Atmospheric concentrations of nitric acid, sulfur dioxide, particulate nitrate and particulate sulfate, and estimation of their dry deposition on the urban- and mountain-facing sides of Mt. Gokurakuji, Western Japan

Atmospheric concentrations of nitric acid (HNO₃), sulfur dioxide (SO₂), particulate nitrate (NO₃ ^-) and particulate sulfate (SO₂^2-) on the urban- and mountain-facing sides of Mt. Gokurakuji were measured from November 2002 to October 2003, in order to evaluate the effects of anthropogenic activity on air quality and dry deposited nitrate and sulfate on the surfaces of pine foliage. The results showed that HNO₃, SO₂ and NO₃^- concentrations were significantly higher (P <0.05) on the urban-facing side (1.54, 2.48 and 0.65 μm^-3, respectively) than the mountain-facing side (0.67, 1.19 and 0.37 μm^-3, respectively), while SO₄^2- concentrations did not differ significantly between the two sides (urban-facing: 2.80 μm^-3; mountain-facing: 2.05 μm^-3). Indirect estimates of dry deposition rates of nitrate and sulfate to the surfaces of pine foliage based on the measured concentrations approximately agreed with the measured values determined by the foliar rinsing technique in a previous study. It was found that HNO₃ was the major source (approximately 80%) of dry deposited nitrate on pine foliage, while the contribution from SO₄^2- was about equal to that from SO₂. In conclusion, HNO₃ and SO₂ appear to be dominant species reflecting higher dry deposition rates of nitrate and sulfate on the urban-facing side compared to the mountain-facing side of Mt. Gokurakuji.