Size fractionated speciation of sulfate and nitrate in airborne particulates in Beijing, China

We report on the speciation of sulfate, nitrate with special attention to their ammonium salts during 1999–2000 in Beijing. Higher concentrations in fine particles were observed for ammonium sulfate and other sulfates during winter. Ammonium sulfate concentration ranged from 2.78 to 23.7 μg m−3 in fine particles, and ranged from 0.15 to 1.39 μg m−3 in coarse particles. Other sulfate concentrations ranged from 1.51 to 11.9 μg m−3 in fine particles, and ranged from 0.10 to 1.00 μg m−3 in coarse particles. Ammonium nitrate was mainly in fine particles with the highest concentration in December (11.9 μg m−3). Other nitrates were mainly distributed in the particles of 2.1–4.7 μm with concentrations ranged between 0.36 and 2.54 μg m−3, and the highest concentration of other nitrates was observed in fine particles in January (9.32 μg m−3). XRD analysis showed that ammonium sulfates existed in different forms in atmospheric aerosols. The results suggested the importance of heterogeneous formations of sulfate and nitrate in Beijing especially in winter.