Patterns and controls of nitrous oxide emissions from waters draining a subtropical agricultural valley
2003; Wiley; Volume: 17; Issue: 3 Linguagem: Inglês
10.1029/2002gb001991
ISSN1944-9224
AutoresJohn A. Harrison, Pamela A. Matson,
Tópico(s)Fish Ecology and Management Studies
ResumoAlthough nitrous oxide (N 2 O) emission from agricultural runoff is thought to constitute a globally important source of this greenhouse gas, N 2 O flux from polluted aquatic systems is poorly understood and scarcely reported, especially in low‐latitude (0°–30°) regions where rapid agricultural intensification is occurring. We measured N 2 O emissions, dissolved N 2 O concentrations, and factors likely to control rates of N 2 O production in drainage canals receiving agricultural and mixed agricultural/urban inputs from the intensively farmed Yaqui Valley of Sonora, Mexico. Average per‐area N 2 O flux in both purely agricultural and mixed urban/agricultural drainage systems (16.5 ng N 2 O‐N cm −2 hr −1 ) was high compared to other fresh water fluxes, and extreme values ranged up to 244.6 ng N 2 O‐N cm −2 hr −1 . These extremely high N 2 O fluxes occurred during green algae blooms, when organic carbon, nitrogen, and oxygen concentrations were high, and only in canals receiving pig‐farm and urban inputs, suggesting an important link between land‐use and N 2 O emissions. N 2 O concentrations and fluxes correlated significantly with water column concentrations of nitrate, particulate organic carbon and nitrogen, ammonium, and chlorophyll a, and a multiple linear regression model including ammonium, dissolved organic carbon, and particulate organic carbon was the best predictor of [N 2 O] (r 2 = 52%). Despite high per‐area N 2 O fluxes, our estimate of regional N 2 O emission from surface drainage (20,869 kg N 2 O‐N yr −1 ; 0.046% of N‐fertilizer inputs) was low compared to values predicted by algorithms used in global budgets.
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