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Abstract
China has been a top producer and exporter of refined lead products in the world since the year 2000. After the phasing-out of leaded gasoline in the late 1990s, non-ferrous metallurgy and coal combustion have been identified as potential major sources of aerosol lead in China. This paper presents the single particle analytical results of ambient aerosol particles collected near a lead smelter using a scanning electron microscopy- energy dispersive x-ray spectroscopy (SEM-EDX). Aerosol particle samples were collected over a 24-hour period, starting from 8 pm on 31 May 2002, using a high volume TSP sampler. For this near source sample, 73 particles among 377 particles analyzed (accounting for 19.4%) were lead-containing particles mixed with other species (S, Cl, K, Ca, and/or C), which probably appeared to be from a nearby lead smelter. Lead-containing particles of less than <TEX>$2{\mu}m$</TEX> size in the near source sample were most frequently encountered with the relative abundances of 42%. SEM-EDX analysis of individual standard particles, such as PbO, PbS, <TEX>$PbSO_4$</TEX>, <TEX>$PbCl_2$</TEX>, and <TEX>$PbCO_3$</TEX>, was also performed to assist in the clear identification of lead-containing aerosol particles. Lead-containing particles were frequently associated with arsenic and zinc, indicating that the smelter had emitted those species during the non-ferrous metallurgical process. The frequently encountered particles following the lead-containing particles were mineral dust particles, such as aluminosilicates (denoted as AlSi), <TEX>$SiO_2$</TEX>, and <TEX>$CaCO_3$</TEX>. Nitrate- and sulfate-containing particles were encountered frequently in <TEX>$2-4{\mu}m$</TEX> size range, and existed mostly in the forms of <TEX>$Ca(NO_3,SO_4)/C$</TEX>, <TEX>$(Mg,Ca)SO_4/C$</TEX>, and <TEX>$AlSi+(NO_3,SO_4)$</TEX>. Particles containing metals (e.g., Fe, Cu, and As) in this near source sample had relative abundances of approximately 10%. Although the airborne particles collected near the lead smelter contained elevated levels of lead, other types of particles, such as <TEX>$CaCO_3$</TEX>-containing, carbonaceous, metal-containing, nitrates, sulfates, and fly-ash particles, showed the unique signatures of samples influenced by emissions from the lead smelter.
Highlights
The main sources of airborne lead particles in the atmosphere can be divided into anthropogenic and natural sources
1 Lead-containing Standard Particles Individual standard particles of PbO, PbS, PbSO4, PbCl2, and PbCO3 were investigated by low-Z particle EPMA to assist in the clear identification of lead-containing particles
The chemical compositions and size distributions of airborne aerosol particles collected near a lead smelter were analyzed by low-Z particle EPMA
Summary
The main sources of airborne lead particles in the atmosphere can be divided into anthropogenic and natural sources. The mean Pb concentrations were reported to be 100-300 ng/m3 during 2000 and 2004 in Beijing (Sun et al, 2006) These studies suggest that the lead level still remained high due to the presence of other sources, even though lead emission from vehicles has been reduced, which was pointed out in other studies (Widory et al, 2010; Xiao et al, 2008; Wang et al, 2006). The highest levels of lead in particulate matter (PM) is normally found near lead smelters (http:// www.epa.gov/oar/lead), and lead refining smelters have been identified as one of the three major sources for airborne lead particles, along with aviation gasoline use and coal combustion in United States (Murphy et al, 2007). Low-Z particle EPMA was performed for individual standard particles, such as PbO, PbS, PbSO4, PbCl2, and PbCO3, to help identify the leadcontaining aerosol particles
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