Denitrification is a process that removes nitrogen from soil and water, and scientists use a radioactive isotope called 13N to measure it. By studying 13N, researchers can directly measure the main denitrification product, N2, in the air. They have found that 13N is very sensitive and helpful in studying denitrification activities. Scientists have used 13N to measure denitrification rates, investigate denitrification intermediates, and understand factors affecting the production of N2O and N2. They have also looked at how nitrate is divided between denitrification and other processes in bacterial cultures and natural samples. Overall, 13N and another isotope, 15N, are both useful tools for studying denitrification in different ways.