Chemical characterization and sources apportionment of fine particulate pollution in a mining town of Vietnam

Monitoring for PM2.5 was conducted in a mining town in Northern Vietnam in both dry and wet seasons from 2009 to 2010. Levels and compositions of PM were characterized at two sites representing two separate air bubbles; an industrial site in Mong Duong (MD) and a reference rural site in Cam Hai (CH). Two MiniVol samplers were collocated to collect 24 h PM2.5 samples for about 30 days at each site in a season, simultaneously with meteorological data recording. All samples were analyzed for mass, black carbon (BC), water soluble ions and elements, while selected samples were also analyzed for OC (organic carbon) and EC (element carbon). Higher PM2.5 levels were observed in the dry season than the wet season at both sites in spite of abnormal rainfall occurrences observed on some days during the dry season. In both seasons, higher PM2.5 levels were observed in the industrial site than the reference rural site. The differences in PM, BC or EC and OC levels between two sites and between two seasons at one site, respectively, were all statistically significant except for that in OC between two sites, and BC between two seasons at MD. The reconstructed PM2.5 mass indicated major contributing groups being organic matter, secondary inorganic particles, crustal and soot in both seasons. Higher values of K-Smoke in the dry season suggested more contribution from biomass burning. The PMF results revealed the largest contribution to PM2.5 mass from secondary PM (35-40%); followed by biomass burning, ship and road traffic (diesel) each had a share of 15-22%; and a small contribution from miscellaneous sources such as industry and construction activities (3-8%). Analysis of HYSPLIT backward trajectory patterns showed a high potential contribution of the long range transport (LRT) pollution when air masses had long continental pathways before arriving at the study area.