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Historical Trends and Chiral Signatures of Organochlorine Pesticides in Sediments of Qiandao Lake, China

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This study investigated the enantiomeric and depth profiles of organochlorine pesticides (OCPs) accumulated in the sediments of Qiandao Lake, China. OCP concentrations in sediments have increased gradually since the early 1960s, when extensive OCPs application in China began. Concentrations reached maximum levels after 1992, this timing corresponds with the emerging of the "new" usage of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethane (DDTs). In addition, the degradation of chiral OCPs were enantioselective, resulting in enriched (-)-enantiomers for α-HCH and o, p'-DDD. However, both preferential depletions of (-) enantiomers and (+) enantiomers were observed for o, p'-DDT. This outcome was indicated by enantiomer fractions (EF) values either greater or less than 0.5.
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Bull Environ Contam Toxicol (2017) 99:350–353
DOI 10.1007/s00128-017-2131-5
1 3
Historical Trends andChiral Signatures ofOrganochlorine
Pesticides inSediments ofQiandao Lake, China
HuayunYang1· WeidongLi1· QiLiu2
Received: 14 March 2017 / Accepted: 20 June 2017 / Published online: 22 June 2017
© Springer Science+Business Media, LLC 2017
urban runoff, spillage, disposal and chemical weathering.
Vertical profiles of residues in dated sediment cores have
long been used as historical records of pollution (Blumer
and Youngblood 1975). For many compounds, there is a
subsurface peak in the sediment profile corresponding to
the period of peak production and/or usage, followed by a
slow decline to the sediment–water interface.
Several organochlorine pesticides (OCPs) are manufac-
tured and used as racemic mixtures. However, microorgan-
isms can selectively degrade one enantiomer over the other,
resulting in non-racemic signatures that are retained during
transport processes. Studying chiral signatures can help
assess OCPs releases, deposition and redistribution in the
region (Ali etal. 2003). Reports since the early 1990s have
documented the presence of non-racemic pesticide residues
in the environment (Aigner etal. 1998; Kurt-Karakus etal.
2005; Garrison 2006). This study investigated the histori-
cal progression of OCPs contamination in the sediments of
Qiandao Lake, China. The study also determined the Enan-
tiomeric fractions (EF) values of α-HCH, o, p’-DDT, o, p’-
DDD, trans- and cis-chlorodane (TC and CC).
Materials andMethods
Sampling for this study was done in March 2013. Sediment
surface samples, each 5-cm in depth, were collected using
a stainless steel grab sampler. Sediment core samples were
collected using a gravity corer. All sediment samples were
freeze-dried, homogenized, passed through a 63-μm sieve
and then stored in pre-cleaned dark glass bottles at −18 °C
prior to analysis.
The sediment core was dated using a 210Pb-dating
method described elsewhere (Zhang et al. 2002). Briefly,
the 210Pb activity in sediment samples was determined by
Abstract This study investigated the enantiomeric and
depth profiles of organochlorine pesticides (OCPs) accu-
mulated in the sediments of Qiandao Lake, China. OCP
concentrations in sediments have increased gradually since
the early 1960s, when extensive OCPs application in China
began. Concentrations reached maximum levels after 1992,
this timing corresponds with the emerging of the “new”
usage of hexachlorocyclohexanes (HCHs) and dichlorodi-
phenyltrichloroethane (DDTs). In addition, the degradation
of chiral OCPs were enantioselective, resulting in enriched
(−)-enantiomers for α-HCH and o, p-DDD. However, both
preferential depletions of (−) enantiomers and (+) enan-
tiomers were observed for o, p-DDT. This outcome was
indicated by enantiomer fractions (EF) values either greater
or less than 0.5.
Keywords Organochlorine pesticides (OCPs)·
Sediment· Chiral· Qiandao Lake
Sediments serve as a sink for many pollutants that enter the
aquatic environment (Sahu etal. 2009). The impact of this
pollution is particularly critical in creek ecosystems, such
as Qiandao Lake, China. This area is landlocked, and the
environment is relatively stagnant. Trace and toxic elements
are brought into the creek in the form of dissolved and par-
ticulate inputs from industrial effluents, sewage discharge,
* Huayun Yang
1 Qianjiang College ofHangzhou Normal University,
Hangzhou310012, China
2 College ofLife andEnvironmental Science, Hangzhou
Normal University, Hangzhou310012, China
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... On the other hand, significant preferential accumulation of (-)-o,p'-DDT (EF ≈ 0.13) was observed in many sediment samples collected from Yueqing and Sanmen Bay [57]. Similar preference was observed in Qiandao Lake sediment [73]. In comparison, comparatively faster attenuation of (-)-o,p'-DDT was observed in soil samples collected from Pearl River Delta [35]. ...
... α−HCH as the only chiral isomer of HCH is a major component of the technical HCH (55-80% in weight), which has been extensively found in worldwide air, water, soil and sediment samples [16,23,25,75,76]. As shown in Fig. 1B, preferential attenuation of (+)-α−HCH (EF < 0.5) was observed in sediment samples of Qiandao Lake, Yueqing Bay and Sanmen Bay [57,73]. Similar preferential depletion of (+)-α−HCH (EF = 0.39) was observed in surficial sediments of Northwater Polynya [77]. ...
... Later on, similar enantiomeric enrichment of the (-)-α−HCH was observed in other aerobic microcosms established with surface seawater or soil samples [108], in line with results obtained in field studies [34,78]. All these evidences working together suggested the important role of aerobic microorganisms in the enantioselective HCH degradation in surface environments (Fig.1B) [57,59,73]. Nonetheless, information on the microbial community composition of these microcosms, as well as taxonomy of the key functional microorganisms, remain scarce [84,110]. ...
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.
... The degradation rates of four stereoisomers of difenoconazole were significantly lower in an anaerobic soil environment than an aerobic soil environment (Dong et al., 2013). Many previous studies indicated that aerobic microorganisms played an important role in enantioselective degradation in surface environments (Yang et al., 2010;Yuan et al., 2014;Yang et al., 2017). ...
Bitertanol is a widely used chiral triazole fungicide. The stereoselective environmental behavior and biological effects of bitertanol are not clear. The present study evaluated the stereoselectivity of bitertanol, including its degradation in five typical soils (under laboratory controlled aerobic, anaerobic and sterilization conditions), metabolism in rat liver microsomes (RLM; in vitro), and the endocrine disruption effects on the estrogen receptor (ER) and thyroid hormone receptor (TR) using reporter gene assays. The results indicated that (1S,2R)-bitertanol and (1R,2S)-bitertanol had faster degradation rates in soil than the other stereoisomers. The half-lives of four bitertanol stereoisomers ranged from 9.1 d to 86.6 d in different soils under different conditions. (1S,2R)-bitertanol was preferentially metabolized in RLM. The molecular docking results confirmed the in vitro experiments that (1S,2R)-bitertanol had shortest binding distances and lowest energies with cytochrome P450 enzymes (CYPs). Four bitertanol stereoisomers showed stereoselective antagonistic effects on ER. Additionally, (1S,2R)-bitertanol and (1R,2S)-bitertanol exhibited antagonistic effects on TR. These results suggest that the use of pure (1S,2R)-bitertanol instead of the commercial stereoisomer mix, may help reduce environmental pollution and biological toxicity.
Full-text available
Most of the pollutants are present in the environment as a mixture of their chiral isomers. Studies have revealed that these isomers have an enantioselective distribution, metabolism, and toxicity of these pollutants, in the light of the toxicity of their individual chiral isomers. We describe here, the different chiral isomers of common pollutants, their metabolism and toxicity, and methods for their separation and quantification. POLLUTION of the environment, one of the most pressing problems of our age, has now reached a level that it poses a potential threat not only to the health of people but also to entire populations. Among various environmental pollutants, organic contaminants, i.e. pesticides, phenols, plasticizers and polyaromatic hydrocarbons are the most toxic due to their carcinogenic nature 1–3 . The monitoring of these pollut-ants in the environment is essential and important. Many reports are available on the analysis of organic pollutants but these do not distinguish which mirror images of pollutants are present and which is harmful in the case of chiral pollut-ants. Scientists and other regulatory authorities are in demand for tackling associated problems in these areas.
In the summers of 1993 and 1994, air and water samples were taken in the Bering and Chukchi Seas and on a transect across the polar cap to the Greenland Sea to measure the air-sea gas exchange of hexachlorocyclohexanes (HCHs) and the enantiomers of alpha-HCH. Atmospheric concentrations of alpha- and gamma-HCH have decreased threefold or more since the mid-1980s, whereas concentrations in surface water have shown little change. The saturation state of surface water (water/air fugacity ratio) was determined from the air and water concentrations of HCHs and their Henry's law constants as a function of temperature. Fugacity ratios >1.0 indicated net volatilization of alpha-HCH in all regions except the Greenland Sea, where concentrations in air and water were close to equilibrium. Net deposition of gamma-HCH in the Chukchi Sea was indicated by fugacity ratios
Chiral organochlorine pesticides were examined in soils collected in 1989 from six farms in the Fraser Valley, British Columbia. Concentrations of pesticide residues were 1−2 orders of magnitude higher in muck soils (27−56% organic matter) than in silt loams (3−7% organic matter). Enantiomeric composition of α-hexachlorocyclohexane residues in muck soils indicated preferential breakdown of the (−) enantiomer, whereas α-hexachlorocyclohexane in the silt loams was racemic. Five of the soils contained racemic o,p‘-DDT, but the (+) enantiomer was selectively lost in one silt loam soil. No enantioselective breakdown of cis- or trans-chlordane was found in any of the soils, but nonracemic traces of oxychlordane were found in one silt loam and three muck soils. Enantiomeric composition of heptachlor and heptachlor exo-epoxide in muck soils indicated loss of (−)-heptachlor and production of (+)-heptachlor exo-epoxide, suggesting that the metabolism of these two compounds in soil may be more complex than a simple conversion of heptachlor to heptachlor exo-epoxide. Keywords: Organochlorine pesticides; chiral pesticides; soils; Fraser Valley; British Columbia
Past research has shown that selective enzymatic degradation of enantiomers by microorganisms does occur. This work was done to determine concentrations and enantiomeric ratios of several chiral organochlorine pesticides in soils from the Corn Belt region. Quantitative analysis was done by gas chromatography with electron capture detection using a DB-5 column. Concentrations were determined for 11 compounds (o,p‘-DDT, p,p‘-DDT, p,p‘-DDD, p,p‘-DDE, cis-chlordane, trans-chlordane, heptachlor, heptachlor epoxide, dieldrin, α-hexachlorocyclohexane, and trans-nonachlor) in 38 agricultural soils and two garden soils. Residues were log-normally distributed, and geometric mean values (ng/g dry wt) were ∑DDT = 9.6, ∑chlordane = 1.4, dieldrin = 1.0, and HEPX = 0.58. HEPT and α-HCH were found infrequently. Concentrations in two garden soils were similar to those for agricultural soils. Enantioselective analysis was done by gas chromatography−mass spectrometry with chiral-phase capillary columns. Evidence of enantioselective degradation of OCs was found in 30 soils. o,p‘-DDT and OXY showed differing enantiomeric patterns in different soils, while (+)TC, (−)CC, and (−)HEPX were in excess in all soils with nonracemic compositions. The two garden soils showed similar patterns of degradation. No correlations were found between ER and pesticide concentration or ER and % TOC for any of the compounds.
A high-resolution gas chromatographic method is described which allows the determination of the enantiomeric ratio of alpha-hexachlorohexane (HCH) in environmental samples within 18 min. A stationary phase with low bleeding was obtained by diluting permethylated heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin in a OH-terminated polysiloxane. It allowed temperature programming with detection in the low-picogram range using electron capture detection and high-resolution mass spectrometry. The separation method is compatible with standard sample cleanup procedures, which facilitate the reanalysis of stored sample extracts. Detailed information is given about the preparation of the separation capillary, the analytical parameters, and the reproducibility of the quantification. Furthermore, the applicability of the method to different environmental samples is demonstrated. First results, which showed an excess of alpha(+)-HCH in all analyzed sample matrices, are discussed.
Organochlorine pesticides (OCPs) were measured in the atmosphere over the period of December 2003–December 2004 at four sampling sites in Guangzhou and Hong Kong. Gas phase and particle phase concentrations of 8 OCP species, including trans-chlordane (t-CHL), cis-chlordane (c-CHL), p,p 0 -DDT, p,p 0 -DDE, o,p 0 -DDT, a-endosulfan, a-and g-hexachlorocyclohexane (HCH), were studied. OCPs were found predominantly in the gas phase in all seasons. t-CHL, c-CHL, o,p 0 -DDT, p,p 0 -DDT and a-endosulfan had significantly (po0.001) higher concentrations than other OCPs, with mean values (gas+particle) typically ranging from 103 to 1440 pg m À3 . In general, the concentrations of OCPs in summer were higher than that in winter, except for a-HCH which showed no clear seasonal pattern. Higher levels of g-HCH and o,p 0 -DDT found in Guangzhou could be attributed to the present usage of lindane and dicofol in the Pearl River Delta (PRD) region. The very high concentrations of p,p 0 -DDT and a-endosulfan were observed at all sampling sites. The results of 7 days air back trajectory analysis indicated that the unusual high p,p 0 -DDT levels in summer in both cities could be related to the seasonal usage of DDT containing antifouling paints for fishing ships in the upwind seaports of the region. The high concentrations of a-endosulfan in winter in the study area suggested an atmospheric transport by the winter monsoon from the East China, where endosulfan is being used as insecticide in cotton fields. The consistency of the seasonal variation of concentrations and isomeric ratios of DDTs and a-endosulfan with the alternation of winter monsoon and summer monsoon suggested that the Asian monsoon plays an important role in the long-range atmospheric transport of OCPs.
Water and snow samples were collected at Amituk Lake on Cornwallis Island to investigate the enantioselective degradation of alpha-hexachlorocyclohexane (alpha-HCH) in the Arctic. The two enantiomers were separated by gas chromatography on permethylated cyclodextrin capillary columns. The enantio- meric ratio (ER = (+)alpha-HCH/(-)alpha-HCH) for an alpha-HCH standard was 1.00 +/- 0.005, which is in excellent agreement with a theoretical ER of 1.00 for unmetabolized alpha-HCH. ERs of snow samples were racemic (0.98 +/- 0.03). Degradation was found in Amituk Lake at 15-21 m where ERs were 0.77 +/- 0.004; however, stream runoff and lake outflow ERs varied considerably during the study. ERs of the outflow traced the meltwater running over the surface of the lake, being close to streamwater values during peak runoff and returning to deep lake water values during low flow. Streamwater ERs decreased within a few weeks of snowmelt and showed a large variability (0.97-0.62), which may be due to the differences in temperature and amount of suspended sediments. The rapid enantioselective breakdown of alpha-HCH suggests that the ability of arctic microbial systems to degrade organic contaminants is greater than commonly thought.
The spatial distributions and chiral signals of organochlorine pesticides (OCPs) in surface sediments from Yueqing Bay and Sanmen Bay, East China Sea were investigated. The total OCPs concentrations ranged from 2.11 to 18.15 ng g(-1) dry weight for all the sampling stations. HCHs and DDTs were dominant, although trans-chlorodane/cis-chlorodane were also observed in some sites. The predominant beta-HCH and the alpha-HCH/gamma-HCH ratios indicated that the residues of HCHs in these places mainly originated from the historical usage of technical HCH. However, the ratios of (DDE+DDD)/DDT reflected a cocktail input pattern of fresh and weathered DDTs. Based on ERL/ERM guidelines, p,p'-DDT and SigmaDDT posed a small risk to the bottom-dwelling consumers, while p,p'-DDD, p,p'-DDE and Sigmachlorodane were not found at concentrations expected to adversely affect sediment biota. Enantiomeric analysis showed that the degradation of chiral OCPs was enantioselective, resulting in enrichment of (-)-enantiomers for alpha-HCH, o,p'-DDT and o,p'-DDD in all samples. These results implied that the sediment quality guidelines of chiral OCPs should be reassessed using concentrations of their individual enantiomers.
Surface soils and sediments were collected in Toronto, Canada to investigate the concentrations and enantiomeric signatures of urban versus rural locations. Samples were analyzed for polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs) and organochlorine pesticides (OCs). In soils, the sum of 10 PCB congeners (Sigma PCB 28, 52, 95, 101, 118, 136, 138, 149, 153, 180) and 15 PAHs (Sigma PAHs) ranged from 0.76-58 to 58-3200 ng g(-1), respectively. The most abundant OCs detected were DDTs, followed by chlordanes and endosulfans. Sigma PAHs exhibited an urban-rural gradient of up to 60 times but a gradient was not observed for Sigma PCBs and OCs which may reflect local sources of these chemicals. In sediments, Sigma PCBs and Sigma PAHs ranged from 0.03-23 ng g(-1) to 42-3300 ng g(-1), respectively. Sigma PCBs, Sigma PAHs, chlordanes and DDTs exhibited weak urban-rural gradients. Chiral signatures of PCB 95, 136, 149, trans-chlordane (TC), cis-chlordane (CC) and o,p-DDT were characterized to study the enantiomeric degradation in urban versus rural areas and its relation to contaminant levels. Supplementary to these data, we also report on the chiral signatures of PCBs in UK lake sediments from a variety of urban and rural locations. The extent of enantiomeric degradation was expressed as the enantiomeric excess (EE%) which is defined as 100x(E1-E2)/(E1+E2), where E1 is always the most abundant enantiomer and E2 is the least abundant enantiomer. The EE% of PCB 149 in the UK sediments was negatively correlated (p<0.05) with Sigma PAHs suggesting either more recent emissions of this PCB congener in the more contaminated urban locations and hence a more racemic signature or less enantiomeric degradation of the congener in more contaminated urban soils. However, no significant correlation was observed between EE% of any of the chiral chemicals and contaminant levels in the Toronto soils.