Anthropogenic sulfate and Asian dust signals in snow from Tien Shan, northwest China

Abstract

Snow samples were collected from a 0.5 m snowpack at Glacier No. 1 and near Bogda Feng, eastern Tien Shan, northwest China. Samples that were melted in the field were analyzed for chloride, nitrate, sulfate, sodium, potassium, magnesium, calcium, and microparticles. Eight samples were returned frozen and were analyzed for the above ions plus ammonium, acetate, formate, methylsulfonate, and hydrogen peroxide. There was no significant difference in measured major ion concentrations between the melted and frozen samples. Measured cations in both sets of samples were two to three times greater than measured anions. Calcium and sodium are the dominant cations while sulfate is the dominant measured anion. High ion burdens are associated with dusty layers in the snowpack, indicating that dust from the vast arid regions of central Asia is the dominant source for major ions in Tien Shan snow. The significant increase in sulfate and decrease in the cation : anion ratio in Bogda Feng snow relative to Glacier No. 1 snow suggest that anthropogenic emissions from Ürümqi are an important source of sulfate to precipitation downwind from the city.

Iron content and solubility in dust from high-alpine snow along a north-south transect of High Asia

“…The pH value of the UG1 and Qiangyong samples differs. In UG1, the pH value averages (Wake et al, 1992). Eastern Tien Shan snow shows a greater pH value than that of Qiangyong and Qilian Shan, in accordance with the proximity to the Central Asian arid regions.…”

Glaciochemical investigation of an ice core from Belukha glacier, Siberian Altai

“…The differing temporal trends observed for sulfate, nitrate and calcium suggest that dust is not the only source of those two anions in the Belukha region. Anthropogenic sulfate was observed in snow from northwest China [Wake et al, 1992] and in snow throughout the former Soviet Union [Belikova et al, 1984]. The maximum (about 1975) observed in the sulfate record from Belukha suggests that at least part of the sulfate originates from SO 2 emissions.…”

The environmental implications for dust in high-alpine snow and ice cores in Asian mountains

“…The isotopic ratios of the silicate fraction of snow dust were closer to those of the desert sand in China than those of the soil and bedrock around the glacier, suggesting that the silicate minerals on the glacier were derived from distant deserts (Nagatsuka et al, 2010). A previous study pointed out that dust from the vast arid regions of central Asia is the dominant source for major ions in Tien Shan snow (Wake et al, 1992). Dust in UG1 snow has been studied for provenance tracing by geochemical methods, showing that dust in this glacier comes from the Tarim and Junggar deserts, and from arid regions in the upwind Central Asia, such as Kazakhstan (Wu et al, 2010a).…”

“…The Asian mountain ranges are located adjacent to or even enclosed by the vast Asian arid region, which is one of the major dust sources in the world (Yang et al, 2007a;Wu et al, 2009a). The widely distributed glaciers on these ranges are excellent media to receive and preserve eolian dust from the deserts (Wake et al, 1992(Wake et al, , 1994Wu et al, 2009b). Dust in ice cores recovered from the low-and mid-latitude Asian mountain ranges has important environmental implications.…”

“…Wake et al, 1992;Liu et al, 2011;Dong et al, 2014). This mixture leads to uncertainty regarding the representative dust proxy in snow and ice cores recovered from Asian ranges.…”