科研之友
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摘要
Northern Chile's oxygen minimum zone (OMZ) is considered to be an important site of N2O production and efflux into the atmosphere, with a potentially global impact. Seawater samples from the OMZ core were used to determine how different O-2 levels and electron donor/acceptor availability affect N2O cycling. N2O production by denitrification (N(2)Opd; acetylene treatment) and nitrification (N(2)Opn; allylthiourea [ATU] treatment), and N2O consumption by denitrification (N(2)Ocd), were determined with in situ O-2, anoxic (0 muM O-2), hypoxic (similar to22.3 muM O-2), and potential (added substrate) experimental conditions. Under in situ O-2 levels (similar to4.6 muM), total N2O production (N(2)Opd + N(2)Opn) was similar to2.62 muM d(-1). Denitrification was responsible for over 92% of the total N(2)Opd and nitrification for less than 8%. Nearly 100% of the N2O produced was, however, consumed by denitrification. NO3 was reduced twice as rapidly as NO2-, Under anoxia, N(2)Opd and N(2)Ocd rates decreased by over 90%. The NO3 reduction was similar to that observed with in situ O-2, whereas a high rate of NO2- accumulation was observed. Conversely, increasing O-2 levels (similar to22.3 muM) doubled N(2)Opd. Consequently, N(2)Opd or NO2- reduction seems to be the process most sensitive to O-2 fluctuations. Adding organic carbon and NO3 increased N(2)Opd and N(2)Ocd slightly, whereas additional N2O increased N(2)Ocd abruptly. The fate of reduced NO3- in the OMZ core was controlled mainly by O-2 concentrations and indirectly by available organic carbon. Both variables are susceptible to the changes experienced in the eastern South Pacific during the El Niho Southern Oscillation cycle.
- 出版日期2004
