Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Tracing nitrogen cycling in mining waters using stable nitrogen isotope analysis
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.ORCID iD: 0000-0002-2720-6442
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
2017 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 84, p. 41-51Article in journal (Refereed) Published
Abstract [en]

We show how we used stable nitrogen and oxygen isotopes in ammonium and nitrate to identify and quantify nitrogen transformation and nitrogen sources at the LKAB mining site in northern Sweden. Stable nitrogen isotope analysis worked as an excellent tool for tracing nitrogen cycling in rapidly moving process waters. The isotope analysis was performed on the mining process waters at seven different key points along the water flow and we identified nitrification, ammonia volatilisation, and ammonium adsorption as nitrogen transformation processes. The source of nitrogen is historically explained as undetonated ammonium-nitrate based explosives. We used nitrate nitrogen and oxygen isotopes to quantify four nitrogen sources in the accumulated water in the mine as well as three sources in an above ground process water reservoir. The nitrate isotope data showed that most of the nitrate (70–80%) in the accumulated water underground originated from a sampling point located close to the surface and only a minor fraction (5–20%) originated directly from undetonated explosives (direct dissolution of NH4NO3 and nitrification of NH4). Nitrate from natural groundwater formed roughly 12% of mine water nitrate. In the above ground process water reservoir isotope data indicated another source of nitrogen coming from undetonated explosives.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 84, p. 41-51
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
URN: urn:nbn:se:ltu:diva-63724DOI: 10.1016/j.apgeochem.2017.05.025ISI: 000410673400004Scopus ID: 2-s2.0-85020263429OAI: oai:DiVA.org:ltu-63724DiVA, id: diva2:1105648
Note

Validerad;2017;Nivå 2;2017-06-14 (rokbeg)

Available from: 2017-06-05 Created: 2017-06-05 Last updated: 2018-10-25Bibliographically approved
In thesis
1. Nitrogen-cycling tracing methods: Case studies at cold-climate mine sites in northern Sweden
Open this publication in new window or tab >>Nitrogen-cycling tracing methods: Case studies at cold-climate mine sites in northern Sweden
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Spårningsmetoder för kvävecykeln : fältstudier vid gruvor i norra Sverige
Abstract [en]

High nitrogen effluents from mine sites is an environmental issue which has received relatively little attention historically. In recent years a number of studies have showed the environmental effects of high nitrogen discharge to natural water bodies, which include local eutrophication, high risk of acute reducing conditions and changed species composition in the receiving waters. Apart from the direct environmental effects of high nitrogen discharge some forms of nitrogen can be directly toxic- ammonia and nitric gas for instance, and some can be indirectly toxic, for instance nitrate which causes methemoglobinemia in infants if ingested.

This thesis shows how the developed nitrogen tracing methods can be applied in complex water transport systems such as in a mining environment. Two main study sites were used in this thesis, the LKAB iron mine at Kiruna and the Aitik copper mine at Gallivare operated by Boliden Mineral AB. The nitrogen tracing methods used in this study are stable isotope analysis, combined nitrogen and oxygen isotope analysis, source partitioning using linear combination of sources, numerical analysis using kinetic nitrogen reaction rates, numerical model verification using stable nitrogen isotopes, and Bayesian statistical models to estimate nitrogen concentrations. The study also demonstrates an experimental method of reducing nitrogen concentrations in the mining pond at the LKAB Kiruna site. The nitrogen reducing method was tested in a small scale mesocosm experiment at the Kiruna site in northern Sweden, where a nitrogen reduction rate of around 0.25 - 0.5% total nitrate per day could be achieved.

The nitrogen treatment method consists of fertilising the pond system with small amounts of bioavailable phosphorus. Phosphorus is generally the limiting factor for primary production and in the studied mining systems which have high nitrogen concentrations the phosphorus is assimilated into organic matter almost immediately after fertilisation. The phosphorus is assimilated into phytoplankton (algae) which then settles and is used as a carbon source during anaerobic decomposition (denitrification). The denitrification reaction reduces nitrate into nitrogen gas. This would reduce the nitrogen release from mine sites significantly, since nitrate is the dominant form of nitrogen at the two studied mine sites.

Concluding the thesis is a 2.5D model which couples a numerical kinetic nitrogen model with a hydrodynamic model. The hydrodynamic model was the Shallow Water Equations (SWE) model that incorporates wind turbulence, inlets, and outlets as source terms for the water velocities. The two models are coupled via velocity, where the nitrogen model couples via chemical mixing and fluxes are calculated from the water velocities in each model cell.

The results of this thesis suggests that nitrogen release from the the Kiruna clarification pond could be reduced significantly via the use of phosphorus fertilisation. This is due to an increased denitrification rate in the pond, and the fact that much of the discharge water from the pond system is recirculated back into the mineral processing plants. The recirculation essentially means that the nitrate in the mine water will have quite a long retention time before being passed out the receiving waters.

Although the presented nitrate reduction approach showed promising reduction rates, the potential risk of eutrophication in the receiving waters is high, as the discharge water will contain high levels of nitrogen and potentially also phosphorus. The transport pathways and possible natural attenuation of phosphorus must be thoroughly investigated before the presented nitrate reduction method can be implemented at full scale in mine ponds.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
urn:nbn:se:ltu:diva-71342 (URN)978-91-7790-246-1 (ISBN)978-91-7790-247-8 (ISBN)
Public defence
2018-12-14, E632, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-10-26 Created: 2018-10-25 Last updated: 2019-01-07Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Authority records BETA

Nilsson, LinoWiderlund, Anders

Search in DiVA

By author/editor
Nilsson, LinoWiderlund, Anders
By organisation
Geosciences and Environmental Engineering
In the same journal
Applied Geochemistry
Geochemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 151 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf