Pollution characteristics and sources of fine particulate matter in ambient air in Tianjin City.

Ambient PM_(2.5) samples were collected using 48 pieces of quartz and organic filter membranes at an urban site of Tianjin City from August to December,2006.Concentrations of water-soluble inorganic ions and elements were determined separately.Major contributing sources to inorganic fine particulates were identified by factor analysis and multiple linear regression(FA-MLR) techniques.The results showed that monthly mean PM_(2.5) mass concentrations ranged from 103.9 to 217.4(μgm~3),with the highest concentration in winter and the lowest in summer.Water-soluble inorganic ions mass concentrations accounted for 24.90%-49.76% of PM_(2.5) mass concentration,and SO_4~(2-),NO_3~-,NH_4~+ and Cl~-were the major ions constituting about 90% of the total ion mass concentrations.The proportion of secondary species in PM_(2.5)was the largest in summer,due to the increased transformation rates of SO_2 to SO_4~(2-),and NO_2 to NO_3~-.The chloride enrichment in PM_(2.5) in the Tianjin atmosphere mostly resulted from anthropogenic emissions such as coal combustion;the contribution of sea salt was less than 20%.Si was the dominant inorganic element,accounting for about 28.4% of elemental mass concentration.Zn and Pb,from coal burning and vehicle exhaust,were the most abundant trace elements.Results of source apportionment indicated that secondary particles,fossil fuel burning,soil dust and construction dust were the major sources of inorganic fine particulates in Tianjin City,with contributions of 53.4%,25.8%,12.3% and 8.6% respectively.