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Diffusion of the synthetic pyrethroid permethrin into bed-sediments

机译：合成拟除虫菊酯苄氯菊酯向床沉积物中的扩散

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Bed-sediments are a sink for many micro-organic contaminants in aquatic environments. The impact of toxic contaminants on benthic fauna often depends on their spatial distribution, and the fate of the parent compounds and their metabolites. The distribution of a synthetic pyrethroid, permethrin, a compound known to be toxic to aquatic invertebrates, was studied using river bed-sediments in lotic flume channels. trans/cis-Permethrin diagnostic ratios were used to quantify the photoisomerization of the trans isomer in water. Rates were affected by the presence of sediment particles and colloids when compared to distilled water alone. Two experiments in dark/light conditions with replicate channels were undertaken using natural sediment, previously contaminated with permethrin, to examine the effect of the growth of an algal biofilm at the sediment-water interface on diffusive fluxes of permethrin into the sediment. After 42 days, the bulk water was removed, allowing a fine sectioning of the sediment bed (i.e., every mm down to 5 mm and then 5-10 mm, then every 10 mm down to 50 mm). Permethrin was detected in all cases down to a depth of 5-10 mm, in agreement with estimates by the Millington and Quirk model, and measurements of concentrations in pore water produced a distribution coefficient (K-d) for each section, High K-d's were observed for the top layers, mainly as a result of high organic matter and specific surface area. Concentrations in the algal biofilm measured at the end of the experiment under light conditions, and increases in concentration in the top 1 mm of the sediment, demonstrated that algal/bacterial biofilm material was responsible for high K-d's at the sediment surface, and for the retardation of permethrin diffusion. This specific partition of permethrin to fine sediment particles and algae may enhance its threat to benthic invertebrates. In addition,the analysis of trans/cis-permethrin isomer ratios in sediment showed greater losses of trans-permethrin in the experiment under light conditions, which may have also resulted from enhanced biological activity at the sediment surface.
机译：床底沉积物是水生环境中许多微生物污染物的汇。有毒污染物对底栖动物的影响通常取决于它们的空间分布以及母体化合物及其代谢产物的命运。合成的拟除虫菊酯，氯菊酯，一种已知对水生无脊椎动物有毒的化合物的分布，是通过在水槽槽中使用河床沉积物进行研究的。反式/顺式-苄氯菊酯的诊断比率用于定量反式异构体在水中的光异构化。与仅蒸馏水相比，沉积物颗粒和胶体的存在会影响速率。在暗/光条件下使用重复通道进行了两次实验，使用了先前被苄氯菊酯污染的天然沉积物，以检验藻类生物膜在沉积物-水界面处的生长对氯菊酯向沉积物中扩散通量的影响。 42天后，除去大量的水，使沉积物床切成细段（即每毫米减小至5毫米，然后5-10毫米，然后每10毫米减小至50毫米）。与Millington和Quirk模型的估计值一致，在所有情况下均检测到了5-10 mm深度的苄氯菊酯，孔隙水中浓度的测量产生了每个截面的分布系数（Kd），高Kd为观察到的顶层，主要是由于高有机质和比表面积。在光照条件下在实验结束时测量的藻类生物膜浓度，以及在沉积物顶部1毫米处的浓度增加，表明藻类/细菌生物膜材料是沉积物表面高Kd的原因，并且氯菊酯的扩散阻滞。苄氯菊酯在细小的沉积物颗粒和藻类中的特定分配可能会增强其对底栖无脊椎动物的威胁。另外，沉积物中反式/顺式-苄氯菊酯异构体比率的分析表明，在光条件下，实验中反式-苄氯菊酯的损失更大，这也可能是由于沉积物表面生物活性增强所致。

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