State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing, 100085, China.
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing, 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China.
Environ Res. 2021 Apr;195:110810. doi: 10.1016/j.envres.2021.110810. Epub 2021 Jan 30.
As an important reservoir of mercury (Hg), cropland play an important role in the Hg cycle, but it was poorly understood in northern China. The major objectives of this study are to ascertain the distribution characteristics of soil Hg and then assess its pollution level and potential risk, and further evaluate the role of cropland in northern China in the global soil-air exchange of Hg based on the simulation experiments and regional survey. The average Hg concentration in surface soils of the 30 sites in northern China was 116.1 ± 135.8 ng g, which was significantly higher than background values. The surface soils show a significant spatial heterogeneity in Hg concentration, and the Hg levels near provincial capitals were higher than those at corresponding prefecture-level cities, revealing that the soil Hg levels were closely associated with the local industrial and economic development. Profile data shows that topsoil Hg concentration was significantly higher than those in deeper layers at most of sites, indicating the more serious pollution situation in recent years. Generally, the higher the surface soil Hg concentration, the more obvious this top-bottom decreasing trend. The planular-vertical distribution patterns of TOM share similar trends as those of soil Hg concentration, indicating Hg concentration was closely associated with TOM content. Statistical results show that the mean CF, E, and I values were 4.0 ± 5.0, 161 ± 198, 0.76 ± 1.34, respectively, and more than two thirds of sampling sites were moderately and considerably polluted. The mean annual accumulative flux of Hg in the northern China was 20.9 ± 43.8 μg m yr, and the total net emission fluxes of Hg from the croplands in six provinces were 8.37 ton yr. This indicates that although the cropland occasionally acts as a sink, it represents an important natural source of atmospheric Hg as a whole.
作为汞（Hg）的重要储存库，农田在汞循环中起着重要作用，但在我国北方地区，这方面的认识还很有限。本研究的主要目的是确定土壤 Hg 的分布特征，然后评估其污染水平和潜在风险，并进一步基于模拟实验和区域调查评估农田在中国北方在全球土壤-大气 Hg 交换中的作用。我国北方 30 个采样点表层土壤的平均 Hg 浓度为 116.1±135.8ng/g，明显高于背景值。表层土壤 Hg 浓度具有显著的空间异质性，省会城市附近的 Hg 水平高于相应的地级市，表明土壤 Hg 水平与当地工业和经济发展密切相关。剖面数据显示，在大多数采样点，表层土壤的 Hg 浓度明显高于深层土壤，表明近年来污染情况更为严重。一般来说，表层土壤 Hg 浓度越高，上下层之间的这种降低趋势越明显。 TOM 的平面-垂直分布模式与土壤 Hg 浓度的分布模式相似，表明 Hg 浓度与 TOM 含量密切相关。统计结果表明，CF、E 和 I 的平均值分别为 4.0±5.0、161±198、0.76±1.34，超过三分之二的采样点处于中度和较重度污染。我国北方地区每年 Hg 的累积通量平均值为 20.9±43.8μg/m2yr，6 个省份农田的总净排放通量为 8.37 吨 yr。这表明，尽管农田偶尔充当汇，但作为大气 Hg 的一个重要自然源，其整体贡献不可忽视。
