Environmental implications of the snow chemistry from Mt. Yulong, southeastern Tibetan Plateau

摘要

Snow chemical records were recovered from fresh and surface snow samples in the Mt. Yulong region. Striking seasonal differences were evident among the major ions. The non-monsoon snow samples show higher ionic concentrations than those of the monsoon season. The observations can be categorized into three groups based on their seasonal behavior and characteristic relationships that were explored using correlation and factor analyses. Calculations of backward trajectory modes suggest that the coarse mode ions (e.g. Ca~(2+), Mg~(2+)) were mainly transported from Central Asia, through the south limb of the westerlies, in non-monsoon seasons. The Indian monsoon and southeast monsoon are the prevailing air masses in the Yulong region during the monsoon season, and can account for the extensive precipitation and lower snow ion concentrations in this season. Ion balance calculations indicate that there is an excess of cations in snow chemistry due to higher concentrations of Ca~(2+). In addition, the low snow Na~+/Cl~- ratio shows an obvious excess of Cl~ concentrations possibly due to the precipitation scavenging of gas-phase HC1 in the air and/or different sources between Na~+ and Cl . The snow chemical data presented here indicate that Mt. Yulong provides a probably unique record of atmospheric and environmental conditions in southwestern China.