Studies On Persistent Organic Pollutants In Sediments From Nansi Lakes, China

Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls(PCBs) and dioxins(PCDD/Fs) are environmental organic pollutants which are harmful to environment and human body. They are referred to as environmental hormones, also called environmental estrogens or endocrine disrupting chemicals. It is mainly by human activities that these substances are released to the environment. They perform similarly to the natural hormones in the human body, so they can produce fault signals and thus interfere the endocrine system, causing abnormality of the metabolism, endocrine and regeneration system. PCBs, PAHs and PCDD/Fs are also persistent organic pollutants that can be transported long-range from source areas. They can be enriched by organisms and are resistant against biodegradation. Particularly, they can induce cancer, gene mutation and hereditaria malformation. Studies on these environmental organics have become an important research topic and issue in many countries. In China, studies in this area have begun only in recent and are still in a preliminary stage, especially on PCDD/Fs, due to the limited analytical means.23 compounds of polycyclic aromatic hydrocarbons (PAHs) as well as 12 compounds of polychlorinated biphenyls(PCBs) were measured by GC-MS in surface sediments at 13 stations and sediment cores at 5 stations in Nansi Lake. 24 compounds of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and) 12 compounds of co-PCBs in surface sediments at 2 stations, from Nansi Lake were analyzed using HRGG-HRMS. The results have been investigated and discussed especially on the spatial variability of these environmental organics, their toxic equivalency quantity, and sources.PAHs were identified at all station. The total concentrations of PAHs range from 221.9 to 2554 ng/g dw in the surface of sediments. PAHs were enriched mainly in the south of Nansi Lake, decreased in the north. The highest concentrations of PAHs occurred at Gaolou station, and the lowest at Zhaoyang Lake. The distribution pattern can be attributed to the following factors. (1) Pollution sources are located mostly ia the south of Nansi Lake named Weishan Lake. (2) The hypsography feature of Nansi Lake area is that there is much lower in the south than in the north. As many rivers with much mud and sand flow into Weishan Lake, a great deal of mud and sand are then filled up at the bottom of Weishan Lake. Furthermore, it is difficult for these pollutants to diffuse from the south to the north. (3) Sediment pain size and composition factors had an influence on the horizontal distribution. There is abundance organic matter in Weishan Lake. Preliminary results of sediment core show that PAHs pollution has occurrd in recent years. P/A, FL/PY ratios and ring numbers of PAHs were used to assess the origins of the pollutants, suggesting possible sourcessuch as combustion of coal, wood and petrogenic sources. The degree of surface sediment contamination by PAHs in study area is moderate/high in comparison with other surface sediments.PCBs were identified at all station. Preliminary results are presented for the concentrations, the historical change of PCBs level and distribution characteristics of 12 PCBs congeners in surface sediments, collected at 13 stations and 5 sediment core. (1) The concentration of PCBs in the southern lake is much higher than in the northern lake. The highest concentrations of PCBs occurred at 5# station, and the lowest at Dushan Lake. The total PCBs contents range from 2.4 to 83.1 ng/g dw. Compared with the reported PCBs concentration in sediments of other areas in China and other countries, the level of PCBs pollution in Nansi Lake is moderate/high. (2) The PCBs are dominated by lower substituted (1 - 5 Cl) PCBs componeats, higer Cl-substituted PCBs components are difficult to inspect for the lower concentration. (3) The results of sediment core samples show that PCBs contents have decreased in recent years. (4)The concentrations of PCBs in rich-rain period are close to that in dry periodThe total PCDD/F...