State Key Laboratory of Cryosphere Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou, 730000, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
State Key Laboratory of Cryosphere Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou, 730000, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences (CAS), Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Environ Pollut. 2020 Jun;261:114114. doi: 10.1016/j.envpol.2020.114114. Epub 2020 Feb 5.
This study employs the grain size distributions and the concentrations and isotopic compositions of Sr, Nd, and Pb in the precipitation samples collected from the Laohugou Glacier (LHG) in northeastern Tibetan Plateau (TP) during August 2014-2015 to investigate seasonal variability in the insoluble precipitation particle sources. Fine dust particle (0.57-27 μm) depositions dominated in autumn and winter, whereas both fine and coarse dust particle (27-100 μm) depositions were found in spring and summer. Furthermore, the concentrations of Sr, Nd, and Pb also varied seasonally-the highest and lowest Sr and Nd concentrations were recorded in spring and autumn, respectively, whereas the highest and lowest Pb concentrations were recorded in winter and summer, respectively. The Sr and Nd isotopes revealed that the dust in the winter precipitation originated predominately from the Taklimakan Desert and that in spring originated from the Badain Jaran and Qaidam deserts. The precipitation residues in summer were derived from a complex mixture of dust sources from the Gobi and other large deserts in northwest China. Autumn residues were predominately sourced from local soil near the LHG as well as from the Qaidam Basin and the northern TP surface soil. The Taklimakan, long suspected as a major source of long-range transported dust, was an insignificant contributor to the precipitation over LHG during spring, summer, and autumn. Further, the Pb isotopic ratios indicated a primary impact of anthropogenic pollutants for most part of the year (except spring). Meteorological data and the MODIS AOD model are in good agreement with the results from the analyses of the Sr, Nd, and Pb isotopes for the LHG particle source, and further clarify the source regions. Thus, this study thus provides new evidence on the seasonal variability of the sources of the residual particles in remote glaciers in Central Asia.
本研究利用 2014 年 8 月至 2015 年 8 月在青藏高原东北部老河沟冰川（LHG）采集的降水样本中的粒度分布以及 Sr、Nd 和 Pb 的浓度和同位素组成，研究了不可溶降水颗粒源的季节性变化。细粉尘颗粒（0.57-27μm）在秋季和冬季占主导地位，而春季和夏季则既有细粉尘又有粗粉尘颗粒（27-100μm）。此外，Sr、Nd 和 Pb 的浓度也随季节变化而变化——春季和秋季的 Sr 和 Nd 浓度最高和最低，而冬季和夏季的 Pb 浓度最高和最低。Sr 和 Nd 同位素表明，冬季降水中的尘埃主要来源于塔克拉玛干沙漠，而春季降水中的尘埃主要来源于巴丹吉林沙漠和柴达木沙漠。夏季降水残留物来源于来自中国西北部戈壁和其他大型沙漠的尘埃源的复杂混合物。秋季残留物主要来源于 LHG 附近的当地土壤以及柴达木盆地和青藏高原北部的表土。一直以来，人们都怀疑塔克拉玛干沙漠是长程传输尘埃的主要来源，但它在春季、夏季和秋季对 LHG 的降水贡献甚微。此外，Pb 同位素比值表明，在一年中的大部分时间（除春季外），人为污染物对大部分地区都有主要影响。气象数据和 MODIS AOD 模型与对 LHG 颗粒源的 Sr、Nd 和 Pb 同位素分析结果非常吻合，进一步阐明了源区。因此，本研究为中亚偏远冰川残留颗粒源的季节性变化提供了新的证据。
