Characteristics and evaluation of temporal and spatial distribution of DDTs in oysters along coastal waters of Hainan Island, China

During 2006~2012, we collected oysters (Crassostrea rivularis) from Dongzhai Harbor, Maniao Harbor, Basuo Harbor and Yulin Harbor which are along the coastal waters of Hainan Island, China, to determine the DDTs contents by gas chromatography with electron capture detector. The results show that the DDTs contents vary from undetectable to 4.51 ngg-1 (wet weight) with an average of 1.45 ngg-1. No significant difference is found in DDTs contents among the 4 sampling sites (P0.05). The level of DDTs residues in oyster from the coastal waters of Hainan Island is relatively lower than the other coastal areas home and abroad. The DDTs content reached the maximum in 2007 then decreased slightly and maintained steady from 2007 to 2012. The DDTs contents in shellfish from Hainan Island in both 1985 and 2006~2012 are within 100 ngg-1. The composition analysis of DDTs in oyster reveals that DDTs residues mainly come from historical usage, but there is probably an input of new DDTs coming from dicofol during 2006~2007. DDTs residues in oyster along the coastal waters of Hainan Island meet with the requirement of the first grade of the National Marine Biological Quality Standard of China, not exceeding the state residual limited standards, and the food safety risk is acceptable.