浙江省某PCBs废物储存点对其邻近滩涂生态系统的毒性风险

Toxicity risks to the closed tidal flat ecosysten of a PCBs waste savepoint at the coast of Zhejiang

在浙江省沿海某化工厂内含PCBs废物储存点邻近滩涂上设6个采样点,用GC-MS方法检测各采样点水样、滩涂泥样及大弹涂鱼样品中毒性最强的12种二噁英类PCB(DL-PCB)异构体的含量。结果表明,所有样品DL-PCBs检出率、样品单邻位异构体PCB118和非邻位异构体PCB81检出率均为100%,且PCB118和81的含量均与总DL-PCBs量有较好的相关性,在水样、泥样和鱼样品中,PCB118与总DL-PCBs含量的相关系数(r)分别为0.97、0.95和0.91,PCB81与总DL-PCBs含量的相关系数(r)分别为0.93、0.99和0.98。环境样品中以低氯异构体(PCB81和77)为主,而生物样品中高氯异构体(PCB118和105)含量较高。采样区域内大弹涂鱼从水体和泥土中的平均富集系数分别为392.54和14.03,且鱼体PCBs含量与沉积物中DL-PCBs浓度高度相关(r=0.97)。在距堆场水沟入海口150 m内水体和沉积物中DL-PCBs含量已处于较高污染水平(分别大于599.34 ng/L和10.97 ng/g),且采样区域内大弹涂鱼PCBs含量(均大于59.19 ng/g脂重)显著高于其它地区。毒性当量研究表明,非邻位的PCB126和PCB169是样品总TEQs的主要贡献者,且所有水样和鱼样的TEQs都分别显著超过日本水环境限值1 pgTEQ/L和欧盟水产品标准值8 pg TEQ/g湿重(P<0.001);应用M acDonald沉积物毒性评价方法研究表明,1—4#泥样已具有较高毒性风险。综合DL-PCBs含量和毒性当量分析表明,清挖4 a后,该PCBs废物堆场仍对周边滩涂生态系统具有一定毒性风险,对人体健康存在潜在危害。

Polychlorinated biphenyls （PCBs） have been widely used in production fields for their excellent chemical characteristics. However, PCBs can be accumulated through the food chain, which directly endangers human health. In May 2004, the Global Environment Facility initiated the demonstration project of PCBs management and treatment in China, specifying Zhejiang Province as the demonstration province, and carried out checking, monitoring, cleaning, treating and managing the PCBs savepoints thoroughly in Zhejiang Province. However, the poor storage conditions and improper managements of savepoints will lead to PCBs leaking and contaminating the surroundings. For this reason, 6 sampling sites were chosen to collect water, sediment and important edible and marine environmental monitoring fish-Boleophthalmus pectinirostris samples in the surrounding areas of a PCBs savepoint located in the coast of Zhejiang Province in August 2009. Contents of the most toxic 12 kinds of the Dioxin-like PCB （DL-PCB） congeners were determined by using GC-MS method. The results showed that all samples contained DL-PCBs. The total DL-PCBs concentrations of water, sediment and B.pectinirostris samples were 88.82 --971.73 ng/L （with the average of 541.71 ng/L）, 1.96 --57.24 ng/g （with the average of 26.10 ng/g） and 59. 19 --301.62 ng/g lipid （with the average of 148.54 ng/g lipid） respectively. The detection rate of the mono-ortho congener PCBll8 and the non-ortho congener PCB81 in all samples reached 100%. Contents of both the PCB118 and PCB81 had significant correlations with the total DL-PCBs. For water, sediment and fish samples, the correlation coefficient （r） values between PCBll8 and total DL-PCBs were 0. 97, 0. 95 and 0. 91 respectively, and the rvalues between PCBS1 and total DL-PCBs were 0.93, 0.99 and 0.98 respectively. The level of low chloride congeners （ PCB81 and 77 ） was higher in environmental samples, while high chloride congeners （ PCB118 and 105） were the main components of biological samples. The average concentration coefficient for B. pectinirostris from the waters and sediments around the PCBs savepoint were 392.54 and 14.03-fold respectively, and there was a high correlation between the DL-PCBs contents of fish and sediments （r = 0.97）. Waters and sediments within 150 m away from the estuary site had a high level of PCBs concentration （exceed 599.34 ng/L and 10.97 ng/g, respectively） , and all the PCBs contents of B. pectinirostris exceeded 59.19 ng/g lipid, which was markedly higher than other areas. The toxic equivalency （TEQ） study indicated that the non-ortho congeners PCB126 and PCB169 were the main contribors for the total TEQs, and all the TEQs values of water and fish samples largely exceeded the Japanese water environment standard （ 1 pg TEQ/L） and the European Union＇ s aquatic standard （ 8 pg TEQ/g） （ P 〈 0. 001 ）. By means of MacDonald＇ s sediment toxicity assessment, the 1 4# sediment samples were revealed at a certain degree of toxicity risks. Considering both the PCBs content and toxic equivalency analysis, after 4 years of being dug and cleaned, this PCBs savepoint still had toxicity risks to the surrounding tidal flat ecosystem and was a potential threat to human health. The results also revealed that it was very necessary and urgent to conduct research on the environmental distributions of PCBs and assess PCBs toxicity risks to the wildlife and human health in surrounding areas of the PCBs savepoints.