Characterization of water-soluble species of PM10 and PM2.5 aerosols in urban area in Nanjing, China

The characterization for water-soluble species of PM10 (particle matter with aerodynamical diameter <10 μm) and PM2.5 (particle matter with aerodynamical diameter <2.5 μm) in five sites of Nanjing, China was carried out during February–May 2001.The pH and conductivity K of water-soluble matters of PM10 and PM2.5 were determined, and the water-soluble fraction of the sample was followed to identify the total carbon (TC), total organic carbon (TOC), inorganic carbon (IC), elements, NO3−, SO42− and NH3-N.The experimental results show that water-soluble matters of PM10 and PM2.5 in Nanjing are acidic, and the pH of PM2.5 is lower than PM10. Conductivity of water-soluble species of PM10 and PM2.5 aerosols varied over a wide range from 1087 to 225 μs/cm. Conductivity between PM10 and PM2.5 has a linear correlationship, and the equation is Y=0.8459X+44.74, r2=0.9376 (Y: conductivity of PM2.5, X: conductivity of PM10). TOC make up the majority of TC and accounts for 3.17–14.13% of PM10 and/or PM2.5 loadings, while IC only accounts for 0.12–0.47% of PM10 and/or PM2.5 mass. Al, As, Ba, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Ti, V and Zn, 17 elements were detected in water-soluble matters of PM10 and/or PM2.5. Ca, K and Na are the most abundant chemical components, which account for more than 95% of total water-soluble elements (TWSE). Of all the five sites, TWSE accounts for 1.80–6.13% of the particle mass and 61.28–72.73% of TWSE of PM10 is enriched in fine particles (<2.5 μm in diameter). Nitrate (NO3−), sulfate (SO42−), ammonia and ammonium (NH3-N) were determined. The highest level of nitrate was 15.49 μg/m3 for PM10 and 12.66 μg/m3 for PM2.5 at site FZ. As was the case for nitrate, the highest level of sulfate was also presented at the same site, which was 28.22 μg/m3 for PM10 and 21.48 μg/m3 for PM2.5. However, a higher level of ammonia and ammonium was presented at site ZS, which was 36.05 μg/m3 for PM10 and 22.06 μg/m3 for PM2.5.