Abstract
In this work, the seasonal variations and sources of trace metal elements in atmospheric fine aerosols (PM2.5) were investigated for a year-long field campaign from July 2012 to June 2013, conducted in suburban Nanjing, eastern China, at a site adjacent to an industry zone. The PM2.5 samples collected across four seasons were analyzed for 17 metal elements, namely, Sodium (Na), Magnesium (Mg), Aluminum (Al), Vanadium (V), Chromium (Cr), Manganese (Mn), Nickel (Ni), Copper (Cu), Zinc (Zn), Arsenic (As), Selenium (Se), Strontium (Sr), Cadmium (Cd), Barium (Ba), Lead (Pb), Molybdenum (Mo), and Antimony (Sb) using an inductively coupled plasma mass spectrometry (ICP-MS). We found that the total concentration of all 17 metal elements was 1.23 μg/m3, on average accounting for 1.0% of the total PM2.5 mass. For our data, mass concentrations of Al, Cd, Ba were highest in summer, Mg, Cu, Zn, Se, Pb peaked in autumn, Cr, Mn, Ni, As, Sr, Sb increased significantly in winter, while the concentrations of Na, V, Mo were at their highest levels in spring. Air mass back trajectory analysis suggested that air parcels that arrived at the site originated from four dominant regions (Japan, yellow sea and bohai; Southeast of China, the Pacific Ocean; Southwest of Jiangsu and Anhui province; Northern Asia inland and Mongolia region), in particular, the one from Northern Asia inland and Mongolia contained the highest concentrations of As, Sb, Sr, and was predominant in winter. Positive matrix factorization (PMF) analyses revealed that the industrial emission is the largest contributor (34%) of the observed metal elements, followed by traffic (25%), soil dust (19%), coal combustion (10%), incineration of electronic waste (9%), and a minor unknown source (3%). In addition, we have also investigated the morphology and composition of particles by using the scanning electron microscopy (SEM)/energy-dispersive spectrometry (EDS) techniques, and identified particles from coal burning sources, etc., similar to the PMF results.
Highlights
The skewness coefficients of 13 elements were within 0~2, indicating that there is little right-skewed distribution in the samples; the median values were typically lower than the mean values except for Al
Most of the kurtosis coefficients were larger than zero. This result demonstrates that concentration distribution of samples was narrower and steeper than the normal distribution, especially for the elements featured with relatively high concentrations, such as Al (10.31), Cu (22.2), Zn (11.8) and Mo (11.55), likely indicating emission sources of soil dust, traffic and Mo source in suburban Nanjing
This study presents measurement results of 17 metal elements in PM2.5 samples collected over a
Summary
Ambient particulate matter (PM) pollution, is emerging as one of the leading risk factors of mortality, ranking in the sixth place in 2010 [1,2] from the 13th place in 2000 among all risk factors [3]. Monitoring networks for PM-metal elements have already been established at urban, suburban, rural, mountain, forest, industrial sites, or near heavy traffic roads in many countries including. Many studies that focused on analysis of the concentrations and size distributions of metal elements were conducted in a few major heavily polluted megacities such as Beijing, Shanghai and Guangzhou, and covered relatively short time periods [40,41,42,43,44,45]. Studies regarding the temporal, seasonal variations and source contributions of atmospheric metal elements in Nanjing are very scarce. We have investigated the mass loadings and sources of 15 trace metals in the PM2.5 samples during the second Asian Youth Games period in urban Nanjing [47]. Our results are valuable for the implementation of appropriate measures to reduce the atmospheric metal and PM2.5 pollution in this region
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