Concentrations of particulates and metallic elements in slow wind (average 1.5 m/s) in the winter season

Abstract

ABSTRACTConcentrations of fine particulates (PM2.5) and metallic elements at three sites in central Taiwan (an urban site, a science park, and a site close to traffic), where the mean wind speed was only 1.5 m/s, were monitored and analyzed. The urban site had the lowest TSP and PM2.5 particulate concentrations in winter. The mean concentrations of metallic elements Ni, Pb, and Cr in PM2.5 exceeded those in TSP at the three characteristic sampling sites in winter. A northeasterly monsoon, slowly moving northern cold air masses, and wind with a low average speed (1.5 m/s) dominated during the sampling period. Atmospheric diffusion was generally low, causing large amounts of local atmospheric pollutants to accumulate. The concentrations of metallic elements that were attached to particulates (PM2.5) increased significantly during the winter season. However, the concentrations of particulate pollutants in ambient air declined throughout the winter. The average TSP and PM2.5 particulate concentrations in ambient air that were obtained in this study with a low average wind speed (1.5 m/s) were about 0.48% and 0.41% lower, respectively, than those obtained in a previous study with a higher average wind speed (of > 3 m/s). The mean low wind speed (1.5 m/s) was the main factor that was responsible for the concentrations of pollutants in ambient air during the winter season.