Abstract
This study investigated PM2.5, specifically, its chemical characteristics and spatiotemporal variation, and identified its potential sources in the Linhai industrial complex of southern Kaohsiung. Seasonal 12-h PM2.5 samples were collected simultaneously at three sampling sites. The results showed that high PM2.5 concentrations mainly occurred during winter and spring, with concentrations at the downwind sites always exceeding those at the upwind sites due to the transport of secondary aerosol by the prevailing winds. 31.4–56.8% of the PM2.5 consisted of water-soluble ions (WSIs), which were dominated by secondary inorganic aerosol (SIA) (SO42– + NO3– + NH4+). High mass ratios between the SIA and the PM2.5 (SIA/PM2.5) were also observed during winter and spring, suggesting that SIA was the primary contributor to the high levels of PM2.5. A neutralization ratio (NR) < 1 indicated that the PM2.5 was acidic, and a nitrogen oxidation ratio (NOR) > 0.1 and a sulfur oxidation ratio (SOR) > 0.25 showed that SIA frequently formed during winter and spring. The metallic elements, which accounted for 12.0–20.2% of the PM2.5, tended to exhibit higher concentrations during daytime than nighttime, and the enrichment factors (EFs) revealed that the trace metals (Ni, Cr, Cu, and Zn) were mainly anthropogenic in origin. Carbonaceous content formed 9.3–24.3% of the PM2.5, and high mass ratios between the organic and the elemental carbon (OC/EC) were also observed during winter and spring. Moreover, the mass ratios between the malonic and the succinic acid (M/S) were always > 1.0 during winter and spring and < 1.0 during summer and fall, demonstrating that organic acids dominated the SOA during the first two seasons. The major sources of PM2.5 in the Linhai industrial complex were steel plants, followed by secondary sulfate and nitrate, vehicular exhaust, petrochemical plants, and incinerators.
Highlights
PM2.5 pollution has been a hot issue nationwide due to the severe threat to human health
The results showed that high PM2.5 concentrations mainly occurred during winter and spring, with concentrations at the downwind sites always exceeding those at the upwind sites due to the transport of secondary aerosol by the prevailing winds. 31.4–56.8% of the PM2.5 consisted of water-soluble ions (WSIs), which were dominated by secondary inorganic aerosol (SIA) (SO42– + NO3– + NH4+)
In terms of spatial distribution, National Open University site (NOU) had the highest average PM2.5 concentration in winter and spring with the prevailing northeastern winds, and Fongyang Elementary School site (FY) has the highest average PM2.5 concentration in summer and fall with the prevailing southern winds, implying that NOU and FY located at the downwind sites of PM2.5 sources were highly affected by local sources in the Linhai industrial complex
Summary
PM2.5 pollution has been a hot issue nationwide due to the severe threat to human health. Long-term exposure to PM2.5 could cause severe impacts on human health since it is highly suspected as carcinogenic, mutagenic, and teratogenic, which make PM2.5 the Type I carcinogenic pollutant issued by World Health Organization (WHO). As the biggest industrial city in southern Taiwan, Kaohsiung suffers from the highest concentrations of criteria air pollutants, PM2.5, among the major cities in Taiwan in the past two decades, due to the most densely distributed heavy industries. The exploration of the spatiotemporal distribution of PM2.5, as well as its chemical characteristic, has attracted much attention, aiming to depict its chemical fingerprint and track the major source. Shen et al (2019) investigated the chemical characteristic of PM2.5 in the urban, petrochemical
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