Influence of local meteorology on the chemical characteristics of fine particulates in Metropolitan Manila in the Philippines

Abstract

The chemical characteristics of fine particulates in Metropolitan Manila, capital of the Philippines, were investigated. Week-long daily PM2.5 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 PM2.5 mass concentration for spring and fall to be 29.07 ±4.69 and 50.06 ±8.79 μg m−3, respectively. Most PM2.5 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 PM2.5 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 PM2.5 contribution of aged secondary aerosol components. Overall, the largest contributors to Metropolitan Manila PM2.5 mass concentration are the primary and secondary aerosols from local vehicular emissions, followed by soil dust and seasalt.