Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis
<p class="Default">A mass balance of the mineralogical sources of fluoride in charnockitic gneiss bedrock and regolith (weathered rock) in Sri Lanka has been undertaken, using optical petrography and Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectrometry (EDX) t...
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| Format: | Article |
| Language: | English |
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Faculty of Science, University of Peradeniya, Sri Lanka
2016-06-01
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| Series: | Ceylon Journal of Science |
| Subjects: | |
| Online Access: | https://cjs.sljol.info/articles/7374 |
| _version_ | 1811193571348316160 |
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| author | H.A. Dharmagunawardhane S.P.K. Malaviarachchi William Burgess |
| author_facet | H.A. Dharmagunawardhane S.P.K. Malaviarachchi William Burgess |
| author_sort | H.A. Dharmagunawardhane |
| collection | DOAJ |
| description | <p class="Default">A mass balance of the mineralogical sources of fluoride in charnockitic gneiss bedrock and regolith (weathered rock) in Sri Lanka has been undertaken, using optical petrography and Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectrometry (EDX) to support development of a conceptual model of fluoride release to groundwater. Bedrock and regolith samples were collected in Polonnaruwa where there is a widespread occurrence of dental fluorosis attributed to excessive fluoride (up 5.25mg/L) in groundwater, while primary minerals of the gneissic bedrock are identified as the ultimate source of fluoride. Fluoride leaching related to long-term weathering of the bedrock and development of the regolith, control the occurrence of F in the groundwater system which is yet unresolved. In the study area, the charnockitic gneiss bedrock is mantled by a few meters thick regolith within which the groundwater table fluctuates seasonally.</p><p class="Default">Mineral abundance and mineral fluoride content were estimated using petrographic and SEM analysis. Plagioclase, hornblende, pyroxene, K-feldspar, quartz, biotite and titanite (sphene) were the major minerals of the rock though the mineral proportions vary widely over the area. Apatite and magnetite were present as accessory minerals. Fluoride concentrations obtained from SEM-EDX analysis were combined with the volume percentage of minerals from petrography to estimate the total rock fluoride concentration.</p><p class="Default">The order of fluoride abundance was apatite (highest), biotite, titanite, and hornblende. Plagioclase, K feldspar, pyroxene and magnetite did not have any noticeable fluoride concentrations. Loss of fluoride from the rock mass upon weathering was clearly evident and hornblende appeared to be the most significant fluoride releasing agent through weathering. Apatite, though present in accessory amounts, is distributed evenly in the rock and hence may be considered as a steady fluoride donor causing elevated and uniform fluoride distribution in groundwater. On the other hand, hornblende and biotite though of irregular occurrence (area wise), may cause high fluoride anomalies in groundwater in areas of high abundance.</p> |
| first_indexed | 2024-04-12T00:11:22Z |
| format | Article |
| id | doaj.art-608ecd85402b4577a0481f52bf706e0f |
| institution | Directory Open Access Journal |
| issn | 2513-2814 2513-230X |
| language | English |
| last_indexed | 2024-04-12T00:11:22Z |
| publishDate | 2016-06-01 |
| publisher | Faculty of Science, University of Peradeniya, Sri Lanka |
| record_format | Article |
| series | Ceylon Journal of Science |
| spelling | doaj.art-608ecd85402b4577a0481f52bf706e0f2022-12-22T03:55:57ZengFaculty of Science, University of Peradeniya, Sri LankaCeylon Journal of Science2513-28142513-230X2016-06-01451576610.4038/cjs.v45i1.73645596Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysisH.A. Dharmagunawardhane0S.P.K. Malaviarachchi1William Burgess2Department of Geology, University of Peradeniya, PeradeniyaDepartment of Geology, University of Peradeniya, PeradeniyaDepartment of Earth Sciences, University College London<p class="Default">A mass balance of the mineralogical sources of fluoride in charnockitic gneiss bedrock and regolith (weathered rock) in Sri Lanka has been undertaken, using optical petrography and Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectrometry (EDX) to support development of a conceptual model of fluoride release to groundwater. Bedrock and regolith samples were collected in Polonnaruwa where there is a widespread occurrence of dental fluorosis attributed to excessive fluoride (up 5.25mg/L) in groundwater, while primary minerals of the gneissic bedrock are identified as the ultimate source of fluoride. Fluoride leaching related to long-term weathering of the bedrock and development of the regolith, control the occurrence of F in the groundwater system which is yet unresolved. In the study area, the charnockitic gneiss bedrock is mantled by a few meters thick regolith within which the groundwater table fluctuates seasonally.</p><p class="Default">Mineral abundance and mineral fluoride content were estimated using petrographic and SEM analysis. Plagioclase, hornblende, pyroxene, K-feldspar, quartz, biotite and titanite (sphene) were the major minerals of the rock though the mineral proportions vary widely over the area. Apatite and magnetite were present as accessory minerals. Fluoride concentrations obtained from SEM-EDX analysis were combined with the volume percentage of minerals from petrography to estimate the total rock fluoride concentration.</p><p class="Default">The order of fluoride abundance was apatite (highest), biotite, titanite, and hornblende. Plagioclase, K feldspar, pyroxene and magnetite did not have any noticeable fluoride concentrations. Loss of fluoride from the rock mass upon weathering was clearly evident and hornblende appeared to be the most significant fluoride releasing agent through weathering. Apatite, though present in accessory amounts, is distributed evenly in the rock and hence may be considered as a steady fluoride donor causing elevated and uniform fluoride distribution in groundwater. On the other hand, hornblende and biotite though of irregular occurrence (area wise), may cause high fluoride anomalies in groundwater in areas of high abundance.</p>https://cjs.sljol.info/articles/7374dental fluorosis, fluoride, groundwater, sri lanka |
| spellingShingle | H.A. Dharmagunawardhane S.P.K. Malaviarachchi William Burgess Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis Ceylon Journal of Science dental fluorosis, fluoride, groundwater, sri lanka |
| title | Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis |
| title_full | Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis |
| title_fullStr | Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis |
| title_full_unstemmed | Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis |
| title_short | Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis |
| title_sort | fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in sri lanka estimates from combined petrographic and electron microprobe analysis |
| topic | dental fluorosis, fluoride, groundwater, sri lanka |
| url | https://cjs.sljol.info/articles/7374 |
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