Atmospheric acid gases in Tokushima, Japan, monitored with parallel plate wet denuder coupled ion chromatograph.

During the summer of 2011 and winter of 2012, we continuously measured trace acid gas concentrations in Tokushima, Japan, using a parallel plate wet denuder coupled ion chromatograph. The average concentrations of hydrochloric acid (HCl), nitrous acid (HONO), nitric acid (HNO(3)), and sulfur dioxide (SO(2)) were, respectively, 0.54, 1.20, 1.17, and 3.22 μg m(-3) in the summer, and 0.09, 1.06, 0.46, and 5.11 μg m(-3) in the winter. In the summer, concentrations of all the acid gases increased after sunrise and showed a strong diurnal pattern with daytime maxima and nighttime minima, but the time at which concentration levels began to increase and the pace of increase differed among the acid gases. The concentration of HONO increased sharply immediately after sunrise, while concentrations of the other three gases began increasing about one and half hours later. SO(2) showed the fastest rate of increase, followed by HNO(3) and HCl. These differences were likely attributable to the formation processes of gaseous substances.