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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.

LinA-type1 and LinA-type2 are two well-characterized variants of the enzyme ‘hexachlorocyclohexane (HCH)-dehydrochlorinase’. They differ from each other at ten amino acid positions and exhibit differing enantioselectivity for the transformation of the (–) and (+) enantiomers of α-HCH. Amino acids responsible for this enantioselectivity, however, are not known. An in silico docking analysis identified four amino acids (K20, L96, A131, and T133) in LinA-type1 that could be involved in selective binding of the substrates. Experimental studies with constructed mutant enzymes revealed that a combined presence of three amino acid changes in LinA-type1, i.e. K20Q, L96C, and A131G, caused a reversal in its preference from the (–) to the (+) enantiomer of α-HCH. This preference was enhanced by the additional amino acid change T133 M. Presence of these four changes also caused the reversal of enantioselectivity of LinA-type1 for δ-HCH, and β-, γ-, and δ-pentachlorocyclohexens. Thus, the residues K20, L96, A131, and T133 in LinA-type1 and the residues Q20, C96, G131, and M133 in LinA-type 2 appear to be important determinants for the enantioselectivity of LinA enzymes.

Purpose The scope of this article was to investigate the spatial and temporal variability of enantiomeric fractions (EFs) of persistent organic pollutants (POPs) in soil compared to the uncertainty of the analytical data. Materials and methods Soil samples were taken with high spatial resolution at two sites in Czech Republic in 2008 to investigate variability on a small spatial scale. In addition, composite soil samples were taken from ten sites in 2005 and 2008 to investigate temporal variations. All samples were analysed for a suite of soil properties as well as concentrations and EFs of polychlorinated biphenyl (PCB) -95, PCB-132 and PCB-149; α-hexachlorocyclohexane (HCH); o , p′ -dichlorodiphenyltrichloroethane (DDT); and o , p′ -dichlorodiphenyldichloroethane (DDD). Results and discussion Median EFs of PCB-95 and PCB-149, α-HCH, o , p′ -DDT and o , p′ -DDD did not change significantly on the sites sampled in 2005 and again in 2008, while PCB-132 changed from EF = 0.38 to EF = 0.53. The sampling methodology is therefore very important, and composite samples will not be the best option if enantioselective degradation processes are investigated. Non-racemic EFs of POPs in the subsampled sites in 2008 were correlated to soil parameters, such as total organic carbon (TOC), total nitrogen and humic acids. These parameters are site specific and might vary on a small scale. This can explain why certain soil parameters are reported as significantly correlated with non-racemic EFs of chiral POPs in some studies, but not always in other similar studies. Conclusions While composite samples may still represent the overall prevailing EF range, they are not ideally suited to study enantiomeric degradation processes, which are taking place at a relative small scale, depending on the heterogeneity of soil parameters such as TOC, total organic nitrogen (TON) and humic acids.

Interest in the analysis of alpha-hexachlorocyclohexane (alpha-HCH) enantiomers as an alternative or complementary approach to elucidating isomer ratios of alpha/gamma-HCH has grown in recent years because it can provide useful information to evaluate the influence of different degradation and transformation processes. In this paper, a simple and rapid method for the determination of alpha-HCH enantiomers in biota samples is described. The method developed consists of ultrasonic extraction, sulfuric acid silica gel cleanup, solid-phase extraction (SPE) column fractionation, and final determination with chiral high-resolution gas chromatography. Ultrasonic extraction greatly shortens the extraction process time, and the sulfuric acid silica gel and SPE cleanup perfectly remove lipids and other interference compounds in the lipid-rich samples. The method is found to be simple, less time-consuming, and easy to operate, thus providing a useful alternative method to assess the enantioselective breakdown of alpha-HCH in biota system.

Concentration and transport of organic pollutants by Arctic sea ice may expose ice-associated fauna to high contaminant concentrations relative to pelagic organisms. Zooplankton and ice-associated amphipods were collected in the marginal ice zone near Svalbard to investigate whether habitat, diet and geographic sampling site influenced their organochlorine burden. Organochlorine concentrations were low in both zooplankton (Calanus hyperboreus,Thysanoessa inermis,Parathemisto libellula, Chaetognatha) and ice-associated amphipods (Apherusa glacialis,Gammarus wilkitzkii,Onisimusspp.), from 0.3 ng g–1lipid weighttrans-chlordane inA. glacialisto 36.9 ng g–1lipid weight hexachlorobenzene (HCB) inG. wilkitzkii. Diet accounted for most of the explained organochlorine variance, followed by habitat and geographic sampling site. The concentrations were higher in carnivores (P. libellula, Chaetognatha,G. wilkitzkii,Onisimusspp.) than in herbivores (C. hyperboreus,T. inermis,A. glacialis). In comparison with zooplankton, ice fauna had high levels of organochlorines with high residence time in surface layers (hexachlorocyclohexane [HCH] and HCB), whereas compounds with higher particle affinity did not differ between habitats. This was attributed to the sea ice serving as a habitat that keeps ice fauna in the surface layer, rather than to the release of contaminants from the sea ice itself. HCHs were the only compounds that differed geographically. Higher α-/γ-HCH ratios inC. hyperboreusandA. glacialisfrom the Greenland Sea relative to North of Svalbard, are consistent with the geographic patterns in HCH levels reported for air, water, ringed sealsPhoca hispidaand polar bearsUrsus maritimus.