Organic C has an essential role in the denitrification process as it supplies the electrons needed for the conversion of NO₂ to gaseous products. Initial studies conducted in the DENIS system showed that C substrates that most readily promote denitrification (e.g. glucose) also lead to a greater N₂O/N₂ ratio in released gaseous N products. Further research will elucidate the mechanisms for this and, through the use of natural abundance isotope and isotopomer studies, the sources of nitrogen and the fate of oxygen at the various stages in the reduction process can be determined. This will be linked to molecular measurements of the changes microbial populations and functioning as a denitrification event occurs (with a typical trend of the peak N₂ release being preceded by the peak N₂O) will add to our understanding of these processes and the role that C quality may play.