Concentration of Sulfate and Other Inorganic Materials in Fog and Cloud Water and in Aerosol

Abstract

Measurements were made of sulfate and other inorganic materials in fog and cloud water in 1963. It was found that in cumulus clouds above Mt. Norikura, sulfate was in the form of ammonium sulfate and sulfuric acid. In upslope fog at Shiobara, and in stratus cloud which covered Mt. Tsukuba, sulfate was supposed to be combined with some metals in addition to ammonium ions, During the periods of September 1962 to February 1963, and of July to December 1966, separate samplings of large and giant particles were made in Tokyo by means of a high volume cascade impactor. It was found that the weight ratio of SO4'`/SO2 was above 0.12 at relative humidity above 55%, wind velocity below 4 m/sec and visibility below 5 km, It seems that atmospheric humidity is an important factor for the atmospheric oxidation of SO2. The relationship of the amounts of sulfate and ammonium was also studied. These studies indicate that various weather and environmental conditions affect the atmospheric oxidation of SO2. The atmospheric concentration of hydrogen ion contained in aerosol was usually below 3 x 10-2 pg/m3 except on October 26, 1966, when the atmospheric concentration of hydrogen in large particles was 1.7 to 7.5 g/m3 in heavy smog.

Chemical Composition of Fog Water near the Summit of Mt. Norikura in Japan

“…Acidic fogs have also been reported in previous observations taken at Mt. Norikura during the summer season (Okita, 1968;Qian et al, 1991Qian et al, , 1992. According to Qian et al (1992), the pH values of fog water were 3.6-5.6 on 2-7 August 1989, 3.6-5.8 during 3-10 July 1990 and 4.8-5.8 over 19-24 August 1991.…”

“…4), with an average ratio of about 2.9. According to Okita (1968) (greater than the SO42-concentrations) in fog water have been observed at mountainous sites near industrial regions of Japan (Ohta et al, 1981;Hosono et al, 1994;Ikeda et al, 1995 is significantly higher than that in autumn (lower panel). The differences between the summer ratio and that in autumn are not due to differences in air masses.…”

“…Excessive values of Cl-in fog water were also observed at Mt. Norikura during the summer of 1963 (Okita, 1968). Amounts of Cl-also contribute to fog water acidification, while the Cl-concentration was less than those of SO42-and NO3-.…”

“…Strongly acidic fogs (pH<4) have been observed not only in urban areas, but also at mountainous sites far from industrial regions (Okita, 1968;Wobrock et al, 1994;Schemenauer et al, 1995). It is thought that acid fog contributes to the decline of forests at high elevation locations, where mountain slopes are frequently immersed in fog and cloud water (Blank, 1985;Saxena et al, 1989;Saxena and Lin, 1990).…”

“…In a previous study in Japan (Okita, 1968), the chemical composition of fog water at a high elevation (Mt. Norikura) was measured in July 1963.…”