Performance Evaluation Of Emergency Measures During Heavy Air Pollution Episodes Using Environmental Monitoring Data

Since the Eleventh Five-Year Plan,air pollution in key areas such as Beijing-Tianj in-Hebei and its surrounding regions(hereinafter referred to as ’2+26’ cities)and Fenwei Plain has been increasingly severe with the rapid growth of economy.To alleviate air pollution,the State Council issued ’Action Plan for the Prevention and Control of Air Pollution’ in 2013,in which emergency measures for heavily polluted weather were put forward to strengthen its response.At present,the emission reduction effects of emergency measures are mainly evaluated by air quality models.This paper proposed a post-assessment method based on routine monitoring data to evaluate the effect of emergency measures for heavily polluted weather.The connotation of Lorenz curve was extended,and the distribution curve of pollutant cumulative concentration was suggested for describing the pollutant concentration distribution in study area in this paper;In order to quantitatively evaluate the uniformity of pollutant concentration distribution,the index of the ratio of high cumulative concentration was proposed based on the cumulative concentration distribution curve of pollutants.Taking PM2.5,PM10,SO2 and NO2 as research objects,the method was applied to evaluate the emission reduction effect of ’2+26’ cities during autumn and winter in 2015-2017.This paper analyzed the distribution characteristic of ratio of high cumulative concentration during autumn and winter in 2017 in the Yangtze River Delta region,the Fenwei Plain and the Chengyu Area.Taking PM2.5 concentration during autumn and winter in 2017 of the above-mentioned key areas as the research object,when the cost-effectiveness coefficient is equal to 2,the number of recommended control days for the above-mentioned regional emergency measures were calculated.The main results were obtained as follows:(1)The ratio of high cumulative concentration of PM2.5,PM10,SO2 and NO2 in’2+26’ cities during autumn and winter in 2016-2017 decreased compared with the same period in 2015,with a decrease of 0.4%～3.8%,indicating that emergency measures implemented in‘2+26’cities had peak-clipping effect on the above four pollutant concentrations;among them,the ratio of high cumulative concentration of particles such as PM2.5 and PM10 decreased more than that of gaseous pollutants such as SO2 and NO2,indicating that the peak-clipping effect of emergency measures on particles was greater than that on gaseous pollutants.(2)From the distribution of pollutant cumulative concentration in the Yangtze River Delta region,Fenwei Plain and Chengyu Area during autumn and winter in 2017,there were differences in the ratio of high cumulative concentration of pollutants between key regions and between cities within regions.It indicated that different regions and cities have different demands for emergency emission reduction due to their own air quality and pollutant concentration distribution.(3)When the cost-effectiveness factor equal to 2,the number of recommended control days of ’2+26’ cities,the Yangtze River Delta region,the Fenwei Plain and the Chengyu Area are[26 days to 60 days],[14 days to 45 days],[7 days to 40 days]and[16 days to 37 days],respectively.The number of recommended control days within the above-mentioned key regions varied greatly.The average number of recommended control days of ’2+26’ cities,the Yangtze River Delta region,the Fenwei Plain and the Chengyu Area were 38 days,33 days,28 days,and 28 days,respectively.The average recommended number of control days of the above four key regions was relatively small.It is recommended that the Yangtze River Delta region,the Fenwei Plain and the Chengyu Area could balance their own demand for emergency emission reduction and the impact on the social economy,and lower the threshold for early warning of each level.Therefore,the emergency measures could be both effective and cost-effective.