M. Kido et al., Diurnal variation of ionic aerosol species and water-soluble gas concentrations at a high-elevation site in the Japanese Alps, J GEO RES-A, 106(D15), 2001, pp. 17335-17345
Size-separated atmospheric aerosol particles, acidic gases, and ammonia wer
e collected during the daytime and nighttime at Murododaira (36.6 degreesN,
137.6 degreesE, 2450 m above sea level), Mount Tateyama, Japan in early wi
nter. 'Non-sea-salt (nss) SO42- in fine fractions (< 2.1 mum in diameter) w
as the most dominant ionic constituent and occupied 44% on average of the i
onic mass concentration other than H-. Concentration levels of aerosol ions
and water-soluble gases were higher during the day and lower at night. Con
centrations of the nighttime aerosol particles and gases (except for SO2) w
ere similar to free-tropospheric background levels at various sites of nort
hern midlatitudes in the literature, suggesting that nighttime data at Muro
dodaira were representative of free-tropospheric conditions. High concentra
tion levels of SO2 at Murododaira. were close to those over the northwest P
acific Rim region during the winter season. Molar ratios of nssSO(4)(2-)/SO
2 can be explained by the transport time from the Asian continent, suggesti
ng that a significant source of fine nssSO(4)(2-) aerosols at Murododaira i
n early winter could be due to the oxidation of anthropogenic SO2 derived f
rom the Asian continent. The equivalent ratios of nssSO(4)(2-) to NH4+ in f
ine particles were close to 0.5 under westerly wind conditions, suggesting
the existence of half-neutralized sulfate on average.