hide
Free keywords:
-
Abstract:
Nitrous oxide production associated with biological nitrogen transformations can contribute
substantially to the CO
2
footprint of both man-
made and natural systems, but the pathways
and regulation of nitrous oxide production are poorly understood. We developed a
15
N/
18
O
dual isotope labelling technique to distinguish and quantify these pathways in mixed
communities. The use of
18
O-O
2
permits differentiation of hydroxylamine oxidation and
nitrifier
-denitrification driven nitrous oxide production by ammonium oxidizing bacteria. We
analyzed
nitrous oxide production pathways during biological nitrogen removal at Lynetten
wastewater treatment plant, Denmark. Under anoxia, nitrous oxide accumulated due to
denitrification, but nitrous oxide accumulation was ~3 and 1.7 times higher at 30 and 100
μ
M O
2
, respectively. Oxic nitrous oxide production was dominated by nitrifier
-denitrification,
reaching 73% of the total, with the remainder due to hydroxylamine oxidation. Our results
demonstrate three active pathways of nitrous oxide production, each with
different
environmental controls. The dual
15
N/
18
O isotope labelling approach can contribute to the
development of strategies to minimize nitrous oxide emissions from man-
made and natural
systems.
