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Geochemical Journal, Vol. 5, pp. 57 to 67, 1971
Ammonia in the oceanic atmosphere and the
cycle of nitrogen compounds through
the atmosphere and the hydrosphere
SHIZUO TSUNOGAI
Department of Chemistry, Faculty of Fisheries,
Hokkaido University, Hakodate, Japan
(Received March 25, 1971; in revised form June 1, 1971)
Abstract -The concentration of ammonia in the atmosphere over the ocean was determined for samples collected on board. The concentration of total ammonia in the
maritime air was 50ngat/m3(STP) on the average which was much lower than that over
the land, and was higher in the air nearer the land. The proportion of aerosol ammonia
to total ammonia in the maritime air was 30% (mean) in the North Pacific, whereas it
was 80% in the South Pacific. These facts together with the residence time of ammonia
in the atmosphere suggest that most of ammonia in the oceanic air is of continental
origin. The amount of combined nitrogen transported from the land to the ocean is
estimated from its concentration in rain water to be 1.5 X 1012gatN/y. Judging from
the budget of the combined nitrogen in the ocean, the large supply of nitrogen from
the land is balanced by the denitrification in the ocean. Its mechanism is discussed
from the quantitative aspect, and two possibilities still remain owing to the lack of
decisive evidences, which are the reduction of nitrate in sea water containing little oxygen
and the denitrification in the respiratory process in oxygenated sea water.