Arid Zone Research ›› 2022, Vol. 39 ›› Issue (2): 347-358.doi: 10.13866/j.azr.2022.02.02

• Weather and Climate • Previous Articles     Next Articles

Chemical characteristics and their influencing factors of precipitation at the end of the Koxkar Glacier, Tianshan Mountains

WANG Jian1(),HAN Haidong2,XU Junli1(),YAN Wei3   

  1. 1. North Jiangsu Research Institute of Agricultural and Rural Modernization, Yancheng Teachers University, Yancheng 224007, Jiangsu, China
    2. State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China
    3. School of Geographic Sciences, Xinyang Normal University, Xinyang 464000, Henan, China
  • Received:2021-08-25 Revised:2021-09-14 Online:2022-03-15 Published:2022-03-30
  • Contact: Junli XU E-mail:wjshuigong@lzb.ac.cn;xujunli01@163.com

Abstract:

Atmospheric precipitation was sampled in the summer at the end of the Koxkar Glacier, Tianshan Mountains, China. Based on analyses of the ion concentration, conductivity, and pH characteristics, we explored the solute sources and control factors for regional precipitation using factor analysis, enrichment factors, and backward trajectory tracking. Atmospheric precipitation was slightly alkaline, with a pH between 7.15 and 8.52, and their anions and cations were dominated by HCO3-and Ca2+, respectively, which belong to the typical HCO3-Ca type. The conductivity and total ion concentration of precipitation during the daytime were 11.56% and 9.40% higher, respectively, than those of the nighttime; this may be caused by the wet deposition of aerosol materials from the piedmont and plain areas with the near-surface wind under the action of valley wind or glacial wind during the daytime. Precipitation ions mainly originated from the supply of crustal source materials, accounting for 85.54% of the total ion content; among them, HCO3-, Ca2+, and Mg2+ were mainly supplied by carbonate rock weathering (CaxMg1-xCO3) in the Jurassic sedimentary layer and Quaternary loess sedimentary layer, whereas Cl-, SO42-, Na+, and K+ were mainly supplied by the evaporation of salt lakes caused by drought or the weathering of saline soil formed by alluvial/proluvial processes in Central Asia and the Tarim Basin. Only 41.52% of Na+ and 96.22% of Cl- in precipitation originated from ocean sources and salt lakes, and their concentration ratio was 2.13:1, indicating that ocean source air masses were affected by the precipitation reevaporation and wind erosion of surface materials during long-distance transportation; this resulted in ocean source recharge only accounting for 4.87% of the total precipitation ions. The solute supplied by human activities was approximately twice that of ocean sources, mainly NH4+,NO3-, and SO42-, which could provide the necessary nitrogen and sulfur for soil formation and alpine vegetation growth in the study area. Air mass backward trajectory tracking showed that westerly circulation had a significant impact on the precipitation and chemical composition in southern Xinjiang. The average proportion due to a water vapor source path and precipitation was 64.35% and 53.04% respectively. Although the total ion concentration in precipitation formed by westerly circulation accounted for only 69.91% of the local circulation, the average NO3-concentration was 1.42 times that of the local circulation precipitation, indicating that the air and water quality in the Tarim Basin may be affected by human activities in Central Asia.

Key words: atmospheric precipitation, solute source, human activity, water vapor transportation, cold alpine regions