Distinction Between N2O Production From Nitrification and Denitrification in Mississippi River Riparian Wetland Sediment Using a Dual Isotope Labeling Method.

Distinction between N₂O Production from Nitrification and Denitrification in Mississippi River Riparian Wetland Sediment using a Dual Isotope Labeling Method

 

Dong Cheol Seo, Ronald D. Delaune^*

 

Department of Oceanography and Coastal Sciences, School of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70803, USA

Abstract

Riparian wetlands contribute substantially to global N₂O emission. It is often speculated whether nitrification or denitrification is the most significant process contributing to N₂O production in sediments. Nitrification, nitrifier denitrification and denitrification were determined by a dual isotope technique in Mississippi River riparian wetland (Redman Point-Loosahatchie Bar Restoration Project-Arkansas). The site is exposed to routine flood water of the Mississippi River which contain elevate level of nitrate. Nitrous oxide (N₂O) from nitrification, nitrifier denitrification and denitrification were distinguished based on a method with single- and double-¹⁵N-labeled ammonium nitrate and ¹⁸O-labelled water. Three sediment (Site 1: Near; Site 2: Mid; Site 3: Far) samples were collected. In site 1 (near), the main sources of N₂O were greater in the order of nitrifier denitrification > fertilizer denitrification > nitrification >> nitrification-coupled denitrifcation �à other sources. In site 2 (mid), the main sources of N₂O were greater in the order of nitrifier denitrification > fertilizer denitrification > nitrification-coupled denitrifcation �à nitrification �à other sources. In site 3 (far), the main sources of N₂O were greater in the order of nitrifier denitrification > fertilizer denitrification > nitrification-coupled denitrifcation > nitrification �à other sources. Therefore, nitrifier denitrification and fertilizer denitrification were the main sources of N₂O in all sites.

*Corresponding Author. Ronald D. DeLaune, Department of Oceanography and Coastal Sciences, School of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70803, USA. Tel.: +1 225 578 6421; Fax: +1 225 578 6423; E-mail: rdelaun@lsu.edu.

Keywords: N₂O production, nitrification, denitrification, dual isotope labeling method, Mississippi River, West Memphis, sediment.