ABSTRACT
Denitrification is the reduction by bacteria of nitrite or nitrate to gaseous nitrogen (N). It is generally considered to be an anaerobic process and requires, in addition to nitrite or nitrate, a source of organic carbon. Denitrification occurs in a wide range of both freshwater and marine sediments. Sources of nitrate or nitrite for denitrification in aquatic sediments include nitrification in the sediments, nitrate in the overlying water, and in some cases, advection of nitrate-contaminated groundwater through the sediments. Denitrification is directly measured as the production of N2 from vertically intact sediment cores. The cores with an overlying water and gas phase are incubated in gas-tight glass incubation chambers. Sediment-water nitrate and ammonium fluxes are measured concurrently with denitrification rates. Advantages of the method are: the end product of denitrification is measured directly; inhibitors, such as acetylene which blocks nitrification, are not used; and nitrification rates and organic N mineralization rates are estimated concurrently with denitrification rates.
