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
Geochemistry of tungsten and molybdenum during fresh water transport and estuarine mixing
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. (Applied geochemistry)ORCID iD: 0000-0003-3424-9552
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. (Applied geochemistry)
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. (Applied geochemistry)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The geochemistry of tungsten (W) in the environment is still poorly studied. Tungsten is little mobile and usually occurs in low concentrations in natural waters. For this study, we analyzed W together with molybdenum (Mo) in the dissolved and particulate fraction of two boreal estuaries during different seasons. Additionally, we sampled first-order streams, draining different landscape types, and the receiving northern Baltic Sea. Furthermore, surface sediment from the estuaries was analyzed to get a comprehensive overview of the distribution of W and Mo in a boreal environment.

Both elements showed different distribution patterns during different seasons. While they decreased in dissolved concentrations during spring discharge, their concentrations were elevated in winter and exhibited non-conservative behavior along the salinity gradient in the estuaries. In the particulate fraction, we found an opposing behavior for Mo and W, with higher particulate W and lower particulate Mo during spring discharge.

Molybdenum and W underwent fractionation from land to sea, indicating different mobility for these oxyanions. The Mo/W ratio in the dissolved fraction was mainly determined by the Mo concentration as the W concentration varied only in a narrow range from first-order streams to the Bothnian Bay. In the particulate fraction, the Mo/W ratio appeared to be affected by scavenging processes and showed only small variations. 

Keyword [en]
Tungsten, Molybdenum, Suspended particles, Estuarine mixing
National Category
Geochemistry
Research subject
Applied Geochemistry
Identifiers
URN: urn:nbn:se:ltu:diva-66850OAI: oai:DiVA.org:ltu-66850DiVA: diva2:1161557
Funder
Swedish Research Council, 150 119
Available from: 2017-11-30 Created: 2017-11-30 Last updated: 2017-11-30
In thesis
1. Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters
Open this publication in new window or tab >>Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Some transition metals and metalloids occur primarily as oxyanions in natural waters including antimony, arsenic, chromium, molybdenum, tungsten and vanadium. These oxyanions can pass through cell walls along the same pathways as phosphate or sulfate. Some of these oxyanions are essential for life, but in high concentrations they become all toxic. Recent studies showed that tungsten probably is posing a risk to human health. The growing use of tungsten in industrial and military applications probably leads to an increased release of tungsten to the environment. It has also been shown that the use of studded winter tires in Sweden significantly increases tungsten concentrations in road runoff. Still, little is known about the geochemical cycling of tungsten in the environment as it has been considered to be a more or less inert element. Only a few studies deal with tungsten in natural waters. For example, for the Baltic Sea no concentration data have been published before this work and data on the suspended particulate fraction of tungsten in terrestrial and marine waters are scarce.

This thesis contributes to the understanding of the distribution and behavior of tungsten, molybdenum and vanadium in natural waters under changing redox conditions, varying pH and different seasons. Particular attention is paid to the suspended particulate fraction of these elements, which is often neglected even though it can be of great importance. Tungsten, molybdenum and vanadium primarily occur as oxyanions in solution and can be adsorbed to particles, which determines their mobility.

Molybdenum usually is very mobile, while vanadium has a tendency to adsorb to iron oxyhydroxides or to form organic complexes. Tungsten has many similarities with molybdenum, but it seems to be less mobile than molybdenum in natural waters.

Tungsten and molybdenum have a similar abundance in the upper continental crust, but in the ocean molybdenum is almost 2000 times more abundant. A strong fractionation of these two elements occurs from land to the ocean, indicating a removal of W during mixing of river and seawater.

This study comprises data from small streams in the boreal landscape of northern Sweden, major rivers (Kalix River and Råne River) and their estuaries discharging into the Baltic Sea. In the marine environment, sediment cores from the Bothnian Bay and water profiles at the stratified Landsort Deep have been studied. Apart from the spatial distribution, the temporal behavior of tungsten, molybdenum, and vanadium in was investigated. In the boreal environment snowmelt is playing a major role for their transport.

All water samples were filtered through 0.22 pore size filters to define dissolved and suspended particulate fractions. The particulate fraction of all studied elements increases from streams to rivers. Especially during spring flood, particle transport becomes even more important. About 80% tungsten, 70% vanadium and 30% molybdenum occur in the particulate fraction during this event. During estuarine mixing, tungsten and molybdenum are released from the particles again. However, vanadium seems to be removed in both fractions, probably due to a different adsorption behavior. In the dissolved fraction molybdenum increased and vanadium decreased from land to the sea, while tungsten showed small variation in all surface waters.

All three elements are affected by manganese redox cycling at the transition zone between oxic and sulfidic water at the Landsort Deep in the Baltic Sea. Adsorption of these oxyanions to the freshly formed manganese oxides plays an important role for their transport to the sulfidic zone. In contrast to molybdenum, dissolved tungsten is accumulated in the sulfidic environment. There is no effective removal mechanisms like for molybdenum, which is adsorbed to sulfides. Also in the sediment, redox cycling of manganese and iron affects the distribution of tungsten and molybdenum close to the water-sediment interface.

Place, publisher, year, edition, pages
Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keyword
tungsten, molybdenum, vanadium, Baltic Sea, redox cycling, suspended particles, boreal rivers
National Category
Geochemistry
Research subject
Applied Geology
Identifiers
urn:nbn:se:ltu:diva-66852 (URN)978-91-7790-013-9 (ISBN)978-91-7790-014-6 (ISBN)
Public defence
2018-02-09, F341, Luleå tekniska universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2017-12-04 Created: 2017-11-30 Last updated: 2017-12-04Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Bauer, Susanne
By organisation
Geosciences and Environmental Engineering
Geochemistry

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 10 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