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首页> 外文期刊>Environmental Science & Technology >Sulfate addition increases methylmercury production in an experimental wetland
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Sulfate addition increases methylmercury production in an experimental wetland

机译：添加硫酸盐可增加实验湿地中甲基汞的产量

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Atmospheric mercury is the dominant Hg source to fish in northern Minnesota and elsewhere. However, atmospherically derived Hg must be methylated prior to accumulating in fish. Sulfate-reducing bacteria are thought to be the primary methylators of Hg in the environment. Previous laboratory and field mesocosm studies have demonstrated an increase in methylmercury (MeHg) levels in sediment and peatland porewaters following additions of sulfate. In the current ecosystem-scale study, sulfate was added to half of an experimental wetland at the Marcell Experimental Forest located in northeastern Minnesota, increasing annual sulfate load by approximately four times relative to the control half of the wetland. Sulfate was added on four separate occasions during 2002 and delivered via a sprinkler system constructed on the southeast half (1.0 ha) of the S6 experimental wetland. MeHg levels were monitored in porewater and in outflow from the wetland. Prior to the first sulfate addition, MeHg concentrations (filtered, 0.7 mu m) were not statistically different between the control (0.47 +/- 0.10 ng L-1, n = 12; mean +/- one standard error) and experimental 0.52 +/- 0.05 ng L-1, n = 18) halves. Following the first addition in May 2002, MeHg porewater concentrations increased to 1.63 +/- 0.27 ng L-1 two weeks after the addition, a 3-fold increase. Subsequent additions in July and September 2002 did not raise porewater MeHg, but the applied sulfate was not observed in porewaters 24 h after addition. MeHg concentrations in outflow from the wetland also increased leading to an estimated 2.4x increase of MeHg flux from the wetland. Our results demonstrate enhanced methylation and increased MeHg concentrations within the wetland and in outflow from the wetland suggesting that decreasing sulfate deposition rates would lower MeHg export from wetlands.
机译：大气汞是明尼苏达州北部和其他地区捕鱼的主要汞来源。但是，在鱼类中积累之前，必须将大气中衍生的汞甲基化。减少硫酸盐的细菌被认为是环境中汞的主要甲基化剂。先前的实验室和现场中观研究表明，添加硫酸盐后，沉积物和泥炭地孔隙水中甲基汞（MeHg）含量增加。在当前的生态系统规模研究中，将硫酸盐添加到了位于明尼苏达州东北部Marcell实验森林的一半实验湿地中，相对于湿地的对照一半，年硫酸盐负荷增加了大约四倍。在2002年期间，在四个不同的场合添加了硫酸盐，并通过在S6实验湿地东南半部（1.0公顷）上建造的洒水系统进行了输送。在孔隙水和湿地的出水中监测甲基汞含量。在第一次添加硫酸盐之前，对照组的MeHg浓度（过滤后为0.7微米）在统计学上没有统计学差异（0.47 +/- 0.10 ng L-1，n = 12；平均值+/-一个标准误差）和实验值0.52 + /-0.05 ng L-1，n = 18）。在2002年5月首次添加后，MeHg孔隙水浓度在添加后两周增加到1.63 +/- 0.27 ng L-1，增加了3倍。随后的2002年7月和2002年9月添加并未增加孔隙水的MeHg，但是添加后24小时在孔隙水中未观察到施用的硫酸盐。从湿地流出的MeHg浓度也增加，导致从湿地流出的MeHg流量估计增加2.4倍。我们的结果表明，在湿地中以及从湿地流出的甲基化增强，MeHg浓度增加，这表明硫酸盐沉积速率的降低将降低湿地的MeHg出口。

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