| Isotopes of nitrogen and oxygen in the nitrate molecule can be used to determine the source of nitrate contamination, and the mechanisms that lead to the removal of nitrates by an aquatic system. This project used the Ichetucknee River system as a model to both understand where the nitrate is from that emerges from the main spring vents, and what the processes are that lead to its dramatic removal along the length of the river. There were three results of particular importance: 1) there appears to be a strong isotopic signature of denitrification occuring in the subsurface for the springs that have lower dissolved oxygen; 2) the isotopic fractionation is dominated by the effects of denitrification, and not assimilation, suggesting that this is the principal mechanism of N removal; and 3) the fractionation rate of N and O during denitrification is far lower than has been observed elsewhere, which suggests that the denitrification is limited principally by the rate at which the nitrate enters the sediment. |
