Liu Nantao, Cai Xinyuan, Jia Longyu, Wang Xun, Yuan Wei, Lin Che-Jen, Wang Dingyong, Feng Xinbin
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
College of Resources and Environment, Southwest University, Chongqing 400715, China.
Environ Sci Technol. 2023 Apr 11;57(14):5903-5912. doi: 10.1021/acs.est.2c09610. Epub 2023 Mar 28.
Long-range transport and atmospheric deposition of gaseous mercury (Hg) result in significant accumulation of Hg in the Qinghai-Tibetan Plateau (QTP). However, there are significant knowledge gaps in understanding the spatial distribution and source contribution of Hg in the surface soil of the QTP and factors influencing Hg accumulation. In this study, we comprehensively investigated Hg concentrations and isotopic signatures in the QTP to address these knowledge gaps. Results show that the average Hg concentration in the surface soil ranks as follows: forest (53.9 ± 36.9 ng g) > meadow (30.7 ± 14.3 ng g) > steppe (24.5 ± 16.1 ng g) > shrub (21.0 ± 11.6 ng g). Hg isotopic mass mixing and structural equation models demonstrate that vegetation-mediated atmospheric Hg deposition dominates the Hg source in the surface soil, with an average contribution of 62 ± 12% in forests, followed by 51 ± 10% in shrub, 50 ± 13% in steppe, and 45 ± 11% in meadow. Additionally, geogenic sources contribute 28-37% of surface soil Hg accumulation, and atmospheric Hg inputs contribute 10-18% among the four types of biomes. The Hg pool in 0-10 cm surface soil over the QTP is estimated as 8200 ± 3292 Mg. Global warming, permafrost degradation, and anthropogenic influences have likely perturbed Hg accumulation in the soil of QTP.
气态汞（Hg）的长距离传输和大气沉降导致汞在青藏高原（QTP）大量积累。然而，在了解青藏高原表层土壤中汞的空间分布、来源贡献以及影响汞积累的因素方面，仍存在重大知识空白。在本研究中，我们全面调查了青藏高原的汞浓度和同位素特征，以填补这些知识空白。结果表明，表层土壤中汞的平均浓度排序如下：森林（53.9±36.9 ng/g）＞草甸（30.7±14.3 ng/g）＞草原（24.5±16.1 ng/g）＞灌丛（21.0±11.6 ng/g）。汞同位素质量混合和结构方程模型表明，植被介导的大气汞沉降主导了表层土壤中的汞来源，在森林中的平均贡献率为62±12%，其次是灌丛中的51±10%、草原中的50±13%和草甸中的45±11%。此外，地质来源对表层土壤汞积累的贡献率为28 - 37%，在四种生物群落类型中，大气汞输入的贡献率为10 - 18%。估计青藏高原0 - 10厘米表层土壤中的汞储量为8200±3292 Mg。全球变暖、多年冻土退化和人为影响可能扰乱了青藏高原土壤中的汞积累。
