A number of stations sampled during the baseline survey contained high levels of Total DDT in the sediments. Stations ES2 (outer Tathong Channel), SS3 (near Lamma Island), VS3 (near North Point in Victoria Harbour), WS1 (located south of Tsing Yi) and DS3 (located in Deep Bay) all showed high Total DDT concentrations over the monitoring period and ISQV-Low exceedances. Sediments could, therefore, be classed as moderately contaminated(26)) . Highest Total DDT found in sediments during this baseline Survey were found at Station VS3 where mean concentrations of 5.3 mg kg-1 were detected. Total DDT levels at the other stations (ie MS15, MS5, NS4, PS6, TS2) were less than this value and may reflect lower DDT input. However, it should be noted that grain size also markedly affects the ability of sediment to 'scavenge' contaminants from overlying water. Sandy sediments for example do not retain contaminants at as high levels as sediments composed of fines. Based on sediment grain size data reported in 1998(27), sediments at Station VS3 were mostly composed of a larger grain sized fraction (ie only contained 17% w/w small [< 63 mm] fraction) whereas the other stations contained proportionally higher small grain fraction (ie TS2 = 68, SS3 = 72, PS6 = 83, DS3 = 82, MS5 = 86, MS15 = 86, NS4 = 54, WS1 = 77 and ES2 = 82 %w/w 63 mm fraction, respectively). The higher Total DDT recorded in the present Study at this station would, therefore, appear to reflect higher inputs rather than greater sediment scavenging capacity.

Total DDT was recorded above the detection limit in most of the biota analysed from the trawling stations (ie 90%, 73%, 87% and 92% for biota trawled in December 1998, January, August and September 1999, respectively) (see Tables 3.4a and 3.4b). These results indicate that biota are the commonest DDT accumulating compartment present in the Hong Kong marine environment. The higher accumulating capacity of DDT in biota compared to Hong Kong sediments is probably related to the physicochemical properties of DDT. DDT is highly lipophilic and is preferentially stored in tissue fats or adsorbed to the organic component of sediments(28) . Longer retention or half-lives for DDT (and DDT derivatives) are thus likely in sediments with a high organic fraction (which contain lipids) and the fatty tissues of biota. Both bioaccumulation and biomagnification from the food chain can enhance DDT levels in biota and may explain why concentrations in tissues were higher than those recorded in the sediments.