US Geological Survey, Western Ecological Research Center, 1 Shields Avenue, University of California, Davis, California 95616, United States.
Sci Total Environ. 2010 Feb 1;408(5):1154-65. doi: 10.1016/j.scitotenv.2009.10.042. Epub 2009 Nov 17.
Decommissioned agricultural salt ponds within south San Francisco Bay, California, are in the process of being converted to habitat for the benefit of wildlife as well as water management needs and recreation. Little is known of baseline levels of contaminants in these ponds, particularly mercury (Hg), which has a well established legacy in the Bay. In this study we described spatial and short-term temporal variations in sediment Hg species concentrations within and among the Alviso and Eden Landing salt ponds in the southern region of San Francisco Bay. We determined total Hg (Hg(t)) and methylmercury (MeHg) in the top 5 cm of sediment of most ponds in order to establish baseline conditions prior to restoration, sediment Hg(t) concentrations in a subset of these ponds after commencement of restoration, and variation in MeHg concentrations relative to sediment Hg(t), pH, and total Fe concentrations and water depth and salinity in the subset of Alviso ponds. Inter-pond differences were greatest within the Alviso pond complex, where sediment Hg(t) concentrations averaged (arithmetic mean) 0.74 microg/g pre and 1.03 microg/g post-restoration activity compared to 0.11 microg/g pre and post at Eden Landing ponds. Sediment Hg(t) levels at Alviso were fairly stable temporally and spatially, whereas MeHg levels were variable relative to restoration activities across time and space. Mean (arithmetic) sediment MeHg concentrations increased (2.58 to 3.03 ng/g) in Alviso and decreased (2.20 to 1.03 ng/g) in Eden Landing restoration ponds during the study. Differences in MeHg levels were related to water depth and pH, but these relationships were not consistent between years or among ponds and were viewed with caution. Factors affecting MeHg levels in these ponds (and in general) are highly complex and require in-depth study to understand.
加利福尼亚州旧金山湾南部已废弃的农用盐田正在被改造成野生动物栖息地，以满足水管理需求和娱乐需求。这些盐田中污染物的基线水平，尤其是汞（Hg）的情况知之甚少，汞在海湾地区有悠久的历史。在这项研究中，我们描述了圣弗朗西斯科湾南部的 Alviso 和 Eden Landing 盐田内和盐田之间沉积物 Hg 形态浓度的空间和短期时间变化。我们测定了大多数盐田中最上层 5 厘米的沉积物中的总汞（Hg(t)）和甲基汞（MeHg），以在修复之前确定基线条件，在这些盐田中一部分开始修复之后测定沉积物 Hg(t)浓度，并测定相对于沉积物 Hg(t)、pH 值、总铁浓度以及 Alviso 盐田一部分中的水深和盐度的 MeHg 浓度的变化。池塘之间的差异在 Alviso 池塘群中最大，其中沉积物 Hg(t)浓度在修复前平均为 0.74 微克/克，修复后为 1.03 微克/克，而 Eden Landing 池塘的修复前和修复后分别为 0.11 微克/克。Alviso 沉积物 Hg(t)水平在时间和空间上相当稳定，而 MeHg 水平相对于整个时空范围内的修复活动变化较大。在研究期间，Alviso 的平均（算术）沉积物 MeHg 浓度从 2.58 增加到 3.03 纳克/克，而 Eden Landing 修复池塘的浓度从 2.20 减少到 1.03 纳克/克。MeHg 水平的差异与水深和 pH 值有关，但这些关系在不同年份或不同池塘之间并不一致，因此需要谨慎看待。影响这些池塘（以及一般情况）中 MeHg 水平的因素非常复杂，需要深入研究才能理解。
