Bureau of Water, The South Carolina Department of Health and Environmental Control, 2600 Bull Street, Columbia, SC 29201, USA.
Ecotoxicology. 2010 Apr;19(4):781-95. doi: 10.1007/s10646-009-0455-6. Epub 2010 Jan 8.
The South Carolina Department of Health and Environmental Control has collected, processed, and analyzed fish tissue total mercury (Hg) since 1976. For this study, skin-on-filet data from 1993 to 2007 were examined to determine biotic, spatial and temporal trends in tissue Hg levels for SC fishes. Because of the relatively high number of tissue Hg values below the analytical detection limits interval censored regression and censored least absolute deviations were used to construct several models to characterize trends. Large pelagic, piscivorous fish species, such as bowfin (Amia calva Linnaeus 1766), had higher levels of tissue Hg than smaller omnivorous species. Estuarine species had relatively low levels of tissue Hg compared to freshwater species, while two large open ocean species, king mackerel (Scomberomorus cavalla Cuvier 1829) and swordfish (Xiphias gladius Linnaeus 1758), had higher tissue Hg readings. For a given fish species, length was an important predictor of tissue Hg with larger individuals having higher levels than smaller individuals. The USEPA Level III ecoregion and water body type from where the fishes were collected were important in predicting the levels of tissue Hg. The Middle Atlantic Coastal Plain ecoregion had fishes with the highest levels of tissue Hg, while the Piedmont and Southern Coastal Plain ecoregions had the lowest. For a given ecoregion, large reservoirs and regulated rivers had fish with lower levels of tissue Hg than unregulated rivers. For reservoirs, the size of the impoundment was a significant predictor of tissue mercury with small reservoirs having higher levels of tissue mercury than large reservoirs. Landuse and water chemistry accounted for differences seen in fish of various ecoregions and waterbody types. Sampling locations associated with a high percentage of wetland area had fish with high levels of tissue Hg. Correlation analysis showed a strong positive relationship between tissue Hg levels and water column iron, total organic carbon, ammonia, and total kjedahl nitrogen, and a negative relationship with alkalinity, dissolved oxygen and pH. Results from principle component analysis revealed patterns between waterbody type and water chemistry variables that suggests hydrologic modification can have profound effects on the levels of fish tissue Hg in riverine systems. From 1993 to 2007, fish tissue Hg levels have trended lower. A spike in tissue Hg levels was observed in 2003-2005. The drying and rewetting of the landscape after the 2002 drought is hypothesized to have caused an increase in the methylation efficiencies of the system.
南卡罗来纳州卫生与环境控制部自 1976 年以来一直收集、处理和分析鱼类组织中的总汞 (Hg)。在这项研究中，对 1993 年至 2007 年的带皮鱼片数据进行了检查，以确定南卡罗来纳鱼类组织中 Hg 水平的生物、空间和时间趋势。由于组织 Hg 值低于分析检测限的数量相对较多，因此使用区间 censored 回归和 censored 最小绝对偏差来构建几个模型来描述趋势。大型掠食性鱼类，如弓鳍鱼（Amia calva Linnaeus 1766），其组织 Hg 水平高于较小的杂食性鱼类。与淡水物种相比，河口物种的组织 Hg 水平相对较低，而两种大型远洋物种，金鲷（Scomberomorus cavalla Cuvier 1829）和剑鱼（Xiphias gladius Linnaeus 1758），则具有较高的组织 Hg 读数。对于给定的鱼类物种，长度是组织 Hg 的重要预测因子，较大的个体比较小的个体具有更高的水平。鱼类采集地的美国环保署三级生态区和水体类型对于预测组织 Hg 水平非常重要。大西洋中部沿海平原生态区的鱼类组织 Hg 含量最高，而皮埃蒙特和南沿海平原生态区的鱼类组织 Hg 含量最低。对于给定的生态区，大型水库和受管制的河流中的鱼类组织 Hg 含量低于不受管制的河流。对于水库而言，水库的大小是组织汞的一个重要预测因子，小水库的组织汞含量高于大水库。土地利用和水化学解释了不同生态区和水体类型鱼类之间的差异。与湿地面积百分比高的采样地点相关的鱼类组织 Hg 含量较高。相关分析显示，组织 Hg 水平与水柱铁、总有机碳、氨和总凯氏氮呈正相关，与碱度、溶解氧和 pH 呈负相关。主成分分析的结果揭示了水体类型和水化学变量之间的模式，表明水文条件的改变可能对河流系统中鱼类组织 Hg 的水平产生深远影响。1993 年至 2007 年间，鱼类组织 Hg 水平呈下降趋势。2003-2005 年期间，组织 Hg 水平出现了一个高峰。据推测，2002 年干旱后景观的干燥和再湿润导致系统的甲基化效率增加。
