Physiochemical characteristics of indoor PM₂.₅ with combustion of dried yak dung as biofuel in Tibetan Plateau, China

Abstract

People inhabiting the Tibetan Plateau rely for survival on the yak, the region's native cattle. One of the important products of yak is dung, which has been served as cooking and heating fuels in the traditional Tibetan pastoralist society for several thousand years. The indoor air quality (IAQ) at eight residential homes with altitudes ranging from 3212 m to 4788 m was investigated in November 2012 to obtain a shot-term profile of emission from combustion of dried yak dung as biofuel in pastoral and agro-pastoral regions on the Tibetan Plateau. The indoor temperature, relative humidity, CO2 and mass concentrations of PM2.5 were monitored for around a 4-h period (5 kg dried fuel was consumed) at each site. Filter-based aerosol samples were also collected to characterize their elemental compositions, water-soluble ions, carbonaceous species and individual particle morphologies. The results showed that combustion of solid biomass fuel in cast-iron stove is the preliminary source of indoor particulate pollution. The average indoor and outdoor PM2.5 mass concentrations were 330.7 and 29.1 μg/m3, respectively. Individual particle analysis showed that most of the particles in smoke from dung burning were in the submicrometer size range. Regular and irregular organic balls and soot aggregates were the predominant species in the smoke (>90% in numbers). The data set in this study can provide significant basis for IAQ and epidemiology study on the Tibetan Plateau.