珠三角地区臭氧来源特征的数值模拟研究

Numerical simulation of ozone source characteristics in the Pearl River Delta region

采用WRF/CAMx模型及臭氧源解析技术(OSAT)模块研究珠三角地区臭氧季节性时空分布特征,对不同污染天气型下的臭氧来源进行解析,评估珠三角各城市臭氧暴露水平,并探究如何根据实际天气状况为不同城市提出切实有效的管控措施.研究结果表明,珠三角地区臭氧浓度遵循夏秋季高、冬季低的季节变化特征.在所有季节中,珠三角地区以外的污染源始终具有最显著的贡献,其平均贡献为76.4%.移动源、面源和植物排放源是三大珠三角内源.在季风气候的影响下,春夏季有明显的区域输送贡献较高的季节性特征,其贡献率分别为16.0%(19.1μg·m^(-3))和23.0%(31.8μg·m^(-3)).此外,在冷高压出海、均压场、副热带高压的特殊气象条件下,臭氧浓度均有所增加,相较年平均浓度,增幅分别为48.2%、89.3%、42.5%.在副热带高压的控制下,来自珠三角地区其他城市的区域输送贡献浓度明显增加,尤其是肇庆和广州,相较于月平均贡献,增幅分别为+96.0%和+52.3%.由于冷高压场的风速及风向的改变,本地源的贡献浓度比月平均有所增加,增幅为49.0%.人均臭氧暴露水平表明珠三角地区人群实际生活在比空间加权更高臭氧浓度的环境中,尤其在副热带高压和均压场控制下的污染事件对健康的威胁更大.建议珠三角地区强化与周边城市的协同减排,并结合气象条件实施精细化污染源排放管控;进一步优化城市规划,降低人口密集区的臭氧污染水平.

In this work,the Comprehensive Air Quality Model with extension(CAMx)modelling system with Ozone Source Apportionment Technology(OSAT)module was applied to analyze the seasonal characteristics of ozone spatial and temporal distribution.The influences of particular synoptic patterns on ozone concentration and source contribution were explored,and the ozone exposure levels of various cities in the Pearl River Delta(PRD)region were evaluated,which will provide a solid foundation for implementing specific and effective ozone control measures.The results show that ozone concentration follows the seasonal variation characteristics.In four seasons,the emission sources outside the PRD region always make the most significant contribution,with an average contribution of 76.4%.The mobile,area and biogenic sources are the three top endogenous sources in the PRD region.Under the influence of the monsoon climate,the contribution of regional ozone sources has prominent seasonal variation characteristics in spring(16.0%)and summer(23.0%).Additionally,compared with the annual average,the concentration of ozone increased by 48.2%,89.3%and 42.5%,respectively,under sea high pressure,equalizing pressure field,and subtropical high pressure.With the control of the subtropical high pressure,the regional contribution in the PRD region increased significantly,especially in Zhaoqing(+96.0%)and Guangzhou(+52.3%),compared with the monthly mean contribution.With the effect of the sea high pressure in April,the contribution of local sources increased by 49.0%,compared with the monthly contribution.The level of ozone exposure indicates that people in the Pearl River Delta are actually living in a higher concentration of O;pollution,and the synoptic patterns of subtropical high and equalizing pressure field pose a more significant threat to health.Therefore,collaborative emission control measures should be strengthened with the surrounding area.Combined with the meteorological situation,controlling the endogenous emission in the PRD plays a pivotal role in preventing O;pollution.Besides,the government can further optimize urban planning and encourage the public to migrate to less polluted areas.