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This study provides: (a) first-known estimates of potential N2O release from aerobic riverine deposits; (b) evidence that simultaneous measures of gas formation and N-transformations can be used to...

Studies in 1981 assessed the role of nitrogen cycle reactions and related microbial and chemical changes in volcanically impacted Spirit Lake and newly created South Castle and North Coldwater Lakes within Mt. St. Helens' blast zone. These lakes displayed characteristics of nutrient limitation and a favorable environment for involvement of mixitrophic bacterial utilization of nitrogen. Mixitrophy was implied by: co-occurrence of both nitrification and denitrification; possible influences of several nitrogen dissimilatory nitrate reduction and assimilatory reactions on the formation and consumption of nitrogen intermediates like N2O; possible Mn/S oxidizing bacteria involvement in denitrification; and changes in concentrations of CO2, CH4 and dissolved inorganic nitrogen, phosphorus, sulfur, Mn and Fe species. Microbial and chemical measurements show: assimilative N-cycle reactions and phosphate limitation playing increasingly important roles in aerobic strata; and dissimilative nitrogen and other...