A Study Of PAHs And OCPs On Water Body And Sediments Of Rivers In Pearl River Delta,Pearl River Estuary And Offshore Of South China Sea

In recent years scientists have become increasing concerned about the situation oforganic pollutants in the tropical and subtropical regions of Asia. The "globaldistillation / fractionation "hypothesis suggest that semivolatile organic compoundsmay be distill or fractionated by differential temperatures around the global. As aresult, these compounds may tend to redistribute from tropical points sources tohigh-latitude areas. Pearl River Detla located in subtropical region. After 20 yearsdrastic economic development, It have led to concerns about whether the aquaticenvironment in this areas and adjacent marine environment have been serious pollutedby organic contamintants. However, the study on organic pollutants in this area,especially for offshore of South China Sea, are very limited. So continued monitoringprogram for varies pollutants are very important for us to understand the temporal andspatial distribution, source, character of composition of organic pollutants and effectof anthropologied activity on the environment of oceans. An understanding of thesource, transport and fate of contaminants in this area has a broader application tounderstanding how these processes may work in other estuary system. Sediments,water and water column samples in Pearl River Delta's rivers, Pearl River estuary andadjacent offshore of South China Sea were collected during 2002 to 2003 and analysisfor polycyclic aromatic hydrocarbons (PAHs) and organchlorinate pesticides(OCPs).These study assess the current sources, distribution and fate of contamintants as wellas providing a comparison with samples collected in 1997. We get followingconclusions from the result:The order of PAHs and OCPs concentration in the sediments samples is: rivers in Pearl River Delta > lingdingyang estuary > offshore of South China Sea. Among the rivers in Pearl River Delta, Guangzhou channel of Zhujian river and north main channel of Dongjiang river have higher PAHs and OCPs concentration than Xijian river and shizhiyang channel of Zhujian river. The overall levels of PAHs in this area are high compared to other places in China but low compare to relevant areas worldwide and rebeal a low to moderate level of PAH pollution. Potential toxicological assessment indicates that adverse biological effects of DDTs may cocur occasionlly in Pearl River Delta's rivers, at some sites in Guangzhou channel of Zhujian and north channel of Dongjian, PAH may cause adverse biological effects on aquatic biota.Pollutants concentration in water body of lingdingyang estuary and adjacent offshore of South China Sea is higher in Spring than in Summer. The content ofsuspended particulate mass, the concentration of contamintants in suspended particulate matter and photolysis are responsible for this temporal difference.PCA analysis revealed that oil spill, natural source, and pyrogenic source all contributed to PAHs in sediments and suspended particulate mass. Pyrogenic PAHs are main contributor of PAH in offshore samples. PAHs in Lingdingyang estuary and rivers of Pearl River Delta have significant contributions from oil spill and combustion. PAHs derived from high temperature combustion and biogemic origin are more abundant in Spring than in Summer for SPM samples. As for low molecular weigh PAHs, a contray case was found. The variety of proportion of LMW PAHs in difference stations and seasons indicated that plankton may contribution to LMW PAHs in SPM samples.PAH isomer pair ratios indicate a main biomass and coal combustion source to the offshore of South China Sea and a main petroleum combustion combustion source to the Pearl Rover Delta's rivers and Lingdingyang estuary. In suspended particulate matter, petroleum spill and combustion are main source of PAHs. In summer, character of coal combustion of SPM showed by Flu/202 may be the influence of particles introduced by sea current. The index of transport of PAHs suggests that PAHs in Xijian river and offshore of South China Sea may undergo a long distance transport, meanwhile, in Zhujian River and Doing jiang River, PAHs were derived from nearby source. Ratio of BeP/BaP and BaA/Chr confirm that photodegradation is one of main factors which produce low PAHs concentration in suspended particulate matter in summer.A comparison of surface sediments data from a study in 1997 with data from present study indicates that organchlorine pesticides have decrease over time in Zhujiang river and Xijiang river while there is no clear change in the PAH concentration, except in Xijiang, PAH appears to decrease slightly. The source of PAHs in Pearl River Delta have been change from a main coal combustion in 1997 study to a main petroleum combustion in present study and be reflect in the sediments in Pearl River Delta's rivers and lingdingyang estuary where there have high sedimentation rate.The features of DDTs in sediments samples, the vertical distribution of DDTs in Macao water column and the difference of DDTs's composition betweem Spring and Summer samples all indicated that DDT was still used in Xijian drainage areas in summer.The relativity analysis between organic pollutants and organic carbon infer thatorganic carbon plays an important role in controlling organic pollutants's fate in this area. The correlation between the partition coefficients of pollutants and TOC,saIinity and total suspended particles contents suggests these factor have influence on controlling pollutant's transport and fate in this area.The vertical distribution and partitions of PAHs and OCPs in three water colume, indicate that the total pollutant content of water body depended on the content of SPM and the concentration of contamintant in SPM. The content of total SPM is main factor in determined the vertical distribution of pollutant in Lingdingyang water column and Baietang water column. Meanwhile, Macao water column were dominated by concentration of contamintants in particles.especially for organochlorine pesticides.Pollutants vertical profiles and their partition between particle and dissolved phase indicate that the release and re-suspended of contaminants resides in sediments is one of main source of pollutants in Baiertang water body, especially in lower layer water. In Macao harbor, sediments act as a reservoir for organchlorine pesticides, introduced by river inflow from Xijiang river, and PAHs inputted by brackish water and fresh water from Lingdingyang estuary. In Lingdingyang water columns, the narrow flucuate range of partition coefficient in water column indicated particle in this water column is homogeneous.