Study On PCBs, PAHs And OCPs In Soil In Harbin City

Due to their persistence, bioaccumulation, toxicity and long-range atmospheric transport, as well as carcinogenicity, mutagenicity and teratogenicity, persistent organic pollutants (POPs) have gained utmost attention in the world. There are a lot of studies to investigate contamination by POPs worldwide,which focused on developed countries. China, one of the members of"Stockholm convention", has been starting some studies on POPs in recent years. Polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) sampled from the soil in Harbin City, Heilongjiang province were pretreated by Soxhlet and detected by GC/MS. The kinds, concentrations, spatial distribution, possible sources of these pollutants were analyzed and discussed.The methods for pretreatment and detection for the three types of POPs in soil have been optimized. The determination limits of the methods for PCBs, PAHs and OCPs are 3.0-21pg/g, 10.15-379.34pg/g and 5.14-16.91pg/g, respectively, which is available for detecting trace materials.Eighteen top-soil samples collected from different functional zones in Harbin City were analyzed by GC-MS. The experimental results have shown that a high variability occurs within different areas, with a ratio of one order of magnitude. Tetra-CBs, Penta-CBs and Hexa-CBs were abundant in all samples,accounted for 60%-90% of total PCBs. Total organic carbon (TOC) is one of the important factors that can influence the concentrations of PCBs in soil. Fourteen congeners of OCPs were detected in all samples, within the range from 0.28ng/g to 81.34ng/g. The predominant compounds in soil were Hexachlorocyclohexanes (HCH) and dichloro-diphenyl-trichloroethane (DDT), whose mean concentrations were 9.3ng/g forΣHCHs and 5.84ng/g forΣDDTs. Sources of PCBs and OCPs in soil were also discussed. Industrial by-products and inadequate disposal of transformers and capacitors were main sources for PCBs. However, the present usage of Dicofon and Lindane maybe explain the results of OCPs.PAHs were also studied in the paper. The totals of 16 types of PAHs were ranged from 16.98ng/g to 3256.21ng/g, with a ratio of up two orders of magnitude. The mean concentration ofΣPAHs for all soil samples is 527.91ng/g. Overall PAHs pollution levels in Harbin were moderate compared to other studies worldwide. From the investigation of PAHs in soil in Harbin by special PAHs compounds ratios, the dominant source in this region is pyrogenic origins, especially coal combustion.PAHs in atmosphere were studied for the comparing with PAHs in soil. The experimental results have shown that the mean concentration ofΣPAHs was 410.38ng/m~3 in eight sites. The PAHs profiles were similar, with high percentages of low-molecular-weights (LMW) PAHs. And three-ring PAHs were predominant in all samples, which was three-quarter to the total PAHs. Coal combustion is also the main source for PAHs in air in Harbin.