Research On Bioavailability Of Sediment-accociated Pyrethroids And Prediction Of Biological Accumulation Based On Solid Phase Microextraction

As a new kind of insecticide, pyrethroid pesticides have been widely used in aquaculture for high efficiency and low toxicity.They tend to accumulate in sediment due to their high hydrophobicity. Assessment of their bioavailability and bioaccumulation in sediment and the related risk they may pose on the environment is of high significance. Research results were as follows.(1)The method was described for measuring lamba-cyhalothrin, bifenthrin, permethrin and fenpropathrin in sediment and aquatic products. The four pyrethroid pesticides residues in samples were extracted by soxtex system for twelve hours, then cleaned up by column chromatography with the purification filler of florisil and the elution of hexane-dichloromethane(7:3) mixture with 30 m L, the fat was to dislodge by pertroleum ether which was saturated with acetonitrile in biological sample, then analyzed by gas chromatograph-mass spectrometer. The percent recoveries of the added test on 5, 20, and 100 ng·g-1was over 65%, and the relative standard deviation was under 15% in sediment and biological sample. The method detertion limit of four pyrethroid pesticides in sediment and biological sample were 0.88~1.5ng/g �'� 1.1~2.1ng/g, which were used for detecting pyrethroid pesticides in real sediment and biological sample.(2)Bioaccumulation test was used to assess the bioavailability of pyrethtoid pesticides in sediment. Venerupis philippinaram and hyriopsis cumingii was exposed to seawter and freshwater sediment added the four pyrethroid pesticides, then used to bioaccumulation test. The results showed that the concentrations of pyrethroid pesticides in seawater and freshwater sediment were 245~387 ng/gdw �'� 132~189 ng/gdw. The concentrations of pyrethroid pesticides in venerupis philippinaram and hyriopsis cumingii were 56.5~204 ng/gdw �'� 14.7 ~ 47.2 ng/gdw for 28 days. Bioconcentration factor(BCF) andIV bio-sediment accumulation factor(BSAF) of four pyrethroid pesticides in venerupis philippinaram and hyriopsis cumingii were 28.0~300、8.80~82.2 and 0.08~0.21、0.03~0.08, and classified as relative low level, because they may have strong ability of biotransformation for pyrethroid pesticides.(3)The freely dissolved concentrations of the four pyrethroid pesticides in added and aged seawater and freshwater sediment pore water were measured in this study based on negligible depletion solid-phase microextraction using the polymer of polydimethylsiloxane(PDMS), and the concentrations of pyrethroids in PDMS were compared with those in two kinds of benthic animal(venerupis philippinaram and hyriopsis cumingii). The results showed that the freely dissolved concentrations(Cfree)of pyrethroids in seawater and freshwater sediment pore-water could be accurately calculated,(range 23.3~255 ng/L and 2.04~34.1ng/L). Concentrations of pyrethroids in PDMS and venerupis philippinaram and hyriopsis cumingii showed a significant correlation(p=0.009, p=0.046). However the comparison between bio-sediment accumulation factor(BSAF) and PDMS-sediment accumulation factor(PSAF)indicated that the application of biomimetic tool using PDMS to predict the bioaccumulation potential of sediment-associated pyrethroid requires further information on the biotransformation of these compounds in venerupis philippinaram and hyriopsis cumingii.(4)Tenax desorption kinetics of four pyrethroids(cyhalothrin, bifenthrin, permethrin and fenpropathrin) were analyzed to evaluate the bioavailability of pyrethroids in added and aged seawater and freshwater sediment, meanwhile results based on Tenax extraction were applied to predict the bioaccumulation of pyrethroids in venerupis philippinaram and hyriopsis cumingii. The results showed that the proportion of rapid desorption(Frap)of pyrethroids was 45.6 ~ 66.5% and 28.6 ~ 37.2% for seawater and freshwater sediment, and the order of the rate constants for the three desorption compartments(fast,slow and very slow) were10-1、10-2、10-3~10-5and 10-2、10-1、10-4~10-5. Significant correlations were observed between Tenax 24 h in seawater sediment and pyrethroid concentrations in venerupis philippinaram(p<0.05), and Significant correlations were also observed between Tenax 6h in freshwater sediment and pyrethroid concentrations in hyriopsis cumingii(p<0.05), so single time-point Tenax extractioncan be used to evaluate the bioavailability of pyrethroid pesticides in sediment. However,Tenax-sediment accumulation factor(TSAF) is bigger than bio-sedimentaccumumlation factor(BSAF) and PDMS-sediment accumulation factor(PSAF), which showed that Tenax need further research to predict pyrethroids of biological accumulation.(5)The concentration of permethrin and 3-phenoxybenic acid(3-PBA) in venerupis philippinaram and hyriopsis cumingii was measured, then to obtain the percent conversion of pyrethroid pesticides, to confirm feasibility of PDMS to predict pyrethroids of biological accumulation. The results showed that the variation tendency of permethrin and 3-PBA in venerupis philippinaram and hyriopsis cumingii was similar,which further indicater that pyrethroid pesticides generate transform in organisms. The percent conversion of pyrethroid pesticides in venerupis philippinaram and hyriopsis cumingii was 44.4% and33.7%.. Which the value of PSAF/BSAF was amended by44.4% and 33.7% of the percent conversion of permethrin in venerupis philippinaram and hyriopsis cumingii, was about 4.7. Therefore, PDMS can be conducted biomimetic tool to predict the concentration of pyrethroid pesticides in organisms.In conclusion, PDMS and Tenax could both evaluate the bioavailability of pyrethroid in sediment. Compared with PDMS, single time-point Tenax was more economically and effectively to evaluate the bioavailability of pyrethroid in sediment.But PDMS was more accuracy to predict the concentration of pyrethroid pesticides in organisms. Both were worth to generalize and utilize in the field of aquaculture.