How Aeolian Dust Deteriorate Ambient Particulate Air Quality along an Expansive River Valley in Southern Taiwan? A Case Study of Typhoon Doksuri

ABSTRACT

Aeolian dust episodes (ADEs) frequently occurred at the bare lands of the riverbeds in Kaoping River are emerging disasters in Southern Taiwan in the past few years. However, their influences on ambient particulate air quality due to the outflow circulation of typhoons have not been addressed in such a subtropical region. This study aims to investigate the association between typhoons and ADEs and their influences on the ambient particulate air quality, which might occur in East Asia. Four sites along the Kaoping River were selected to collect PM₁₀ with high-volume samplers during and after the ADE accompanying with Typhoon Doksuri on June 29, 2012. During the ADE, PM₁₀ concentration rose as high as 30–40 folds higher than those on regular days. Chemical composition of PM₁₀ was further analyzed to verify several valuable indicators including the molar ratios of [Cl^–]/[Na⁺] (0.95–1.02), the mass ratios of Fe/Cd (211.6–3957), and the mass ratios of OC/EC (1.18–1.35). Nevertheless, the chloride deficit phenomenon was not favorable during the ADE. Moreover, CMB receptor modeling results showed that aeolian dust and sea-salts were major contributors of PM₁₀ during the ADE. Along the Kaoping River, the contribution of aeolian dust to PM₁₀ ranged from 11.5 to 33.1% during the ADE, and reduced to 7.2–23.0% after the ADE. However, a small amount of finer aeolian dust could be still suspended in the ambient air after the ADE. Moreover, integrating SURFER software and WRF model was appropriate to locate the hot spots influenced by the ADE.