Spatial and temporal distribution of chiral pesticides in Calanus spp. from three Arctic fjords

A review on the enantioselective distribution and toxicity of chiral pesticides in aquatic environment

Chiral pesticides account for about 40% of the total pesticides. In the process of using pesticides, it will inevitably flow into the surface water and even penetrate into the groundwater through surface runoff and other means, as a consequence, it affects the water environment. Although the enantiomers of chiral pesticides have the same physical and chemical properties, their distribution, ratio, metabolism, toxicity, etc. in the organism are often different, and sometimes even show completely opposite biological activities. In this article, the selective fate of different types of chiral pesticides such as organochlorine, organophosphorus, triazole, pyrethroid and other chiral pesticides in natural water bodies and sediments, acute toxicity to aquatic organisms, chronic toxicity and other aspects are summarized to further reflect the risks between the enantiomers of chiral pesticides to non-target organisms in the water environment. In this review, we hope to further explore its harm to human society through the study of the toxicity of chiral pesticide enantiomers, so as to provide data support and theoretical basis for the development and production of biochemical pesticides.

Influences of climate change on long-term time series of persistent organic pollutants (POPs) in Arctic and Antarctic biota

Time series of contaminants in the Arctic are an important instrument to detect emerging issues and to monitor the effectiveness of chemicals regulation, based on the assumption of a direct reflection of changes in primary emissions. Climate change has the potential to influence these time trends, through direct physical and chemical processes and/or changes in ecosystems. This study was part of an assessment of the Arctic Monitoring and Assessment Programme (AMAP), analysing potential links between changes in climate-related physical and biological variables and time trends of persistent organic pollutants (POPs) in Arctic biota, with some additional information from the Antarctic. Several correlative relationships were identified between POP temporal trends in freshwater and marine biota and physical climate parameters such as oscillation indices, sea-ice coverage, temperature and precipitation, although the mechanisms behind these observations remain poorly understood. Biological data indicate changes in the diet and trophic level of some species, especially seabirds and polar bears, with consequences for their POP exposure. Studies from the Antarctic highlight increased POP availability after iceberg calving. Including physical and/or biological parameters in the POP time trend analysis has led to small deviations in some declining trends, but did generally not change the overall direction of the trend. In addition, regional and temporary perturbations occurred. Effects on POP time trends appear to have been more pronounced in recent years and to show time lags, suggesting that climate-related effects on the long time series might be gaining importance.

The influence of global climate change on accumulation and toxicity of persistent organic pollutants and chemicals of emerging concern in Arctic food webs

This review summarizes current understanding of how climate change-driven physical and ecological processes influence the levels of persistent organic pollutants (POPs) and contaminants of emerging Arctic concern (CEACs) in Arctic biota and food webs. The review also highlights how climate change may interact with other stressors to impact contaminant toxicity, and the utility of modeling and newer research tools in closing knowledge gaps on climate change-contaminant interactions. Permafrost thaw is influencing the concentrations of POPs in freshwater ecosystems. Physical climate parameters, including climate oscillation indices, precipitation, water salinity, sea ice age, and sea ice quality show statistical associations with POPs concentrations in multiple Arctic biota. Northward range-shifting species can act as biovectors for POPs and CEACs into Arctic marine food webs. Shifts in trophic position can alter POPs concentrations in populations of Arctic species. Reductions in body condition are associated with increases in levels of POPs in some biota. Although collectively understudied, multiple stressors, including contaminants and climate change, may act to cumulatively impact some populations of Arctic biota. Models are useful for predicting the net result of various contrasting climate-driven processes on POP and CEAC exposures; however, for some parameters, especially food web changes, insufficient data exists with which to populate such models. In addition to the impact of global regulations on POP levels in Arctic biota, this review demonstrates that there are various direct and indirect mechanisms by which climate change can influence contaminant exposure, accumulation, and effects; therefore, it is important to attribute POP variations to the actual contributing factors to inform future regulations and policies. To do so, a broad range of habitats, species, and processes must be considered for a thorough understanding and interpretation of the consequences to the distribution, accumulation, and effects of environmental contaminants. Given the complex interactions between climate change, contaminants, and ecosystems, it is important to plan for long-term, integrated pan-Arctic monitoring of key biota and ecosystems, and to collect ancillary data, including information on climate-related parameters, local meteorology, ecology, and physiology, and when possible, behavior, when carrying out research on POPs and CEACs in biota and food webs of the Arctic.

POPs in Antarctic ecosystems: is climate change affecting their temporal trends?

Climate change is affecting Antarctica and the Southern Ocean and effects have been already reported for the abiotic compartments of the ecosystems, e.g. ice loss and iceberg calving. Global warming can alter also the distribution of persistent organic pollutant (POPs) both at a global scale and in the Antarctic Region, due to their physical-chemical characteristics. Effects of climate changes have been already reported on feeding behaviour and reproductive process of organisms. Another consequence for organisms includes the POP bioaccumulation. Here we review the literature reporting the linkage between recorded effects of climate changes and POP bioaccumulation in resident marine Antarctic species (fish and penguins). Notwithstanding Antarctica is a final sink for persistent contaminants due to the extreme cold climate, a general decreasing POP trend has been observed for some POPs. Their concentrations in biota are reported to be linked to ice melting and large iceberg calving; the peculiar marine Antarctic ecosystems and the pelagic-benthic coupling may also contribute to alterations in the bioaccumulation processes. These effects are similar in polar regions, although the comparison with the Arctic biota is not possible due to the lack of data in the Antarctic Region. It remains an open question if the POP amount accumulated in the Antarctic ecosystems is decreasing or not.

Uptake and Metabolization of HCH Isomers in Trees Examined over an Annual Growth Period by Compound-Specific Isotope Analysis and Enantiomer Fractionation

To understand the role of plants for natural attenuation, a field study was conducted to characterize the fate of HCH in trees over an annual growth period using compound-specific isotope analysis and enantiomer fractionation. Stable and slightly higher δ¹³C and δ³⁷Cl values of HCH of host soil samples compared to the muck (consisting nearly exclusively of HCH) revealed that masking isotope effects caused by the limited bioavailability may underestimate the real extent of HCH transformation in soil. In contrast, an increase of δ¹³C and δ³⁷Cl values in trees indicated the transformation of HCH. A large variability of δ¹³C and δ³⁷Cl values in trees over the growth period was observed, representing different transformation extents among different growth times, which is further supported by the shift of the enantiomer fraction (EF), indicating the preferential transformation of enantiomers also varied over the different growth periods. Based on dual-element isotope analysis, different predominant transformation mechanisms were observed during the growing seasons. Our observation implies that plants are acting as biological pumps driving a cycle of uptake and metabolization of HCH and refeed during littering to soil catalyzing their transformation. The changes of the transformation mechanism in different seasons have implications for phytoscreening and shed new light on phytoremediation of HCH at field sites.

Is Glacial Meltwater a Secondary Source of Legacy Contaminants to Arctic Coastal Food Webs?

Climate change-driven increases in air and sea temperatures are rapidly thawing the Arctic cryosphere with potential for remobilization and accumulation of legacy persistent organic pollutants (POPs) in adjacent coastal food webs. Here, we present concentrations of selected POPs in zooplankton (spatially and seasonally), as well as zoobenthos and sculpin (spatially) from Isfjorden, Svalbard. Herbivorous zooplankton contaminant concentrations were highest in May [e.g., ∑polychlorinated biphenyls (₈PCB); 4.43, 95% CI: 2.72-6.3 ng/g lipid weight], coinciding with the final stages of the spring phytoplankton bloom, and lowest in August (∑₈PCB; 1.6, 95% CI: 1.29-1.92 ng/g lipid weight) when zooplankton lipid content was highest, and the fjord was heavily impacted by sediment-laden terrestrial inputs. Slightly increasing concentrations of α-hexachlorocyclohexane (α-HCH) in zooplankton from June (1.18, 95% CI: 1.06-1.29 ng/g lipid weight) to August (1.57, 95% CI: 1.44-1.71 ng/g lipid weight), alongside a higher percentage of α-HCH enantiomeric fractions closer to racemic ranges, indicate that glacial meltwater is a secondary source of α-HCH to fjord zooplankton in late summer. Except for α-HCH, terrestrial inputs were generally associated with reduced POP concentrations in zooplankton, suggesting that increased glacial melt is not likely to significantly increase exposure of legacy POPs in coastal fauna.

Bioaccumulation of PCBs, HCB and PAHs in the summer plankton from West Spitsbergen fjords

Concentrations of seven polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and twelve polycyclic aromatic hydrocarbons (PAHs) were examined in plankton collected in summer from different Arctic fjords (Hornsund, Kongsfjorden, Adventfjorden). The levels of all target contaminants in arctic protists have been analyzed for the first time. This is also the first report on PAH levels in arctic fjords zooplankton. ∑7 PCB, HCB and ∑12 PAH concentrations were up to 3.58 ng/g w.w., 0.28 ng/g w.w. and 249 ng/g w.w., respectively. Among the zooplankton species, the highest concentrations of the most analyzed contaminants were detected in Themisto abyssorum. This could be explained by the predatory feeding strategy of this species. The importance of diet was confirmed by the low concentrations of contaminants detected in the herbivorous copepod Calanus spp. Depending on contaminant, bioaccumulation occurred in 50 to 100% studied cases. Studies have shown significant biomagnification of PCBs and PAHs in zooplankton predator-prey pairs.

Dual C-Cl Isotope Analysis for Characterizing the Reductive Dechlorination of α- and γ-Hexachlorocyclohexane by Two Dehalococcoides mccartyi Strains and an Enrichment Culture

Hexachlorocyclohexanes (HCHs) are persistent organic contaminants that threaten human health. Microbial reductive dehalogenation is one of the most important attenuation processes in contaminated environments. This study investigated carbon and chlorine isotope fractionation of α- and γ-HCH during the reductive dehalogenation by three anaerobic cultures. The presence of tetrachlorocyclohexene (TeCCH) indicated that reductive dichloroelimination was the first step of bond cleavage. Isotope enrichment factors (ε_C and ε_Cl) were derived from the transformation of γ-HCH (ε_C, from -4.0 ± 0.5 to -4.4 ± 0.6 ‰; ε_Cl, from -2.9 ± 0.4 to -3.3 ± 0.4 ‰) and α-HCH (ε_C, from -2.4 ± 0.2 to -3.0 ± 0.4 ‰; ε_Cl, from -1.4 ± 0.3 to -1.8 ± 0.2 ‰). During α-HCH transformation, no enantioselectivity was observed, and similar ε_c values were obtained for both enantiomers. The correlation of ¹³C and ³⁷Cl fractionation (Λ = Δδ¹³C/Δδ³⁷Cl ≈ ε_C/ε_Cl) of γ-HCH (from 1.1 ± 0.3 to 1.2 ± 0.1) indicates similar bond cleavage during the reductive dichloroelimination by the three cultures, similar to α-HCH (1.7 ± 0.2 to 2.0 ± 0.3). The different isotope fractionation patterns during reductive dichloroelimination and dehydrochlorination indicates that dual-element stable isotope analysis can potentially be used to evaluate HCH transformation pathways at contaminated field sites.

Isotope fractionation approach to characterize the reactive transport processes governing the fate of hexachlorocyclohexanes at a contaminated site in India

The transformation processes of hexachlorocyclohexane isomers (HCHs) from production sites of Lindane across the landscape and along the food web were studied as an example to understand the fate of POPs in the environment. Therefore, we studied the concentration and isotope composition of HCHs in different matrices in the vicinity of a dumpsite and a chemical plant producing HCHs in India. Carbon isotope compositions (δ¹³C) of HCHs and the enantiomer fraction (EF) of α-HCH were used as indicators to characterize in situ degradation in soil, groundwater, and sediment as well as along the food web. The HCHs were detected in plants growing on contaminated soil. Elevated concentrations of HCHs were found in a number of crops, which indicates an important transfer pathway of HCHs entering food webs. The EF value of α-HCH and the δ¹³C signature of HCHs indicated that degradation processes occurred in the rhizosphere or within the plants potentially attenuating the contamination of HCHs. The isotope enrichment of HCHs in dung and milk samples showed that degradation of HCHs may take place in the digestive track of cow and buffalo as well as during their metabolism. The δ¹³C of HCHs was used to analyze the potential dispersion routes on the landscape scale in order to understand the reactive transport pathways starting at the source of HCHs. In this study, the potential of carbon isotope fractionation and EF for characterizing uptake of HCHs into plants and accumulation in the food web were examined. To the best of our knowledge, this is the first study using the combination of stable isotope fractionation and EF to track the reactive transport processes in a complex environment including the food web.

Polychlorinated biphenyls (PCBs) as sentinels for the elucidation of Arctic environmental change processes: a comprehensive review combined with ArcRisk project results

Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropogenic influences on Arctic environmental change. We present an overview of studies on PCBs in the Arctic and combine these with the findings from ArcRisk-a major European Union-funded project aimed at examining the effects of climate change on the transport of contaminants to and their behaviour of in the Arctic-to provide a case study on the behaviour and impact of PCBs over time in the Arctic. PCBs in the Arctic have shown declining trends in the environment over the last few decades. Atmospheric long-range transport from secondary and primary sources is the major input of PCBs to the Arctic region. Modelling of the atmospheric PCB composition and behaviour showed some increases in environmental concentrations in a warmer Arctic, but the general decline in PCB levels is still the most prominent feature. 'Within-Arctic' processing of PCBs will be affected by climate change-related processes such as changing wet deposition. These in turn will influence biological exposure and uptake of PCBs. The pan-Arctic rivers draining large Arctic/sub-Arctic catchments provide a significant source of PCBs to the Arctic Ocean, although changes in hydrology/sediment transport combined with a changing marine environment remain areas of uncertainty with regard to PCB fate. Indirect effects of climate change on human exposure, such as a changing diet will influence and possibly reduce PCB exposure for indigenous peoples. Body burdens of PCBs have declined since the 1980s and are predicted to decline further.

Enantioselective apoptosis induced by individual isomers of bifenthrin in Hep G2 cells

Bifenthrin (BF) has been used in racemate for agricultural purposes against soil insects, leading to increased inputs into soil environments. However, most of the studies about the toxicology research on BF were performed in its racemic form. The aim of the present study was to evaluate the enantiomer-specific cis-BF-induced apoptosis and intracellular reactive oxygen species (ROS) generation on human hepatocarcinoma cells (Hep G2). The results of cell viability assay and cytoflow assay indicated an obvious enantioselective hepatocyte toxicity of 1S-cis-BF in Hep G2 cells. 1S-cis-BF also induced ROS production, up-regulated Bax protein expression and down-regulated Bcl-2 expression levels. The present study suggested that enantioselective toxicity should be evaluated on currently used chiral pesticides, such as synthetic pyrethroids.