The plum rain season in Taiwan is in May and June. The severest plum rain season over the last 21 years was in 2017. This study involves the collection of mercury wet depositions in the plum rain season of May-June in 2017. A DMA-80 (Direct Mercury Analyzer) was used to analyze the precipitated mercury concentrations and calculate the wet depositions of mercury in the plum rain season. The results indicate that the highest wet depositions of mercury in the aqueous phase were on 6/16, reaching 209.04 μg/m2 * day, while the lowest were on 5/15, at 0.18 μg/m2 * day. The mercury wet depositions in the particulate phase were highest on 6/17, when it exceeded 100 μg/kg, and lowest on particulate phase were occurred in 6/11, when it was 3.64 μg/m2 * day. The relationship between the wet depositions of mercury in the aqueous phase and rainfall was insignificant, while that between the wet depositions of mercury in the particulate phase and rainfall was significant. The wet depositions of mercury in this study were second highest (30.73 μg/m2 day) when compared with those in studies in the years 2007-2017. Although the rainfall in this study was only 564 mm H2O, high mercury concentrations obtained from the plum rain season result in the high wet depositions of mercury in Taichung, Taiwan.
Keywords: Mercury; Plum rain season; Rainfall; Wet deposition.