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Figure 6.1 Estimation of Nitrate Loss due to denitrification (Lund et al., 2000).
Lund et al. (2000) have used this method to estimate the percent of nitrate removed due
to denitrification in a wetlands environment in southern California. Using this method
and by considering a laboratory derived value of −17‰ as the enrichment factor strictly
due to denitrification, 63 % of the losses could be attributed to denitrification.
The main disadvantage to this approach is that there is a range of enrichments factors for
denitrification. The enrichment factors are derived based on laboratory testing and as
such there is a wide range of values that can be used, while this may possibly be
attributed to differences in methodology it may be possible that the differences in the
enrichment factor are due to different denitrification rate constants and substrate
concentration. (Ostrom et al., 2002).
Pintar et al. (2008) and Sovik and Morkved (2007) have used this method to estimate the
percent of nitrate lost due to denitrification in wetlands and have found that isotopes can
be a useful semi-quantitative tool to quantify denitrification. Several other authors
(Steingruber et al., 2001; Smith et al., 1978, 2004) have used isotopes to measure
denitrification.
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