Emission factors of environmentally persistent free radicals in PM2.5 from rural residential solid fuels combusted in a traditional stove.

ABSTRACT

Emission factors (EFs) are crucial for establishing emission inventory and subsequent health risk assessment of pollutants. However, the EFs of environmentally persistent free radicals (EPFRs) in PM2.5 have not been well investigated. We measured EPFRs in PM2.5 from burning of different solid fuels in a traditional stove widely used in rural China and calculated the EFs of EPFRs (EFEPFRs). The characteristics of EPFRs varied greatly with PM2.5 depending on the feedstock, and the EFEPFRs of crop residue, firewood and bitumite was 2.13 ± 1.04, 1.40 ± 0.76 and 1.08 ± 0.39 (1020 spins·kg-1), respectively. The estimated results of EPFRs emission associated with PM2.5 showed that the crop residue was the main contributor to the top four provinces with high EPFRs emissions in China in 2010. A wide range (0.03-4.89 cig·person-1·day-1) of equivalent cigarette number converted by inhaling EPFRs in PM2.5 was observed. Provinces with higher equivalent cigarette number were mainly agricultural provinces, because the rural residents tend to use readily available fuels. Additionally, EPFRs in collected PM2.5 during 2 - month photoaging were more stable in particles with higher organic carbon contents. Our findings provided a new insight into the risk assessment of PM2.5 from different sources by taking EPFRs into consideration.