Objective To determine the pollution sources that influence the level of exposure to particulate matter 2.5 (PM2.5) in the elderly,and calculate the quantitative contributions of difference sources.Methods Personal exposure PM samples were collected in the summer and winter of 2011 from 101 elderly men in a Tianjin community.Chemical species (elements,water-soluble ions and carbonaceous species) were analyzed in PM samples to determine PM2.5 concentrations and chemical compositions.The Positive Matrix Factorization (PMF) model,which is recommended by the US Environmental Protection Agency,was employed to quantitatively analyze the contribution of each potential sources to personal levels of PM2.5 exposure.Results In both summer and winter,the model identified the same six sources of personal exposure to PM2.5 in the elderly:fugitive dust (marker species:Si,Al,Ca,Mg,Fe etc.),coal combustion emissions (marker species:organic carbon (OC) and SO42-),vehicle exhausts (marker species:inorganic carbon and NO3),secondary sulfates and nitrates (marker species:NO3-,SO42-and NH4 +),industrial emissions (marker species:Mn,Ni,Cu,Zn,Pb etc.),and indoor sources (marker species:OC,K,Si,Al etc.).Among these six potential sources,vehicle exhausts (summer:33.6％,winter:24.2％),secondary sulfates and nitrates (summer:27.4％,winter:29.1％),as well as coal combustion emissions (summer:19.9％,winter:24.1％) were the greatest contributors.Conclusions Coal combustion and vehicle exhaust emissions were the major sources of personal exposure to PM2.5 in the elderly,suggesting that these two sources were the key contributors to the precursor gases of secondary sulfate and nitrate.Key Project of Chinese National Programs for Fundamental Research and Development (2011CB503801)

Objective To determine the pollution sources that influence the level of exposure to particulate matter 2.5 (PM2.5) in the elderly,and calculate the quantitative contributions of difference sources.Methods Personal exposure PM samples were collected in the summer and winter of 2011 from 101 elderly men in a Tianjin community.Chemical species (elements,water-soluble ions and carbonaceous species) were analyzed in PM samples to determine PM2.5 concentrations and chemical compositions.The Positive Matrix Factorization (PMF) model,which is recommended by the US Environmental Protection Agency,was employed to quantitatively analyze the contribution of each potential sources to personal levels of PM2.5 exposure.Results In both summer and winter,the model identified the same six sources of personal exposure to PM2.5 in the elderly:fugitive dust (marker species:Si,Al,Ca,Mg,Fe etc.),coal combustion emissions (marker species:organic carbon (OC) and SO42-),vehicle exhausts (marker species:inorganic carbon and NO3),secondary sulfates and nitrates (marker species:NO3-,SO42-and NH4 +),industrial emissions (marker species:Mn,Ni,Cu,Zn,Pb etc.),and indoor sources (marker species:OC,K,Si,Al etc.).Among these six potential sources,vehicle exhausts (summer:33.6％,winter:24.2％),secondary sulfates and nitrates (summer:27.4％,winter:29.1％),as well as coal combustion emissions (summer:19.9％,winter:24.1％) were the greatest contributors.Conclusions Coal combustion and vehicle exhaust emissions were the major sources of personal exposure to PM2.5 in the elderly,suggesting that these two sources were the key contributors to the precursor gases of secondary sulfate and nitrate.Key Project of Chinese National Programs for Fundamental Research and Development (2011CB503801)