Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin
Abstract Ordovician-Cambrian aquifer system (O-Cm) in the northern part of the Baltic Artesian Basin (BAB), Estonia, is part of a unique groundwater reservoir where groundwater originating from glacial meltwater recharge from the Scandinavian Ice Sheet is preserved. The distribution of redox zones i...
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Online Access: | https://doi.org/10.1016/j.chemgeo.2018.04.027 http://ecite.utas.edu.au/132044 |
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ftunivtasecite:oai:ecite.utas.edu.au:132044 2023-05-15T16:40:34+02:00 Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin Parn, J Affolter, S Ivask, J Johnson, S Kirsimae, K Leuenberger, M Martma, T Raidla, V Schloemer, S Sepp, H Vaikmae, R Walraevens, K 2018 https://doi.org/10.1016/j.chemgeo.2018.04.027 http://ecite.utas.edu.au/132044 en eng Elsevier Science Bv http://dx.doi.org/10.1016/j.chemgeo.2018.04.027 Parn, J and Affolter, S and Ivask, J and Johnson, S and Kirsimae, K and Leuenberger, M and Martma, T and Raidla, V and Schloemer, S and Sepp, H and Vaikmae, R and Walraevens, K, Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin, Chemical Geology, 488 pp. 149-161. ISSN 0009-2541 (2018) [Refereed Article] http://ecite.utas.edu.au/132044 Earth Sciences Physical Geography and Environmental Geoscience Hydrogeology Refereed Article PeerReviewed 2018 ftunivtasecite https://doi.org/10.1016/j.chemgeo.2018.04.027 2019-12-13T22:29:54Z Abstract Ordovician-Cambrian aquifer system (O-Cm) in the northern part of the Baltic Artesian Basin (BAB), Estonia, is part of a unique groundwater reservoir where groundwater originating from glacial meltwater recharge from the Scandinavian Ice Sheet is preserved. The distribution of redox zones in the anoxic O-Cm aquifer system is unusual. Strongly reducing conditions are found near the modern recharge area characterized by low concentrations of sulphate (<5 mgL −1 ) and the presence of CH 4 (up to 3.26 vol%). The concentrations of SO 4 2− increase and concentrations of CH 4 decrease farther down the groundwater flow path. Sulphate in fresh glacial palaeogroundwater originates probably from pyrite oxidation while brackish waters have gained their sulphate through mixing with relict saline formation waters residing in the deeper parts of the aquifer system. Stable isotopic composition of sulphate, especially relations between δ 18 O SO4 -δ 18 O water (∆ 18 O SO4-H2O from +20.5 to +31.1) and δ 34 S SO4 -δ 34 S H2S (∆ 34 S SO4-H2S value of +47.9) support a widespread occurrence of bacterial sulphate reduction in fresh glacial palaeogroundwater. We propose, that the observed unusual redox zonation is a manifestation of two different flow systems in the O-Cm aquifer system: 1) the topographically driven flow system which drives the infiltration of waters through the overlying carbonate formation in the modern recharge area; 2) the relict flow system farther down the groundwater flow path which developed as a response to large hydraulic gradients imposed by the Scandinavian Ice Sheet in Pleistocene. Thus, the strongly reducing conditions surrounding the modern recharge area may show the extent to which post-glacial recharge has influenced the aquifer system. O-Cm aquifer system is an example of an aquifer that has not reached a near-equilibrium state with respect to present day flow conditions and still exhibits hydrogeochemical patterns established under the influence of a continental ice sheet in Pleistocene. Article in Journal/Newspaper Ice Sheet eCite UTAS (University of Tasmania) Chemical Geology 488 149 161 |
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Open Polar |
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eCite UTAS (University of Tasmania) |
op_collection_id |
ftunivtasecite |
language |
English |
topic |
Earth Sciences Physical Geography and Environmental Geoscience Hydrogeology |
spellingShingle |
Earth Sciences Physical Geography and Environmental Geoscience Hydrogeology Parn, J Affolter, S Ivask, J Johnson, S Kirsimae, K Leuenberger, M Martma, T Raidla, V Schloemer, S Sepp, H Vaikmae, R Walraevens, K Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
topic_facet |
Earth Sciences Physical Geography and Environmental Geoscience Hydrogeology |
description |
Abstract Ordovician-Cambrian aquifer system (O-Cm) in the northern part of the Baltic Artesian Basin (BAB), Estonia, is part of a unique groundwater reservoir where groundwater originating from glacial meltwater recharge from the Scandinavian Ice Sheet is preserved. The distribution of redox zones in the anoxic O-Cm aquifer system is unusual. Strongly reducing conditions are found near the modern recharge area characterized by low concentrations of sulphate (<5 mgL −1 ) and the presence of CH 4 (up to 3.26 vol%). The concentrations of SO 4 2− increase and concentrations of CH 4 decrease farther down the groundwater flow path. Sulphate in fresh glacial palaeogroundwater originates probably from pyrite oxidation while brackish waters have gained their sulphate through mixing with relict saline formation waters residing in the deeper parts of the aquifer system. Stable isotopic composition of sulphate, especially relations between δ 18 O SO4 -δ 18 O water (∆ 18 O SO4-H2O from +20.5 to +31.1) and δ 34 S SO4 -δ 34 S H2S (∆ 34 S SO4-H2S value of +47.9) support a widespread occurrence of bacterial sulphate reduction in fresh glacial palaeogroundwater. We propose, that the observed unusual redox zonation is a manifestation of two different flow systems in the O-Cm aquifer system: 1) the topographically driven flow system which drives the infiltration of waters through the overlying carbonate formation in the modern recharge area; 2) the relict flow system farther down the groundwater flow path which developed as a response to large hydraulic gradients imposed by the Scandinavian Ice Sheet in Pleistocene. Thus, the strongly reducing conditions surrounding the modern recharge area may show the extent to which post-glacial recharge has influenced the aquifer system. O-Cm aquifer system is an example of an aquifer that has not reached a near-equilibrium state with respect to present day flow conditions and still exhibits hydrogeochemical patterns established under the influence of a continental ice sheet in Pleistocene. |
format |
Article in Journal/Newspaper |
author |
Parn, J Affolter, S Ivask, J Johnson, S Kirsimae, K Leuenberger, M Martma, T Raidla, V Schloemer, S Sepp, H Vaikmae, R Walraevens, K |
author_facet |
Parn, J Affolter, S Ivask, J Johnson, S Kirsimae, K Leuenberger, M Martma, T Raidla, V Schloemer, S Sepp, H Vaikmae, R Walraevens, K |
author_sort |
Parn, J |
title |
Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
title_short |
Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
title_full |
Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
title_fullStr |
Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
title_full_unstemmed |
Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin |
title_sort |
redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the baltic artesian basin |
publisher |
Elsevier Science Bv |
publishDate |
2018 |
url |
https://doi.org/10.1016/j.chemgeo.2018.04.027 http://ecite.utas.edu.au/132044 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_relation |
http://dx.doi.org/10.1016/j.chemgeo.2018.04.027 Parn, J and Affolter, S and Ivask, J and Johnson, S and Kirsimae, K and Leuenberger, M and Martma, T and Raidla, V and Schloemer, S and Sepp, H and Vaikmae, R and Walraevens, K, Redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the Baltic Artesian Basin, Chemical Geology, 488 pp. 149-161. ISSN 0009-2541 (2018) [Refereed Article] http://ecite.utas.edu.au/132044 |
op_doi |
https://doi.org/10.1016/j.chemgeo.2018.04.027 |
container_title |
Chemical Geology |
container_volume |
488 |
container_start_page |
149 |
op_container_end_page |
161 |
_version_ |
1766030976831455232 |