The temporal and spatial variations of acid aerosols in the geothermal area of metropolitan Taipei, Taiwan

This study involved sampling over 1 year of data on exposure to acid aerosols in the geothermal area of metropolitan Taipei. The temporal and spatial variations of the concentrations of acid aerosols were assessed by sampling at three sites: A, B, and C. Results indicate that the SO₂ concentrations lead the concentrations of other acid aerosols at site C because two active fumaroles surround this site. The mean SO₂ concentrations at sites A, B, and C were 2.4, 2.4, and 6.2 ppb. Previous studies have found that H₂S levels were highest at site C. However, the SO₄ ^-2 and H⁺ concentrations among the three sites were similar. The mean aerosol SO₄ ^-2 concentrations were 7.0, 5.7, and 5.7 μg m^-3 at sites A, B, and C, respectively; their H⁺ concentrations were 5.5, 4.2, and 5.4 nmolm^-3. No seasonal variations are observed for most of the acid aerosols in the geothermal area except that the types of hot spring affect the SO₄ ^-2 concentration nearby. The different seasonal fluctuation among the sites reflect the determinant of SO₄ ^-2 emission from different geothermal sources. Sulfur-rich aerosols and some SO₂ emitted from geothermal sources are obvious. The predominance of nitrogen-containing gases (sum of NO₂ + HNO₂ + HNO ₃) over SO₂ indicates the importance of the anthropogenic origin of emissions. The effect of multiple exposures to sulfur-rich aerosol (including H₂S, SO₂, and SO₄ ^-2), H⁺, and nitrogen-containing aerosols on the health of nearby residents warrants concern.