Abstract: Pyrethroids have been widely used in agriculture, forestry and fisheries as pesticide, and frequently detected in sediment because of their high hydrophobicity and lipotrophy. It is, therefore, of great significance to the assessment of environmental quality and risk to study bioavailability of these compounds in sediments. Tenax desorption kinetics of four pyrethroids (cyhalothrin, bifenthrin, permethrin and fenpropathrin) were analyzed to evaluate bioavailability of the pyrethroids in sediments of the tidal zone in the Yangshan Port, meanwhile results of the Tenax extraction were compared with those of the experiment on bioaccumulation of pyrethroids in Ruditapes philippinarum. Results show that the faction of readily desorbable pyrethroids (F_rap) accounted for over 50% in the surface sediments low in organic carbon(OC) content, and the desorption rate of the fractions of readily, slowly and very slowly desorbable pyrethroids varied in magnitude order, being 10^-1, 10^-2 and 10^-5-10^-3, respectively. Compared with F_rap, single time-point Tenax extraction can be used to evaluate bioavailability of pyrethroid pesticides in sediments, rapidly, economically and effectively. Correlation analysis shows that 24 h Tenax (C_{s,24 h}) extraction is more suitable to application to the prediction of pyrethroid accumulation concentrations in Ruditape sphilippinarum (C_b) (lg C_b=4.03 lg C_{s,24 h}-17.02；R²=0.88，P<0.05). The findings of this study may not only provide reliable scientific basis for simple rapid evaluation of bioavailability of pyrethroids in sediments and assessment of environmental quality and risk of marine sediments, but also be used to predict bioaccumulation of permethrin pesticides in bivalve oobenthos, and furthermore, as a simpler and easier method for environmental risk assessment of aquaculture sediments and food risk assessment of relevant aquatic products.  

Key words: strong adsorptive resins(Tenax), desorption kinetic, pyrethroids, bioavailability, bioaccumulation