Modeling horizontal and vertical variation in intraurban exposure to PM_(2.5) concentrations and compositions

摘要

Land use regression (LUR) models are increasingly used to evaluate intraurban variability in population exposure to fine paniculate matter (PM_(2.5)). However, most of these models lack information on PM_(2.5) elemental compositions and vertically distributed samples. The purpose of this study was to evaluate intraurban exposure to PM_(2.5) concentrations and compositions for populations in an Asian city using LUR models, with special emphasis on examining the effects of having measurements on different building stories. PM_(2.5) samples were collected at 20 sampling sites below the third story (low-level sites). Additional vertically stratified sampling sites were set up on the fourth to sixth (mid-level sites, n=5) and seventh to ninth (high-level sites, n=5) stories. LUR models were built for PM_(2.5), copper (Cu), iron (Fe), potassium (K), manganese (Mn), nickel (Ni), sulfur (S), silicon (Si), and zinc (Zn). The explained concentration variance (R~2) of the PM_(2.5) model was 65%. R~2 values were ＞ 69% in the Cu, Fe, Mn, Ni, Si, and Zn models and ＜ 44% in the K and S models. Sampling height from ground level was a significant predictor in the PM_(2.5) and Si models. This finding stresses the importance of collecting vertically stratified information on PM_(2.5) mass concentrations to reduce potential exposure misclassification in future health studies. In addition to traffic variables, some models identified gravel-plant, industrial, and port variables with large buffer zones as important predictors, indicating that PM from these sources had significant effects at distant places.