Aquaculture-derived enrichment of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in coastal sediments of Hong Kong and adjacent mainland China

To evaluate contamination of sediments along the coast of Hong Kong and adjacent mainland China, concentrations of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in surface and core sediments were measured in six mariculture zones. In surface sediments (0 to 5cm), concentrations of ∑HCHs and ∑DDTs in mariculture sediments were approximately 1.3- and 7.7-fold greater, respectively, than those detected in sediments at corresponding reference sites, which were 1 to 2km away in areas where there was no mariculture. Similarly, in cores of sediments, concentrations of ∑HCHs and ∑DDTs were 1.2- and 14-fold greater in mariculture zones, respectively. Enrichment relative to regional background concentrations, expressed as percentages was as large as 8.67×10³% for o,p'-DDD. The major sources of the enriched organochlorine pesticides (OCPs) were hypothesized to be derived from the use of contaminated fish feeds and anti-fouling paints for maintaining fish cages. Results of ecological risk assessments revealed that enriched OCPs had a large potential to contaminate the surrounding marine environment and lead to adverse effects on the associated biota. To our knowledge, this is the first study to evaluate the differences of OCP contaminations between mariculture and natural coastal sediments.