Source Contributions to PM2.5 under Unfavorable Weather Conditions in Guangzhou City,China

Historical haze episodes（2013–16） in Guangzhou were examined and classified according to synoptic weather systems.Four types of weather systems were found to be unfavorable, among which ＂foreside of a cold front＂（FC） and ＂sea high pressure＂（SP） were the most frequent（〉 75% of the total）. Targeted case studies were conducted based on an FC-affected event and an SP-affected event with the aim of understanding the characteristics of the contributions of source regions to fine particulate matter（PM（2.5）） in Guangzhou. Four kinds of contributions—namely, emissions outside Guangdong Province（super-region）, emissions from the Pearl River Delta region（PRD region）, emissions from Guangzhou–Foshan–Shenzhen（GFS region）, and emissions from Guangzhou（local）—were investigated using the Weather Research and Forecasting–Community Multiscale Air Quality model. The results showed that the source region contribution differed with different weather systems. SP was a stagnant weather condition, and the source region contribution ratio showed that the local region was a major contributor（37%）, while the PRD region, GFS region and the super-region only contributed 8%, 2.8% and 7%, respectively, to PM（2.5） concentrations. By contrast, FC favored regional transport. The super-region became noticeable,contributing 34.8%, while the local region decreased to 12%. A simple method was proposed to quantify the relative impact of meteorology and emissions. Meteorology had a 35% impact, compared with an impact of-18% for emissions, when comparing the FC-affected event with that of the SP. The results from this study can provide guidance to policymakers for the implementation of effective control strategies.

Impact of energy structure adjustment on air quality:a case study in Beijing,China

Energy consumption is a major cause of air pollution in Beijing,and the adjustment of the energy structure is of strategic importance to the reduction of carbon intensity and the improvement of air quality.In this paper,we explored the future trend of energy structure adjustment in Beijing till 2020,designed five energy scenarios focusing on the fuel substitution in power plants and heating sectors,established emission inventories,and utilized the Mesoscale Modeling System Generation 5(MM5)and the Models-3/Community Multiscale Air Quality Model(CMAQ)to evaluate the impact of these measures on air quality.By implementing this systematic energy structure adjustment,the emissions of PM_(10),PM_(2.5),SO_(2),NO_(x),and non-methane volatile organic compounds(NMVOCs)will decrease distinctly by 34.0%,53.2%,78.3%,47.0%,and 30.6%respectively in the most coalintensive scenario of 2020 compared with 2005.Correspondingly,MM5-Models-3/CMAQ simulations indicate significant reduction in the concentrations of major pollutants,implying that energy structure adjustment can play an important role in improving Beijing’s air quality.By fuel substitution for power plants and heating boilers,PM_(10),PM_(2.5),SO_(2),NO_(x),and NMVOCs will be reduced further,but slightly by 1.7%,4.5%,11.4%,13.5%,and 8.8%respectively in the least coal-intensive scenario.The air quality impacts of different scenarios in 2020 resemble each other,indicating that the potential of air quality improvement due to structure adjustment in power plants and heating sectors is limited.However,the CO_(2) emission is 10.0%lower in the least coal-intensive scenario than in the most coal-intensive one,contributing to Beijing’s ambition to build a low carbon city.Except for energy structure adjustment,it is necessary to take further measures to ensure the attainment of air quality standards.