1. Nitrogen enrichment and the emission of nitrous oxide from streams.
- Author
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Baulch, Helen M., Schiff, Sherry L., Maranger, Roxane, and Dillon, Peter J.
- Subjects
WATER pollution ,NITROGEN & the environment ,NITROUS oxide & the environment ,GREENHOUSE gases & the environment ,NITRATES & the environment ,NITROGEN cycle - Abstract
Nitrous oxide (N
2 O) is a potent greenhouse gas produced during nitrogen cycling. Global nitrogen enrichment has resulted in increased atmospheric N2 O concentrations due in large part to increased soil emissions. There is also a potentially important flux from streams, rivers and estuaries; although measurements of these emissions are sparse, and role of aquatic ecosystems in global N2 O budgets remains highly uncertain. Using the longest-term measurements of N2 O fluxes from streams to date, we found annual fluxes from 14 sites in five streams of south-central Ontario, Canada varied widely-from net uptake of 3.2 ± 0.2 (standard deviation) μmol N2 O m-2 d-1 to net release of 776 ± 61 μmol N2 O m-2 d-1 . N2 O consumption was associated with very low nitrate concentrations (<2.7 μM). Mean annual (log-transformed) N2 O emissions from our study streams (across sites and years) were positively related to nitrate concentrations (r2 = 0.59).This nitrate-N2 O relationship can be generalized across all 20 streams (in Canada, Japan, Mexico, and the midwestern United States) for which published data now exist and could provide a new basis for the IPCC to calculate agricultural emissions from streams. In addition to predicting annual emissions, we present the first measurements of N2 O concentrations under ice in streams. Nitrate was a strong predictor of N2 O % saturation during periods of ice cover (r2 = 0.89), when gas exchange is negligible. Given the small surface area of streams within a catchment and the fact our measured areal fluxes are comparable to reported fluxes from agricultural soils, this suggests streams are a small regional N2 O source. [ABSTRACT FROM AUTHOR]- Published
- 2011
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