PM2.5 Characteristics in Qingdao and across Coastal Cities in China

Abstract

A year-long study was performed to comprehensively investigate the mass concentration, water-soluble ions, organic and elemental carbons, and elemental components of atmospheric fine particles from March 2006 to February 2007 in Qingdao. The results showed that PM 2.5 concentration was over twice the National Ambient Air Quality Standards of 35 µg/m 3 (GB3095-2012), with the highest value in winter (110 µg/m 3 ) and the lowest in summer (42.8 µg/m 3 ). Non-sea salt-SO 4 2− (nss-SO 4 2− ), NO 3 − , and NH 4 + were the dominant water-soluble ions in PM 2.5 , and showed the highest concentrations in autumn, winter and autumn, respectively, and all had the lowest concentrations in summer. Organic carbon (OC) and elemental carbon (EC) had the lowest levels in summer and the highest values in winter and autumn, respectively. The lower acetic/formic acid (A/F) ratio in summer suggested a predominant secondary formation of water-soluble organic acids. Cl-depletion mainly occurred in summer, along with the largest sea salt proportion in particles in a year when winds came from the southeastern sea. The enrichment factors (EFs) of elements followed an increasing order: Si, Al, Ti, Mg, Ca, Fe, Na, Sr, K, Mn, Ba, V, Cr, Ni, Co, Sc, Cu, As, Cl, Zn, Pb, S, Br, Cd, and Se. The higher EFs from 10.1 to 10,487 for Sr, K, Mn, Ba, V, Cr, Ni, Co, Sc, Cu, Cl, Zn, Pb, S, Br, Cd, and Se suggested the significant influence of anthropogenic sources in the area. Mass closure showed that (NH 4 ) 2 SO 4 , organic matter, and NH 4 NO 3 were the main components, and contributed 31.0%, 25.2%, and 14.0% of PM 2.5 mass in Qingdao, respectively. Source apportionment results showed that secondary sulfate, nitrate, and coal combustion were the main sources. Based on this study and previous publications, the PM 2.5 characteristics-including seasonality in mass and chemical species concentrations and Cl-depletion in summer-were obtained across coastal cities in China.

Statistical Analysis of Spatiotemporal Heterogeneity of the Distribution of Air Quality and Dominant Air Pollutants and the Effect Factors in Qingdao Urban Zones

“…The burning of carbon for heat in winter raises the concentration of PM 2.5 , which leads to its being the dominant air pollutant. There were consistent results in previous studies: e.g., the dominant air pollutant was PM 10 [64], and PM 2.5 was the dominant pollutant contributing to pollution in winter in Qingdao [15,42]. In the Beijing-Tianjin-Hebei Region, the dominant air pollutant was PM 2.5 in the periods from January to March, July, and from September to December, while PM 10 and PM 2.5 were the dominant air pollutants in April and May and O 3 was dominant in June and August [5].…”

“…In recent years air pollution has become a serious issue which threatens people's health generally and the economic development in urban Qingdao [42][43][44] particularly. Comprehensive understanding of the distribution characteristics of pollutants is significant and is indispensable for air pollution control [15].…”

“…Qingdao is a typical coastal tourist city, and air pollution greatly impacts both tourism and the people living there [15,[42][43][44]. There are seven administrative zones in the city of Qingdao.…”

“…Population and residential areas are more concentrated in the Shibei and Licang zones; the greening rate is larger in the Laoshan and Licang zones, and there are more polluting enterprises, such as two key state monitored gas-exhausting enterprises, in the Licang zone ( Figure 1 and Table 1). South (S) and south-east (S-E) are the prevailing wind directions in spring (March, April, and May) and summer (Jun, July, and August), while north-west (N-W) is the prevailing wind in autumn (September, October, and November) and winter (December, January, and February) ( Table 1) [15,42]. Considering the different natural conditions and economic functions in these four zones, we selected four environmental monitoring sites across the four zones, all built by the Qingdao Environmental Monitoring Center Station in this paper.…”

“…PM 10 concentration was higher and the number of days of PM 10 dominance was larger at the Licang site than at the other three sites throughout the year, especially in spring and summer (Figures 5 and 6). This was because there was some industrial dust and construction dust [19,27], as well as more wind at the Licang site in spring and summer (Figure 1) [42]. The Licang site is located in the northern foothills of Laoshan Mountain, and the dust transport from the north is also another important reason for this difference.…”