3Judith C.Chow,etal.Chemical composition of PM2.5and PM10in Mexico City during winter 1997[J].The Science of the Total Environment,2002,287:177-201.
4Puja Khare,B.P.Baruah.Elemental characterization and source identification of PM2.5using multivariate analysis at the suburban site of North-East India[J].Atmospheric Research 2010,98:148-162.
8Samuel Melaku,etal.Seasonal variation of heavy metals in ambient air and Precipitation at a single site in Washington,DC[J].Environmental Pollution 2008,155:88-98.