Marcotte, Pascal 
ORCID: https://orcid.org/0000-0002-7589-9538; Neculita, Carmen M. ORCID: https://orcid.org/0000-0002-8388-7916; Cloutier, Vincent ORCID: https://orcid.org/0000-0002-7343-8850; Bordeleau, Geneviève ORCID: https://orcid.org/0000-0002-6711-2758 et Rosa, Eric
(2022).
Tracing the sources and fate of nitrogen at a Canadian underground gold mine.
Applied Geochemistry
, vol. 142
.
p. 105238.
DOI: 10.1016/j.apgeochem.2022.105238.
Résumé
The contamination of mine water by nitrogen-based compounds represents an ongoing challenge for the mining industry. These contaminants, often present in concentrations that are toxic to aquatic life, need to be carefully managed. This study aims at developing hydrogeochemical mass balances and isotopic approaches to trace the sources, fluxes and transformations of nitrogen bearing species in a mining context. The work was carried out at an underground gold mine located in Quebec, Canada. The main sources of nitrogen at this mine site are explosive residues and cyanide derivatives. The management of ammoniacal nitrogen (NH3 − NH+ 4 ) is of particular interest to the mining company operating the site. Analyses were carried out for concentrations of nitrite (NO− 2 ), nitrate (NO− 3 ), NH3 − NH+ 4 , total Kjeldahl nitrogen (TNK), total cyanide (CN− ), cyanate (CNO− ), thiocyanate (SCN− ), chloride (Cl− ) and sulfate (SO2− 4 ), as well as the isotopic composition of the water molecule (δ2HH2O, δ18OH2O), nitrate (δ15NNO− 3 , δ18ONO− 3 ) and ammoniacal nitrogen (δ15NNH+ 4 ). Mass balance calculations performed using the δ2HH2O and δ18OH2O of water suggest evaporation over inflow (E/I) ratios ranging between 0% and 34% onsite. Mass balances using the δ2HH2O and δ18OH2O of water and dissolved Cl− concentrations allow for estimating that 65% of the water, 43% of the NH+ 4 and 84% of the NO− 3 in the final effluent originated from the dewatering of the underground workings. The chemical and isotopic analyses of nitrogen bearing species revealed that nitrification and denitrification are the most likely mechanisms transforming nitrogen onsite. From these findings, recommendations were elaborated to optimize the management of the water on the mine site, with a focus on promoting the reactions that lead to a decrease in the concentration of NH+ 4 prior to the final effluent discharge to the environment. The proposed approach is innovative for the mining context and has great potential for applications at other mine sites.
| Type de document: | Article |
|---|---|
| Mots-clés libres: | ammoniacal nitrogen; cyanide; thiocyanate; cyanate; isotopic tracing; mine water |
| Centre: | Centre Eau Terre Environnement |
| Date de dépôt: | 15 mai 2024 17:49 |
| Dernière modification: | 15 mai 2024 17:49 |
| URI: | https://espace.inrs.ca/id/eprint/15333 |
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