Journal of Food, Agriculture and Environment

Nitrogen transformation in wetlands and marshes

Author(s):

Shuhui Huang ^{1, 2}, Hari K. Pant ²

Recieved Date: 2009-04-10, Accepted Date: 2009-10-06

Abstract:

Biogeochemical cycling of nitrogen (N) in wetlands and marshes is complex, involving inter-conversions between different N species, as well as transfers among various storage compartments. This review attempts to provide concise information on N dynamics in wetlands and marshes, and discuss contributing factors that may help to maximize removal of N from wastewater and stormwater runoffs at the same time reduce nitrous oxide (N₂O) emissions to the atmosphere. In addition to interstitial water, N may be stored in above and belowground, live and dead plant material, invertebrates and microbes, and sorbed on the surfaces of organic and inorganic materials. The structure and functioning of the wetlands and marshes are subjected to anthropogenic activities, such as waterworks, land reclamation grazing and mowing, fertilization and various types of pollution, including heavy metals, nutrients, oil, etc. Nitrogen turnover in salt marshes is of particular interest since the primary production in salt marshes, as well as in adjacent coastal waters is considered to be limited by the supply of dissolved inorganic N. Salt marshes can function as sinks or as sources of N depending on their morphology and vegetation. Conversion pathways include ammonia volatilization, ammonification, nitrification, denitrification, anammox (anaerobic ammonium oxidation), dissimilatory reduction, and plant and microbial assimilation and remineralization during decomposition. The existence of an atmospheric sink, coupled with ammonia volatilization and microbially mediated nitrification and denitrification, make N as an excellent target for removal from wastewaters by constructed wetlands and marshes. However, such removal, specifically as N₂O, a potent greenhouse gas, into the atmosphere may not be as wise as previously thought as the concerns of global warming keeps looming. It is apparent that unless human-derived N inputs are regulated at the source, substantial biogeochemical modification of the global coastal ocean may occur because of cyclic processes within the coastal ocean system that are not rapid enough to dissipate the effects of the perturbations. Identifying the relative importance of various permanent and temporary sinks for N in wetlands may lead to methods of optimizing the utilization of constructed wetlands for wastewater treatment. The dynamics of N transformation within constructed wetlands is particularly a good candidate for long-term study to maximize the beneficial functions that wetlands can provide, and minimize adverse effects such as N₂O emission to the atmosphere.

Keywords:

Nitrogen, biogeochemical cycle, wetlands, primary production, sediments

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Journal: Journal of Food, Agriculture and Environment
Year: 2009
Volume: 7
Issue: 3&4
Category: Environment
Pages: 946-954

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