiral compounds were generally nonracemic in the soils and showed preferential degradation of (-) o,p'- dichlorodiphenyltrichloroethane, (+) trans-chlordane, and (-) cis-chlordane in both the O- and A-horizons. The enantiomeric fraction (EF) distributions of chiral OCPs displayed no differences across the forest sites in the O-horizon or the A-horizon. Comparing the deviation of EFs from racemic (DEVrac = absolute value of 0.500 - EF) with environmental parameters, we found that DEVrac of cis-chlordane demonstrated a strong positive correlation with TOC (p < 0.05) and the C/N ratio (p < 0.01). This relationship suggests that these factors could affect the microbial activity and significantly impact the extent of enantioselective degradation of chiral compounds in the soils. Fresh and historical applications of DDT and historical chlordane and endosulfan uses may be prominent sources of OCP accumulation in Chinese forest soils.

Application of enantiomeric fractions in environmental forensics: Uncertainties and inconsistencies

The assumption that only biological processes are enantioselective introduces challenges in the reliability of enantioselective analysis as a tool for discriminating biotic and abiotic processes in the environmental fate of chiral pollutants. Enantioselectivity does not depend on the nature of the fate process a chiral contaminant undergoes but on the interaction of the chiral contaminant with homochirality inducing external agents (e.g. chiral molecules, macromolecules or surfaces such as enzymes, blood plasma, proteins, chiral co-pollutants, humic acid and soil organominerals). The environmental behavior of a chiral contaminant is difficult to anticipate because the interactions between the chiral contaminants and the homochirality inducing external agents is often complex and strongly influenced by local environment conditions such as pH, redox conditions, organic carbon, organic nitrogen, humic acid, and redox conditions. Furthermore, the use of enantioselective analysis in environmental forensics depend on the adequate separation and accurate identification and quantification of the enantiomers of the chiral contaminant. Matrix effects, instrument effects, inadequate enantioselective separation, and poor quantification techniques introduce uncertainties in the determination of enantiomeric composition. Here we present the weaknesses of this assumption and recommend using enantiomeric fractions as chemical markers of biotransformation with caution. We recommend using stable isotopes, including abiotic controls to determine if enantioselective sorption occurs, and determining stability of enantiomers in solvent or at elevated temperatures to account for confounding factors arising from matrix effects, enantioselective abiotic processes, and enantiomerization due solvent and thermal lability of the chiral analyte, respectively to maintain the integrity of the utility of enantiomeric composition changes as an environmental forensics tool.

Assessment of Pesticide Residue Content in Polish Agricultural Soils

Pesticides belong to a group of xenobiotics harmful to humans and wildlife, whose fate and activity depends on their susceptibility to degradation. Therefore, the monitoring of their residue level in agricultural soils is very important because it provides very valuable information on the actual level of soil contamination and environmental risk resulting from their application. The aim of this study was to evaluate contemporary concentrations of organochlorine (OCPs) and non-chlorinated pesticides (NCPs) in arable soils of Poland as an example of Central and Eastern European countries. The results were assessed in relation to Polish regulations, which are more restrictive compared to those of other European countries. The sampling area covered the territory of arable lands in Poland (216 sampling points). The distribution of sampling points aimed to reflect different geographical districts, conditions of agricultural production, and various soil properties. The collected soil samples were extracted with organic solvents in an accelerated solvent extractor (ASE 2000). The OCPs, including α-HCH, β-HCH, γ-HCH, and p,p’DDT, p,p’DDE, and p,p’DDD, were extracted with a hexane/acetone mixture (70:30 v/v) and determined by gas chromatography with an electron capture detector (GC-μECD). NCPs included atrazine, carbaryl, and carbofuran were extracted with a dichloromethane/acetone mixture (50:50 v/v), while maneb was extracted by intensive shaking the sample with acetone (1:1 v/v) and ethylenediamine-tertraacetic acid. The NCPs were identified by a dual mass- spectrometry (GC-MS/MS). The total content of individual OCPs ranged from 0.61 to 1031.64 µg kg⁻¹, while the NCP concentrations were significantly lower, from 0.01 to 43.92 µg kg⁻¹. DDTs were detected in all soils samples (p,p’DDD (23.60 µg kg⁻¹) > p,p’DDT (18.23 µg kg⁻¹) > p,p’DDE (4.06 µg kg⁻¹), while HCHs were only in 4% of the analyzed samples (β-HCH (339.55 µg kg⁻¹) > α-HCH (96.96 µg kg⁻¹) > γ-HCH (3.04 µg kg⁻¹)), but in higher values than DDTs. Among NCPs, higher concentration was observed for carbaryl (<0.01–28.07 µg kg⁻¹) and atrazine (<0.01–15.85 µg kg⁻¹), while the lower for carbofuran (<0.01–0.54 µg kg⁻¹). Maneb was not detected in analyzed soils. Assessment of the level of soil pollution based on Polish regulations indicated that several percentages of the samples exceeded the criterion for OCPs, such as ∑3DDTs (14 samples; 6.5% of soils) and HCH congeners (α-HCH in one sample; 0.5% of soils), while NCP concentration, such as for atrazine, carbaryl and carbofuran were below the permissible levels or were not detected in the analyzed soils, e.g., maneb. The obtained results indicated that residues of the analyzed pesticides originate from historical agricultural deposition and potentially do not pose a direct threat to human and animal health. The behavior and persistence of pesticides in the soils depend on their properties. Significantly lower NCP concentration in the soils resulted from their lower hydrophobicity and higher susceptibility to leaching into the soil profile. OCPs are characterized by a high half-life time, which affect their significantly higher persistence in soils resulting from affinity to the soil organic phase.

Microbial transformation of chiral organohalides: Distribution, microorganisms and mechanisms

Chiral organohalides including dichlorodiphenyltrichloroethane (DDT), Hexabromocyclododecane (HBCD) and polychlorinated biphenyls (PCBs) raise a significant concern in the environmental occurrence, fate and ecotoxicology due to their enantioselective biological effects. This review provides a state-of-the-art overview on enantioselective microbial transformation of the chiral organohalides. We firstly summarized worldwide field assessments of chiral organohalides in a variety of environmental matrices, which suggested the pivotal role of microorganisms in enantioselective transformation of chiral organohalides. Then, laboratory studies provided experimental evidences to further link enantioselective attenuation of chiral organohalides to specific functional microorganisms and enzymes, revealing mechanistic insights into the enantioselective microbial transformation processes. Particularly, a few amino acid residues in the functional enzymes could play a key role in mediating the enantioselectivity at the molecular level. Finally, major challenges and further developments toward an in-depth understanding of the enantioselective microbial transformation of chiral organohalides are identified and discussed.

Characterization of Tibetan Soil As a Source or Sink of Atmospheric Persistent Organic Pollutants: Seasonal Shift and Impact of Global Warming

Background soils are reservoirs of persistent organic pollutants (POPs). After decades of reduced primary emissions, it is now possible that the POPs contained in these reservoirs are being remobilized because of climate warming. However, a comprehensive investigation into the remobilization of POPs from background soil on the largest and highest plateau on Earth, the Tibetan Plateau (TP), is lacking. In this study, a sampling campaign was carried out on the TP at three background sites with different land cover types (forest, meadow and desert). Field measurements of the air-soil exchange of POPs showed that previous prediction using empirical models overestimated the values of the soil-air partitioning coefficient ( K_SA), especially for chemicals with K_OA > 9. The direction of exchange for γ-HCH, HCB, and PCB-28 overlapped with the air-soil equilibrium range, but with a tendency for volatilization. Their emission fluxes were 720, 2935, and 538 pg m^-2 day^-1, respectively, and were similar in extent to those observed for background Arctic soil in Norway. Nam Co and Ngari are also permafrost regions, and most chemicals at these two sites exhibited volatilization. This is the first result showing that permafrost can also emit POPs. Seasonally, we found that chemicals tended to be re-emitted from soils to the atmosphere in winter and deposited from the air to the soil in summer. This finding is opposite to most previous results, possibly because of the higher air-soil concentration gradient caused by the prevailing transport of POPs in summer. Climate warming exerts a strong influence on air-soil exchange, with an increase of 1 °C in ambient temperature likely leading to an increase of Tibetan atmospheric inventories of POPs by 60-400%.

Air monitoring of new and legacy POPs in the Group of Latin America and Caribbean (GRULAC) region

A special initiative in the Global Atmospheric Passive Sampling (GAPS) Network was implemented to provide information on new and emerging persistent organic pollutants (POPs) in the Group of Latin America and Caribbean (GRULAC) region. Regional-scale atmospheric concentrations of the new and emerging POPs hexachlorobutadiene (HCBD), pentachloroanisole (PCA) and dicofol indicators (breakdown products) are reported for the first time. HCBD was detected in similar concentrations at all location types (<20-120 pg/m³). PCA had elevated concentrations at the urban site Concepción (Chile) of 49-222 pg/m³, with concentrations ranging <1-8.5 pg/m³ at the other sites in this study. Dicofol indicators were detected at the agricultural site of Sonora (Mexico) at concentrations ranging 30-117 pg/m³. Legacy POPs, including a range of organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs), were also monitored to compare regional atmospheric concentrations over a decade of monitoring under the GAPS Network. γ-hexachlorocyclohexane (HCH) and the endosulfans significantly decreased (p < 0.05) from 2005 to 2015, suggesting regional levels are decreasing. However, there were no significant changes for the other legacy POPs monitored, likely a reflection of the persistency and slow decline of environmental levels of these POPs. For the more volatile OCs, atmospheric concentrations derived from polyurethane foam (PUF) (acting as an equilibrium sampler) and sorbent impregnated PUF (SIP) (acting as a linear phase sampler), were compared. The complimentary methods show a good agreement of within a factor of 2-3, and areas for future studies to improve this agreement are further discussed.

Biodegradability and biodegradation pathways of chlorinated cyclodiene insecticides by soil fungi

An aerobic dieldrin-degrading fungus, Mucor racemosus strain DDF, and two aerobic endosulfan-degrading fungal strains, Mortierella sp. strains W8 and Cm1-45, were isolated from soil contaminated with organochlorine pesticides. Strain DDF degraded more than 90% dieldrin during 10-days of incubation at 25°C and showed the production of a small amount of aldrin trans-diol. Moreover, strain DDF reduced levels of aldrin trans-diol while producing unknown metabolites that were determined to be aldrin trans-diol exo- and endo-phosphates. On the other hand, Mortierella sp. strains W8 and Cm1-45 degraded more than 70% and 50% of α and β-endosulfan, respectively, over 28 days at 25°C, in liquid cultures containing initial concentrations of 8.2 µM of each substance. Only a small amount of endosulfan sulfate, a persistent metabolite, was detected in the both cultures, while these strains could not degrade endosulfan sulfate when this compound was provided as the initial substrate. Both strains generate endosulfan diol as a first step in the degradation of endosulfan, then undergo further conversion to endosulfan lactone.

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.

Estimation of p,p'-DDT degradation in soil by modeling and constraining hydrological and biogeochemical controls

Despite not being used for decades in most countries, DDT remains ubiquitous in soils due to its persistence and intense past usage. Because of this it is still a pollutant of high global concern. Assessing long term dissipation of DDT from this reservoir is fundamental to understand future environmental and human exposure. Despite a large research effort, key properties controlling fate in soil (in particular, the degradation half-life (τ_soil)) are far from being fully quantified. This paper describes a case study in a large central European catchment where hundreds of measurements of p,p'-DDT concentrations in air, soil, river water and sediment are available for the last two decades. The goal was to deliver an integrated estimation of τ_soil by constraining a state-of-the-art hydrobiogeochemical-multimedia fate model of the catchment against the full body of empirical data available for this area. The INCA-Contaminants model was used for this scope. Good predictive performance against an (external) dataset of water and sediment concentrations was achieved with partitioning properties taken from the literature and τ_soil estimates obtained from forcing the model against empirical historical data of p,p'-DDT in the catchment multicompartments. This approach allowed estimation of p,p'-DDT degradation in soil after taking adequate consideration of losses due to runoff and volatilization. Estimated τ_soil ranged over 3000-3800 days. Degradation was the most important loss process, accounting on a yearly basis for more than 90% of the total dissipation. The total dissipation flux from the catchment soils was one order of magnitude higher than the total current atmospheric input estimated from atmospheric concentrations, suggesting that the bulk of p,p'-DDT currently being remobilized or lost is essentially that accumulated over two decades ago.

Organochlorine pesticides in the sedimentary core of the southern Tibetan Plateau: The missing pieces induced by lateral remobilization

The sedimentary core in remote alpine lakes has been recognized as an ideal proxy to reconstruct the emission and air deposition histories of persistent organic pollutants (POPs). Nevertheless, POPs formerly stored in a catchment might also contribute to the variation in the lake sediment by lateral remobilization. In this study, to reveal the relative importance of lateral remobilization, we measured the vertical profiles and isomeric ratios of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and endosulfan in a dated sedimentary core collected from Lake Yamzho Yumco in the southern Tibetan Plateau. In addition to the flux peaks in the 1970s corresponding to the heavy atmospheric deposition of DDTs and HCHs, these pollutants' fluxes displayed rebounds in the flood periods, with characteristic low ratios of DDT/DDE (α-/β-HCH). This might indicate a massive remobilization of "weathered" pesticides from catchment soil to the lake because of strong hydro-dynamics. Moreover, the relative contribution of lateral remobilization to the lake sediment in the past decades was recognized through the correlation between DDT/DDE (α-/β-HCH) ratios and ∑DDT (∑HCH) fluxes. The results showed that the lateral remobilization contributed to 20-42% of the total fluxes. This study discriminated the air deposition from the contribution of lateral remobilization, which improves current understanding of the vertical POPs profiles in the sedimentary core.

Simultaneous degradation of refractory organic pesticide and bioelectricity generation in a soil microbial fuel cell with different conditions

In this study, the soil microbial fuel cells (MFCs) were constructed based on sandy soil to remove the refractory organic pesticide hexachlorobenzene (HCB) in topsoil by a simple method. The construction of membraneless single-chamber soil MFCs by setting up the cathode- and the anode-activated carbon, inoculating the sludge and adding the co-substrates can promote HCB removal significantly. The results showed that HCB removal efficiencies in the soils contaminated with 40, 80  and 200 mg/kg were 71.14%, 62.15% and 50.06%, respectively, which were 18.65%, 18.46% and 19.17% higher than the control, respectively. The electricity generation of soil MFCs in different HCB concentrations was analyzed. The highest power density reached was 70.8 mW/m², and an internal resistance of approximately 960 Ω was obtained when an external resistance loading of 1000 Ω was connected. Meanwhile, the influences of temperature, substrate species and substrate concentrations on soil MFCs initial electricity production were investigated. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) into the soil MFCs system contributed to the improvement in HCB removal efficiency.

Sequestration of HCHs and DDTs in sediments in Dongting Lake of China with multiwalled carbon nanotubes: implication for in situ sequestration

Organochlorine pesticides (OCPs) in sediments could be released into water, posing great threats to human health and organisms. In this study, the treatment effectiveness of in situ sequestration of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in sediments was explored using multiwalled carbon nanotubes (MWCNTs) as adsorbents. Physicochemical tests (aqueous equilibrium concentrations, semipermeable membrane device (SPMD) uptake, and quiescent flux to overlying water) were conducted to evaluate the sequestration effectiveness of MWCNTs. Compared to the control, the MWCNT-treated sediments showed great reductions of HCHs and DDTs in aqueous equilibrium concentrations, SPMD uptake, and quiescent flux to overlying water. And the effects of dose of MWCNTs, diameter of MWCNTs, and contact time between MWCNTs and sediments on sequestration effectiveness were studied. Increased dose, decreased MWCNT diameter, and prolonged contact time resulted in a better sequestration effectiveness. The results indicated that the addition of MWCNTs to sediment could reduce the content of HCHs and DDTs released from sediments, reducing bioavailability of HCHs and DDTs and minimizing risks to ecosystem and human. MWCNTs have potential applications as adsorbents for in situ treatment of OCP-contaminated sediments.

Development of a Model Immunoassay Utilizing Monoclonal Antibodies of Different Specificities for Quantitative Determination of Dieldrin and Heptachlors in Their Mixtures

The presence of dieldrin and heptachlor residues in cucurbitaceous crops at concentrations exceeding the limits set by the Japanese Food Sanitation Law constitutes a serious problem. To prevent accumulation of these residues in cucurbitaceous crops, development of high-throughput analysis methods for the detection of contaminants in the soil before cultivation is required. This study aimed to develop a model immunoassay using new monoclonal antibodies (MAbs) to quantitatively determine dieldrin and heptachlor contents in their mixtures. Three distinctive MAbs were obtained from mice immunized with the respective immunogens. MAb DrA-04 showed high reactivity toward dieldrin with ca. 20% cross-reactivity toward heptachlors. MAb DrC-02 displayed a similar reactivity toward dieldrin and heptachlors. The specificity and sensitivity of MAbs DrA-04 and DrC-02 were largely unaffected by the composition ratio of heptachlors in a mixture. Six standard mixtures with different dieldrin and heptachlor contents were prepared. Concentrations of dieldrin and heptachlors in standard mixtures, calculated on the basis of an immunoassay with MAbs DrA-04 and DrC-02, were 88.1-125 and 96.2-115% of the theoretical values, respectively, revealing excellent sensitivity and specificity of this assay. The developed method paves the way for a facile and rapid quantitative determination of chlorinated cyclodiene pesticides in soil.

Local organochlorine pesticide concentrations in soil put into a global perspective

In this work, agricultural and background soil concentrations of p,p'-DDT, p,p'-DDE, HCB, α-, β- and γ-HCH from 1993 to 2012 were collected from 73 peer-reviewed publications, and analysed statistically. For the period 2003-2012 and for all chemicals, the mean concentration in agricultural soil is significantly higher than the concentration in background soil. In addition to the statistical analysis, concentrations of p,p'-DDT and α-HCH in soils were calculated with a global environmental fate and transport model. A decrease in the mean soil concentration from the first decade to the second was observed with the model, but this decrease is not visible in the measured concentrations, which could result from ongoing use of p,p'-DDT and α-HCH Furthermore, modelled background soil concentrations are generally lower than measurements. This implies that background soil may have received p,p'-DDT and α-HCH through additional routes not described by the model such as spray drift.

Employing Solid Phase Microextraction as Extraction Tool for Pesticide Residues in Traditional Medicinal Plants

HS-SPME was optimised using blank plant sample for analysis of organochlorine pesticides (OCPs) of varying polarities in selected medicinal plants obtained from northern part of Botswana, where OCPs such as DDT and endosulfan have been historically applied to control disease carrying vectors (mosquitos and tsetse fly). The optimised SPME parameters were used to isolate analytes from root samples of five medicinal plants obtained from Maun and Kasane, Botswana. The final analytes determination was done with a gas chromatograph equipped with GC-ECD and analyte was confirmed using electron ionisation mass spectrometer (GC-MS). Dieldrin was the only pesticide detected and confirmed with MS in the Terminalia sericea sample obtained from Kasane. The method was validated and the analyte recoveries ranged from 69.58 ± 7.20 to 113 ± 15.44%, with RSDs ranging from 1.19 to 17.97%. The method indicated good linearity (R² > 0.9900) in the range of 2 to 100 ng g^-1. The method also proved to be sensitive with low limits of detection (LODs) ranging from 0.48 ± 0.16 to 1.50 ± 0.50 ng g^-1. It can be concluded that SPME was successfully utilized as a sampling and extraction tool for pesticides of diverse polarities in root samples of medicinal plants.

The influence of tree species composition on the storage and mobility of semivolatile organic compounds in forest soils

Soil contamination with PCBs and PAHs in adjacent forest plots, characterized by a distinct composition in tree species (spruce only, mixed and beech only), was analyzed to investigate the influence of ecosystem type on contaminant mobility in soil under very similar climate and exposure conditions. Physical-chemical properties and contaminant concentrations in litter (L), organic (F, H) and mineral (A, B) soil horizons were analyzed. Contaminant distribution in the soil core varied both in relation to forest type and contaminant group/properties. Contaminant mobility in soil was assessed by examining the ratios of total organic carbon (TOC)-standardized concentrations across soil horizons (Enrichment factors, EFTOC) and the relationship between EFTOC and the octanol-water equilibrium partitioning coefficient (KOW). Contaminant distribution appeared to be highly unsteady, with pedogenic/biogeochemical drivers controlling contaminant mobility in organic layers and leaching controlling accumulation in mineral layers. Lighter PCBs displayed higher mobility in all forest types primarily controlled by leaching and, to a minor extent, diffusion. Pedogenic processes controlling the formation of soil horizons were found to be crucial drivers of PAHs and heavier PCBs distribution. All contaminants appeared to be more mobile in the soil of the broadleaved plot, followed by mixed canopy and spruce forest. Increasing proportion of deciduous broadleaf species in the forest can thus lead to faster degradation or the faster leaching of PAHs and PCBs. The composition of humic substances was found to be a better descriptor of contaminant concentration than TOC.

4,4'-DDE and Endosulfan Levels in Agricultural Soils of the Çukurova Region, Mediterranean Turkey

Mediterranean Turkey has long been at the forefront of Turkish agriculture and the use of organochlorinated pesticides (OCPs) in this area rose considerably between the 1940s and 1980s. This study aimed to determine OCP residue levels in agricultural soils collected from the Mersin and Adana Districts, Çukurova Basin in Mediterranean Turkey. Most soil samples were contaminated with one, or both, of two OCP metabolites; 4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE) and endosulfan sulfate. 4,4'-DDE occurred in 27 of the 29 samples and ranged from 6 to 1090 µg kg(-1)-dry soil (ds)(-1), while six samples contained endosulfan sulfate ranging between 82 and 1226 µg kg(-1)-ds(-1). Generally, horticultural and corn-planted soils contained only 4,4'-DDE, whereas greenhouse cultivation appeared to accumulate both residues. This study indicated that 4,4'-DDE occurred above acceptable levels of risk in agricultural soils of Mersin District and further studies on the qualitative and quantitative assessment of OCPs in other agricultural regions with intensive pesticide use are necessary to fully understand the impact of OCPs on agricultural soil in Turkey.

Spatial distribution, source apportionment and ecological risk assessment of residual organochlorine pesticides (OCPs) in the Himalayas

The Indian Himalayan Region (IHR) is one of the important mountain ecosystems among the global mountain system which support wide variety of flora, fauna, human communities and cultural diversities. Surface soil samples collected from IHR were analysed for 23 organochlorine pesticides (OCPs). The concentration of ∑OCPs ranged from 0.28 to 2143.96 ng/g (mean 221.54 ng/g) and was mostly dominated by DDTs. The concentration of ∑DDTs ranged from 0.28 to 2126.94 ng/g (mean 216.65 ng/g). Other OCPs such as HCHs, endosulfan and heptachlor, Aldrin and dieldrin were detected in lower concentration in IHR. Their concentrations in soil samples ranged from ND to 2.79 ng/g for HCHs, ND to 2.83 ng/g for endosulfans, NDto 1.46 ng/g for heptachlor, ND to 2.12 ng/g for Aldrin and ND to 1.81 ng/g for dieldrin. Spatial distribution of OCPs suggested prevalence of DDTs and HCHs at Guwahati and Itanagar, respectively. The close relationship between total organic carbon (TOC) and part of OCP compounds (especially α- and γ-HCH) indicated the important role of TOC in accumulation, binding and persistence of OCP in soil. Diagnostic ratio of DDT metabolites and HCH isomers showed DDT contamination is due to recent application of technical DDT and dicofol, and HCH contamination was due to mixture of technical HCH and lindane source. This was further confirmed by principal component analysis. Ecological risk analysis of OCP residues in soil samples concluded the moderate to severe contamination of soil.

Chiral xenobiotics bioaccumulations and environmental health prospectives

The chiral xenobiotics are very dangerous for all of us due to the different enantioselective toxicities of the enantiomers. Besides, these have different enantioselective bioaccumulations and behaviors in our body and other organisms. It is of urgent need to understand the enantioselective bioaccumulations, toxicities, and the health hazards of the chiral xenobiotics. The present article describes the classification, sources of contamination, distribution, enantioselective bioaccumulation, and the toxicities of the chiral xenobiotics. Besides, the efforts are also made to discuss the prevention and remedial measures of the havoc of the chiral xenobiotics. The challenges of the chiral xenobiotics have also been highlighted. Finally, future prospectives are also discussed.

Assessing the effects of urbanization on the environment with soil legacy and current-use insecticides: a case study in the Pearl River Delta, China

To evaluate the impacts of anthropogenic events on the rapid urbanized environment, the levels of legacy organochlorine pesticides (OCPs) and current-use insecticides (CUPs), i.e., dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), pyrethroids and organophosphates in soil of the Pearl River Delta (PRD) and surrounding areas were examined. Spatial concentration distributions of legacy OCPs and CUPs shared similar patterns, with higher concentrations occurred in the central PRD with more urbanization level than that in the PRD's surrounding areas. Furthermore, relatively higher concentrations of OCPs and CUPs were found in the residency land than in other land-use types, which may be attributed to land-use change under rapid urbanization. Moderate correlations between gross domestic production or population density and insecticide levels in fifteen administrative districts indicated that insecticide spatial distributions may be driven by economic prosperity. The soil-air diffusive exchanges of DDTs and HCHs demonstrated that soil was a sink of atmospheric o,p'-DDE, o,p'-DDD, p,p'-DDD and o,p'-DDT, and was a secondary source of HCHs and p,p'-DDT to atmosphere. The soil inventories of DDTs and HCHs (100 ± 134 and 83 ± 70 tons) were expected to decrease to half of their current values after 18 and 13 years, respectively, whereas the amounts of pyrethroids and organophosphates (39 and 6.2 tons) in soil were estimated to decrease after 4 and 2 years and then increase to 87 and 1.0 tons after 100 years. In this scenario, local residents in the PRD and surrounding areas will expose to the high health risk for pyrethroids by 2109. Strict ban on the use of technical DDTs and HCHs and proper training of famers to use insecticides may be the most effective ways to alleviate the health effect of soil contamination.

Stereoselective quantitation of haloxyfop in environment samples and enantioselective degradation in soils

The chiral separation of haloxyfop enantiomers was first performed on (R, R) Whelk-O1 chiral column (pirkle type) by high-performance liquid chromatography (HPLC). Chromatographic conditions such as mobile phase composition and column temperature were optimized, and the best resolution was obtained using hexane/n-propanol (98/2) with Rs value of 3.43. Chiral residue analysis methods for haloxyfop enantiomers in environmental matrices, such as soil and water, were developed with recoveries ranging from 85.95% to 104.25%. The results showed that these methods were effective enough for detecting the residual enantiomers environmental matrices. The behavior of haloxyfop in four soils was studied and the enantioselective degradation was found with enantiomer fraction values ranging from 0.058 to 0.61. The research work was extremely useful for investigating the fate of individual enantiomers in environment, the mechanism of the stereoselective behaviors, and the risk assessment of chiral pesticide.

Occurrence and possible sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Chao River, China

To analyze the possible influence of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) on Miyun Reservoir, 14 soil samples and 1 water sample were collected along the Chao River, which is the main upstream source of the reservoir. A total of 24 kinds of OCPs and 12 kinds of dioxin-like PCBs were measured. Results showed that the ∑OCPs concentration ranged from 0.8145 to 16.8524 ng g(-1), and the ∑PCBs ranged from 0.0039 to 0.0365 ng g(-1). Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the three dominant kinds of OCPs in this region, and the majority component of the PCBs was PCB-118 in both water and soil samples. The OCP ratios suggest that new inputs of lindane exist. DDTs mainly come from old technical inputs. HCHs might come from a new application of lindane, which highlights the importance of prohibited pesticide control. OCP concentrations were higher in corn fields and orchards and lower in forest lands and grasslands, which indicated that OCPs were very much influenced by human activities. The proportion of PCB components in this study area suggested that they mainly came from atmospheric deposition.

River otters as biomonitors for organochlorine pesticides, PCBs, and PBDEs in Illinois

The North American river otter (Lontra canadensis) is a biomonitor for organohalogenated compounds (OHCs) associated with a wide range of deleterious health effects in wildlife and humans. We determined concentrations of twenty OHCs in livers of 23 river otters salvaged by the Illinois Department of Natural Resources from 2009 to 2011, determined sex-dependent distribution of OHCs, and compared our results to the reported concentrations of four OHCs in Illinois river otters from 1984 to 1989. Since these contaminants have been banned for over 30 years, we predicted smaller mean concentrations than those previously reported in Illinois otters. We detected eleven of twenty OHCs; PCBs (polychlorinated biphenyls), dieldrin, and 4,4'-DDE (dichlorodiphenyldichloroethylene) were present in the greatest mean concentrations. We report the largest mean concentration of dieldrin to date in the liver of North American river otters (mean: 174, range: 14.4-534 parts per billion wet wt [ppb]). Mean PCB concentrations were significantly higher in males (mean: 851; range: 30-3450 ppb) than females (mean: 282; range: 40-850 ppb; p=0.04). Mean concentrations of dieldrin were greater than those detected in otters from 1984 to 1989 (mean: 90; range: 30-130 ppb; p<0.05). Our results suggest OHC exposure remains a concern. Future research in Illinois should focus on evaluating OHCs exposures, particularly dieldrin, at the watershed level.

Spatial and seasonal variations of pesticide contamination in agricultural soils and crops sample from an intensive horticulture area of Hohhot, North-West China

The spatial variability and temporal trend in concentrations of the organochlorine pesticides (OCPs), hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), in soils and agricultural corps were investigated on an intensive horticulture area in Hohhot, North-West China, from 2008 to 2011. The most frequently found and abundant pesticides were the metabolites of DDT (p,p'-DDE, p,p'-DDT, o,p'-DDT and p,p'-DDD). Total DDT concentrations ranged from ND (not detectable) to 507.41 ng/g and were higher than the concentration of total HCHs measured for the range of 4.84-281.44 ng/g. There were significantly positive correlations between the ∑DDT and ∑HCH concentrations (r (2)>0.74) in soils, but no significant correlation was found between the concentrations of OCPs in soils and clay content while a relatively strong correlation was found between total OCP concentrations and total organic carbon (TOC). β-HCH was the main isomer of HCHs, and was detected in all samples; the maximum proportion of β-HCH compared to ∑HCHs (mean value 54%) was found, suggesting its persistence. The α/γ-HCH ratio was between 0.89 and 5.39, which signified the combined influence of technical HCHs and lindane. Low p,p'-DDE/p,p'-DDT in N1, N3 and N9 were found, reflecting the fresh input of DDTs, while the relatively high o,p'-DDT/p,p'-DDT ratios indicated the agricultural application of dicofol. Ratios of DDT/(DDE+DDD) in soils do not indicate recent inputs of DDT into Hohhot farmland soil environment. Seasonal variations of OCPs featured higher concentrations in autumn and lower concentrations in spring. This was likely associated with their temperature-driven re-volatilization and application of dicofol in late spring.

Selected organochlorine pesticides (OCPs) in surface soils from three major states from the northeastern part of India

Eighty-two surface soil samples were collected from forest, grassland, tea estate, wildlife sanctuary, wetland, and roadside areas from the northeastern states of India, viz., Tripura, Manipur, and Assam. Thirteen different organochlorine pesticides (OCPs) were detected from background soils using gas chromatography electron capture detector. Manipur soils were found to be with higher concentration of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfan followed by Tripura and Assam. The spearman correlation coefficient shows significant correlation between HCHs, DDTs, and endosulfan isomers (r (2) > 0.5 and p < 0.05). Additionally, α-HCH, δ-HCH, o,p'-DDE, and endosulfan-sulfate shows good correlation with total organic carbon in soil (r (2) = 0.5, p = 0.05), indicating that the soil organic matter could enhance adsorption of these compounds, also demonstrating that the present OCPs in the background soil were from similar source. Further principal component analysis evaluates that most of the higher volatile compounds where clustered together in soil. However, after comparing with different states of Indian soil samples, the concentrations of OCPs in the present study areas are much lower and comparable with background soil across the globe.

Influence of climate and land use change on spatially resolved volatilization of persistent organic pollutants (POPs) from background soils

The subject of this study is the assessment of the influence of climate and land use change on the potential re-emission of organochlorine pesticides (OCPs) from background and agricultural soils. A deterministic spatially and temporally explicit model of the air-surface exchange was created, fed with distributed data of soil and atmospheric concentrations from real measurements, and run under various scenarios of temperature and land use change for a case study area representative of central European conditions. To describe land use influence, some important features were implemented including effect of plowing, influence of land cover, temperature of soil, and seasonal changes of air layer stability. Results show that volatilization of pesticides from soil largely exceeded dry gas deposition in most of the area. Agricultural soils accounted for more than 90% of the total re-emissions both because of the generally higher soil fugacities (higher loads of chemicals and relatively low organic carbon content), but also due to physical characteristics and land management practices enhancing the dynamics of the exchange. An increase of 1 °C in air temperature produced an increase of 8% in the averaged total volatilization flux, however this effect can be neutralized by a change of land use of 10% of the arable lands to grassland or forest, which is consistent with projected land use change in Europe. This suggests that future assessment of climate impact on POP fate and distribution should take into consideration land use aspects.

Organochlorine pesticides in soil, moss and tree-bark from North-Eastern Romania

Concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDE) have been determined in soil, mosses and tree bark samples collected from the same locations in North-Eastern Romania (region of Moldavia). PCBs and PBDEs were under the limit of quantification in all investigated samples. OCPs were the principal pollutants found in the analysed samples. In soil, moss and tree bark samples, DDT together with its metabolites, was the most abundant OCP ranging between 4.4-79, 5.8-95 and 11-440 ng g(-1) in the individual matrices, followed by HCH isomers with levels between 1.1-9.8, 8.9-130 and 12-130 ng g(-1) in soil, moss and bark respectively. To distinguish between the previous and current pollutant input and preferential biodegradation of DDT metabolites, the degradation ratios were calculated between the parent substances and their metabolites (DDT and HCH isomers). The investigation indicates no important pollution sources near sampling sites and reveals that OCPs originate mainly from long-range air transport processes and through atmospheric deposition of isomers volatilised from secondary sources. Discriminant function analysis was performed to determine whether OCPs uptake differ among the three matrices (soil, moss and tree bark). A good separation was observed between tree bark and the other two matrices. The most redundant variable appears to be p,p'-DDE (R(2)=0.336), while the most informative variable seems to be o,p'-DDT (R(2)=0.0361). Significant correlations were found between bark and moss concentrations for most α-HCH and p,p'-DDD (p<0.01). We have also investigated the enantiomeric signature of α-HCH. For bark and moss, EF values suggest preferential degradation of the (-)α-HCH enantiomer.

Perfluorinated compounds and organochlorine pesticides in soils around Huaihe River: a heavily contaminated watershed in Central China

Perfluorinated compounds (PFCs) and organochlorine pesticides (OCPs) were analyzed in surface soils along the Huaihe River. Sixteen target PFCs and nine OCPs were quantified in soils from a region of intensive industrial and agricultural development. Concentrations of PFCs and OCPs ranged from less than the limit of detection (LOD) to 1.22 ng/g and 3.63 to 227 ng/g, respectively. Contamination by OCPs was more serious than that of PFCs, which was consistent with the fact that OCPs were widely used in agriculture of the district while there was no known production or application of PFCs in the study area. The predominant PFCs in soils were PFOA and PFOS with concentrations that ranged from <LOD to 0.20 ng/g and <LOD to 0.21 ng/g, respectively. Among the three groups of OCPs, average concentrations of HCHs, DDTs, and HCB were 4.7, 23.7, and 1.4 ng/g, respectively. Results of principal component analysis revealed relatively weak associations between concentrations of PFCs and those of OCPs, while concentrations of OCPs exhibited similar patterns of distributions. Among the mainstream and five tributaries, the highest concentrations of PFCs were observed along the Pihe River, while the highest concentrations of OCPs occurred along the Xifeihe River. In general, concentrations of PFCs were evenly distributed, while those of OCPs exhibited relatively greater spatial differences.

Organochlorine pesticides and polychlorinated biphenyls in soils surrounding the Tanggu Chemical Industrial District of Tianjin, China

The spatial distribution of persistent organic pollutants (POPs) was examined in soils surrounding the Tanggu Chemical Industrial District in Tianjin, China. The concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), hexachlorobenzenes (HCBs), and polychlorinated biphenyls (PCBs) were determined in 70 surface soils using accelerated solvent extraction and gas chromatography with electron capture detection. The results showed that the ranges of ∑HCH, ∑DDT, ΣHCB, and ∑PCB concentrations in soils were 2.1-12,549 μg kg(-1) (average, 965 μg kg(-1)), n.d.-2,033 μg kg(-1) (average, 88.4 μg kg(-1)), n.d.-1,924 μg kg(-1) (average, 349 μg kg(-1)), and n.d.-373 μg kg(-1) (average, 46.2 μg kg(-1)), respectively. Of these, HCHs were the dominant POPs, accounting for 75 % of the total organochlorine pesticide (OCP) residues. Overall, the spatial distribution of OCP concentrations showed a decreasing trend from the center of the Tanggu District to the surrounding areas. Two major pollution sources were Tianjin Dagu Chemical Co., Ltd. in the district center and the Tianjin Chemical Plant in Hangu District. In contrast, PCB concentrations were relatively high in the Haihe estuary to the east and low to the west of the study area. Component analysis of OCPs in these soils showed that they mainly came from industrial point sources. Compared with soils in other regions, soil DDT pollution was at a medium level in the Tanggu Chemical Industrial District, but associated HCH, HCB, and PCB pollution was relatively heavy. By multivariate statistical analyses, Tianjin Dagu Chemical Co., Ltd. was recognized as the main source of POPs, and soil properties were clarified to play an important role on the distribution and composition of POPs, especially the organic carbon content.

Enhanced solubilization and desorption of organochlorine pesticides (OCPs) from soil by oil-swollen micelles formed with a nonionic surfactant

The effect of oil-swollen micelles formed with nonionic surfactant polyoxyethylene sorbitan monooleate (Tween 80), cosurfactant 1-pentanol, and linseed oil on the solubilization and desorption of organochlorine pesticides (OCPs) including DDT and γ-HCH from both loam soil and clay soil were investigated. Results showed that the solubilizing capacities of oil-swollen micelles were dependent on the critical micelle concentration (CMC) of Tween 80. Once the concentrations of oil-swollen micelles exceeded the CMC of Tween 80, the oil-swollen micelles exhibited much higher solubilizing capacity than empty Tween 80 micelles for the two OCPs. Desorption tests revealed that oil-swollen micelles could successfully enhance desorption of OCPs from both loam soil and clay soil. However, compared with the efficiencies achieved by empty Tween 80 micelles, oil-swollen micelles exhibited their superiority to desorb OCPs only in loam soil-water system while was less effective in clay soil-water system. Distribution of Tween 80, 1-pentanol and linseed oil in soil-water system revealed that the difference in the sorption behavior of linseed oil onto the two soils is responsible for the different effects of oil-swollen micelles on the desorption of OCPs in loam soil and clay soil systems. Therefore, oil-swollen micelles formed with nonionic surfactant Tween 80 are better candidates over empty micelle counterparts to desorb OCPs from soil with relatively lower sorption capacity for oil fraction, which may consequently enhance the availability of OCPs in soil environment during remediation processes of contaminated soil.

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.

Historical contamination of the Anacostia River, Washington, D.C

The tidal Anacostia River in Washington DC has long been impacted by various sources of chemical pollution over the past 200 years. To explore more recent inputs of various chemicals, six sediment cores were collected for dating and chemical analysis in the downstream section of the tidal Anacostia River. Profiles of contaminants in sediment cores can be useful in determining management direction and effectiveness of pollution controls over time. There were two main objectives for this investigation: (1) determine current sediment contaminant levels; (2) determine a historical perspective of the sediment changes in contamination using (137)Cs and (210)Pb dating. The determination of an age-depth relationship using (210)Pb and (137)Cs dating gave somewhat different results, suggesting that the assumptions of (210)Pb dating were not met. Using the (137)Cs horizon allowed an assignment of approximate sediment accumulation rates and hence an age-depth relationship to contaminant events in the upper portions of the cores. Total PAHs showed higher concentrations at depth and lower surface concentrations. In the upper sections, PAHs were a mixture of combustion and petrogenic sources, while at depth the signature appeared to be of natural origins. Total PCBs, DDTs and chlordane concentrations showed a maximum in recent sediments, decreasing towards the surface. PCBs had lower molecular weight congeners near the surface and higher molecular weights at depth. A phthalate ester, DEHP, appeared in the mid 1940-1950s, and decreased towards the surface. Trace elements fell roughly into three groups. Fe, Mn, and As were in approximately constant proportion to Al, except in some deeper, sandy sediments, where they showed enrichments linked to redox conditions. Ag, Cd, Cu, Hg, Pb, and Zn had low concentrations in the deepest sediments, high concentrations at mid-depths, and declines to intermediate levels at the surface. Ni and Cr followed neither of these patterns closely. We observed that many contaminants appeared in the Anacostia sediments at various times, and reached relatively high concentrations in the past, but are now showing declines in loadings. In some cases, such as PCBs, DDT, chlordane, and Pb from leaded gasoline, these declines can be clearly linked to the discontinuation of their use for environmental reasons. For other contaminants (e.g., PAHs, DEHP, selected metals) these declines are more likely the result of changes in production, usage and waste control.

Applicability of Corbicula as a bioindicator for monitoring organochlorine pesticides in fresh and brackish waters

The applicability of Corbicula as a bioindicator for monitoring organochlorine pesticides (OCPs) in fresh and brackish waters is presented here. Differences in isomer compositions and OCP bioaccumulation levels were analyzed in western Japan and the Pearl River Delta (PRD) in China. Isomer compositions of DDTs, chlordanes, and HCHs were significantly different between the two areas because of their different historical uses and property of the chemicals. This is represented by the (DDE + DDD)/DDT ratio in Corbicula, ranging 4.9-39 in western Japan and 1.1-2.4 in the PRD. However, isomer compositions in Corbicula reflected those in water, and the different patterns in Corbicula likely reflected the usage history. Concentrations of dissolved oxygen, suspended solids, and volatile suspended solids in water, and the difference in species did not influence OCP bioaccumulative levels in Corbicula when conducting biomonitoring. These levels are likely similar to those in Mytilus galloprovincialis. Therefore, Corbicula could be an appropriate bioindicator for monitoring OCPs in fresh and brackish waters.