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[Display omitted] • The MAC-ZIF-8 was successfully synthesized for the immobilization of CRL. • The biosensors can be used to detect methyl parathion and chlornitrofen residues. • The biosensors demonstrated wide linear range, low LOD and good recovery rate. • The biosensors showed good reusability after scanning continuously for 100 times. The high toxicity and bioaccumulation effects of nitroaromatic pesticides and their serious environmental risks have led to a sharp increase in public concern about pesticide residues. Present work developed a direct, rapid, sensitive and reliable Candida rugosa lipase (CRL)@ the ordered macro-microporous ZIF-8 (MAC-ZIF-8) nanofibers biosensor (CRL@MAC-ZIF-8 nanofibers) for methyl parathion and chlornitrofen residues detection in lake water. The biosensors fabricated by the CRL@MAC-ZIF-8 nanofibers demonstrated wide linear range for both methyl parathion (0.5–114 µM) and chlornitrofen (1–40 µM) detection. The biosensors also demonstrated good reusability for methyl parathion detection with retainment of more than 97% of its initial response after scanning continuously for 100 times. During 1 month storage stability test at 4 °C, the fabricated biosensor demonstrated excellent stability for methyl parathion detection with retainment of 86%-100% of its initial response. Meanwhile, the biosensors also demonstrated good recovery rates when the biosensors were used to detect methyl parathion and chlornitrofen residues in lake water sample. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of a fungicide, chlornitrofen ( Cnf ), was carried out on a renewable silver amalgam film electrode (Hg(Ag)FE). A new and sensitive square-wave adsorptive stripping voltammetric (SWAdSV) method of its determination was developed. The cathodic signal of Cnf at about − 0.6 V vs. Ag/AgCl/KCl was investigated in Britton–Robinson (B–R) buffer, pH 8.8. Under optimized conditions, a linear calibration curve in the concentration range from 1.0 × 10 − 7 mol L − 1 to 1.5 × 10 − 6 mol L − 1 was obtained. The proposed SWAdSV method exhibited acceptable analytical performance in terms of the detection limit ( LOD = 3.0 × 10 − 8 mol L − 1 ). The satisfactory repeatability of the voltammetric response for the different concentrations of Cnf was obtained ( RSD = 1.1% ÷ 6.6%). Additionally, the practical applicability of the method was verified by the quantitative analysis of micromolar concentrations of Cnf in Warta River water samples. The corrosivity of pesticide Cnf towards stainless steel was tested using electrochemical techniques. [ABSTRACT FROM AUTHOR]

Abstract: In Japan, Ayase River is one of the most polluted rivers by PCDDs, PCDFs and dioxin-like PCBs, which are referred to as dioxins in this paper. The water samples of the river were collected once per month for a year, and dioxins were analyzed to examine the dioxin sources and their contributions to toxic equivalent (TEQ). The WHO-2006 TEQs ranged from 0.26 to 7.0pg-TEQL−1 and the average was 2.7pg-TEQL−1; eight of 12 samples exceeded the environmental quality standard in Japan (1.0pg-TEQL−1). The TEQ value was high during the irrigation period from May to August. The most part of the dioxins in the river water existed in suspended solids (SS) and it seemed that the river received water with highly-dioxin-contaminated SS in the irrigation period. The homologue profiles of the water samples suggested that the dioxins were influenced by pentachlorophenol (PCP) and chlornitrofen (CNP) formulations which were widely used as herbicides for the paddy fields in Japan. According to TEQ apportionment estimated by using indicative congeners, the TEQ was mainly contributed by PCP. Moreover, it was also shown that the TEQ contributions of PCP and CNP formulations increased along with the increase of the total TEQ and the TEQ contribution was dominated by these herbicides during the irrigation period. Therefore, it was concluded that the herbicides-originated dioxins run off from the paddy fields into the river during the irrigation period and increased the dioxins level in the river water. The result from the principal component analysis was consistent with these conclusions. [Copyright &y& Elsevier]

Abstract: Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs) contained in the smoke generated from rice straw burning in post-harvest paddy fields in Japan were analyzed to determine their congener profiles. Both the apportionment of toxic equivalent (TEQ) by using indicative congeners and the comparison of the homolog profiles showed that the PCDDs/PCDFs/DL-PCBs present in the rice-straw smoke were greatly influenced by those present as impurities in pentachlorophenol (PCP) and chlornitrofen (CNP, 4-nitrophenyl-2,4,6-trichlorophenyl ether) formulations that had been widely used as herbicides in paddy fields in Japan. Further, in order to investigate the effects of paddy-field soil on the PCDDs/PCDFs/DL-PCBs present in rice-straw smoke, PCDD/PCDF/DL-PCB homolog profiles of rice straw, rice-straw smoke and paddy-field soil were compared. Rice-straw smoke was generated by burning rice straw on a stainless-steel tray in a laboratory. The results suggested that the herbicides-originated PCDDs/PCDFs/DL-PCBs and the atmospheric PCDDs/PCDFs/DL-PCBs contributed predominantly to the presence of PCDDs/PCDFs/DL-PCBs in the rice-straw smoke while the contribution of PCDDs/PCDFs/DL-PCBs formed during rice straw burning was relatively minimal. The major sources of the PCDDs/PCDFs/DL-PCBs found in the rice-straw smoke were attributed primarily to the paddy-field soil adhered to the rice straw surface and secondarily to the air taken by the rice straw. The principal component analysis supported these conclusions. It is concluded that rice straw burning at paddy fields acts as a driving force in the transfer of PCDDs/PCDFs/DL-PCBs from paddy-field soil to the atmosphere. [Copyright &y& Elsevier]

We investigated dioxin concentrations in freshwater fish in Japan by standardizing species to detect subtle decreasing trends of dioxin concentrations in the future with the reinforcement of regulations. The fish studied were crucian carp (Carassius auratus (gibelio) langsdorfii), an omnivorous species. Fish and sediments were collected from 14 rivers and lakes located in remote areas, agricultural areas, and small and large cities throughout Japan. The total toxic equivalent (TEQ) dioxin concentrations at the three remote sites were about 20% of the concentrations at the other 11 sites, which all had similar concentrations. The average concentrations in fish collected from these 11 sites were 0.69pgTEQg−1 wet wt. (95% CI 0.52–0.85) or 57.3pgTEQg−1 fat (95% CI 47.9–66.7). There were notable differences in congener profiles of polychlorinated p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) between sampling areas. A chemical mass balance method was used to estimate the proportions of dioxin contributions from different sources. The sampling areas were classified into four groups on the basis of the predominant source of dioxin contamination: a combustion group, a chlornitrofen herbicide group, a chlornitrofen and pentachlorphenol herbicide group, and a remote group. The congener profiles of dioxin like polychlorinated biphenyls (DL-PCBs) were almost the same in all areas and close to those in Kanechlor, which indicates that pollution from PCB products has spread throughout Japan. From samples collected during the spawning season, it was determined that about 20% of the dioxins in adult females were transferred to the eggs, resulting in higher dioxin concentrations in adult males than in females. Biota–sediment accumulation factors (BSAFs) of 2,3,7,8-substituted PCDDs/DFs for crucian carp were larger than those of non-2,3,7,8-substituted congeners, and BASFs decreased with increasing number of chlorines. The BSAFs of DL-PCBs were 10 times greater than those of PCDDs/DFs, and BSAFs of mono-ortho type DL-PCBs were higher than those of non-ortho types. [Copyright &y& Elsevier]

We examined the effect of two nitrogenous diphenyl ether pesticides, nitrofen (NIP) and chlornitrofen (CNP), on mast cell activation. RBL-2H3 (rat basophilic leukemia) cells were exposed to NIP or CNP for 30 min to investigate their effect on degranulation, and for 3 h to investigate their effect on cytokine production and gene expression. NIP and CNP increased IgE receptor-mediated β-hexosaminidase release, MCP-1 release, and TNF-α release in a dose-dependent manner. The increasing effect of CNP on their release was greater than that of NIP. In the gene expression experiment, 30 μg/ml CNP significantly upregulated Egr-1, MCP-1 and GADD45a gene expression. These results suggest that at higher concentrations (more than 30 μg/ml) the nitrogenous diphenyl ether pesticides had both a degranulation-enhancing effect and proinflammatory cytokine-production enhancing effect through the expression of some transcription factors in RBL-2H3 cells. [Copyright &y& Elsevier]

We used the Ames assay to investigate changes in the mutagenicity of chlornitrofen during its aerobic biodegradation. Although a mixed culture of bacteria obtained from river water degraded chlornitrofen and reduced its concentration from 39 to 6 μg/l in 21 days, the indirect mutagenicity of the solution to Salmonella strains TA98, YG1021, and YG1026 increased gradually. This finding suggests that mutagenic metabolites were produced during the aerobic biodegradation. The increase in the mutagenicity was, however, much smaller under aerobic than under anaerobic conditions. The differing sensitivities of our test strains to the functional groups on the mutagens showed that the mutagenic metabolites were indirect frameshift-type mutagens that might have neither nitro nor amino groups. [Copyright &y& Elsevier]