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Changes in trace metal sedimentation during freshening of a coastal basin
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.ORCID-id: 0000-0003-2276-0564
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.ORCID-id: 0000-0003-3424-9552
Vise andre og tillknytning
2014 (engelsk)Inngår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 167, s. 2-12Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Holocene freshening has turned the Bothnian Bay, northern Baltic Sea into an oligotrophic basin. Sequestering of trace elements has changed significantly during the oligotrophication process. In principle, trace metals have been transferred from permanently buried sulfides to Fe–Mn-oxyhydroxides in the top layers of the sediment. The oxyhydroxide layers restrict the flux of trace metals from the sediment to the oxic bottom water. Hence, Fe–Mn cycling in the suboxic sediment enriches a number of trace metals in the surface sediment. Arsenic, Sn, Ge and Bi show enrichment in the Fe-oxyhydroxide layer, whereas Mo, Cd, Ni, Co, Cu, and Sb are enriched in the uppermost Mn-oxyhydroxide layer. This natural redox cycling in the sediment obscures pollution effects.The oligotrophication process started approximately 3500 years ago, reflected in decreasing deposition of Zn, a proxy for phytoplankton production, and formation of Mn oxyhydroxide layers. Similarly, Ba/Al data indicate a decrease in the pelagic input of plankton. Barium data also suggest that dissolved sulfide in the sediment never reached high concentrations. Germanium is closely related to Ba, suggesting that Ge can be used as a proxy for phytoplankton production. Vanadium, U, Re, and Mo all indicate that the bottom water never has been significantly sulfidic during the last 5500 years. Rhenium data indicate that the organic carbon oxidation rate has decreased during the last 5500 years. Cadmium follows the organic matter distribution, but started to increase 1000 YBP (years before present). The reason for this enhanced input of Cd is unclear.

sted, utgiver, år, opplag, sider
2014. Vol. 167, s. 2-12
Emneord [en]
Earth sciences - Exogenous eart sciences
Emneord [sv]
Geovetenskap - Exogen geovetenskap
HSV kategori
Forskningsprogram
Tillämpad geologi; Prospekteringsgeofysik
Identifikatorer
URN: urn:nbn:se:ltu:diva-5774DOI: 10.1016/j.marchem.2014.06.010ISI: 000345805700002Scopus ID: 2-s2.0-84910049803Lokal ID: 3f465607-16e1-43ab-b560-6484e509aba7OAI: oai:DiVA.org:ltu-5774DiVA, id: diva2:978649
Merknad
Validerad; 2014; 20140812 (andbra)Tilgjengelig fra: 2016-09-29 Laget: 2016-09-29 Sist oppdatert: 2018-07-10bibliografisk kontrollert
Inngår i avhandling
1. Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters
Åpne denne publikasjonen i ny fane eller vindu >>Dissolved and suspended transport of tungsten, molybdenum, and vanadium in natural waters
2018 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Luleå University of Technology, 2018
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Emneord
tungsten, molybdenum, vanadium, Baltic Sea, redox cycling, suspended particles, boreal rivers
HSV kategori
Forskningsprogram
Tillämpad geologi
Identifikatorer
urn:nbn:se:ltu:diva-66852 (URN)978-91-7790-013-9 (ISBN)978-91-7790-014-6 (ISBN)
Disputas
2018-02-09, F341, Luleå tekniska universitet, Luleå, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2017-12-04 Laget: 2017-11-30 Sist oppdatert: 2018-01-19bibliografisk kontrollert

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