高温天气对生物源排放及其O_(3)生成贡献的影响:以四川盆地2022年7-8月为例

Effects of High Temperature on Biogenic Emissions and O_(3)Generation:A Case Study of Sichuan Basin from July to August 2022

2022年7—8月,四川盆地气温同比上升3.63℃,O_(3)污染天比往年大幅增加.为了解高温天气对四川盆地生物源排放及其O_(3)生成贡献的影响,基于WRF模拟获取的气象数据,利用MEGAN模型估算了四川盆地2022年7—8月生物源挥发性有机物(BVOCs)排放量,分析了BVOCs及其化学物种的时空分布特征,并利用空气质量模型CMAQ定量评估了高温天气下BVOCs排放对O_(3)生成的影响.结果表明:(1)四川盆地2022年7—8月BVOCs排放量为86.30×10^(4)t,其中,异戊二烯、甲醇、单萜烯的排放量分别为42.16×10^(4)、17.32×10^(4)、9.92×10^(4)t;成都平原、川南、川东北城市群BVOCs排放强度分别为3.61、6.55、5.00t/km^(2).(2)BVOCs排放高值区主要集中在川南城市群的宜宾市和泸州市中部、成都平原城市群的乐山市东北部以及川东北城市群的巴中市和达州市北部;异戊二烯和单萜烯排放空间分布特征与BVOCs排放空间分布特征基本一致,而甲醇空间分布特征具有显著差异.(3)BVOCs排放有明显的日变化特征,最大排放量出现在14:00.(4)CMAQ模拟结果显示,BVOCs排放对O_(3)生成贡献率较大的城市有乐山市、眉山市、雅安市和内江市,其贡献率均超过30%.空间分布上,成都平原城市群的乐山市北部和眉山市中西部BVOCs排放对O_(3)生成贡献最显著.2022年7—8月高温天气下BVOCs排放对O_(3)生成贡献同比增长4.99%.研究显示,四川盆地BVOCs排放对O_(3)污染有重要影响,且高温天气下其对O_(3)生成的贡献率进一步增加,是O_(3)污染防治关注的重点.

From July to August 2022,the temperature in the Sichuan Basin was 3.63℃higher than that of last year,and the number of ozone pollution days increased significantly compared to previous years.To understand the effects of high temperature on biogenic emissions and O_(3)generation contribution in the Sichuan Basin,the Model of Emissions of Gases and Aerosols from Nature(MEGAN)was used to estimate the emissions of biogenic volatile organic compounds(BVOCs)in the Sichuan Basin from July to August 2022 based on the meteorological data obtained by Weather Research and Forecasting(WRF)simulations.The spatiotemporal distribution characteristics of BVOCs and chemical species were analyzed.The impact of BVOCs emissions on O_(3)generation in high temperature weather was quantitatively evaluated by a Community Multi-Scale Air Quality(CMAQ)model.The results showed that:(1)From July to August 2022,BVOCs emissions in the Sichuan Basin were 86.30×10^(4)t,and the emissions of isoprene,methanol and monoterpenes were 42.16×10^(4),17.32×10^(4)and 9.92×10^(4)t,respectively.The BVOCs emission intensities of Chengdu Plain urban agglomeration,South Sichuan urban agglomeration,and Northeast Sichuan urban agglomeration were 3.61,6.55 and 5.00 t/km2,respectively.(2)The high emission areas of BVOCs were mainly concentrated in the central parts of Yibin City and Luzhou City in the South Sichuan urban agglomeration,the northeastern part of Leshan City in the Chengdu Plain urban agglomeration,and the northern parts of Bazhong City and Dazhou City in the Northeastern Sichuan urban agglomeration.The spatial distribution characteristics of isoprene and monoterpene emissions were basically consistent with those of BVOCs emissions,while the spatial distribution characteristics of methanol showed significant differences.(3)BVOCs emissions had an obvious diurnal characteristic and the highest emission occurred at 14:00.(4)The CMAQ simulation results showed that the cities with large contributions of BVOCs emissions to O_(3)generation were Leshan,Meishan,Ya′an,and Neijiang,with contribution rate of over 30%.In terms of spatial distribution,BVOCs emissions in the northern part of Leshan and the central-western parts of Meishan in Chengdu Plain urban agglomeration had the most significant contribution to O_(3)generation.From July to August 2022,the contribution of BVOCs emissions to O_(3)generation in high temperature weather was 4.99%higher than that of last year.Based on the above research results,BVOCs emissions in Sichuan Basin has an significant impact on O_(3)pollution,and the contribution rate to O_(3)generation further increases in high temperature weather,which is the focus for O_(3)pollution prevention and control.