Distributions And Sedimentary Records Of Polycyclic Aromatic Hydrocarbons And Organochlorine Pesticids In The Mud Areas Of The East China Sea

Persistent organic pollutants(POPs) are of great concern for the environment due to its long-range atmospheric transporting, global polluting and harm to human and environment.The East China Sea (ECS) with a broad continental shelf receives large particulate organic pollutants fluxes annually from the Changjiang, Huaihe, Minjiang, Qiantangjiang, and so on. The pollutants can be preserved easily in the mud area of the ECS, which make it possible to study the distributions and sedimentary records of the POPs in the ECS.The distributions, composition, sources, biologic risk assessments in the surface sediment and sedimentary records of POPs in the core N6 of the mud area was studied in order to establish the historical records of the POPs and its response to the development of industry and agriculture. The mud areas of the ECS are divided into four parts: the south coastal mud area, the north coastal mud area, the mud area to the southwest of Cheju Island and the Okinawa Trough.The distribution pattern of average concentration of PAHs in the mud areas of the ECS is: south coastal mud area >north coastal mud area > the Okinawa Trough >the southwest of Cheju Island. The concentration of PAHs in the coastal mud area is higher than that of the offshore suggesting that the distance from their sources is the important factors effecting the concentrations .The distribution pattern of PAHs in the study area is controlled by the distance from their sources, grain- sizes and TOC of surface sediments which are closely related with the circulation system of the ECS. The PAHs in the surface sediments are mainly pyrogenic. Atmospheric deposition and land runoff may be the important pathway of the input of PAHs to the sediments.OCPs were detected in every sample, indicating that human activities have had asignificant impact on the mud areas of the ECS. The distribution of OCPs is similar to that of PAHs.The distribution characteristic of DDTs and HCHs in each mud area is different from that of the others in the East China Sea. The Okinawa Trough has the highest average concentration of HCHs and its distribution characteristic is different from that of the other mud areas, indicating that its' source may be different from the others. The Ratios of (DDD+DDE) /DDT suggestes that the DDTs in the mud areas is relatively new.Based on the 2!0Pb dating, the sedimentary record was reconstructed in the core N6. It is showed that the vertical distribution of PAH in the core can be divided into four different parts: in 1940s, in 1950s to 1970s and in thel970s to 1980s and in the year after 1990s. The OCPs' pollution history can be reconstructed by sedimentary record in the core from its use to its ban. Being baned since 1983 the OCPs have a small decrease, but they still exist in the environment. It is supported that the vertical variation of POPs is a response to the development of industry and agriculture of China.The overall level of PAHs in the study area is moderate compared to those of the other areas including some estuaries, bays and shallow continental shelves. The OCPs are relatively lower compared to that of the other areas in China. Comparing to the biologic threshold, PAHs in the mud areas of the ECS are of low potential biologic impairment. But the concentration of DDT in most samples exceed the effect range low (ERL), which might be of potential damage to the ECS ecosystems.