Gustin Mae Sexauer, Chavan Prithviraj V, Dennett Keith E, Marchand Eric A, Donaldson Susan
Dep. of Natural Resources and Environmental Sciences, Univ. of Nevada, Reno, NV 89557, USA.
J Environ Qual. 2006 Oct 27;35(6):2352-9. doi: 10.2134/jeq2005.0478. Print 2006 Nov-Dec.
Mercury associated with natural enrichment, historic mining, and ore processing is a contaminant of concern in watersheds of the western USA. In this region, water is a highly managed resource and wetlands, known to be important sites of methyl mercury production, are often an integral component of watersheds. This study applied controlled manipulations of four replicated experimental wetland designs with different water and soil mercury concentrations to determine the potential impacts on methyl mercury export. Wetlands were manipulated by drying and wetting, changing hydraulic retention time, and adding sulfate and nitrate to influent waters. In a summer drying and wetting manipulation, an immediate increase in total methyl mercury release was observed with rewetting, however, concentrations decreased quickly. Drying all wetlands over the winter and rewetting in the spring resulted in high net methyl mercury output relative to that observed before drying. Net methyl mercury output was not influenced by changes in hydraulic retention time from 4 to 8 h or to 30 min, or by increasing the nitrate concentration from 0.1 to 10 mg L(-1). The addition of sulfate to the inlet waters of two mesocosms to increase concentrations from approximately 100 to 250 mg L(-1) did not result in a clear effect on methyl mercury output, most likely due to sulfate concentrations being higher than optimal for methyl mercury production. Despite the lack of response to sulfate amendments, the change in sulfate concentration between the inlet and outlet of the mesocosms and temperature were the parameters best correlated with methyl mercury outputs.
与自然富集、历史采矿及矿石加工相关的汞是美国西部流域令人担忧的污染物。在该地区，水是一种管理严格的资源，而湿地作为已知甲基汞产生的重要场所，通常是流域的一个组成部分。本研究对四个具有不同水和土壤汞浓度的重复实验湿地设计进行了控制性操作，以确定对甲基汞输出的潜在影响。通过干湿交替、改变水力停留时间以及向进水添加硫酸盐和硝酸盐来对湿地进行操作。在夏季的干湿交替操作中，重新湿润时总甲基汞释放量立即增加，然而，浓度迅速下降。冬季将所有湿地干涸并在春季重新湿润，相对于干涸前观察到的情况，导致了较高的甲基汞净输出。甲基汞净输出不受水力停留时间从4小时变为8小时或30分钟的变化影响，也不受硝酸盐浓度从0.1毫克/升增加到10毫克/升的影响。向两个中宇宙的进水添加硫酸盐以使浓度从约100毫克/升增加到250毫克/升，对甲基汞输出没有产生明显影响，最可能的原因是硫酸盐浓度高于甲基汞产生的最佳浓度。尽管对硫酸盐添加没有响应，但中宇宙进水和出水之间的硫酸盐浓度变化以及温度是与甲基汞输出相关性最好的参数。
