Abstract
Compilation of N2O accumulation data in the low-oxygen zone of Lake Kizaki revealed a marked variation in the maximum N2O concentrations observed, ranging from 0.17 to 26.5 ug atomN⋅1-1. The N2O accumulation level differed noticeably from year to year: from less than 0.6, ug atomN⋅1-1 in 1983 and 1988, to more than 2.4 pg atomN⋅1-1 in three other years. The maximum N2O concentrattion was correlated with its relative peak position in the low-oxygen zone, with the smaller peak at the "shallower" layer, the larger peak at the "deeper" layer. It was inferred from the N20, NO3- and O2 profile characteristics that the shift in N2O production-consumption balance during the denitrification process may be responsible for such a wide variation in N2O accumulation level and that organic matter availability in the hypolimnion may play a key role in this phenomenon.
