Savannah River Ecology Laboratory, University of Georgia. PO Drawer E, Aiken, SC 29802, USA.
Savannah River Ecology Laboratory, University of Georgia. PO Drawer E, Aiken, SC 29802, USA.
Sci Total Environ. 2019 Jun 10;668:261-270. doi: 10.1016/j.scitotenv.2019.02.301. Epub 2019 Feb 20.
Water, sediment, and biota from two streams on the Savannah River Site were sampled to study mercury (Hg) biogeochemistry. Total and methyl- Hg (MHg) concentrations were measured for all samples, speciation models were used to explore Hg speciation in the water, and Diffusive gradients in thin films (DGT) were applied to indicate the vertical profiles of labile Hg (DGT-Hg). Trophic position (δN) was estimated for biota and used to establish MHg biomagnification model. The speciation model indicated Hg methylation in the water occurred on settling particles and the most bioavailable Hg species to bacteria were complexes of inorganic Hg and labile organic ligands. Correspondingly, dissolved organic carbon concentrations were positively related to MHg concentrations in the water. In the sediment, the sharp increase of DGT-Hg around the sediment water interface underscores the importance of this interface, which determines the differences in the accumulation and generation of labile Hg among different waterbodies. The positive correlation between sediment MHg and sulfate concentrations suggested possible methylation reaction by dissimilatory sulfate reducing bacteria in the sediment. The food web magnification factors of MHg were 9.6 (95% CI: 4.0-23.4) and 4.4 (95% CI: 2.5-7.7) for the two streams established with trophic data of biofilm, invertebrates, and fish. Meanwhile, DGT-Hg concentrations in the water were positively correlated to biofilm Hg concentrations, which can be combined with the MHg biomagnification model to generate a modified biomagnification model that estimate MHg bioaccumulation with only labile Hg concentrations in the water. With this approach, Hg accumulation in abiotic and biotic environmental compartments was connected and the different bioaccumulation patterns of Hg in different waterbodies were explained with both geochemical and biological factors.
采集了萨凡纳河场址两条溪流的水、沉积物和生物群，以研究汞（Hg）的生物地球化学。对所有样品进行了总汞（THg）和甲基汞（MHg）浓度的测量，使用形态模型来探索水中的 Hg 形态，并用扩散梯度薄膜（DGT）来指示可利用 Hg 的垂直分布（DGT-Hg）。为生物群估计了营养位置（δN），并用于建立 MHg 生物放大模型。形态模型表明，水中的 Hg 甲基化发生在沉降颗粒上，对细菌最具生物利用性的 Hg 物种是无机 Hg 和可利用的有机配体的复合物。相应地，水中溶解有机碳浓度与 MHg 浓度呈正相关。在沉积物中，DGT-Hg 在沉积物-水界面附近急剧增加，强调了这个界面的重要性，它决定了不同水体中可利用 Hg 的积累和产生的差异。沉积物中 MHg 与硫酸盐浓度之间的正相关表明，沉积物中异化硫酸盐还原菌可能发生了甲基化反应。利用生物膜、无脊椎动物和鱼类的营养数据建立的两条溪流的 MHg 食物链放大因子分别为 9.6（95%置信区间：4.0-23.4）和 4.4（95%置信区间：2.5-7.7）。同时，水中的 DGT-Hg 浓度与生物膜 Hg 浓度呈正相关，这可以与 MHg 生物放大模型结合，生成一个仅用水中可利用 Hg 浓度来估算 MHg 生物积累的改良生物放大模型。通过这种方法，将非生物和生物环境成分中的 Hg 积累联系起来，并利用地球化学和生物学因素解释了不同水体中 Hg 的不同生物积累模式。
