青藏高原贡嘎山冰川区水体中Hg的空间分布及其源汇特征

Spatial distribution and source / sink characteristic of mercury in the water samples from the Mt. Gongga area in the Tibetan Plateau

通过测定青藏高原东北部贡嘎山冰川区流域尺度的雪样、冰川、地表水、地下渗透水的汞(Hg)含量及形态,发现流域水样的总Hg浓度介于1.74—17.8 ng·L^(-1)之间,其60%以上的形态为颗粒态汞;Hg的空间分布存在明显的海拔效应,即低温高海拔区域具有Hg的冷捕获和放大积累效应;从降雪到冰雪融化形成汇流河水再到地下渗透的过程中,Hg发生了重要的沉淀作用,土壤能够吸附大量的Hg.进一步通过主成分分析,建立多重线性回归模型,定量确定了水体环境中大气沉降的正贡献为163.3%,沉淀作用的负贡献为-69.8%.这些结果表明,大气沉降的颗粒物不仅是水体环境的Hg输入的主要来源,还是土壤Hg的重要来源,青藏高原可能是全球大气Hg循环中重要的沉降汇集区.

The Tibetan Plateau has been considered as one of the sensitive ecosystems to suffer from global environmental changes and pollutants inputs. In this study, surface snow, glacial, surface water and seepage water were sampled and analyzed for total mercury （HgT） in the Mt. Gongga area, China. The total mercury concentrations in these samples ranged from 1.74 to 17.8 ng.L-1. Particle bound mercury predominated the atmospheric mercury inputs. The concentration of HgT increased with the increase of altitude, suggesting mercury accumulated by ＂cold trapping＂ in high elevated regions. In addition, HgT concentration exhibited a diseasing trend from surface snow, surface river, and to the underground seepage water. This reveals the sedimentation of mercury during runoff transportation occurred. Principal component analysis （PCA） and multiple linear regression （MLR） suggested that atmospheric deposition mainly contributed to the accumulation of HgT （163.3%）, and sedimentation of Hg during runoff transportation was attributed to the decrease HgT （-69.8%）. This study suggests sedimentation of Hg with particle is the main source for Hg accumulation in water bodies and soil, and the Tibetan Plateau may present a significant Hg sink in the global Hg cycling.