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

ABSTRACT

Concentrations of fine particulates (PM_2.5) 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 PM_2.5 particulate concentrations in winter. The mean concentrations of metallic elements Ni, Pb, and Cr in PM_2.5 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 (PM_2.5) increased significantly during the winter season. However, the concentrations of particulate pollutants in ambient air declined throughout the winter. The average TSP and PM_2.5 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.

KEYWORDS:

• TSP
• PM_2.5
• metallic elements
• back trajectories
• concentration scatter diagrams

Funding

The authors gratefully acknowledge the National Science Council of the ROC (Taiwan) for financial support under project No. MOST 104-2632-E-241-001.