基于随机森林算法的山东省区域臭氧污染事件中气象条件和排放贡献影响研究

Random Forest-Based Analysis of Meteorological Condition and Emission Contribution to Regional Ozone Pollution Incidents in Shandong Province

山东省作为我国东部的工业大省,近年在经济快速发展的同时也面临着严重的臭氧(O_(3))污染;在不利气象条件的影响下,发生过多次影响范围大、持续时间长的O_(3)污染事件.因此,如何基于地面观测数据剥离气象条件及排放的影响,成为O_(3)污染防控政策评估和政策制定中的重要问题.为此,本研究基于2020−2022年山东省地面国控监测站点O_(3)浓度逐时观测数据及对应气象数据,运用随机森林模型对气象条件和排放的贡献进行了剥离;基于沙普利加和模型,定量分析了各气象因子对O_(3)污染的影响;此外,研究中定义了区域O_(3)污染事件,并对事件期间气象条件及排放的影响进行了深入的对比分析.结果表明:2020−2022年山东省3个亚区域O_(3)前体物排放影响呈逐年上升趋势,年变化速率分别为3.3%(鲁西)、7.8%(鲁中)和4.4%(鲁东),2020年和2021年气象条件有利于高浓度O_(3)的消减,导致O_(3)年均浓度下降2.27~8.26μg/m^(3),属于“天帮忙”;而2022年气象条件相对不利,气象条件贡献了O_(3)年均浓度的5.16~10.69μg/m^(3).排放对O_(3)浓度的相对贡献在24个O_(3)区域污染期间与非污染期间较为一致,不利的气象条件是O_(3)污染形成的主要诱因.在各气象因子中,温度和相对湿度是影响O_(3)浓度最主要的气象因素,其中温度的影响最为显著,对O_(3)小时浓度的贡献为33.36~89.61μg/m^(3).研究显示,2020−2022年山东省O_(3)前体物排放贡献的年际变化差异不显著,不利气象条件则是造成O_(3)污染的重要因素,后续应更加重视在高温低湿条件下的O_(3)污染防控工作.

Shandong Province,a major industrial region in eastern China,suffers from long-term ozone pollution throughout the year.In recent years,adverse meteorological conditions have exacerbated the problem,causing persistent and widespread ozone pollution events.Therefore,using ground observation data to assess the effects of meteorological factors and emissions on ozone levels has become a crucial concern in evaluating and formulating policies for ozone pollution prevention and control.To address this challenge,this study utilizes hourly ozone(O_(3))concentration data and corresponding meteorological data from state control ground monitoring stations in Shandong Province from 2020 to 2022.The research employs a random forest model to separate the contributions of meteorological conditions and emissions.Additionally,the Shapley additive explanation(SHAP)model is used to quantify the impact of various meteorological factors on O_(3).Furthermore,the study defines regional ozone pollution cases and performs a comprehensive comparative analysis of meteorological condition and emission effects during these cases.The results indicate that influence of O_(3)precursors emissions exhibited an increasing trend in the three regions in Shandong,with annual growth rates of 3.3%,7.8%and 4.4%in west,central,and east Shandong,respectively.Meteorological conditions in 2020 and 2021 were favorable for reducing high O_(3)concentrations,resulting in a decrease of 2.27-8.26μg/m³in annual average O_(3)concentration.However,in 2022,the meteorological conditions were relatively adverse,and the annual average O_(3)concentration increased to 5.16-10.69μg/m^(3).The relative contribution of emissions in the 24 regional ozone pollution events consistent with that during non-polluted period,and unfavorable meteorological conditions were the main cause of O_(3)pollution.Among meteorological factors,temperature and relative humidity have the greatest impact on O_(3)concentration,with temperature having the most significant effect,the contribution on O_(3)hourly concentration can reach as high as 33.36-89.61μg/m³.The results highlight relatively stable interannual emission contributions during 2020 to 2022 in Shandong and emphasize adverse meteorological conditions as a key driver of ozone pollution.Thus,it underscores the importance of focusing on ozone pollution prevention and control,especially under high temperature and low humidity conditions.