| Power industry plays an important role in energy consumption and air pollutant emission in China,and pollutants including SO2 and NOx from coal burning were the key precursors of regional fine particulate matter and acid deposition.Analyzing the emission characteristics of air pollutants and exploring the environment and health benefits of emission control policies for coal-fired power plants help to improve air quality and protect population health in China.As the input of air quality modeling,emission inventory is the basis of studying the transmission and chemical transformation of air pollutants in the atmosphere,and is crucial to efficiently evaluating regional air pollution situation and developing emission reduction plans.In recent years,a series of emission control measurements have been implemented for coal-fired power plants in China.However,due to insufficient on-site measurements and slow updates of emission factors,previous emission inventory of coal-fired power sector could not quantify the emission change characteristics and emission control effects.Therefore,the establishment and improvement of emission inventory of coal-fired power plants based on real-time online monitoring information,the reliability evaluation of emission inventory and the emission control benefit analysis based on air quality modeling help to understand the emission characteristics and pollution causes of key industries in China and provide more effective service for air quality management.In this study,the online measurement data of continuous emission monitoring system?CEMS?in coal-fired power plants in 2015 were collected and processed from various sources.The emission information were further screened thoroughly and evaluated reasonably based on the mass balance method and statistical approach.Then an establishment method of emission inventory for coal-fired power sector based on CEMS data was developed combining the environmental statistics.Furthermore,the results were compared with those calculated based on the traditional "bottom-up" method to quantify the emission differences between them and evaluate the effects of different method and data.The results showed that the derived national average emission factors of SO2,NOx and particulate matter?PM?were 1.00,1.00 and 0.25 kg/t respectively for 2015 based on CEMS data,78%,71%and 94%lower than those based on traditional method,which might underestimate the emission reduction effect resulted from the improvement of emission control equipment in coal-fired power sector in recent years.The annual emissions of SO2,NOx and PM from the sector were recalculated at 1321,1430 and 334 Gg respectively,75%,63%and 76%smaller than our estimates based on a previous approach without the benefit of CEMS data.Online measurement with proper data screening could better track the actual emission characteristics of coal-fired power plants,and the differences between the two methods reflected the significant effects of emission control measurements for this sector.In order to quantify the improvement of regional air quality simulation resulted from the incorporation of CEMS data,we applied the Models-3/CMAQ?Community Multi-scale Air Quality?using the two emission inventories of coal-fired power plants without/with CEMS data and compared the simulated pollutants'concentrations with ground observations in the Yangtze River Delta?YRD?region.The normalized mean bias?NMB?of annual SO2,NO2,O3 and PM2.5 between ground observation and simulations with CEMS data incorporated were-3.10%?56.27%?-19.46%and-1.39%,respectively,while those based on traditional method were 8.21%?68.90%?-24.61%and 7.61%,respectively.The results showed that CEMS data helped to reduce the biases between pollutant simulations and observations,better reflecting the actual situation of air pollution.The simulation performance of pollutants were significantly improved in specific months.For SO2 simulation,the improvements of NMB significantly passed the confidence level of 99%in July and October,confirming the effective improvements of air pollutant emission inventory of power industry with CEMS data incorporated.Based on the CEMS data,the pollutant emissions from coal-fired power plants under different emission scenarios were predicted and the air quality improvement in YRD resulted from the ultra-low emission policy was quantified.In the scenario where all power plants meet the emission limit in the current standard?GB13223-2011?,the SO2,NOx and PM emissions of coal-fired power plants in China were 1171,1229 and 255 Gg,respectively,reducing by 11%,14%and 24%compared with the current emissions.The emission reduction potential was small,indicating that the current emission standard for power sector has been implemented widely.The emission reduction rates were larger under the scenario where all the power plants meet the emission limit in ultra-low emission policy.The SO2,NOx and PM emissions were 417,653 and 63 Gg,decreasing by 68%,55%and 81%respectively compared with the current emissions.The regional air quality simulations showed that under the ultra-low emission scenario,the rangeability of the simulated SO2,NO2,O3 and PM2.5 in the YRD region were all less than 7%compared with the current emission This was mainly due to the limited proportions of SO2,NOx and PM emissions from power sector in current total emissions in YRD?11%,7%and 2%,respectively?,therefore the air quality benefit of the emission control for coal-fired power sector was not significant.If power plants and industry boilers in the region all meet the emission limit in ultra-low emission policy,the pollutant simulations all showed obvious changes.Compared to the current emission,the simulated SO2,NO2 and PM2.5 concentrations reduced by 32.9%-64.1%?16.4%-22.8%and 6.2%-21.6%respectively in all the simulation periods?January,Aprnl,July and October?.The health benefits resulted from different emission control policies for YRD region were quantified based on Models-3/CMAQ and Integrated Exposure Response?IER?Model.When all coal-fired power plants in YRD meet the ultra-low emission policy,305 of deaths and 874 years of life loss attributable to PM2.5 exposure could be avoided.If industry boilers in the region also meet the ultra-low emission policy,10,651 of deaths and 316,562 years of life loss year could be avoided.The results showed that in order to further improve the air quality and obtain more population health benefits,the cooperative control of various pollution sources should be carried out and the promotion of ultra-low emission control policy in industry boiler and other non-electric industries should be strengthened. |
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