Groundwater-borne geogenic phosphorus: A potential contributor to eutrophication of freshwater ecosystems

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

Standard

Groundwater-borne geogenic phosphorus : A potential contributor to eutrophication of freshwater ecosystems. / Madsen, Catharina Simone Nisbeth.

Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, 2019. 129 s.

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

Harvard

Madsen, CSN 2019, Groundwater-borne geogenic phosphorus: A potential contributor to eutrophication of freshwater ecosystems. Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen. <https://soeg.kb.dk/permalink/45KBDK_KGL/16bqo9j/alma99123302263805763>

APA

Madsen, C. S. N. (2019). Groundwater-borne geogenic phosphorus: A potential contributor to eutrophication of freshwater ecosystems. Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen. https://soeg.kb.dk/permalink/45KBDK_KGL/16bqo9j/alma99123302263805763

Vancouver

Madsen CSN. Groundwater-borne geogenic phosphorus: A potential contributor to eutrophication of freshwater ecosystems. Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, 2019. 129 s.

Author

Madsen, Catharina Simone Nisbeth. / Groundwater-borne geogenic phosphorus : A potential contributor to eutrophication of freshwater ecosystems. Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, 2019. 129 s.

Bibtex

@phdthesis{d3ba61981c71443d8e19c88d2d101cab,
title = "Groundwater-borne geogenic phosphorus: A potential contributor to eutrophication of freshwater ecosystems",
abstract = "It is a well-established problem that phosphorus (P) enrichment of freshwater ecosystems initiates eutrophication and thus deterioration of the water quality. Transport of P is often associated with surface hydrological pathways, due to the common assumption that P is immobilized in the vadose zone during percolation. However, opposing this common perception, emerging studies suggest that groundwater may contain elevated P concentrations, subsequently posing an important and unrecognized threat to freshwater ecosystems. This Ph.D. study explores this under-investigated issue, both by detailed field investigations and method development of the application of stable 18O in orthophosphate (δ18OP) as a tracer for P origins in freshwater.The study presents research results from N{\o}rres{\o}, a Danish hypereutrophic lake. A yearlong record of the lake{\textquoteright}s water levels, stream and spring discharges, and geochemical parameters was sampled and used to determine the water balance of the lake. The relative importance of different sources of external waterborne P to the lake was inferred from this data, combined with P measurements. Overall, the results showed that even though groundwater only accounts for about half of the total water contribution, it is still by far the biggest external contributor of P entering the lake.Enriched P concentrations in groundwater can mainly be attributed to two mechanisms:i) A downward migration of contaminating P, originating from anthropogenic surficial deposited P, or ii) Mobilization of geogenic P within the aquifer. Nevertheless, geogenic P is only rarely considered and documented, especially when it comes to groundwater-Ptransported to freshwater ecosystems.The aquifer in this study, which is locally discharging groundwater into the lake, is confined by a thick layer of clay. This suggests that the elevated P concentration in the groundwater has a geogenic origin, as it was deemed unlikely that surface deposited P has percolated down to the aquifer. This assumption is supported by paleolimnological data of the lakebed sediment, indicating that N{\o}rres{\o} has always been meso-eutrophic, even beforethe introduction of agriculture at about 6000 years BP. Thus, we presumed the lake to be naturally eutrophic.By comparing the P internally released from the lake sediment with the total external P contribution, we found internal-phosphorus cycling to be the immediate controller of the trophic state of the lake. Yet, we demonstrated that geogenic groundwater-borne P is the decisive cause of P accumulation in the sediment.The findings from N{\o}rres{\o} underline the significance of the impact of groundwaterborne geogenic P on the trophic state of freshwater ecosystems, and highlights the necessity of taking this into consideration when designing effective mitigation and restoration measures.The ability to identify where the P originates from is equally essential for this mitigation and restoration. The concentration of δ18OP has been suggested as a possible tracer for the origin of P. However, currently there are still some methodological challenges involved in accurately determining δ18OP. This is especially true when it comes to its applicability for freshwater ecosystems. As a part of the Ph.D. research, numerous samples were collected and tests conducted to investigate the potential and the pitfalls of the use δ18OP as a tracer in freshwater ecosystems. From this, we constructed a protocol compiling experience from previous studies in combination with our own experience.",
author = "Madsen, {Catharina Simone Nisbeth}",
year = "2019",
month = jun,
language = "English",
publisher = "Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen",

}

RIS

TY - BOOK

T1 - Groundwater-borne geogenic phosphorus

T2 - A potential contributor to eutrophication of freshwater ecosystems

AU - Madsen, Catharina Simone Nisbeth

PY - 2019/6

Y1 - 2019/6

N2 - It is a well-established problem that phosphorus (P) enrichment of freshwater ecosystems initiates eutrophication and thus deterioration of the water quality. Transport of P is often associated with surface hydrological pathways, due to the common assumption that P is immobilized in the vadose zone during percolation. However, opposing this common perception, emerging studies suggest that groundwater may contain elevated P concentrations, subsequently posing an important and unrecognized threat to freshwater ecosystems. This Ph.D. study explores this under-investigated issue, both by detailed field investigations and method development of the application of stable 18O in orthophosphate (δ18OP) as a tracer for P origins in freshwater.The study presents research results from Nørresø, a Danish hypereutrophic lake. A yearlong record of the lake’s water levels, stream and spring discharges, and geochemical parameters was sampled and used to determine the water balance of the lake. The relative importance of different sources of external waterborne P to the lake was inferred from this data, combined with P measurements. Overall, the results showed that even though groundwater only accounts for about half of the total water contribution, it is still by far the biggest external contributor of P entering the lake.Enriched P concentrations in groundwater can mainly be attributed to two mechanisms:i) A downward migration of contaminating P, originating from anthropogenic surficial deposited P, or ii) Mobilization of geogenic P within the aquifer. Nevertheless, geogenic P is only rarely considered and documented, especially when it comes to groundwater-Ptransported to freshwater ecosystems.The aquifer in this study, which is locally discharging groundwater into the lake, is confined by a thick layer of clay. This suggests that the elevated P concentration in the groundwater has a geogenic origin, as it was deemed unlikely that surface deposited P has percolated down to the aquifer. This assumption is supported by paleolimnological data of the lakebed sediment, indicating that Nørresø has always been meso-eutrophic, even beforethe introduction of agriculture at about 6000 years BP. Thus, we presumed the lake to be naturally eutrophic.By comparing the P internally released from the lake sediment with the total external P contribution, we found internal-phosphorus cycling to be the immediate controller of the trophic state of the lake. Yet, we demonstrated that geogenic groundwater-borne P is the decisive cause of P accumulation in the sediment.The findings from Nørresø underline the significance of the impact of groundwaterborne geogenic P on the trophic state of freshwater ecosystems, and highlights the necessity of taking this into consideration when designing effective mitigation and restoration measures.The ability to identify where the P originates from is equally essential for this mitigation and restoration. The concentration of δ18OP has been suggested as a possible tracer for the origin of P. However, currently there are still some methodological challenges involved in accurately determining δ18OP. This is especially true when it comes to its applicability for freshwater ecosystems. As a part of the Ph.D. research, numerous samples were collected and tests conducted to investigate the potential and the pitfalls of the use δ18OP as a tracer in freshwater ecosystems. From this, we constructed a protocol compiling experience from previous studies in combination with our own experience.

AB - It is a well-established problem that phosphorus (P) enrichment of freshwater ecosystems initiates eutrophication and thus deterioration of the water quality. Transport of P is often associated with surface hydrological pathways, due to the common assumption that P is immobilized in the vadose zone during percolation. However, opposing this common perception, emerging studies suggest that groundwater may contain elevated P concentrations, subsequently posing an important and unrecognized threat to freshwater ecosystems. This Ph.D. study explores this under-investigated issue, both by detailed field investigations and method development of the application of stable 18O in orthophosphate (δ18OP) as a tracer for P origins in freshwater.The study presents research results from Nørresø, a Danish hypereutrophic lake. A yearlong record of the lake’s water levels, stream and spring discharges, and geochemical parameters was sampled and used to determine the water balance of the lake. The relative importance of different sources of external waterborne P to the lake was inferred from this data, combined with P measurements. Overall, the results showed that even though groundwater only accounts for about half of the total water contribution, it is still by far the biggest external contributor of P entering the lake.Enriched P concentrations in groundwater can mainly be attributed to two mechanisms:i) A downward migration of contaminating P, originating from anthropogenic surficial deposited P, or ii) Mobilization of geogenic P within the aquifer. Nevertheless, geogenic P is only rarely considered and documented, especially when it comes to groundwater-Ptransported to freshwater ecosystems.The aquifer in this study, which is locally discharging groundwater into the lake, is confined by a thick layer of clay. This suggests that the elevated P concentration in the groundwater has a geogenic origin, as it was deemed unlikely that surface deposited P has percolated down to the aquifer. This assumption is supported by paleolimnological data of the lakebed sediment, indicating that Nørresø has always been meso-eutrophic, even beforethe introduction of agriculture at about 6000 years BP. Thus, we presumed the lake to be naturally eutrophic.By comparing the P internally released from the lake sediment with the total external P contribution, we found internal-phosphorus cycling to be the immediate controller of the trophic state of the lake. Yet, we demonstrated that geogenic groundwater-borne P is the decisive cause of P accumulation in the sediment.The findings from Nørresø underline the significance of the impact of groundwaterborne geogenic P on the trophic state of freshwater ecosystems, and highlights the necessity of taking this into consideration when designing effective mitigation and restoration measures.The ability to identify where the P originates from is equally essential for this mitigation and restoration. The concentration of δ18OP has been suggested as a possible tracer for the origin of P. However, currently there are still some methodological challenges involved in accurately determining δ18OP. This is especially true when it comes to its applicability for freshwater ecosystems. As a part of the Ph.D. research, numerous samples were collected and tests conducted to investigate the potential and the pitfalls of the use δ18OP as a tracer in freshwater ecosystems. From this, we constructed a protocol compiling experience from previous studies in combination with our own experience.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/16bqo9j/alma99123302263805763

M3 - Ph.D. thesis

BT - Groundwater-borne geogenic phosphorus

PB - Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen

ER -

ID: 226830807