Toshiichi Okita

Long term measurements of atmospheric gaseous and aerosol species using an annular denuder system in Nara, Japan

During the period from June 1994 to May 1995 a three-line annular denuder filter system was used to sample atmospheric gas phase SO2, HNO3, HNO2, HCl, and NH3 and aerosol phase SO2-4, NO-3, Cl-, NH+4, Na+, K+, Ca2+, and Mg2+ in Nara, Japan. The average annual concentrations of these species were determined together with their seasonal variations. It was found that even in a medium-sized city such as Nara HNO3 and HNO2 concentrations were fairly high. The present system also enabled the determination of the percent loss of aerosol components NO-3, Cl- and NH+4 collected on filters.

Measurement of gaseous and particulate nitrates in the atmosphere

Abstract Gaseous and particulate nitrates are simultaneously sampled on a train consisting of a Millipore FHLP filter and a Toyo 51A filter impregnated with NaCl, extracted from the filters and colorimetrically determined. The interferences of NO 2 , of a mixture of NO 2 and O 3 , of PAN and of organic nitrate were examined and found to be negligible in most of the measurements. The field study indicated that the inorganic gaseous nitrate concentration was significantly correlated with the oxidant level, whereas the concentration of particulate nitrate had no correlation with the oxidant level.

Measurements of the concentration in rainwater and of the Henry's law constant of hydrogen peroxide

A chemiluminescent method for measuring hydrogen peroxide was developed using hemin as a catalyst for luminol-based H2O2 oxidation, which gave a detection limit below 0.1 μg ∝−1 in the solution. It was shown that most atmospheric species did not give serious interference, and that negative interference of SO2; could be eliminated if pH of the collecting solution was above 10 whereas O3, gave significant positive interference. The Henrys law constant of H2O2 was experimentally determined to be 1.42 × 105 M atm−1 at 20°C at ambient concentration levels of H2O2. This method was also applied to the measurements of H2O2 concentration in rainwater in Tokyo, Japan, which was in the range of 5–1065μg ∝−1.

Determination of gaseous and particulate chloride and fluoride in the atmosphere

Abstract The measurement of gaseous and particulate chloride and fluoride in the atmosphere was accomplished using a combination of a Millipore filter and a sodium carbonate impregnated filter. The sampling flow rate was about 201 min−1, and the Millipore pre-filter was heated during the sampling. The measurements in many places in Japan and Manila, Philippines, indicate that the gaseous chloride concentration is high at the coast and on mountains, but the sources of gaseous chloride still remain obscure. The samplings of fluoride revealed that near and in an aluminum refining plant the precentage of particulate component is higher than that of the gaseous component.

Measurements of atmospheric SO2 and SO42−, and determination of the wet scavenging coefficient of sulfate aerosols for the winter monsoon season over the sea of Japan

Abstract In order to determine the scavenging coefficient of oxides of sulfur in winter monsoon over the Sea of Japan both air and precipitation concentrations of sulfur dioxide and sulfate were measured on Sado Island on the Sea of Japan coast. The measurements were taken during the period between 28 January and 3 February 1992. The atmospheric concentrations of SO42− were 0.57–1.11 μg S m−3 whereas those of SO2, were below 0.27 μg S m−3, much lower than SO42− concentration. A back trajectory analysis showed that these sulfur species would have been transported from Eurasian continent over the Sea of Japan. A layer-average scavenging coefficient, k, for sulfate by precipitation including snow, graupel and rain was determined on the basis of the equation k = HP/h, where H, P and h are the scavenging ratio, precipitation intensity and mixing layer height, respectively, under the assumption of a uniformly mixed layer over the warm sea current along the Sea of Japan coast. The scavenging coefficients were calculated to be 3.5 × 105−2.9 × 10−4S−1 for precipitation intensities of 0.13–3.1 mm h−1. A regression analysis of these datasets gave a k value for submicron SO42− aerosol over the Sea of Japan of k = 1.38 × 10−4P0.74, where p is precipitation intensity. These values are very close to a recently obtained result by Jylha for radioactive aerosols. Summarizing the measurements taken by the authors and other investigators the wet scavenging coefficient k may be represented by k = aPb where a is around 10−4, and b is between 0.67 and 0.76.

Quantitative estimation of sodium- and ammonium-nitrate, ammonium chloride, and ammonium sulfate in ambient particulate matter

In recent years the behavior of particulate nitrate has been of great concern with respect to gas-to-particle conversion in the atmosphere. The detailed structure of particulate nitrate collected on high volume sampling filters is evaluated on the basis of ammonium nitrate volatility. The filters were stored at room temperature without containers in a laboratory for 15 months and periodically analyzed for NO/sub 3//sup -/, NH/sub 4//sup +/, and SO/sub 4//sup - -/. Losses of NO/sub 3//sup -/ and NH/sub 4//sup +/ were observed while sulfate content did not change. The loss seemed to be almost complete after 15 months. 31 references, 3 figures.

Formation of Aerosols in the Atmosphere

Atmospheric aerosol is one of the most important factors affecting the Earth’s climatic and weather conditions. The study of the mechanisms of formation and evolution of atmospheric aerosols is of primary importance for predictions of the climatic changes on our planet. We hope that this short overview of the modern state of art in aerosol science will be of use to all those who are involved to the study of atmospheric processes that form the Earth’s climate. We introduce the readers to the basics of physical chemistry of aerosols. Special attention is given to the latest achievements in the theory of particle formation and their subsequent growth.

Measurements of air pollution associated with oil fires in Kuwait by a Japanese research team

Abstract During the period 28 April 5 May 1991 a Japanese research team monitored the air pollution in Kuwait caused by oil-well fires. Monitoring was conducted at nine sites using lightweight samplers. A major monitoring site was located at Ahmadi near the fires. High levels of total airborne particulate matter, soot, organic carbon. SO 4 2 , and Cl + were detected, but the levels of SO 2 , NO 2 , CO and benzo( a )pyrene were rather low.

Some Measurement Results on Sulfate Aerosol Concentration in and above a Pine Canopy

Profile of sulfate aerosol (SO42−) concentration was measured for four days at six heights in and above a 15m-high canopy of pine plantation during 6th and 10th August. 1999. The concentration was the lowest (about 2 nmol/m3) on 6th, and gradually increased to 9th showing the maximum values of about 13 nmol/m3, and then decreased to 2 nmol/m3 on 10th. The vertical profiles of SO42− concentration showed mostly higher in the canopy than above the canopy. As for the vertical profiles above the canopy on 8th and 10th, the minimum was observed just above the canopy (16m), showing SO42− transport from the upper air layer to the canopy. While on 9th the profiles that are higher concentration just above the canopy and lower at the upper air layer were observed, suggesting SO42− emission from the canopy to the upper air layer.