Trace elements in particulate matter from metropolitan regions of Northern China: Sources, concentrations and size distributions.
Public concerns over airborne trace elements (TEs) in metropolitan areas are increasing, but long-term and multi-site observations of size-resolved aerosol TEs in China are still lacking. Here, we identify highly elevated levels of atmospheric TEs in megacities and industrial sites in a Beijing-Tianjin-Hebei urban agglomeration relative to background areas, with the annual mean values of As, Pb, Ni, Cd and Mn exceeding the acceptable limits of the World Health Organization. Despite the spatial variability in concentrations, the size distribution pattern of each trace element was quite similar across the region. Crustal elements of Al and Fe were mainly found in coarse particles (2.1-9 μm), whereas the main fraction of toxic metals, such as Cu, Zn, As, Se, Cd and Pb, was found in submicron particles (<1.1 μm). These toxic metals were enriched by over 100-fold relative to the Earth's crust. The size distributions of Na, Mg, K, Ca, V, Cr, Mn, Ni, Mo and Ba were bimodal, with two peaks at 0.43-0.65 μm and 4.7-5.8 μm. The combination of the size distribution information, principal component analysis and air mass back trajectory model offered a robust technique for distinguishing the main sources for airborne TEs, e.g., soil dust, fossil fuel combustion and industrial emissions, at different sites. In addition, higher elemental concentrations coincided with westerly flow, indicating that polluted soil and fugitive dust were major sources of TEs on the regional scale. However, the contribution of coal burning, iron industry/oil combustion and non-ferrous smelters to atmospheric metal pollution in Northern China should be given more attention. Considering that the concentrations of heavy metals associated with fine particles in the target region were significantly higher than those in other Asian sites, the implementations of strict environmental standards in China are required to reduce the amounts of these hazardous pollutants released into the atmosphere.
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Electronic address: panyuepeng@mail.iap.ac.cn.
Yuepeng
Y
Pan
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
Shili
S
Tian
Department of Chemistry, Analytical and Testing Center, Capital Normal University, Beijing 100048, China.
Xingru
X
Li
Department of Chemistry, Analytical and Testing Center, Capital Normal University, Beijing 100048, China.
Ying
Y
Sun
Department of Atmospheric Sciences, Colorado State University, Fort Collins, CO 80523, United States.
Yi
Y
Li
Department of Chemistry, University of Toronto, 80 St. George Street, M5S 3H6 Toronto, Canada.
Gregory R
GR
Wentworth
State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Electronic address: wys@mail.iap.ac.cn.
Yuesi
Y
Wang
D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D002681:China; D004784:Environmental Monitoring; D052638:Particulate Matter / Q000032:analysis*; D014131:Trace Elements / Q000032:analysis*
D000393:Air Pollutants; D052638:Particulate Matter; D014131:Trace Elements
Northern China; Particulate matter; Size distribution; Source apportionment; Trace elements