河北省衡水湖沉积物中汞的分布特征及生态风险

衡水湖是华北平原上第一个国家级内陆淡水湖泊湿地类型的自然保护区,为了解衡水湖沉积物中汞的分布特征及生态风险,于2013年8月在衡水湖采集了5根柱状沉积物,对其中的总汞、甲基汞、孔隙水溶解态汞、有机质、pH以及含水率进行了分析。结果表明,衡水湖沉积物中总汞的平均含量为22.5 ng·g-1,低于全国及河北省表层土壤背景值。但表层沉积物汞含量明显高于底层,说明近年来的外源汞输入对湖泊汞负荷产生了一定影响,且靠近湖泊东部106国道的采样点汞含量明显高于湖泊中西部的采样点,暗示交通运输等人为活动是该湖泊的一个重要汞输入源。利用潜在生态危害指数法进行评估,显示汞的生态风险较低,说明现阶段衡水湖的沉积物汞浓度不会对生态环境产生不利影响。

Distribution and Risk Assessment of Mercury in the Sediments of Hengshuihu Lake, Hebei Province

Hengshuihu Lake is the first national inland freshwater wetland nature reserve in North China Plain. To reveal the status of mercury distribution and ecological risk in sediments of Hengshuihu lake, we collected five columnar sediment cores in August 2013. The total mercury, methyl mercury, dissolved mercury in pore waters, organic matter, pH and moisture content were analyzed. The average total mercury content in the sediments was 22.5 ng·g^-1, which is lower than the national and Hebei Provincial surface soil background value. Within in the sediment cores, the mercury in the upper layer was higher than that of the lower parts, hinting the recent input by human activities. Meanwhile, the total mercury in the sediment cores in eastern part of the lake, which is closer to the national highway 106, was significantly higher than the central and western sites, indicating that the transportation has important impacts on the Hg accumulation. Nevertheless, based on potential ecological harm index assessment, ecological risk by mercury in the sediment was very low. This suggests there is no adverse ecological impact on the lake environment at this stage.