Effects of forest belt in park on the chemical composition for PM2.5

Abstract

Abstract This paper represents results on the effects of forest belt on seasonal variation on the main chemical components for PM2.5 in the park environment in Beijing. PM2.5 samples were collected inside and outside a conifer forest simultaneously for 1 year in Beijing Olympic Forest Park. Chemical components including organic carbon (OC), elemental carbon (EC), water-soluble ions and elements in PM2.5 were measured. Results indicated that forest belt had significant impacts on PM2.5 chemical compositions of park. Organic matter, SO4 2-, NO3 −, NH4+, and crustal matter were the dominant components of PM2.5. The measured OC was divided into primary OC (POC) and second OC (SOC) parts following the method of EC tracer. Concentrations of OC, SOC, as well as SO4 2-, NO3 −, NH4+ and K+ in PM2.5 inside of forest were markedly higher than those outside of forest. The highest concentrations of OC, EC, and SO4 2- were observed in winter and the lowest values were found in summer. In contrast, the highest concentrations of most crustal elements were observed in spring, and the highest levels of pollutant elements were found in winter. Among these elements, annual mean concentrations of As and Cr exceeded WHO standard during monitoring period.