hello i 'm a PhD student and i want to know
if we want to search about the origine of nitrates in groundwater what are the things we should knew before?the datas we need to have ?? which isotope is used N14 or N15??
Hello Zahra,
The biogeochemical transformation to nitrate is far quicker compared to the thermochemical conversions in the geological time scale and hence most of the nitrates formed are either biological in origin or is mediated by organisms. With this in mind, I would recommend the usage of stable isotopes like N15 to serve your purpose.
Thanking you,
Dr. Abhishek Mukherjee
Flood survey of nitrate behaviour using nitrogen isotope tracing in the critical zone of a French agricultural catchment
- July 2015 Comptes Rendus Geosciences 347 (7) DOI: 10.1016/j.crte.2015.06.002
- Alexia Paul, Issam Moussa ...
Abstract
Measurements of δ15N–NO3– were taken in a highly flood-responsive agricultural catchment in the southwest of France to trace the sources and transfer pathways of nitrates during flood events. From January to March 2013, surface water samples were collected every week at the outlet, and four floods were sampled with a high resolution. Sampling was also performed in surface waters and sand lenses from the rest of the basin to trace nitrate sources and processes spatially. Nitrate extractions were performed using a method based on the solubility difference between inorganic salts and organic solutions. The δ15N values were in the range of surface water contaminated by N-fertilisers. Depending on the hydroclimatic event, nitrates resulted from a combination of sources and processes. At the start of the floods, the values of δ15N–NO3– and nitrate concentrations were low, demonstrating the dilution of water with rainwater. During a second phase, the nitrate concentration and the δ15N were higher. Deeper waters and soil solutions were the second source of nitrates. When the water level was low, both nitrate concentration and isotopic composition were high. These values reflected the denitrification processes that occurred in the soil under anaerobic conditions. An analysis of δ15N–NO3– in stream water in a small agricultural catchment was efficient at determining the origin of nitrates during flood events using a simple method.
Please see the attached paper that may interest you regarding your question.
All the best
As far as groundwater is concerned N-15 as well as O-18 of Nitrates are good tracers.
However, you could also combine the use of recent and old water indicators such as Tritium and CFCs, plotted against nitrate contents to confirm whether the origin is anthropogenic or geological as the latter is also a possibility.
Good luck !
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