溶解有机质对生物富集因子计算的影响:以东江鱼体中多溴联苯醚的生物富集为例

准确获取化合物的生物富集因子(BAF)对于判定化合物是否属于潜在毒害性污染物、评价其生态环境风险都具有重要的意义。为探究水体中溶解有机质(DOM)对BAF值的影响,以东江三角洲流域为研究区域,以多溴联苯醚(PBDEs)为目标化合物,研究了PBDEs各单体在3种鱼体中的富集特征。结果表明,PBDEs在3种鱼体中的浓度范围为42~825 ng·g-1脂肪,log BAF值位于5.0~7.4之间。由于脱溴代谢的种间差异,3种鱼类表现出2种PBDE的组成模式。在缺乏脱溴代谢途径的鱼体内,log BAF与化合物辛醇/水分配系数(log KOW)之间存在统计意义上的抛物线关系。但当BAF进行DOM的校正之后,二者之间抛物线形式的相关性消失,而呈现出显著的正线性相关性。以往研究对BAF值在化合物的log KOW达到一定程度后(7~8附近)出现下降的解释是高KOW化合物较大的分子体积降低了其穿过生物膜的可能性,但我们的研究结果表明,这种下降很可能是由于忽视了水体中DOM影响的结果。

Influence of Dissolved Organic Matter on Bioaccumulation Factor: A Case Study of Bioaccumulation of Polybrominated Diphenyl Ethers (PBDEs) in Fish from Dongjiang River

Bioaccumulation factor (BAF) plays key role in identification of bioaccumulative substance and in assessment of chemical risk. In order to reveal the effect of dissolved organic matter (DOM) on the calculated bioaccumulation factor, water and fish samples were collected from Dongjiang River and polybrominated diphenyl ethers (PBDEs) were measured. The concentrations of PBDEs in three fish species varied from 42 to 825 ng?g-1 lipid weight and the BAFs were between 5.0 and 7.4. There are two distinct PBDE congener profiles among three fish species due to the difference in metabolic debromination. A statistically significant parabolic relationship between log BAF and log KOW was found for fish exhibited no metabolic debromination. However, after correction with DOM, the log BAF was positively correlated with log KOW. Previous studies demonstrated that the BAF decreases with increasing log KOW when log KOW of chemical was larger than certain values such as 7 or 8. It is suggested that the larger molecular size of chemical block or retard the chemical to penetrate cell membrane. However, the results of the present study indicated that the decreasing trend of BAF with increasing lipophilicity of chemicals can be ascribed to the influence of DOM on the calculated BAF.