Snow is the most active element in the climate system and the most sensitive to environmental change. It has important effects on regional climate, natural environment and human activities. Snow can collect, capture and accumulate atmospheric particles efficiently. Therefore, snow is an effective indicator in atmosphere pollution.

Recent years, the concentration of atmospheric particulate matters (including ionic and carbonaceous compounds, and trace metals) in urban increased significantly with the development of economy. Trace metals have significant impacts on environment and human health. They can deposit into snow by dry and wet depositions. So, analyzing the spatial distribution and potential sources of trace metals in snow is important to assess the air pollution in urban.

Urumqi is a city suffering from very serious atmospheric pollution. It is of vital importance to assess air pollution by measuring concentrations of trace metals in insoluble particulate matters of snow in Urumqi. Using 102 snow samples collected in and around urban areas of Urumqi on 16–20 January 2013, LI Xiaolan et al. discussed the spatial distribution patterns of 11 trace metals (Mn, Cu, Zn, Be, Cd, U, Ni, Cu, Co, Cr and Pb) in insoluble particulate matters (IPM) of snow in this city. The trace metals in IPM of snow were determined by using inductively coupled plasma-mass spectrometry.

The elements Mn, Cu, Zn, Ni and Pb had similar spatial distribution patterns. These metals showed declining trends along the urban–suburb gradient with a high-value area in the south of the city, and two significant high-value areas in the west and east, respectively. The high-value areas of Cr, Ni, and V occurred in the northeast corner, and the high-value areas of Be and Co presented in the west and northeast of the city, respectively. Moreover, Cd and U displayed relatively even spatial patterns in the urban area.

The elements Mn, Cu, Zn, Be, V, Cr, Co, Ni, Pb and U may originate from similar pollution sources, e.g. domestic heating, industrial and road traffic activities. The high-value areas of Cr, Ni, and V in the northeast corner was related to the pollutant emissions from an oil refinery, and the high-value region of Co was linked to the local soil dust. Moreover, wind direction is also an important factor influencing concentrations and spatial patterns of trace metals in snow in Urumqi.

The result was published in Environmental Monitoring and Assessment on 21 November 2014.