Prevailing concepts relating to the non-enzymatic gaseous
loss of nitrite from soil are thought to be inadequate as regards
to the mechanisms involved. The conventional explanation for
nitric oxide formation i.e., the acid decomposition of nitrite,
is held to be insufficient in substrates of only mild or slight
acidity. A criticism is presented wherein it is maintained that
certain past practices in methodology have created rather than
eliminated confusion. Positive suggestions are proposed which
may help to eliminate confusion in future experiments.
Evidence was obtained from soil and clay systems which attest
to a mechanism of loss whereby nitrite may react with certain
metals to yield nitric oxide as a primary gaseous product. A
conventional half-cell reaction is presented wherein a transition-like metal is oxidized and nitrite is reduced to nitric oxide
with the formation of water. It is implied that hydrogen ions
may be necessary--acid conditions favor the reduced state of the
metals which is a more active state with respect to the formation of nitric oxide--for such reactions, but that they are not sufficient
in substrates of only mild acidity.
An apparent corollary to this study is that the very conditions
which favor classical denitrification from nitrate also favor
metal-nitrite reactions. Under such conditions both nitrate and
the metals involved would be expected to undergo reduction resulting
in an increased possibility for nitric oxide formation. This
possibility places in question the status of nitric oxide as a
direct biochemical intermediate in the microbial formation of
nitrogen gas.
It is suggested that a mechanism involving transition -like
metals may account for significant losses of mineral nitrogen
from field soils capable of accumulating nitrite under conditions
of moderate or slight acidity
