A large field campaign was conducted in northwestern China from January to February 2012 to measure the insoluble light-absorbing particles (ILAPs) and chemical species in the snow, and two hundred eighty-four snow samples were collected at 38 sites in Xinjiang Province and 6 sites in Qinghai Province. The cleanest snow was found in northeastern Xinjiang along the border of China, and it presented an estimated black carbon (BC) (CBCest) of approximately 5 ng g−1. The dirtiest snow was found near industrial cities, and it presented a CBCest of approximately 450 ng g−1. Overall, the CBCest of most of the snow samples collected in this campaign was 10–150 ng g−1. Vertical variations in the snowpack ILAPs indicated a probable shift in emission sources with the progression of winter. An analysis of the fractional contributions to absorption implied that organic carbon (OC) dominated the 450-nm absorption in Qinghai, whereas the contributions from BC and OC were comparable in Xinjiang. A Positive Matrix Factorization (PMF) model was run to explore the sources of particulate light absorption, and the results indicated an optimal 3-factor/source solution that included industrial pollution, biomass burning, and soil dust. In addition, the chemical components were evaluated to examine the mass contributions. In Qinghai, biomass burning was the dominant absorption factor despite the high mass contribution from soil dust. In Xinjiang, the primary absorption source was industrial pollution at sites near cities and biomass burning at most sites in other regions. A negative correlation was observed between the BC mixing ratio and altitude in Xinjiang. An analysis based on the PMF 3-factor solution showed that this relationship likely resulted from gradient variations in the contributions of industrial pollution sources.
