The chemical characteristics of fine particulates in Metropolitan Manila, capital of the Philippines, were investigated. Week-long daily PM_2.5 sampling observations were done in the months of May and October of 2018 in the Manila Bay area. May and October correspond to the boreal spring and fall monsoon transition periods, respectively. The sampling periods were selected to minimize the contribution of transboundary pollutants and to determine the influence of local mesoscale weather under similar synoptic flow conditions. Results show the daily average PM_2.5 mass concentration for spring and fall to be 29.07 $\pm$4.69 and 50.06 $\pm$8.79 μg ${\text{m}}^{-3}$, respectively. Most PM_2.5 components were also found to be higher during fall. The difference in concentration between the two seasons is mainly due to the strong land/sea-breeze in spring induced by warmer land surface temperature. In spring, strong sea-breeze disperses PM_2.5 inland, and the nighttime land-breeze serves as the outflow path of fine aerosols from Metropolitan Manila. In fall, the opposing flow of the weaker sea-breeze to the prevailing easterly produces stagnant air that leads to higher accumulated particulate concentration. Moreover, the suppressed outflow during fall season resulted in higher PM_2.5 contribution of aged secondary aerosol components. Overall, the largest contributors to Metropolitan Manila PM_2.5 mass concentration are the primary and secondary aerosols from local vehicular emissions, followed by soil dust and seasalt.

调查了菲律宾首都马尼拉大都会的细颗粒的化学特性。在马尼拉湾地区，于2018年5月和10月进行了为期一周的每日PM _2.5采样观察。5月和10月分别对应于北方春季和秋季季风过渡期。选择采样周期是为了最大程度地减少跨界污染物的影响，并确定在类似天气条件下局部中尺度天气的影响。结果显示，春季和秋季的日平均PM _2.5质量浓度为29.07$\pm$4.69和50.06 $\pm$8.79  μ克 ${\text{米}}^{-3}$， 分别。秋季发现大多数PM _2.5成分也较高。两个季节之间的集中度差异主要是由于春季地表温度升高引起的春季强陆/海风。春季，强劲的海风将PM _2.5散布到内陆，夜间的陆风则是马尼拉大都会细小气溶胶的流出路径。在秋天，海风减弱到盛行的东风的逆流产生了停滞的空气，导致了更高的累积颗粒物浓度。此外，秋季抑制的流出导致了老化的次级气溶胶成分对PM _2.5的贡献更高。总体而言，马尼拉大都会区PM _2.5的最大贡献者 质量浓度是当地车辆排放的主要和次要气溶胶，其次是土壤粉尘和海盐。