Characterizing ionic species in PM2.5 and PM10 in four Pearl River Delta cities, south China.

PM2.5 and PM10 samples were collected at four major cities in the Pearl River Delta (PRD), South China, during winter and summer in 2002. Six water-soluble ions, Na+, NH4+, K+, Cl-, NO3- and SO4(2-) were measured using ion chromatography.