多氯联苯性质、危害及降解方法

介绍了多氯联苯的性质、危害及其降解方法。     

Lipid peroxidation and antioxidant status in workers exposed to PCDD/Fs of metal recovery plants

Secondary copper smelters, which primarily utilize the waste materials that contain organic impurities, and the zinc recovery plant, which handles mostly fly ash and slag from the iron and steel industry, are major emission sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in Taiwan. In this study, we compared the levels of erythrocyte glutathione (GSH), erythrocyte superoxide dismutase (SOD) and plasma malondialdehyde (MDA) in workers at a secondary copper smelting plant and a zinc recovery plant who may have been exposed to PCDD/Fs. Though the PCDD/F levels were higher in workers of zinc recovery plant than those of secondary copper smelting plant, no significant difference was found for serum PCDD/F levels between the two kinds of plants. We observed a significant difference in plasma MDA levels between workers at the zinc recovery plant (2.54 microM) and those at the copper smelting plant (1.79 microM). There was and a significant positive correlation between plasma MDA levels and the PCDD/Fs levels. In addition, we observed that the MDA levels were not affected by smoking and exercise status. Therefore, the data suggest that the MDA levels of the metal recovery workers are influenced by their PCDD/F exposure. The erythrocyte SOD activity in workers from the zinc recovery plant was marginally higher than that from the secondary copper plant (196 vs. 146 units/ml, p<0.06). In both plants, large variations in the MDA and SOD levels were found, especially in the high-PCDD/Fs-exposure group, which may be attributed, at least partially, to the differences in smoking status and the number of cigarettes smoked. Overall, our results indicate a higher oxidative stress in workers of the zinc recovery plant than in workers of the secondary copper smelting plant in Taiwan.     

Non-dioxin like polychlorinated biphenyls in mackerel (Scomber scombrus) available on the Serbian market

Mackerel is rich in omega-3 fatty acids, but this fish may be contaminated with environmental pollutants. The aim of this study was to evaluate concentrations of non-dioxin like polychlorinated biphenyls (ndl-PCBs) in 160 samples of mackerel available on the Serbian market. Average and maximum ndl-PCB concentrations were 7.9 ng/g and 74 ng/g, respectively. A higher average level of ndl-PCBs was found in mackerel from Spain, but this was still three times lower than the permitted level. We conclude that levels of ndl-PCBs in mackerel available on the Serbian market are acceptable.     

Supercritical water oxidation of transformer oil contaminated with PCBs—A road to commercial plant from bench-scale facility

Polychlorinated biphenyls (PCBs) are one of the eradication compound lists of Stockholm convention. Korea started to analyze the PCBs concentration in high-voltage transformers in June 2004 and is developing PCBs disposing technology. As most of the transformers in Korea were contaminated at very low level of less than 5 ppm, it was decided that SCWO (supercritical water oxidation) process is suitable to treat them.The destroying parameters of SCWO process including optimum process temperature, pressure, residence time, and amount of oxidant were studied with a bench-scale facility. Based on these results and simulation, a pilot plant was designed and built to confirm the suggested condition. Recently detail design of a commercial plant was completed based on these results. In this paper, the procedures to scale up the design from a bench-scale facility to a commercial plant and major check points in each stage are introduced.     

多氯联苯的生物处理技术进展

综述了多氯联苯生物降解的研究进展,介绍了多氯联苯代谢的两种途径:厌氧过程和需氧过程。降解的途径取决于多氯联苯同源物的复杂程度、微生物的种类及微生物间的相互作用。     

Experimental study on low temperature thermal treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) in fly ash

The effects of temperature and time on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) distribution in fly ash of a municipal solid waste incinerator (MSWI) were studied in a tubular oven under nitrogen atmosphere. The PCDD/Fs in the gas phase and solid phase were detected by high-resolution gas chromatography coupled with low resolution mass spectrometry (HRGC/LRMS) separately. The experimental results showed that the major congener was octa-chlorinated dibenzo-p-dioxin (OCDD) in the gas phase and the low chlorinated congeners were the major products in the solid phase. There were high levels of OCDD in the gas phase in several experimental conditions although the PCDD/Fs in the solid phase could be decomposed. The optimum condition for PCDD/Fs decomposition in fly ash was a heating time of 60 min at 400 °C under nitrogen atmosphere. Translated from Proceedings of the CSEE, 2005, 25(23): 95–99 [译自:中国电机工程学报]     

The use of mechanical alloying for the preparation of palladized magnesium bimetallic particles for the remediation of PCBs

The kinetic rate of dechlorination of a polychlorinated biphenyl (PCB-151) by mechanically alloyed Mg/Pd was studied for optimization of the bimetallic system. Bimetal production was first carried out in a small-scale environment using a SPEX 8000M high-energy ball mill with 4-μm-magnesium and palladium impregnated on graphite, with optimized parameters including milling time and Pd-loading. A 5.57-g sample of bimetal containing 0.1257% Pd and ball milled for 3 min resulted in a degradation rate of 0.00176 min⁻¹ g⁻¹ catalyst as the most reactive bimetal. The process was then scaled-up, using a Red Devil 5400 Twin-Arm Paint Shaker, fitted with custom plates to hold milling canisters. Optimization parameters tested included milling time, number of ball bearings used, Pd-loading, and total bimetal mass milled. An 85-g sample of bimetal containing 0.1059% Pd and ball-milled for 23 min with 16 ball bearings yielded the most reactive bimetal with a degradation rate of 0.00122 min⁻¹ g⁻¹ catalyst. Further testing showed adsorption did not hinder extraction efficiency and that dechlorination products were only seen when using the bimetallic system, as opposed to any of its single components. The bimetallic system was also tested for its ability to degrade a second PCB congener, PCB-45, and a PCB mixture (Arochlor 1254); both contaminants were seen to degrade successfully.     

Are PCB Levels in Fish from the Canadian Great Lakes Still Declining?

Long- and short-term levels and trends of polychlorinated biphenyls (PCBs) in lake trout (Salvelinus namaycush) and walleye (Sander vitreus) from the Canadian waters of the Great Lakes are examined using the bootstrap resampling method in light of the Great Lakes Strategy 2002 (GLS-2002) objective of decrease in concentrations by 25% during 2000–2007. This objective has been set as an indicator of progress toward the long-term goal of all Great Lakes fish being safe to eat without restriction. Lake Superior lake trout and walleye PCB concentrations were almost unchanged between 1990-2006, and the bootstrap analysis suggests that the probability of achieving the GLS-2002 objective is negligible (< 2%). The PCB levels in Lake Huron lake trout and walleye are decreasing; the declines between 2000–2007 are estimated to be 25–35% and 5–30%, respectively. In contrast, Lake Erie walleye concentrations will likely increase by 25–50% between 2000–2007. For Lake Ontario lake trout, achieving the 25% reduction target seems highly probable with a likely decrease of 45–55%; for Lake Ontario walleye, the probability of achieving such a reduction is only 8% with an expected change of −13 to +15%. Although the targeted reduction may not be achieved for walleye from Lakes Superior, Huron, and Ontario, their best projected 2007 PCB levels are below the unlimited fish consumption guideline of 105 ng/g wet weight used by the Ontario Ministry of the Environment. In contrast, although there are high probabilities of achieving the goal for lake trout from Lakes Huron and Ontario, their best projected 2007 PCB levels (160 and 370 ng/g ww, respectively) will continue to result in consumption restrictions. Lake Superior lake trout concentrations may remain unchanged at the current elevated level of 160 ng/g ww. For Lake Erie fish, the projected 2007 concentrations and the increasing trends are both worrisome. Additional measurements beyond 2007 are necessary to confirm these estimates because of the observed periodic oscillations in the concentrations.     

Occurrence of polybrominated diphenyl ethers and polychlorinated biphenyls in shark liver oil supplements

Results are reported of a pilot survey of concentrations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in shark liver oil supplements. Eleven brands of dietary supplements were analysed using an isotope dilution GC/MS method. Total concentrations of 10 PBDE congeners (BDE-28, -47, -49, -66, -99, -100, -153, -154, -155 and -183) ranged from 0.1 to 53 ng g^-1 oil weight and total concentrations of six PCB congeners (CB-28/31, -52, -118, -153 and -180) in the samples ranged from 16 to 340 ng g^-1 oil weight (undetected values are not included). Two brands of Japanese deep-sea shark liver oil contained the highest levels of PBDEs (49-53 ng g^-1 oil weight) and PCBs (290-340 ng g^-1 oil weight). These results indicate that PBDEs may have entered Japanese deep-sea waters.     

Bioassessment of contaminant transport and distribution in aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia)

Burrowing mayfly nymphs (Ephemeroptera) inhabit and ingest fine-grained sediments and detritus that may be enriched with metals and persistent organic compounds. The burrowing nymphs can externally adsorb and internally assimilate these contaminants, providing a link for the food chain transfer of potentially toxic substances from sediments to organisms in higher trophic levels. The emergent adults are short-lived and do not feed, thus their gut contents do not contribute greatly to their total contaminant burden. These characteristics make Hexagenia spp. and certain other burrowing mayflies useful for assessing ecosystem contamination. General protocols are presented for the collection, processing and analysis of emergent mayflies to assess the spatial distribution and bioaccumulation of sediment-associated contaminants in aquatic ecosystems. Two essential components of this bioassessment approach are a network of on-site volunteers with the materials and instructions needed to correctly collect and store samples and quality assurance procedures to estimate the accuracy of chemical analyses. The utility of this approach is demonstrated with an example of its application to the Upper Mississippi River (USA). Determination of cadmium, mercury and polychlorinated biphenyl congeners in emergent Hexagenia bilineata from a 1250km reach of this river revealed (1) several source areas of contaminants and (2) distinct patterns in the bioaccumulation (and apparent sediment-associated transport) of each residue on both small and large spatial scales.