Contribution of transregional transport to particle pollution and health effects in Shanghai during 2013–2017
Graphical abstract
Introduction
Atmospheric particles, including PM2.5 and PM10, are the main pollutants that cause haze and, more importantly, pose harmful effects to human health. These effects are closely related to the toxic components such as heavy metals and polycyclic aromatic hydrocarbons (PAHs). Animal, epidemiological and clinical studies agree that exposure to PM2.5 and PM10 is a relevant risk factor (Hwang et al., 2005; Polichetti et al., 2009). For example, PM10 and PM2.5 cause damage to the brain and cardiovascular system of mammals, affect body temperature, and lead to lung function decline (Guo et al., 2012; Hwang et al., 2005; Polichetti et al., 2009; Rice et al., 2015). PM2.5 is more hazardous than PM10 because it contains smaller and more hazardous species that can penetrate deeper into the human body. For example, PM2.5-bound PAHs accounted for >80% of PM10-bound PAHs in a Chinese coal-based industrial city (Wu et al., 2014). A review study involving >120 cities in China found that a 10 μg/m3 increase in PM2.5 was associated with increases of 0.40%, 0.63%, and 0.75% in total non-accidental mortality, mortality due to cardiovascular disease, and mortality due to respiratory disease, respectively, while the increases associated with PM10 were 0.36%, 0.36%, and 0.42%, respectively (Lu et al., 2015). Shanghai is the leading city in the Yangtze River Delta region. With a population over 20 million, the population density of Shanghai (3816/km2 in 2016) is the highest in China. The health effects caused by particle pollution, especially PM2.5, are likely to be more serious in a mega city such as Shanghai.
Transregional or inter-regional transport plays an important role in air pollution. Ying et al. (2014) conducted a comprehensive and in-depth study on inter-regional (North, Northeast, East, Central, South, Southwest and Northwest) contributions to PM2.5 nitrate and sulfate in China. For instance, nitrate in the North China Plain and the Middle and Lower Yangtze Plain regions significantly influenced nitrate concentrations in downwind areas as far as the Pearl River Delta (PRD) (Ying et al., 2014). The impact of long-range transport was especially obvious for sulfate in the PRD region in winter, with a transregional (North, East and Central China) contribution >80% (Ying et al., 2014). Focusing on mega cities, including Beijing, Shanghai, and Chongqing, and a large city cluster in the PRD, the results indicated stronger and more frequent interregional transport in winter (Ying et al., 2014). The impact of transregional or inter-regional transport has also been highlighted in a large number of previous studies (Chen et al., 2017; Fu et al., 2016; Hu et al., 2015; Wang et al., 2015b; Wang et al., 2014). However, very few studies have quantified the health impact of PM2.5 attributable to transregional transport. Wang et al. (2017a) evaluated the effects of interprovincial trade on PM2.5 pollution and public health across China. An investigation focusing on the contribution of transregional transport (CTRT) to particle pollution and the subsequent health burden in a mega city is desirable.
The aims of this study were thus to (1) identify potential regional source areas and quantify the CTRT to PM2.5 and PM10 pollution in Shanghai from 2013 to 2017; and (2) assess the short-term health effects associated with PM2.5 attributed to transregional transport. The study hypothesized that Shanghai is a receptor site and polluted air masses are transported from upwind areas to Shanghai, causing air pollution and the subsequent health burden.
Section snippets
Potential source contribution function (PSCF)
The PSCF method, which associates concentrations of pollutants measured at a receptor site with backward trajectory simulations, has been widely used to locate the potential source areas of receptor sites (Han et al., 2018; Jeong et al., 2011; Jeong et al., 2013; Yao et al., 2016). The PSCF value indicates the probability that a source is located at latitude i and longitude j, described by Eq. (1) (Jeong et al., 2017):where nij is the total number of trajectory endpoints falling in
PM2.5 and PM10 concentrations
The hourly PM2.5 and PM10 concentrations in Shanghai from January 1, 2013 to December 31, 2017 were obtained from the Shanghai Environmental Monitoring Center. The distributions of these concentrations are plotted in Fig. 1. The annual concentrations of PM2.5 and PM10 were 62 and 82 μg/m3, 52 and 71 μg/m3, 53 and 68 μg/m3, 45 and 59 μg/m3, and 39 and 57 μg/m3 from 2013 to 2017, respectively. The annual mass ratio of PM2.5/PM10 ranged from 0.69 to 0.78, with a mean of 0.74. Compared with 2013,
Conclusions
This study aimed to quantify the CTRT to ambient particle concentrations and the consequent health effects (deaths, hospital admissions, and outpatient visits) in Shanghai from 2013 to 2017 based on hourly PM2.5 and PM10 concentrations. Transregional transport contributed to 31–37% of the annual PM2.5 (PM2.5_CTRT) and PM10 (PM10_CTRT) in Shanghai over the five-year study period, which highlights the importance of both local emission and inter-regional emission control in the future. The number
Acknowledgements
This work was supported by the Ministry of Science and Technology of the People's Republic of China (2016YFC0202700, 2018YFC0213800), the National Natural Science Foundation of China (91743202, 21527814), and the Natural Science Foundation of Shanghai (18ZR1403000).
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