Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research, IDAEA-CSIC, Jordi Girona, 18-26. E-08034 Barcelona, Spain.
Environ Int. 2011 Oct;37(7):1213-8. doi: 10.1016/j.envint.2011.05.004. Epub 2011 Jun 11.
The low Ebro River basin (NE Spain) represents a particular case of chronic and long-term mercury pollution due to the presence of an industrial waste (up to 436 μg/g of Hg) coming from a chlor-alkali plant Albeit high total mercury (THg) levels have been previously described in several aquatic species from the surveyed area, methylmercury (MeHg) values in fish individuals have never been reported. Accordingly, in order to investigate bioaccumulation patterns at different levels of the aquatic food web of such polluted area, crayfish and various fish species, were analysed for THg and MeHg content. At the hot spot, THg mean values of crayfish muscle tissue and hepatopancreas were 10 and 15 times, respectively, greater than the local background level. Higher mean THg concentrations were detected in piscivorous (THg=0.848 ± 0.476 μg/g wet weight (ww); MeHg=0.672 ± 0.364 μg/g ww) than in non-piscivorous fish (THg=0.305 ± 0.163 μg/g ww; MeHg=0.278 ± 0.239 μg/g ww). Although these results indicated that THg in fish increased significantly with increasing trophic position, the percentage of the methylated form of Hg was not strongly influenced by differences in relative trophic position. This is an important finding, since the fraction of THg as MeHg in the top fish predator was unexpectedly lower than for other species of the aquatic food chain. Moreover, mean THg concentrations in piscivorous fish exceed the maximum level recommended for human consumption. From our findings, it is clear that for this specific polluted system, speciation becomes almost mandatory when risk assessment is based on MeHg, since single measurements of THg are inadequate and could lead to an over- or under-estimation of contamination levels.
西班牙东北部的埃布罗河流域是一个长期受到汞污染的典型案例，污染的主要来源是一家氯碱厂的工业废物（汞含量高达 436μg/g）。尽管此前在该地区的几种水生物种中已经描述了总汞（THg）的含量较高，但从未报道过鱼类个体中的甲基汞（MeHg）值。因此，为了研究受污染地区水生食物网不同层次的生物积累模式，对螯虾和各种鱼类的 THg 和 MeHg 含量进行了分析。在热点地区，螯虾肌肉组织和肝胰腺中的 THg 平均值分别比当地背景水平高出 10 倍和 15 倍。肉食性鱼类（THg=0.848±0.476μg/g 湿重（ww）；MeHg=0.672±0.364μg/g ww）的 THg 浓度平均值高于非肉食性鱼类（THg=0.305±0.163μg/g ww；MeHg=0.278±0.239μg/g ww）。尽管这些结果表明，鱼类的 THg 随营养级的增加而显著增加，但汞的甲基化形式的比例并没有受到相对营养级差异的强烈影响。这是一个重要的发现，因为顶级鱼类捕食者中 THg 的甲基汞比例出乎意料地低于其他水生食物链物种。此外，肉食性鱼类的 THg 浓度平均值超过了人类食用的最大推荐水平。从我们的研究结果可以清楚地看出，对于这个特定的污染系统，在基于 MeHg 进行风险评估时，形态分析几乎是强制性的，因为 THg 的单一测量是不充分的，可能导致对污染水平的高估或低估。
