Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation
Hydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in Fe<sup>II</sup> (average ~5911 µmol/L) and SO<sub>4</sub> (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subse...
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MDPI AG
2023-12-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/15/24/4273 |
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| author | Khawar Sultan Turki Kh. Faraj Qamar uz Zaman |
| author_facet | Khawar Sultan Turki Kh. Faraj Qamar uz Zaman |
| author_sort | Khawar Sultan |
| collection | DOAJ |
| description | Hydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in Fe<sup>II</sup> (average ~5911 µmol/L) and SO<sub>4</sub> (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subsequent precipitation of poorly crystallized Fe-oxyhydroxysulfate (schwertmannite) occurs and causes acidification (pH~2.8). However, the removal of dissolved loads as solid phases significantly improves the groundwater quality of the downgradient as an outflow. The rainwater isotopic values (δD ~−8.88‰ and δ<sup>18</sup>O ~−65.86‰) closely matched with the groundwater showing very little isotopic modification, which points to a short residence time of groundwater. The displacement of δD and δ<sup>18</sup>O values (slope = 5.3) from the meteoric water line reflected the evaporative enrichment of the lake water. The isotopic signature also revealed longer residence times of epilimnion than the hypolimnion waters which are dominated by groundwater. The lake is dimictic and showed abrupt changes in physicochemical parameters along the interface (~0.30 m thick) when separating the epilimnion (upper 4 m) from the hypolimnion (bottom 1.5 m). Lake sediments were found to be dominated by clay size fraction occurring as laminations (thickness: 1~0.5 mm) that reflect seasonal sedimentation. Higher schwertmannite formation in the south as compared to the north (recharge side) also serves as a scavenger of potentially toxic elements which is probably a natural solution to man-made problems. Schwertmannite transformation to goethite releases sulfate which is reduced and fixed as secondary sulfide minerals over time. Overall, waters are of a Ca–SO<sub>4</sub> to Ca–Mg–SO<sub>4</sub> type with distinct inflow (Fe<sup>II</sup>/Fe<sup>III</sup> > 2.5) and outflow (Fe<sup>II</sup>/Fe<sup>III</sup> < 0.5) of groundwater. |
| first_indexed | 2024-03-08T20:17:27Z |
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| id | doaj.art-b5a5033dd27e4a2bacb54f4f36065648 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-08T20:17:27Z |
| publishDate | 2023-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-b5a5033dd27e4a2bacb54f4f360656482023-12-22T14:49:54ZengMDPI AGWater2073-44412023-12-011524427310.3390/w15244273Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical InvestigationKhawar Sultan0Turki Kh. Faraj1Qamar uz Zaman2Department of Hydrology, University of Bayreuth, 95440 Bayreuth, GermanyDepartment of Soil Science, College of Food and Agriculture Sciences, King Saud University, P.O. Box 145111, Riyadh 11362, Saudi ArabiaDepartment of Environmental Sciences, The University of Lahore, Lahore 54590, PakistanHydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in Fe<sup>II</sup> (average ~5911 µmol/L) and SO<sub>4</sub> (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subsequent precipitation of poorly crystallized Fe-oxyhydroxysulfate (schwertmannite) occurs and causes acidification (pH~2.8). However, the removal of dissolved loads as solid phases significantly improves the groundwater quality of the downgradient as an outflow. The rainwater isotopic values (δD ~−8.88‰ and δ<sup>18</sup>O ~−65.86‰) closely matched with the groundwater showing very little isotopic modification, which points to a short residence time of groundwater. The displacement of δD and δ<sup>18</sup>O values (slope = 5.3) from the meteoric water line reflected the evaporative enrichment of the lake water. The isotopic signature also revealed longer residence times of epilimnion than the hypolimnion waters which are dominated by groundwater. The lake is dimictic and showed abrupt changes in physicochemical parameters along the interface (~0.30 m thick) when separating the epilimnion (upper 4 m) from the hypolimnion (bottom 1.5 m). Lake sediments were found to be dominated by clay size fraction occurring as laminations (thickness: 1~0.5 mm) that reflect seasonal sedimentation. Higher schwertmannite formation in the south as compared to the north (recharge side) also serves as a scavenger of potentially toxic elements which is probably a natural solution to man-made problems. Schwertmannite transformation to goethite releases sulfate which is reduced and fixed as secondary sulfide minerals over time. Overall, waters are of a Ca–SO<sub>4</sub> to Ca–Mg–SO<sub>4</sub> type with distinct inflow (Fe<sup>II</sup>/Fe<sup>III</sup> > 2.5) and outflow (Fe<sup>II</sup>/Fe<sup>III</sup> < 0.5) of groundwater.https://www.mdpi.com/2073-4441/15/24/4273acid mine lakeisotopesFe-OxidationsulfateREEsLusatia |
| spellingShingle | Khawar Sultan Turki Kh. Faraj Qamar uz Zaman Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation Water acid mine lake isotopes Fe-Oxidation sulfate REEs Lusatia |
| title | Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation |
| title_full | Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation |
| title_fullStr | Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation |
| title_full_unstemmed | Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation |
| title_short | Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation |
| title_sort | ferric oxyhydroxylsulfate precipitation improves water quality in an acid mining lake a hydrogeochemical investigation |
| topic | acid mine lake isotopes Fe-Oxidation sulfate REEs Lusatia |
| url | https://www.mdpi.com/2073-4441/15/24/4273 |
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