LAUSR

PM 0.1 has been believed to have adverse short- and long-term effects on human health. However, the information of PM 0.1 that is needed to fully evaluate its influence on human health and environment is still scarce in many developing countries. This is a comprehensive study on the levels, chemical compositions, and source apportionment of PM 0.1 conducted in Hanoi, Vietnam. Twenty-four-hour samples of PM 0.1 were collected during the dry season (November to December 2015) at a mixed site to get the information on mass concentrations and chemical compositions. Multiple linear regression analysis was utilized to investigate the simultaneous influence of meteorological factors on fluctuations in the daily levels of PM 0.1 . Multiple linear regression models could explain about 50% of the variations of PM 0.1 concentrations, in which wind speed is the most important variable. The average concentrations of organic carbon (OC), elemental carbon (EC), water-soluble ions (Ca 2+ , K + , Mg 2+ , Na + , NH 4 + , Cl − , NO 3 − , SO 4 2− , C 2 O 4 2− ), and elements (Be, Al, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Tl, Pb, Na, Fe, Mg, K, and Ca) were 2.77 ± 0.90 μg m −3 , 0.63 ± 0.28 μg m −3 , 0.88 ± 0.39 μg m −3 , and 0.05 ± 0.02 μg m −3 , accounting for 51.23 ± 9.32%, 11.22 ± 2.10%, 16.28 ± 2.67%, and 1.11 ± 0.94%, respectively. A positive matrix factorization model revealed the contributions of five major sources to the PM 0.1 mass including traffic (gasoline and diesel emissions, 46.28%), secondary emissions (31.18%), resident/commerce (12.23%), industry (6.05%), and road/construction (2.92%).