珠江广州河段不同粒径沉积物中多氯联苯(PCBs)的分布特征

Grain-size distribution of polychlorobiphenyls in sediments of the Pearl River

采用湿分法分别将采自珠江广州河段芳村和黄埔水域的沉积物样品分成5个粒径的组分,并测定各组分中多氯联苯(PCBs)、矿物组成、总有机碳(TOC)和碳黑的含量。结果表明,有机质类型是控制多氯联苯在不同粒径组分中的分布特征和富集能力的主要因素。不同粒径组分对含不同氯原子数PCB同系物的富集能力也受有机质类型的影响。在本实验中,含煤屑和焦碳的粒径组分对含有较多氯原子(≥4)PCB同系物的富集能力较强,而含无定型有机质的粒径组分对含较少(2～3)氯原子PCB同系物的富集能力较强。

Congener specific analysis of PCBs in two sediments of the Pearl River are conducted to gain better understanding of the distribution of this class of contaminants in relation to the grain size of sediments. PCB concentrations, TOC, black carbon and their distribution profiles are studied in five different grain size sediment fractions (> 500 μm, 500～220 μm, 220～63 μm, 63～220 μm, < 22 μm). The compositions of different grain size particles are identified through petrography analysis to study the relationship between the PCBs concentrations and the compositions of minerals and organic matter in different grain size particles. The results show that the total PCB concentration is not significantly correlated with the TOC and black carbon content. The results show preferential association of low chlorinated congeners with the fraction (< 22 μm) which is rich in amorphous organic matter, however, the specific affinity of highly chlorinated congeners with the fraction (63～220 μm) which is abundant of coal derived matter and coke carbon particles. It is illustrated that the type of organic matter plays an important role in the distribution of total PCBs and PCB congeners with different number of chlorine atoms in different grain size particles in sediments.