基于Brute-Force方法的京津冀区域夏季臭氧反应机制

近年来京津冀区域夏季臭氧（O₃）体积分数仍居高位，轻中度污染频繁发生，相关反应机制研究亟需开展.利用WRF-Chem模式对该区域2018年夏季代表月O₃浓度进行模拟，并基于Brute-Force方法探究了区域层面前体物减排的O₃变化.O₃在不同排放情景的变化表明，该区域O₃反应机制以VOCs控制区与非敏感区为主，VOCs控制区主要聚集京津冀中部，呈南北带状分布，面积占比15.60%~26.59%.区域各市城区的O₃浓度对前体物排放的相对响应强度（RRI）具有很大的空间差异性，对于VOCs，RRI_VOC在0.03~0.16范围内；而对于NO_x，RRI_NO_x在-0.40~0.03范围内.纬度越高的城区，RRI值越剧烈，表明了越为显著的区域输送影响.前体物排放强度高的城区，RRI_NO_x值越低，暗示RRI_NO_x对当地NO₂浓度的负向依赖；但RRI_VOC与NO₂水平无明显关联，更依赖于对前体物相对丰度（VOCs ：NO_x）.RRI_VOC与RRI_NO_x比值在多数城市表现为负值，VOCs协同减排以抑制O₃浓度恶化十分必要；该比值的绝对值在工业化和城市化高的城市远低于普通中小城市，意味着这些城市VOCs协同减排的要求将更高.然而，即使在前体物50%减排下，区域各城市O₃浓度改善仍然有限，毗邻省份的区域外联合治理也依然重要.

Summer Ozone Mechanism and Control Strategy in Beijing-Tianjin-Hebei Region Using Brute-Force Method

In recent years, the ozone (O₃) volume fraction in the Beijing-Tianjin-Hebei Region in summer have remained high, light to moderate pollution occurs frequently, and research on related response mechanisms is urgently needed. This study applied the WRF-Chem model to simulate the change in ozone volume fraction in this region by setting 13 precursor emission scenarios in a representative month in the summer of 2018. The results revealed that VOC-sensitivity and no-sensitivity regimes commonly occurred in the Beijing-Tianjin-Hebei Region in July, and the VOC-sensitivity regimes were mainly accumulated in the central Beijing-Tianjin-Hebei Region, with a north-to-south zonal distribution and an area share of 15.60%-26.59%. The relative response intensity (RRI) of O₃ volume fraction to precursor emissions in urban areas had large spatial variability, with RRI_VOC and RRI_NO_x in the ranges of 0.03-0.16 and -0.40-0.03, respectively. The higher the latitude of urban areas, the more dramatic were the RRI values, indicating a more significant regional transport influence. The lower RRI_NO_x values in urban areas with high intensity of precursor emissions implied a negative dependence of RRI_NO_x on local NO₂ concentrations; however, RRI_VOC was not significantly correlated with NO₂levels and was more dependent on the relative abundance of precursors (VOCs:NO_x). The ratio of RRI_VOC to RRI_NO_x showed negative values in majority of the cities; therefore, collaborative VOCs emission reduction is necessary to suppress the deterioration of O₃ volume fraction. The absolute value of this ratio was much lower in cities with high industrialization and urbanization than in ordinary small and medium-sized cities, implying that the demand for collaborative VOCs emission reduction in these cities will be higher. However, even under 50% reduction of precursors, the improvement in O₃ volume fraction was limited in regional cities, and the combined prevention in neighboring cities remains important.