State Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
Collaborative Innovation Center for Regional Environmental Quality, Tsinghua University, Beijing 100084, China.
Environ Sci Technol. 2020 Mar 3;54(5):2772-2779. doi: 10.1021/acs.est.9b06715. Epub 2020 Feb 21.
Comprehensive mercury (Hg) budgets were constructed in two typical subtropical forests in southern China in 2014 to quantify Hg (gaseous elemental Hg, Hg, and reactive Hg, Hg) input and output fluxes and Hg retention in forests, consequently exploring the roles of subtropical forests in the global Hg cycle. At site Qianyanzhou, representing a background region with an enhanced atmospheric Hg concentration, the total Hg deposition (67.7 μg·m·year, 73% as dry Hg deposition) was found to be slightly higher than the Hg emission above the canopy (58.5 μg·m·year), indicating that the forest is a minor Hg sink but a significant net Hg source on a yearly basis. In contrast, the forest in the moderately polluted region (site Huitong) acted as a significant Hg sink but a minor net Hg source with a higher Hg deposition (73.7 μg·m·year) and relatively negligible Hg emission (2.65 μg·m·year). The decreasing atmospheric Hg concentrations declined the total Hg sink based on the Hg budgets synthesized of this and previous studies and may promote forest Hg emissions. Consequently, it was expected that the re-emission of historically deposited Hg may be enhanced from subtropical forests by recent decreases in atmospheric Hg concentrations throughout China.
2014 年，在中国南方的两个典型亚热带森林中构建了全面的汞（Hg）预算，以量化森林中 Hg（气态元素 Hg、Hg 和反应性 Hg、Hg）输入和输出通量以及 Hg 滞留量，从而探索亚热带森林在全球 Hg 循环中的作用。在 Qianyanzhou 站点，代表大气 Hg 浓度增强的背景区域，总 Hg 沉积（67.7μg·m·年，73%为干 Hg 沉积）略高于冠层以上的 Hg 排放（58.5μg·m·年），表明森林是一个次要的 Hg 汇，但在每年的基础上是一个重要的净 Hg 源。相比之下，在中度污染地区（Huitong 站点）的森林作为一个显著的 Hg 汇，但净 Hg 源较小，Hg 沉积量较高（73.7μg·m·年），Hg 排放量相对较小（2.65μg·m·年）。大气 Hg 浓度的降低降低了基于本研究和以前研究综合 Hg 预算的总 Hg 汇，这可能会促进森林 Hg 排放。因此，预计中国大气 Hg 浓度的近期降低可能会增强历史上沉积 Hg 的再排放，这主要来自亚热带森林。
