Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis

作者：Fujii Ayako^*; Toyoda Sakae; Yoshida Osamu; Watanabe Shuichi; Sasaki Ken' ichi; Yoshida Naohiro

来源：Journal of Oceanography, 2013, 69(2): 147-157.

DOI：10.1007/s10872-012-0162-4

• Nitrous oxide
• Isotopomer
• Production mechanism
• The eastern subtropical North Pacific
• Greenhouse gas
• Nitrification
• Nitrifier denitrification
• Denitrification
• N2O reduction
• CFCs

N2O concentration and its isotopomer ratios were measured over a wide area from San Diego to Honolulu in the eastern subtropical North Pacific (ESNP). Waters in the study area had an N2O maximum (38.2-50.5 nmol kg(-1)) at 600-1000 m depth, which is similar to the profiles obtained previously in other areas in the North Pacific. We separated the seawater into five water masses (two for the surface layer, two for the middle layer, and one for the deep layer) and deduced N2O production-consumption mechanisms in each water body by use of N2O isotopomer ratios. The results showed that the mechanisms differ slightly among water masses. In the %26quot;coastal%26quot; surface layer, N2O is produced by nitrification (NH2OH oxidation). In the %26quot;open ocean%26quot; surface layer, it is produced mainly by nitrifier denitrification and to a lesser extent by nitrification under substrate-limited conditions. In both %26quot;upwelling%26quot; and %26quot;open ocean%26quot; middle layers it is produced mainly by denitrification and to a lesser extent by nitrifier denitrification. It is also partly reduced. In the deep layer, it is produced predominantly by denitrification with partial reduction. In this way, isotopomers aid elucidation of production-consumption mechanisms of N2O in the sea even though the mechanisms cannot always be ascertained.

• 出版日期2013-4