School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China.
Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100085, China.
Environ Pollut. 2020 Oct;265(Pt B):115079. doi: 10.1016/j.envpol.2020.115079. Epub 2020 Jun 25.
Soils, especially permafrost in the Arctic and the Tibetan Plateau, are one of the largest reservoirs of mercury (Hg) in the global environment. The Hg concentration in the grassland soils over the Tibetan Plateau and its driving factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in grassland soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric Hg deposition. The relationship between STHg and soil organic carbon (SOC), as well as atmospheric deposition, are explored. Our results show that the STHg concentrations in the Tibetan Plateau are 19.8 ± 12.2 ng/g. The concentrations are higher in the south and lower in the north in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 μg m yr, with 57% contributed by dry deposition of elemental mercury (Hg), followed by dry (19%) and wet (24%) deposition of divalent mercury. We calculate the Hg to carbon ratio (R) as 5.6 ± 6.5 μg Hg/g C, and the estimated STHg is 86.6 ± 101.2 Gg in alpine grasslands in the Tibetan Plateau. We find a positive relationship between STHg and SOC in the Tibetan Plateau (r = 0.36) and a similar positive relationship between STHg and atmospheric total Hg deposition (r = 0.24). A multiple linear regression involving both variables better model the observed STHg (r = 0.42). We conclude that SOC and atmospheric deposition influence STHg simultaneously in this region. The data provides information to quantify the size of the soil Hg pool in the Tibetan Plateau further, which has important implications for the Hg cycles in the permafrost regions as well as on the global scale.
土壤，特别是北极和青藏高原的永久冻土，是全球环境中最大的汞（Hg）储存库之一。青藏高原草原土壤中的 Hg 浓度及其驱动因素研究较少。本研究分析了青藏高原草原土壤样品中的土壤总汞（STHg）浓度及其垂直分布。我们采用嵌套网格高分辨率 GEOS-Chem 模型模拟大气 Hg 沉积。探讨了 STHg 与土壤有机碳（SOC）以及大气沉积之间的关系。结果表明，青藏高原的 STHg 浓度为 19.8±12.2ng/g。与以往研究结果一致，青藏高原南部浓度较高，北部浓度较低。模型表明，Hg 的平均沉积通量为 3.3μg m yr，其中 57%由元素汞（Hg）的干沉降贡献，其次是干沉降（19%）和湿沉降（24%）。我们计算了 Hg 与碳的比值（R）为 5.6±6.5μg Hg/g C，估计青藏高原高山草原的 STHg 为 86.6±101.2Gg。我们发现青藏高原 STHg 与 SOC 之间存在正相关关系（r=0.36），与大气总 Hg 沉积之间也存在类似的正相关关系（r=0.24）。同时考虑这两个变量的多元线性回归更好地模拟了观测到的 STHg（r=0.42）。我们得出结论，SOC 和大气沉积同时影响该地区的 STHg。该数据进一步提供了量化青藏高原土壤 Hg 库大小的信息，这对永久冻土地区以及全球范围内的 Hg 循环具有重要意义。
