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Fluoride in surface water and groundwater in southeast Sweden: sources, controls and risk aspects
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis is to determine the sources, controls and risk aspects of fluoride in surface water and groundwater in a region of southeastern Sweden where the fluorine-rich 1.45 Ga circular Götemar granite (5 km in diameter) crops out in the surrounding 1.8 Ga granites and quartz monzodiorites (TIB rocks). The materials of this thesis include both primary data, collected for the purpose of this thesis, and a large set of secondary data, retrieved from the Swedish Nuclear Fuel and Waste Management Co., the Swedish Geological Survey and the Kalmar County Council. A characteristic feature of the area is high fluoride concentrations in all kinds of natural waters, including surface waters (such as streams) and groundwater in both the Quaternary deposits (regolith groundwater) and bedrock fractures (fracture groundwater). A number of potential sources and controls of the high fluoride concentrations were investigated, including a variety of geological, mineralogical, mineral-chemical and hydrological features and processes. For the stream waters and regolith groundwater, high fluoride concentrations were correlated with the location of the Götemar granite. This finding is explained by the discharge of fluoride-rich groundwater from fractures in the bedrock and/or the release of fluoride due to the weathering of fluorine-bearing minerals in the Quaternary deposits; however, the Quaternary deposits had considerably lower fluoride concentrations than the underlying bedrock. The high fluoride concentrations in the fresh fracture groundwater (up to 7.4 mg/L) in the TIB-rocks are proposed to be the result of long residence times and the alteration/dissolution of fluorine-bearing primary and secondary minerals along the fracture walls. In terms of risk aspects, this thesis shows that fluoride can add to the transport and inorganic complexation of aluminium in humic-rich, acidic streams. Additionally, 24 % of the children in households with private wells in Kalmar County were assessed to be at risk of excess fluoride intake based on the WHO drinking water guideline value (1.5 mg/L). However, the risk increased significantly when instead the US EPA reference dose (0.06 mg/kg-day) was used, both when all relevant exposure pathways were taken into account as well as water consumption alone. Hence, it is shown that the risk of an excess intake of fluoride is strongly dependent on the basis for evaluation.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2016.
Series
Linnaeus University Dissertations, 253/2016
Keyword [en]
fluorine, fluoride, water-rock interaction, granite, crystalline bedrock, surface water, groundwater, Götemar, drinking water quality, aluminium, speciation, fluorosis, PBA
National Category
Environmental Sciences
Research subject
Natural Science, Environmental Science
Identifiers
URN: urn:nbn:se:lnu:diva-52562ISBN: 978-91-88357-20-5OAI: oai:DiVA.org:lnu-52562DiVA: diva2:929470
Public defence
2016-06-10, Fullriggaren, Sjöfartshögskolan, Kalmar, 09:30 (Swedish)
Opponent
Supervisors
Available from: 2016-05-20 Created: 2016-05-18 Last updated: 2016-11-22Bibliographically approved
List of papers
1. Impact of a Fluorine-Rich Granite Intrusion on Levels and Distribution of Fluoride in a Small Boreal Catchment
Open this publication in new window or tab >>Impact of a Fluorine-Rich Granite Intrusion on Levels and Distribution of Fluoride in a Small Boreal Catchment
2012 (English)In: Aquatic geochemistry, ISSN 1380-6165, E-ISSN 1573-1421, Vol. 18, no 2, 77-94 p.Article in journal (Refereed) Published
Abstract [en]

This paper explores the influence of a fluorine-rich granite on fluoride concentration in a small boreal catchment in northern Europe. The materials include stream water and shallow groundwater sampled in spatial and temporal dimensions, and analytical data on fluoride and a number of ancillary variables. Fluoride increased strongly towards the lower reaches of the catchment—at the stream outlet the concentrations were up to 4.2 mg L −1 and 1.6–4.7 times higher than upstream. Additionally, fluoride concentrations were particularly high in groundwater and small surface-water bodies (including quarries) above or in direct contact with the granite and showed a strong inverse correlation with water discharge in the stream. Taken together, these data and patterns pin-point the granite intrusion as the ultimate source, explaining the abundance and distribution of dissolved fluoride within the catchment. The granite most likely deliver fluoride to the stream by three mechanisms: (1) weathering of the fine fraction of glacial deposits, derived from the granite and associated fluorine-rich greisen alterations, (2) large relative input of baseflow, partially originating in the granite and greisen, into the lower reaches during low flow in particular, and (3) water-conducting fractures or fracture zones running through the fluorine-rich granite and greisen.

National Category
Geochemistry
Research subject
Environmental Science, Environmental Chemistry
Identifiers
urn:nbn:se:lnu:diva-16870 (URN)10.1007/s10498-011-9151-2 (DOI)
Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2016-10-05Bibliographically approved
2. The impact of fluoride on Al abundance and speciation in boreal streams
Open this publication in new window or tab >>The impact of fluoride on Al abundance and speciation in boreal streams
Show others...
2015 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 409, 118-124 p.Article in journal (Refereed) Published
Abstract [en]

The impact of fluoride on the abundance and speciation of aluminium (Al) was investigated in three boreal streams characterised by overall high concentrations of fluoride and dissolved organic matter. Stream-water sampling was carried out several times a year for at least 4 years, and a chemical equilibrium model (Visual MINTEQ) was applied in order to model the proportion of colloidal and organically/inorganically complexed Al in the waters. The Al concentrations in filtered (0.45 mu m) water samples were inversely correlated with pH, and reached values up to approximately 1 mg/L during low pH conditions (pH < 6.0). In a stream with high fluoride concentrations, as compared to a similar stream with only moderately elevated fluoride concentrations, the Al concentrations were consistently elevated. For the stream with high concentrations of fluoride and Al, the model predicted both high concentrations and proportions of Al-fluoride complexation. This prediction indicates that high fluoride levels contribute to raise both the Al abundance and the ratio of inorganic to organic Al complexation in stream water. In contrast, for another stream with high fluoride concentrations and consistently high (near neutral) pH, there was no evidence of fluoride affecting Al concentration or complexation. These results show that it is important to focus future studies on the role of high levels of dissolved fluoride on both the speciation and the toxicity of Al in stream water.

National Category
Environmental Sciences
Research subject
Natural Science, Environmental Science
Identifiers
urn:nbn:se:lnu:diva-44138 (URN)10.1016/j.chemgeo.2015.05.013 (DOI)000358525500012 ()
Available from: 2015-06-12 Created: 2015-06-12 Last updated: 2016-10-05Bibliographically approved
3. Fluorine geochemistry of Quaternary deposits in a nemo-boreal catchment with elevated dissolved fluoride in surface waters and groundwater
Open this publication in new window or tab >>Fluorine geochemistry of Quaternary deposits in a nemo-boreal catchment with elevated dissolved fluoride in surface waters and groundwater
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Geochemistry
Identifiers
urn:nbn:se:lnu:diva-52559 (URN)
Available from: 2016-05-18 Created: 2016-05-18 Last updated: 2016-11-18Bibliographically approved
4. Geological, mineralogical and hydrological controls of fluoride in fresh groundwater in Quaternary deposits and bedrock fractures in a coastal area with Proterozoic granitoids
Open this publication in new window or tab >>Geological, mineralogical and hydrological controls of fluoride in fresh groundwater in Quaternary deposits and bedrock fractures in a coastal area with Proterozoic granitoids
(English)Manuscript (preprint) (Other academic)
National Category
Geochemistry
Identifiers
urn:nbn:se:lnu:diva-52560 (URN)
Available from: 2016-05-18 Created: 2016-05-18 Last updated: 2016-05-20
5. Assessing the risk of an excess fluoride intake among Swedish children in households with private wells: Expanding static single-source methods to a probabilistic multi-exposure-pathway approach
Open this publication in new window or tab >>Assessing the risk of an excess fluoride intake among Swedish children in households with private wells: Expanding static single-source methods to a probabilistic multi-exposure-pathway approach
2014 (English)In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 68, 192-199 p.Article in journal (Refereed) Published
Abstract [en]

It is often assumed that water consumption is the major route of exposure for fluoride and analysis of water fluoride content is the most common approach for ensuring that the daily intake is not too high. In the present study, the risk of excess intake was characterized for children in households with private wells in Kalmar County, Sweden, where the natural geology shows local enrichments in fluorine. By comparing water concentrations with the WHO drinking water guideline (1.5 mg/L), it was found that 24% of the ca. 4800 sampled wells had a concentration above this limit, hence providing a figure for the number of children in the households concerned assessed to be at risk using this straightforward approach. The risk of an excess intake could, alternatively, also be characterized based on a tolerable daily intake (in this case the US EPA RfD of 0.06 mg/kg-day). The exposure to be evaluated was calculated using a probabilistic approach, where the variability in all exposure factors was considered, again for the same study population. The proportion of children assessed to be at risk after exposure from drinking water now increased to 48%, and when the probabilistic model was adjusted to also include other possible exposure pathways; beverages and food, ingestion of toothpaste, oral soil intake and dust inhalation, the number increased to 77%. Firstly, these results show how the risk characterization is affected by the basis of comparison. In this example, both of the reference values used are widely acknowledged. Secondly, it illustrates how much of the total exposure may be overlooked when only focusing on one exposure pathway, and thirdly, it shows the importance of considering the variability in all relevant pathways.

Place, publisher, year, edition, pages
Elsevier, 2014
National Category
Environmental Sciences
Research subject
Natural Science, Environmental Science
Identifiers
urn:nbn:se:lnu:diva-33952 (URN)10.1016/j.envint.2014.03.014 (DOI)000337874300022 ()
Available from: 2014-04-23 Created: 2014-04-23 Last updated: 2016-05-20Bibliographically approved

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