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    基于机器学习的北京市城区大气PM2.5和O3污染驱动因素挖掘

    Machine Learning-Based Analysis of Driving Factors for PM2.5 and O3 Pollution in Urban Beijing

    • 摘要: 为克服传统模型受排放清单不确定性限制及统计方法难以解析多因子交互效应的局限,本研究基于北京市城区2015-2023年PM2.5、O3及相关气象要素的小时观测数据,构建随机森林-气象归一化的量化模型,解析排放调控与气象变化对两类主要污染物的非线性影响。结果表明,PM2.5年均浓度持续下降,主要得益于排放源结构调整与有利气象条件的共同作用;O3浓度受人为减排、区域传输及高温低湿等不利气象条件共同影响,维持在185 μg·m-3附近。特征分析表明,相对湿度(41.6%)和温度(60.2%)分别是PM2.5和O3的核心影响因子。当相对湿度处于80.0%-100.0%、温度在-15℃-0℃范围时,易发生PM2.5的高浓度污染;当温度处于30℃-40℃,相对湿度在0%-20%范围时,O3污染将加重。风速处于5~7.5 m·s-1且风向为东北-西南风时,均有利于PM2.5污染的形成与区域传输;风速处于0~5 m·s-1且风向为西南-东南风时可能因前体物充分混合与区域传输加剧O3污染。建议北京市加强人为源持续减排,并强化京津冀及周边地区城市联防联控机制,重点管控东北-西南走向城市带的区域传输污染。

       

      Abstract: To address the limitations of conventional models constrained by emission inventory uncertainties and statistical methods in disentangling multi-factor interactions, this study developed a random forest-meteorological normalization model based on hourly observations of PM2.5, O3, and meteorological factors in urban Beijing (2015–2023). The model quantifies the nonlinear impacts of emission controls and meteorological variations on these pollutants. Results show that the declining trend in annual PM2.5 concentrations was driven by emission source restructuring and favorable meteorological conditions, while O3 levels remained around 185 μg·m-3 due to combined effects of anthropogenic emission reductions, regional transport, and adverse meteorological conditions (e.g., high temperature and low humidity). Feature importance analysis identified relative humidity (41.6%) and temperature (60.2%) as the dominant factors influencing PM2.5 and O3, respectively. High PM2.5 pollution typically occurred under conditions of 80%–100% relative humidity and temperatures between ?15°C and 0°C, whereas O3 pollution intensified at 30°C–40°C with 0%–20% humidity. PM2.5 formation and regional transport were enhanced under northeast-southwest winds (5–7.5 m·s-1), while O3 pollution worsened under southwest-southeast winds (0–5 m·s-1) due to enhanced precursor mixing and transport. We recommend sustained anthropogenic emission reductions in Beijing and strengthened regional joint prevention and control mechanisms, particularly targeting pollution transport along the northeast-southwest urban corridor.

       

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