Bioaccumulation And Geographical Distribution Of HCH, DDT And PCB Residues In Antodonta Woodianda From Selected Areas Of The Taihu Lake

"Mussel Watch" has been proven successful as a very applicable approach to monitorthe status and temporal changes in organochlorine pollutants using marine bivalve musselsas sentinel organisms, owing to their sessile lifestyle, wide distribution, high tolerance tocontaminants, and the convenience of sampling. However, few studies are available onmonitoring of freshwater pollution with bivalves so far.In this study, edible bivalve mussel Anodonta woodiana were collected from fourseparate water areas (i.e., Huzhou city, Dapu of Yixing city, Xueyan of Changzhou city, andWulihu of Wuxi city) around the Taihu Lake and investigated, firstly, for thebioaccumulation of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes(DDTs), and polychlorinated biphenyls (PCBs). Also, the potential health risks toconsumers were assessed with their residue levels of the organochlorines. Meanwhile, thepresent study was initiated as a pilot study to understand the feasibility of the future"Freshwater Mussel Watch" system for the inland fishery environment.1. Hexachlorocyclohexanes: a total of 46 mussels (10 from Wulihu of Wuxi city in 2003,36 from the four sites above in 2004) were analyzed by a Varian CP3380 gaschromatography coupled with a ⁶³Ni electron capture detector. The HCH detection ratewas 100ï¼…in the soft tissue of all bivalves investigated. The total HCH residue levels inthe mussels from the four sites of 2004 were the order of Dapu (3.20±0.74, 1.97-4.17;mean±S.D., ranges; ng/g on weight weight basis)≈Huzhou (3.15±1.18, 2.00-5.44)＞Xueyan (2.21±0.69, 1.42-3.49)＞Wulihu (1.25±0.73, 0.47-2.34) with a generalsignificant geographical difference from each other. In addition, lower levels could befound in the mussels from Wulihu in 2004, compared with those (4.00±1.22, 2.45-6.46)of the mussels from same site in 2003. A high ratio ofγ-HCH was detected in themussels from Huzhou, Dapu and Xueyan in 2004. Noticeably, noβ-HCH could bedetected in the present study. Although the HCH residue in Anodonta woodiana was ina medium level or slightly higher when compared with those in marine mussels inprevious literatures, it is still lower than the corresponding Food Maximum Residue Limits of FAO and Ministry of Agriculture of China.2. Dichlorodiphenyltrichloroethanes: DDTs analysis was performed on the same 46mussels Anodonta woodiana in the above-mentioned HCH study by a Varian CP3380gas chromatography coupled with a ⁶³Ni electron capture detector. The detection rate ofDDT was 100ï¼…in the soft tissue of these bivalves. The order of total DDT residuelevels in the mussels from the four sites of 2004 was Wulihu (10.97±2.36, 7.78-14.4;mean±S.D., ranges; ng/g on weight weight basis)＞Huzhou (7.77±2.97, 3.75-11.61)≈Xueyan (6.46±2.94, 3.44-11.10)＞Dapu (2.88±0.46, 2.27-3.79) and significantgeographical difference was found between these sites. Unlike total HCH, the residuesof total DDTs in the mussels from Wulihu in 2004 showed similar levels with themussels from the same areas in 2003 (9.27±3.04, 6.76-14.13). P, p'-DDT was onlydetected in the mussels of 2004 from Huzhou. In Wulihu area the increment of p.p'-DDE in the mussels of 2004 approximately equaled the decrement of p,p'-DDT inthe mussels of 2003. The total DDT residue in Anodonta woodiana was a medium levelin comparison with those in marine mussels of previous literatures, and is lower thanthe corresponding Food Maximum Residue Limits of FDA and Ministry of Agricultureof China.3. Polychlorinated biphenyls: a total of 40 mussels collected from Wulihu area in 2003,Huzhou,Xueyan,Dapu areas in 2004, and Sanshandao of Wuxi city in 2005 wereanalyzed for PCBs using an Agilent 6890N gas chromatograph. The detection rate ofPCBs was 95ï¼…in the soft tissue of these mussels. Total PCBs residue levels ranged inthe mussels from 0.68-58.09 ng/g wet weight without significant spatial/temporaldifferences. PCB congener 1, 5 and 11 dominated in most mussels. The residue levelsof total PCBs in the bivalves were lower than the corresponding Food MaximumResidue Limits of FDA and Ministry of Health of China.As an initial systematic attempt to monitor organochlorine compounds for freshwaterenvironment in China using the "Mussel Watch" approach, this dissertation effectivelyprovided the most recent information, by Anodonta woodiana as a bioindicator, on theHCHs, DDTs, and PCBs residual situations, characteristics of the isomer/congenercomposition, contamination levels, and hygienic quality of this edible mussel in different water areas around the Taihu Lake. All results of the present pilot study will lay a solidfoundation for establishment of the future "Freshwater Mussel Watch" system for theChinese fishery environment.