武汉城市湖泊表层底泥汞分布、风险评价及影响因素

底泥作为汞重要的"汇"及二次"源"，在湖泊系统汞生物地球化学循环中起到了重要作用。本文以武汉主要城市湖泊为研究对象，探究了表层底泥中总汞（THg）和甲基汞（MeHg）的分布特征、潜在生态风险及主要影响因素。结果表明，武汉15个城市湖泊表层底泥THg平均浓度为152±170 ng/g （24~611 ng/g），与国内其它湖泊系统相比处于较高水平；MeHg浓度为52.0±46.8 pg/g （ND~161.0 pg/g），低于其它湖泊系统。空间分布上，底泥THg浓度呈现由武汉市中心向外逐渐递减的趋势，MeHg含量并未呈现类似THg的分布趋势。潜在生态风险评价（PERI）结果显示，所有采样点位中汞潜在生态风险极高和高风险等级占比均为5.7%，且主要分布在市中心附近，说明武汉市中心附近湖泊底泥汞污染程度较重，而市中心外围湖泊底泥汞生态风险较低。相关性分析结果显示，有机质可能是影响武汉城市湖泊底泥THg分布的重要因素之一，而MeHg主要受控于无机汞的原位甲基化过程。底泥THg浓度-湖泊距市中心距离间显著的负相关关系、THg浓度-湖泊所在区GDP/人均GDP间的显著正相关关系均表明人为活动对武汉城市湖泊汞分布影响明显。

Distribution, Risk Assessment and Influencing Factors of Mercury in the Surface Sediment of Urban Lakes in Wuhan City

As an important "sink" and secondary "source" of mercury (Hg), sediment plays an important role in biogeochemical cycling of Hg in lake system. In this study, sediment samples from 15 urban lakes of Wuhan City were collected to analyze the distribution characteristics of total Hg (THg) and methylmercury (MeHg), and to assess the ecological risk of Hg and to distinguish the influencing factors. The results showed that the average concentration of THg in sediment was 152±170 ng/g (24-611 ng/g), and occupied the higher rank among the reported domestic lake systems. However, MeHg concentration (52.0±46.8 pg/g, ranged from ND to 161.0 pg/g) in sediment of this study was lower compared with other lake systems. Concentration of THg in sediment showed a significantly decreasing trend from the center of Wuhan to the outside, and MeHg displayed no significant trend. The potential ecological risk index (PERI) revealed that the proportion of very high and high risk of Hg was 11.4% accounted for total sampling sites, and was mainly located near the city center, suggesting that Hg pollution in the lake near city center was more serious than other lakes. Correlation analysis showed that organic matter was one of important factors affecting THg distribution in sediment, and MeHg was mainly controlled by in-situ methylation process of inorganic Hg. The significantly negative correlation between THg concentration in sediment and the distance of lakes away city center, and the positive relationships between THg concentrations and GDP/Per Capita GDP indicated that human activities can obviously influence the distribution of Hg in urban lakes of Wuhan City.