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Nitrous oxide emissions from the Gulf of Mexico Hypoxic Zone
WALKER, J. T., C. A. STOW, AND CHRIS GERON. Nitrous oxide emissions from the Gulf of Mexico Hypoxic Zone. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 44(5):1617-1623, (2010).
The production of nitrous oxide (N2O), a potent greenhouse gas, in hypoxic coastal zones remains poorly characterized due to a lack of data, though large nitrogen inputs and deoxygenation typical of these systems create the potential for large N2O emissions. We report the first N2O emission measurements from the Gulf of Mexico Hypoxic Zone, including an estimate of the emission “pulse” associated with the passage of Tropical Storm Edouard in August, 2008. Pre-storm emission rates (25 to 287 nmol per square meter per hour) and dissolved N2O concentrations (5 to 30 nmol per liter) were higher than values reported for the Caribbean and western Tropical Atlantic, and on the lower end of the range of observations from deeper coastal hypoxic zones. During the storm, N2O rich subsurface water was mixed upward, increasing average surface concentrations and emission rates by 23% and 61% respectively. Approximately 20% of the N2O within the water column vented to the atmosphere during the storm, equivalent to 13% of the total “hypoxia season” emission. Relationships between N2O and NO3, and apparent oxygen utilization, suggest enhanced post storm N2O production. Mixing related emissions contribute significantly to total seasonal emissions and must therefore be included in emission models and inventories for shallow coastal hypoxic zones.