Fine particulate pollution driven by nitrate in the moisture urban atmospheric environment in the Pearl River Delta region of south China.

To identify potential sources of fine particles (PM2.5, with aerodynamic diameter (Da) ≤ 2.5 µm) in urban Dongguan of south China, a comprehensive campaign was carried out in the whole 2019. Hourly PM2.5 and its dominant chemical components including organic carbon (OC), elemental carbon (EC), water-soluble inorganic ions (WSIIs) and thirteen elements were measured using online instruments. Gaseous pollutants including NH3, HNO3, NO2, NO and O3 and meteorological parameters were also synchronously measured. PM2.5 was dominated by carbonaceous aerosols in summer and by WSIIs in the other seasons. PM2.5 and its dominant chemical components mostly peaked around noon (10:00-14:00 LST). Furthermore, high PM2.5 levels during the daytime were closely related with the increased NO3- levels. The high mass concentrations of NO3- in urban Dongguan during the daytime were likely related with regional transport of NO3- from suburban Dongguan, which was originated from the reaction between NO2 and O3 under the moisture condition during the nighttime. Seven major source factors for PM2.5 including secondary sulfate, ship emission, traffic emission, secondary nitrate, industrial processes, soil dust and coal combustion were identified by positive matrix factorization (PMF) analysis, which contributed 26 ± 14%, 16 ± 16%, 16 ± 10%, 14 ± 11%, 12 ± 11%, 8 ± 6% and 8 ± 6%, respectively, to annual PM2.5 mass concentration. Although secondary sulfate contributed much more than secondary nitrate to PM2.5 on annual basis, the latter exceeded the former source factor when daily PM2.5 mass concentration was higher than 60 µg m-3, indicating the critical role nitrate played in PM2.5 episode events.

[Elemental Characteristics and Health Risk Assessment of Heavy Metals in Atmospheric PM2.5 in a Suburb of Zhuhai City].

To investigate the characteristics, sources, and health risks of trace heavy metals in fine particles, PM2.5 samples were collected at a suburban site of Zhuhai in the Pearl River Delta Region. Fifteen elements in the PM2.5 were analyzed by an X-ray fluorescence method. The results showed that the total mass concentrations of crustal elements (Al, Si, Ca, Fe, and Ti) in a typical month during spring, summer, autumn, and winter were (708±213), (645±269), (1155±503), and (1466±492) ng·m-3, respectively, while the total mass concentrations of the rest of the trace elements (Ba, Co, Cr, Cu, Mn, Ni, Pb, Sb, V, and Zn) were (271±124), (163±87.6), (424±192), and (546±183) ng·m-3, respectively. The element concentrations decreased in the following order:Si > Al > Fe > Zn > Ca > Pb > Ba > Mn > Sb > Cu > Ti > V > Ni > Cr > Co. Enrichment factors (EFs) analysis showed that Sb, Zn, Pb, Cu, Ni, Ba, Ca, and Co were heavily enriched, with EFs values ranging from 172 to 2426. Principal component analysis further showed that regional transport, ship emissions, coal combustion, and the electronics industry were the major sources of heavy metals, contributing 53.4%, 13%, 7.6%, and 6.8% of the total, respectively. Health risk assessment results indicated that Mn may pose a non-carcinogenic risk to children, and Cr, Pb, and Co may pose cancer risks to humans.