Black Friank J, Paytan Adina, Knee Karen L, De Sieyes Nicholas R, Ganguli Priya M, Gray Ellen, Flegal A Russell
WIGS Laboratory, Department of Environmental Toxicology, and Institute of Marine Sciences, University of California, Santa Cruz, California 95064, USA.
Environ Sci Technol. 2009 Aug 1;43(15):5652-9. doi: 10.1021/es900539c.
Fluxes of total mercury (Hg(T)) and monomethylmercury (MMHg) associated with submarine groundwater discharge (SGD) at two sites onthe central California coast were estimated by combining measurements of Hg(T) and MMHg in groundwater with the use of short-lived, naturally occurring radium isotopes as tracers of groundwater inputs. Concentrations of Hg(T) were relatively low, ranging from 1.2 to 28.3 pM in filtered groundwater, 0.8 to 11.6 pM in filtered surface waters, and 2.5 to 12.9 pM in unfiltered surface waters. Concentrations of MMHg ranged from < 0.04 to 3.1 pM in filtered groundwater, < 0.04 to 0.53 pM in filtered surface waters, and 0.07 to 1.2 pM in unfiltered surface waters. Multiple linear regression analysis identified significant (p < 0.05) positive correlations between dissolved groundwater concentrations of Hg(T) and those of NH4+ and SiO2, and between dissolved groundwater concentrations of MMHg and those of Hg(T) and NH4+. However, such relationships did not account for the majority of the variability in concentration data for either mercury species in groundwater. Fluxes of Hg(T) via SGD were estimated to be 250 +/- 160 nmol day m(-1) of shoreline at Stinson Beach and 3.0 +/- 2.0 nmol m(-2) day(-1) at Elkhorn Slough. These Hg(T) fluxes are substantially greater than net atmospheric inputs of Hg(T) reported for waters in nearby San Francisco Bay. Calculated fluxes of MMHg to coastal waters via SGD were 10 +/- 12 nmol day(-1) m(-1) of shoreline at Stinson Beach and 0.24 +/- 0.21 nmol m(-2) day at Elkhorn Slough. These MMHg fluxes are similar to benthic fluxes of MMHg out of surface sediments commonly reported for estuarine and coastal environments. Consequently, this work demonstrates that SGD is an important source of both Hg(T) and MMHg to coastal waters along the central California coast.
通过将地下水中总汞（Hg(T)）和甲基汞（MMHg）的测量值与使用短寿命天然镭同位素作为地下水输入示踪剂相结合，估算了加利福尼亚州中部海岸两个地点与海底地下水排放（SGD）相关的Hg(T)和MMHg通量。Hg(T)浓度相对较低，过滤后的地下水中为1.2至28.3皮摩尔，过滤后的地表水中为0.8至11.6皮摩尔，未过滤的地表水中为2.5至12.9皮摩尔。MMHg浓度在过滤后的地下水中为<0.04至3.1皮摩尔，过滤后的地表水中为<0.04至0.53皮摩尔，未过滤的地表水中为0.07至1.2皮摩尔。多元线性回归分析确定，地下水中溶解态Hg(T)浓度与NH4+和SiO2浓度之间存在显著（p<0.05）正相关，地下水中溶解态MMHg浓度与Hg(T)和NH4+浓度之间也存在显著正相关。然而，这种关系并不能解释地下水中两种汞形态浓度数据的大部分变异性。通过SGD的Hg(T)通量估计在廷森海滩为250±160纳摩尔·天·米-1海岸线，在埃尔克霍恩湿地为3.0±2.0纳摩尔·米-2·天-1。这些Hg(T)通量大大高于附近旧金山湾水域报告的Hg(T)净大气输入量。通过SGD计算得出的向沿海水域的MMHg通量在廷森海滩为10±12纳摩尔·天-1·米-1海岸线，在埃尔克霍恩湿地为0.24±0.21纳摩尔·米-2·天。这些MMHg通量与河口和沿海环境中通常报告的表层沉积物中MMHg的底栖通量相似。因此，这项工作表明SGD是加利福尼亚州中部海岸沿海水域Hg(T)和MMHg的重要来源。
