Oxidation efficiencies of nitrite to nitrate by freezing of field rain samples

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:466124

Takenaka, Norimichi; Daimon, Tohru; Sato, Keiichi ^[1]

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1. Osaka Prefecture Univ. (Japan)

Nitrite is known to be oxidized to nitrate by freezing much more rapidly than in solution. Furthermore, the oxidation efficiency of nitrite to nitrate by freezing is varied by pH or kinds and concentration of coexistences. We report here the oxidation efficiencies of nitrite to nitrate by freezing of field rain samples. The field rain samples were collected at Mt. Ikoma, which is located at about 20 km east of Osaka city, and Osaka Prefecture University. Concentration of nitrite was usually sub to a few {mu}mol/L order in rain and {mu}mol/L order in fog and less than 1 {mu}mol/L in snow. The highest value of nitrite concentration was 43 {mu}mol/L in rain and 620 {mu}mol/L in fog. Nitrite was oxidized immediately to nitrate by freezing at pH lower than 5.2, even when the sample droplet (about 1 mm diameter) was frozen very quickly in liquid nitrogen (77K). The oxidation efficiency was higher at lower pH. However, the efficiency varied from sample to sample. This is probably due to that kinds and concentration of coexistences were difference between samples. The effect of solutes will be also reported. Freezing of rain droplets are observed in freezing of super cooled droplets, growing of graupel and hail, growing of cumulonimbus, and so on. Ratio of nitrate to nitrite was higher in snow than that in rain or fog.

• OSTI ID: 466124
• Report Number(s): CONF-9606185--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
NITRATES
NITRITES
OXIDATION
RAIN
SNOW
TEMPERATURE DEPENDENCE