Although the soil of our wetland site has low standing stocks of inorganic N ([less than] 1 g/[m.2.sup]), it receives significant influx of N from the upland manure application site, most of which is rapidly denitrified
(the average rate is 68 kg [N.sup.2]O-N.[ha.sup.-1].[yr.sup.-1] [Lowrance et al.
The rest, he says, is lost to the environment: "Unless an equivalent amount is denitrified
back to molecular [N.sub.2], then that means reactive nitrogen is accumulating in the environment, in the atmosphere, in the groundwater, in the soils, in the biota."
Small N-loads (185 kg N/ha) in the non-Pin Gin soils imply that [approximately equal to] 1315 kg/ha of the nitrate-N that leached below the root-zone during the last 50 years, under the minimum leaching scenario, either denitrified
or entered lateral-flow and/or deep groundwater.
The [NO.sub.3.sup.-] is completely water soluble and moves with the water until it re-enters the available soil pool, is utilized by microbes or plants, becomes denitrified
, is deposited and buried, or enters and possibly degrades surface and/or groundwaters.
Water that has been nitrified in later aerobic stages is recirculated back into the first anoxic basin where it is denitrified
using carbonaceous material present in raw wastewater as the carbon source.
Native soil N[O.sub.3.sup.-] concentrations had decreased by over 90% of their original value by the end of the experiment, although some of this N[O.sub.3.sup.-] could have been denitrified
prior to substrate addition.
This water seeps through 15 m (50 ft) of soils before entering the stream and is almost completely denitrified
in the process.
In sediments, inorganic nitrogen (ie., ammonium, nitrate, nitrite) can diffuse to overlying water, be adsorbed onto sediments, or be denitrified
Post-treatments, such as oxygenation, filtration, and chlorination of denitrified
water are necessary before use as drinking water can be considered.
The initial [N.sub.2]O flux on Day 1 was possibly due to the native inorganic-N, already in the soil, being denitrified
in response to the formation of transient anaerobic microsites upon the addition of the aqueous amendments.
Between 25%, and 75% of the nitrogen regenerated in the sediments was estimated to have been denitrified
(Table I), indicating that denitrification is a significant sink for nitrogen in Parker River Estuary.
If the soil is saturated with water, the nitrate form can be converted to nitrous N gas and volatilized (denitrified