Snow chemical characteristics and meteorological controlling factors from three snowfalls of Gande in the Tibetan plateau

Abstract

Water-soluble ions (Cl−, SO42−, NO3−, Ca2+, Mg2+, Na+, K+ and NH4+) and trace elements (Pb, Cd, Cr and As) in snow samples were analyzed from three different snowfall events (Ⅰ, Ⅱ, Ⅲ) in December 2019 at Gande Meteorological Station, located in the southeastern part of the Tibetan Plateau region. From event Ⅰ to Ⅲ, the total concentration of water-soluble ions presented an increasing trend of 0.92, 1.43 and 3.01 mg L−1, respectively. The dominant cation was Ca2+ for all the events, while the dominate anion was SO42−, SO42− and Cl− in the event Ⅰ, Ⅱ and Ⅲ, respectively. Meteorological field and backward trajectory cluster analysis presented three different large-scale predominant wind directions of northwest wind, southwest wind and west wind for each event, revealing different transport processes and sources for snow components. The total concentration of water-soluble ions was mainly related to PM10 as the in-situ PM10 observation showed a similar increasing trend. The dominant trace element was different Pb, Cr and Pb in each event. The mixed source of crustal and industrial inputs was the key factor in three snowfalls, and its contribution was consistent with the concentration of dominant trace element. Herein, high fractions of Pb and Ca2+ were appeared in the event Ⅰ and Ⅲ, but largest proportion to Cr was enhanced in the event Ⅱ.