Spatiotemporal Variations and Factors of Air Quality in Urban Central China during 2013-2015

Spatiotemporal behaviors of particulate matter (PM_2.5 and PM₁₀) and trace gases (SO₂, NO₂, CO, and O₃) in Hefei during the period from December 2013 to November 2015 are investigated. The mean annual PM_2.5 (PM₁₀) concentrations are 89.1 ± 59.4 µg/m³ (118.9 ± 66.8 µg/m³) and 61.6 ± 32.2 µg/m³ (91.3 ± 40.9 µg/m³) during 2014 and 2015, respectively, remarkably exceeding the Chinese Ambient Air Quality Standards (CAAQS) grade II. All trace gases basically meet the requirements though NO₂ and O₃ have a certain upward trend. Old districts have the highest pollution levels, followed by urban periphery sites and new districts. Severe haze pollution occurs in Hefei, with frequent exceedances in particulate matter with 178 (91) days in 2014 (2015). The abnormal PM_2.5 concentrations in June 2014 attributed to agricultural biomass burning from moderate resolution imaging spectroradiometry (MODIS) wildfire maps and aerosol optical depth (AOD) analysis. PM_2.5 is recognized as the major pollutant, and a longer interspecies relationship is found between PM_2.5 and other criteria pollutants for episode days as compared to non-episode days. The air pollution in Hefei tends to be influenced by local primary emissions, secondary formation, and regional transport from adjacent cities and remote regions. Most areas of Anhui, southern Jiangsu, northern Zhejiang, and western Shandong are identified as the common high-potential source regions of PM_2.5. Approximately 9.44 and 8.53 thousand premature mortalities are attributed to PM_2.5 exposure in 2014 and 2015. The mortality benefits will be 32% (24%), 47% (41%), 70% (67%), and 85% (83%) of the total premature mortalities in 2014 (2015) when PM_2.5 concentrations meet the CAAQS grade II, the World Health Organization (WHO) IT-2, IT-3, and Air Quality Guideline, respectively. Hence, joint pollution prevention and control measures need to be strengthened due to pollutant regional diffusion, and much higher health benefits could be achieved as the Hefei government adopts more stringent WHO guidelines for PM_2.5.