Single Particle Analysis Of Heavy Metal (Pb, Zn, Cu) Pollution In Shanghai's Atmosphere

Aerosol time of flight mass spectrometry(ATOFMS) determines aerodynamic size in the 0.1-2.5μm range and chemical composition of single particles in near real-time. Lead(Pb),zinc(Zn) and copper(Cu) in individual aerosol particles was measured using ATOFMS in August of 2007(summer),and in February,March of 2008(winter) in Shanghai,China.In general,heavy metal pollution in winter is more severe than in summer.Specifically,number concentration of Pb and Cu in winter is 2 times higher than that in summer,and no zinc containing particles were observed in summer while a large number of zinc containing particles exists in winter.Using the ART-2a neural network algorithm,these fine Pb,Zn and Cu containing particles were classified into several main classes by their mass spectral patterns and obvious sources.All heavy metal containing particles contain chemical composition of organic carbon-sulfate,nitrate and elemental carbon.A part of Pb and Cu containing particles in summer still contains chlorine.The combinations of heavy metal,such as Pb and Cu,Pb and Zn and Mn,Cu and V,also exist in heavy metal containing particles.In size distribution,particles containing elemental carbon are the smallest particles, peaked in 0.4μm.The second smallest particles are particles containing organic carbon-sulfate,nitrate,chlorine and phosphate,peaked in 0.5-0.6μm.The biggest particles are particles containing rich potassium and combination of heavy metals, peaked 1μm.Based on the temporal variation of number density,chemical composition and the correlation between different chemical species,several major emission sources were identified.About 50%in summer and 45%in winter of heavy metal containing particles were attributed to waste incineration according to good correlation between the number concentration of Pb and Cu containing particles.About 40%of heavy metal containing particles in winter was attributed to metallurgical processes and coal combustion due to good correlation among number concentration of Pb,Zn,Mn containing particles.About 35%of heavy metal containing particles in summer was assigned to heavy oil combustion because of chemical composition combination of vanadium and copper.A unique class in summer contains strong peak of phosphate and lead,which were assigned to phosphate processing industry.