Use of 13N in Studies of Denitrification

Denitrification results in major losses of fertilizer and native nitrogen from soil, fresh water, and marine habitats. The radioactive isotope, 13 N, allows direct measurement of N 2, the principal denitrification product, in any atmosphere and provides a very sensitive measure of denitrification activities. The findings of laboratories that have used 13 N in denitrification studies are summarized in this chapter. Emphasis is placed on the methods for production, purification, and detection of 13 N forms important to denitrification investigations. The summary of research results includes information on the following: measurement of denitrification rates, isotope dilution experiments to investigate denitrification intermediates, factors influencing the proportion of N 2 O vs. N 2 produced, and the partitioning of nitrate between denitrification and dissimilatory nitrate reduction to ammonium for bacterial cultures and natural samples. 13 N and 15 N are considered complementary methods, since each is uniquely suited to certain aspects in the study of denitrification.