This report does not necessarily reflect the opinion of the members of the Monitoring Committee. ... more This report does not necessarily reflect the opinion of the members of the Monitoring Committee. Information on the ESPON Programme and projects can be found on www.espon.eu The web site provides the possibility to download and examine the most recent documents produced by finalised and ongoing ESPON projects. This basic report exists only in an electronic version.
A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea i... more A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea is vulnerable to changes in groundwater recharge, sea-level rise and human activities. Assessment of the intrinsic vulnerability of groundwater under climate scenarios was performed for the aquifer area by utilising the results of a published study on the impacts of climate change on groundwater recharge and sea-level rise on groundwater-seawater interaction. Three intrinsic vulnerability mapping methods, the aquifer vulnerability index (AVI), a modified SINTACS and GALDIT, were applied and compared. According to the results, the degree of groundwater vulnerability is greatly impacted by seasonal variations in groundwater recharge during the year, and also varies depending on the climate-change variability in the long term. The groundwater is potentially highly vulnerable to contamination from sources on the ground surface during high groundwater recharge rates after snowmelt, while a high vulnerability to seawater intrusion could exist when there is a low groundwater recharge rate in dry season. The AVI results suggest that a change in the sea level will have an insignificant impact on groundwater vulnerability compared with the results from the modified SINTACS and GALDIT. The modified SINTACS method could be used as a guideline for the groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow unconfined low-lying coastal aquifers under future climate-change conditions.
A shallow low-lying coastal sand aquifer in southern Finland is vulnerable to the climate change ... more A shallow low-lying coastal sand aquifer in southern Finland is vulnerable to the climate change and human activities. Under future climate change, a rise in sea-level would cause some parts of the aquifer and the water intake well to be under seawater. This, together with the predicted increase in precipitation, would enhance groundwater recharge and raise the water table, consequently contributing to the potential deterioration of groundwater quality or potential flooding in the low-lying aquifer area. An information on geological and hydrogeological characteristics of the aquifer for the climate change adaptation plan including the possible new locations of water intake wells was needed. This study aimed to construct a three-dimensional geological model and evaluate heterogeneity of the aquifer to provide a geological framework for groundwater flow model and the assessment of groundwater vulnerability. The methods used consist of a stochastic-geostatistical approach incorporated with groundwater flow model to predict the distributions of the superficial layers of a heterogeneous aquifer and to identify the distributions of the aquifer medias (sand and gravel) as well as groundwater flow system. In addition, the LiDAR-based digital elevation model was utilized to define the flood prone areas under the climate change scenarios. The three-dimensional geological model provides a better characterization of the heterogeneity of the aquifer and improved reliability of subsequent groundwater flow model and vulnerability assessment in the aquifer area. The proposed new locations of water intake wells and the results of the study provided useful information for local authorities for groundwater management in future.
The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unc... more The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unconfined, low-lying coastal aquifer in Hanko, southern Finland, was assessed using the UZF1 model package coupled with the three-dimensional groundwater flow model MODFLOW to simulate flow from the unsaturated zone through the aquifer. The snow and PET models were used to calculate the surface water availability for infiltration from the precipitation data used in UZF1. Infiltration rate, flow in the unsaturated zone and groundwater recharge were then simulated using UZF1. The simulation data from climate and sea level rise scenarios were compared with present data. The results indicated changes in recharge pattern during 2071-2100, with recharge occurring earlier in winter and early spring. The seasonal impacts of climate change on groundwater recharge were more significant, with surface overflow resulting in flooding during winter and early spring and drought during summer. Rising sea level would cause some parts of the aquifer to be under sea level, compromising groundwater quality due to intrusion of sea water. This, together with increased groundwater recharge, would raise groundwater levels and consequently contribute more surface leakage and potential flooding in the low-lying aquifer.
Luoma, S. 2016. Groundwater vulnerability of a shallow low-lying coastal aquifer in southern Finl... more Luoma, S. 2016. Groundwater vulnerability of a shallow low-lying coastal aquifer in southern Finland under climate change. Geological Survey of Finland, Espoo. 37 pages, 5 figures and 2 tables, with original articles (I-III).
<p>The impact of submarine groundwater discharge (SGD) on coastal sea biogeochemist... more <p>The impact of submarine groundwater discharge (SGD) on coastal sea biogeochemistry and water quality has been demonstrated in many recent studies. However, the isotopic behavior of terrestrially-derived solutes in the groundwater-seawater mixing zone of coastal aquifers (the subterranean estuary, STE) has been less studied, although solutes such as Li, S and Sr are commonly used as tracers of weathering and biogeochemical processes taking place in aquifers and in coastal sea sediments.</p><p>This study investigated the behavior of <sup>87</sup>Sr/<sup>86</sup>Sr, δ<sup>7</sup>Li and δ<sup>34</sup>S in the STE and three seafloor pockmarks with different degrees of groundwater influence, as constrained based on δ<sup>2</sup>H and δ<sup>18</sup>O, at the Hanko SGD site in Finland, in the northern Baltic Sea. These data were supplemented by groundwater and seawater measurements. <sup>87</sup>Sr/<sup>86</sup>Sr showed non-conservative behavior with values elevated up to 0.0167 units above that expected for the conservative mixing in the STE and in the most groundwater-dominated pockmark (up to 100% groundwater), but the deviation was masked by much stronger seawater contributions in the other pockmarks. δ<sup>7</sup>Li values were shifted down to −1.75‰ below that expected for conservative mixing in the STE and in groundwater-influenced pockmark porewaters, whereas δ<sup>7</sup>Li was elevated up to 1.53‰ in the porewater of organic-rich mud in a pockmark where groundwater influence had ceased. δ<sup>34</sup>S deviated between −16.78‰ and 10.51‰ from the conservative mixing in the STE and porewaters of groundwater-influenced pockmarks, while δ<sup>34</sup>S was elevated up to 16.85‰ in the porewater of the pockmark with no groundwater influence.</p><p>In the Hanko STE, the isotopic fractionation of Sr and Li was explained by chemical weathering of silicate minerals and clay minerals, respectively, whereas δ<sup>34</sup>S was fractionated by complex interactions of microbial sulfate reduction and sulfide reoxidation. In the pockmark porewater with no groundwater influence, δ<sup>7</sup>Li and δ<sup>34</sup>S isotopes were enriched in the heavier isotopes as a consequence of early-diagenetic mineral formation in the organic-rich muds. The measured <sup>87</sup>Sr/<sup>86</sup>Sr and δ<sup>7</sup>Li were higher than the previously estimated isotopic compositions of their groundwater-derived fluxes to the oceans, and partly higher than the global riverine values. The heterogeneity in the seafloor biogeochemical environment, caused by the focusing of SGD in pockmarks, resulted in strongly variable δ<sup>34</sup>S of groundwater-derived S flux to the coastal ocean at a spatial scale of a few hundreds of meters.</p><p>Original publication: Ikonen, J., Hendriksson, N., Luoma, S., Lahaye, Y. and Virtasalo, J. J.: Behavior of Li, S and Sr isotopes in the subterranean estuary and seafloor pockmarks of the Hanko submarine groundwater discharge site in Finland, northern Baltic Sea, Applied Geochemistry, 147, 105471, https://doi.org/10.1016/j.apgeochem.2022.105471, 2022.</p>
Hanke: Risk Assessment and Risk Management Procedure for Arsenic in the Tampere Region.Nimekkeen ... more Hanke: Risk Assessment and Risk Management Procedure for Arsenic in the Tampere Region.Nimekkeen selvennys: Arseeni ja eräitä muita alkuaineita Suomen maatalousekosysteemeissä, etenkin Pirkanmaalla.vokMAA. Yksikön huom.: MAA, MPLMP
Sediment samples were collected using a box corer, and cut in 1-cm sub-sample slices. The Cs-137 ... more Sediment samples were collected using a box corer, and cut in 1-cm sub-sample slices. The Cs-137 activity content of sub-samples was measured for 60 min using a BrightSpec bMCA-USB pulse height analyser coupled to a well-type NaI(Tl) detector. The same sub-samples were then analysed for water content and weight loss on ignition (LOI) by weighing sub-samples fresh, weighing after drying at 105 °C for 16 h, and weighing again after ignition at 550 °C for 2 h.
Water column profiles were measured at the locations of pockmarks B, D and E, using a Sea & Sun C... more Water column profiles were measured at the locations of pockmarks B, D and E, using a Sea & Sun CTD90M multiprobe. The sensors for pressure, temperature, conductivity and optical dissolved oxygen in the multiprobe were manufactured by Sea & Sun Technology GmbH. The turbidity sensor was manufactured by Seapoint Sensors Inc., and the ISM-2001C inductive 2D current meter with compass by HS Engineers GmbH.
Sea surface radon-222 measurements were carried out onboard the research boat Gridi. The survey w... more Sea surface radon-222 measurements were carried out onboard the research boat Gridi. The survey was run at 1.4 knots, with the boat position recorded by DGPS. Two pumps that continuously supplied water for the measurements were fixed at ca. 50 cm water depth with a Sea & Sun Technology CTD90M multiprobe that was recording pressure (depth), temperature and conductivity (salinity). The radon measurements were carried out using two identical systems in parallel, each equipped with a 3M MiniModule gas contractor that separates the dissolved gas from the continuously pumped water. The gas was dried with a Drierite gas-drying unit, and analysed with a Durridge RAD7 radon detector. The radon-in-water activity concentrations were calculated using the salinity and temperature dependent fractionation of radon-222 between air and water.
This report presents the final results of an Applied Research Project conducted within the framew... more This report presents the final results of an Applied Research Project conducted within the framework of the ESPON 2013 Programme, partly financed by the European Regional
Potential risks for shallow groundwater aquifers in coastal areas of the Baltic Sea, a case study... more Potential risks for shallow groundwater aquifers in coastal areas of the Baltic Sea, a case study in the Hanko area in South Finland
A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea i... more A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea is vulnerable to changes in groundwater recharge, sea-level rise and human activities. Assessment of the intrinsic vulnerability of groundwater under climate scenarios was performed for the aquifer area by utilising the results of a published study on the impacts of climate change on groundwater recharge and sea-level rise on groundwater-seawater interaction. Three intrinsic vulnerability mapping methods, the aquifer vulnerability index (AVI), a modified SINTACS and GALDIT, were applied and compared. According to the results, the degree of groundwater vulnerability is greatly impacted by seasonal variations in groundwater recharge during the year, and also varies depending on the climate-change variability in the long term. The groundwater is potentially highly vulnerable to contamination from sources on the ground surface during high groundwater recharge rates after snowmelt, while a high vulnerability to seawater intrusion could exist when there is a low groundwater recharge rate in dry season. The AVI results suggest that a change in the sea level will have an insignificant impact on groundwater vulnerability compared with the results from the modified SINTACS and GALDIT. The modified SINTACS method could be used as a guideline for the groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow unconfined low-lying coastal aquifers under future climate-change conditions.
Concern over arsenic (As)-rich drinking water has gained worldwide attention since the 1990s, whe... more Concern over arsenic (As)-rich drinking water has gained worldwide attention since the 1990s, when the problem was discovered in West Bengal in India and in Bangladesh. Since then, authorities and research institutes have focused on risk assessment and management for As in Finland. Nationwide geochemical mapping projects determined background levels and revealed regions with a higher than average As content in bedrock and soil. Approximately 10% of the citizens in Finland use drinking water from private wells. Groundwater, especially from drilled bedrock wells, may contain As concentrations higher than 10 μg/L, the European Union quality guideline for As in drinking water. Here, we present the outcome of two European Union projects, RAMAS and ASROCKS, which based their conclusions on nationwide databases and thousands of samples. Both RAMAS and ASROCKS focused on the Tampere-Häme region of Southern Finland, where bedrock and soil contain more As than in other parts of Finland on average. Over 1000 groundwater samples revealed that drilled bedrock wells may contain As-rich water in certain geological units. Naturally occurring As in bedrock and soil may also cause the mobilization of As during rock aggregate production and construction activities, potentially impacting on groundwater aquifers, surface waters, and biota. Arsenic concentrations in aggregate production and construction exceeded the regional background levels in some bedrock and aggregate product samples, but during leaching tests As concentrations were found to be low. Based on the results, risk management tools were revised and guidelines for the rock aggregate industry were established in cooperation with authorities, companies, and other stakeholders. To our knowledge, the guidelines established were the first in the world. The guidelines for As for the aggregate and construction industries can be applied in other countries and adapted to local conditions.
This report does not necessarily reflect the opinion of the members of the Monitoring Committee. ... more This report does not necessarily reflect the opinion of the members of the Monitoring Committee. Information on the ESPON Programme and projects can be found on www.espon.eu The web site provides the possibility to download and examine the most recent documents produced by finalised and ongoing ESPON projects. This basic report exists only in an electronic version.
A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea i... more A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea is vulnerable to changes in groundwater recharge, sea-level rise and human activities. Assessment of the intrinsic vulnerability of groundwater under climate scenarios was performed for the aquifer area by utilising the results of a published study on the impacts of climate change on groundwater recharge and sea-level rise on groundwater-seawater interaction. Three intrinsic vulnerability mapping methods, the aquifer vulnerability index (AVI), a modified SINTACS and GALDIT, were applied and compared. According to the results, the degree of groundwater vulnerability is greatly impacted by seasonal variations in groundwater recharge during the year, and also varies depending on the climate-change variability in the long term. The groundwater is potentially highly vulnerable to contamination from sources on the ground surface during high groundwater recharge rates after snowmelt, while a high vulnerability to seawater intrusion could exist when there is a low groundwater recharge rate in dry season. The AVI results suggest that a change in the sea level will have an insignificant impact on groundwater vulnerability compared with the results from the modified SINTACS and GALDIT. The modified SINTACS method could be used as a guideline for the groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow unconfined low-lying coastal aquifers under future climate-change conditions.
A shallow low-lying coastal sand aquifer in southern Finland is vulnerable to the climate change ... more A shallow low-lying coastal sand aquifer in southern Finland is vulnerable to the climate change and human activities. Under future climate change, a rise in sea-level would cause some parts of the aquifer and the water intake well to be under seawater. This, together with the predicted increase in precipitation, would enhance groundwater recharge and raise the water table, consequently contributing to the potential deterioration of groundwater quality or potential flooding in the low-lying aquifer area. An information on geological and hydrogeological characteristics of the aquifer for the climate change adaptation plan including the possible new locations of water intake wells was needed. This study aimed to construct a three-dimensional geological model and evaluate heterogeneity of the aquifer to provide a geological framework for groundwater flow model and the assessment of groundwater vulnerability. The methods used consist of a stochastic-geostatistical approach incorporated with groundwater flow model to predict the distributions of the superficial layers of a heterogeneous aquifer and to identify the distributions of the aquifer medias (sand and gravel) as well as groundwater flow system. In addition, the LiDAR-based digital elevation model was utilized to define the flood prone areas under the climate change scenarios. The three-dimensional geological model provides a better characterization of the heterogeneity of the aquifer and improved reliability of subsequent groundwater flow model and vulnerability assessment in the aquifer area. The proposed new locations of water intake wells and the results of the study provided useful information for local authorities for groundwater management in future.
The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unc... more The impact of climate change and Baltic Sea level rise on groundwater resources in a shallow, unconfined, low-lying coastal aquifer in Hanko, southern Finland, was assessed using the UZF1 model package coupled with the three-dimensional groundwater flow model MODFLOW to simulate flow from the unsaturated zone through the aquifer. The snow and PET models were used to calculate the surface water availability for infiltration from the precipitation data used in UZF1. Infiltration rate, flow in the unsaturated zone and groundwater recharge were then simulated using UZF1. The simulation data from climate and sea level rise scenarios were compared with present data. The results indicated changes in recharge pattern during 2071-2100, with recharge occurring earlier in winter and early spring. The seasonal impacts of climate change on groundwater recharge were more significant, with surface overflow resulting in flooding during winter and early spring and drought during summer. Rising sea level would cause some parts of the aquifer to be under sea level, compromising groundwater quality due to intrusion of sea water. This, together with increased groundwater recharge, would raise groundwater levels and consequently contribute more surface leakage and potential flooding in the low-lying aquifer.
Luoma, S. 2016. Groundwater vulnerability of a shallow low-lying coastal aquifer in southern Finl... more Luoma, S. 2016. Groundwater vulnerability of a shallow low-lying coastal aquifer in southern Finland under climate change. Geological Survey of Finland, Espoo. 37 pages, 5 figures and 2 tables, with original articles (I-III).
<p>The impact of submarine groundwater discharge (SGD) on coastal sea biogeochemist... more <p>The impact of submarine groundwater discharge (SGD) on coastal sea biogeochemistry and water quality has been demonstrated in many recent studies. However, the isotopic behavior of terrestrially-derived solutes in the groundwater-seawater mixing zone of coastal aquifers (the subterranean estuary, STE) has been less studied, although solutes such as Li, S and Sr are commonly used as tracers of weathering and biogeochemical processes taking place in aquifers and in coastal sea sediments.</p><p>This study investigated the behavior of <sup>87</sup>Sr/<sup>86</sup>Sr, δ<sup>7</sup>Li and δ<sup>34</sup>S in the STE and three seafloor pockmarks with different degrees of groundwater influence, as constrained based on δ<sup>2</sup>H and δ<sup>18</sup>O, at the Hanko SGD site in Finland, in the northern Baltic Sea. These data were supplemented by groundwater and seawater measurements. <sup>87</sup>Sr/<sup>86</sup>Sr showed non-conservative behavior with values elevated up to 0.0167 units above that expected for the conservative mixing in the STE and in the most groundwater-dominated pockmark (up to 100% groundwater), but the deviation was masked by much stronger seawater contributions in the other pockmarks. δ<sup>7</sup>Li values were shifted down to −1.75‰ below that expected for conservative mixing in the STE and in groundwater-influenced pockmark porewaters, whereas δ<sup>7</sup>Li was elevated up to 1.53‰ in the porewater of organic-rich mud in a pockmark where groundwater influence had ceased. δ<sup>34</sup>S deviated between −16.78‰ and 10.51‰ from the conservative mixing in the STE and porewaters of groundwater-influenced pockmarks, while δ<sup>34</sup>S was elevated up to 16.85‰ in the porewater of the pockmark with no groundwater influence.</p><p>In the Hanko STE, the isotopic fractionation of Sr and Li was explained by chemical weathering of silicate minerals and clay minerals, respectively, whereas δ<sup>34</sup>S was fractionated by complex interactions of microbial sulfate reduction and sulfide reoxidation. In the pockmark porewater with no groundwater influence, δ<sup>7</sup>Li and δ<sup>34</sup>S isotopes were enriched in the heavier isotopes as a consequence of early-diagenetic mineral formation in the organic-rich muds. The measured <sup>87</sup>Sr/<sup>86</sup>Sr and δ<sup>7</sup>Li were higher than the previously estimated isotopic compositions of their groundwater-derived fluxes to the oceans, and partly higher than the global riverine values. The heterogeneity in the seafloor biogeochemical environment, caused by the focusing of SGD in pockmarks, resulted in strongly variable δ<sup>34</sup>S of groundwater-derived S flux to the coastal ocean at a spatial scale of a few hundreds of meters.</p><p>Original publication: Ikonen, J., Hendriksson, N., Luoma, S., Lahaye, Y. and Virtasalo, J. J.: Behavior of Li, S and Sr isotopes in the subterranean estuary and seafloor pockmarks of the Hanko submarine groundwater discharge site in Finland, northern Baltic Sea, Applied Geochemistry, 147, 105471, https://doi.org/10.1016/j.apgeochem.2022.105471, 2022.</p>
Hanke: Risk Assessment and Risk Management Procedure for Arsenic in the Tampere Region.Nimekkeen ... more Hanke: Risk Assessment and Risk Management Procedure for Arsenic in the Tampere Region.Nimekkeen selvennys: Arseeni ja eräitä muita alkuaineita Suomen maatalousekosysteemeissä, etenkin Pirkanmaalla.vokMAA. Yksikön huom.: MAA, MPLMP
Sediment samples were collected using a box corer, and cut in 1-cm sub-sample slices. The Cs-137 ... more Sediment samples were collected using a box corer, and cut in 1-cm sub-sample slices. The Cs-137 activity content of sub-samples was measured for 60 min using a BrightSpec bMCA-USB pulse height analyser coupled to a well-type NaI(Tl) detector. The same sub-samples were then analysed for water content and weight loss on ignition (LOI) by weighing sub-samples fresh, weighing after drying at 105 °C for 16 h, and weighing again after ignition at 550 °C for 2 h.
Water column profiles were measured at the locations of pockmarks B, D and E, using a Sea & Sun C... more Water column profiles were measured at the locations of pockmarks B, D and E, using a Sea & Sun CTD90M multiprobe. The sensors for pressure, temperature, conductivity and optical dissolved oxygen in the multiprobe were manufactured by Sea & Sun Technology GmbH. The turbidity sensor was manufactured by Seapoint Sensors Inc., and the ISM-2001C inductive 2D current meter with compass by HS Engineers GmbH.
Sea surface radon-222 measurements were carried out onboard the research boat Gridi. The survey w... more Sea surface radon-222 measurements were carried out onboard the research boat Gridi. The survey was run at 1.4 knots, with the boat position recorded by DGPS. Two pumps that continuously supplied water for the measurements were fixed at ca. 50 cm water depth with a Sea & Sun Technology CTD90M multiprobe that was recording pressure (depth), temperature and conductivity (salinity). The radon measurements were carried out using two identical systems in parallel, each equipped with a 3M MiniModule gas contractor that separates the dissolved gas from the continuously pumped water. The gas was dried with a Drierite gas-drying unit, and analysed with a Durridge RAD7 radon detector. The radon-in-water activity concentrations were calculated using the salinity and temperature dependent fractionation of radon-222 between air and water.
This report presents the final results of an Applied Research Project conducted within the framew... more This report presents the final results of an Applied Research Project conducted within the framework of the ESPON 2013 Programme, partly financed by the European Regional
Potential risks for shallow groundwater aquifers in coastal areas of the Baltic Sea, a case study... more Potential risks for shallow groundwater aquifers in coastal areas of the Baltic Sea, a case study in the Hanko area in South Finland
A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea i... more A shallow unconfined low-lying coastal aquifer in southern Finland surrounded by the Baltic Sea is vulnerable to changes in groundwater recharge, sea-level rise and human activities. Assessment of the intrinsic vulnerability of groundwater under climate scenarios was performed for the aquifer area by utilising the results of a published study on the impacts of climate change on groundwater recharge and sea-level rise on groundwater-seawater interaction. Three intrinsic vulnerability mapping methods, the aquifer vulnerability index (AVI), a modified SINTACS and GALDIT, were applied and compared. According to the results, the degree of groundwater vulnerability is greatly impacted by seasonal variations in groundwater recharge during the year, and also varies depending on the climate-change variability in the long term. The groundwater is potentially highly vulnerable to contamination from sources on the ground surface during high groundwater recharge rates after snowmelt, while a high vulnerability to seawater intrusion could exist when there is a low groundwater recharge rate in dry season. The AVI results suggest that a change in the sea level will have an insignificant impact on groundwater vulnerability compared with the results from the modified SINTACS and GALDIT. The modified SINTACS method could be used as a guideline for the groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow unconfined low-lying coastal aquifers under future climate-change conditions.
Concern over arsenic (As)-rich drinking water has gained worldwide attention since the 1990s, whe... more Concern over arsenic (As)-rich drinking water has gained worldwide attention since the 1990s, when the problem was discovered in West Bengal in India and in Bangladesh. Since then, authorities and research institutes have focused on risk assessment and management for As in Finland. Nationwide geochemical mapping projects determined background levels and revealed regions with a higher than average As content in bedrock and soil. Approximately 10% of the citizens in Finland use drinking water from private wells. Groundwater, especially from drilled bedrock wells, may contain As concentrations higher than 10 μg/L, the European Union quality guideline for As in drinking water. Here, we present the outcome of two European Union projects, RAMAS and ASROCKS, which based their conclusions on nationwide databases and thousands of samples. Both RAMAS and ASROCKS focused on the Tampere-Häme region of Southern Finland, where bedrock and soil contain more As than in other parts of Finland on average. Over 1000 groundwater samples revealed that drilled bedrock wells may contain As-rich water in certain geological units. Naturally occurring As in bedrock and soil may also cause the mobilization of As during rock aggregate production and construction activities, potentially impacting on groundwater aquifers, surface waters, and biota. Arsenic concentrations in aggregate production and construction exceeded the regional background levels in some bedrock and aggregate product samples, but during leaching tests As concentrations were found to be low. Based on the results, risk management tools were revised and guidelines for the rock aggregate industry were established in cooperation with authorities, companies, and other stakeholders. To our knowledge, the guidelines established were the first in the world. The guidelines for As for the aggregate and construction industries can be applied in other countries and adapted to local conditions.
This thesis clarifies the potential impacts of climate change and sea-level rise under future cli... more This thesis clarifies the potential impacts of climate change and sea-level rise under future climate scenarios on groundwater recharge and surface leakage, and consequently on the groundwater vulnerability of a shallow, unconfined, low-lying coastal sedimentary aquifer in southern Finland. The study utilised multiple approaches, including field investigations, well monitoring, three-dimensional (3D) geological modelling, 3D groundwater flow modelling, multivariate statistical approaches (principal component analysis (PCA) and hierarchical cluster analysis (HCA)), the stable isotopes δ2H and δ18O, conventional hydrogeochemistry and groundwater intrinsic vulnerability assessment methods. The UZF1 model was coupled with the 3D groundwater MODFLOW model to simulate flow from the unsaturated zone through the aquifer. The well-calibrated groundwater flow model was used to simulate and predict the potential impacts of climate change on groundwater recharge under future climate and sea-level rise scenarios. The results indicate changes in the groundwater recharge patterns during the years 2071–2100, with recharge occurring earlier in winter and early spring. Because the aquifer is located in a cold snow-dominated region, the seasonal impacts of climate change on groundwater recharge were more significant, with land surface overflow resulting in flooding during the winter and early spring and drought during the summer. Rising sea levels would cause some parts of the aquifer to be submerged under the sea, compromising groundwater quality due to the intrusion of seawater. This, together with increased groundwater recharge, would raise the groundwater level and consequently contribute to more surface leakage. The groundwater geochemistry of the coastal aquifer in Hanko is very similar to that of inland shallow aquifers generally in Finland, where the groundwater is mainly of the Ca–HCO3 type, with low dissolved element concentrations, low pH and alkalinity, and low Ca and Mg concentrations due to rapid percolation or the short residence time. The stable isotopes δ2H and δ18O clearly suggest that the Hanko aquifer recharges directly from meteoric water (snowmelt and rainfall), with minor or insignificant contributions from the Baltic Sea and surface water. However, the geochemistry of the groundwater suggests sulphate reduction in the mixed zone between freshwater and seawater, indicating that local seawater intrusion may temporarily take place, although the contribution of seawater was found to be very low. Further inland, the influence of surface water could be observed from higher levels of KMnO4 consumption in wells near the lake above the aquifer. The findings also demonstrated that the use of stable isotopes δ2H and δ18O alone to identify seawater–aquifer interaction is not sufficient to determine the rate of water exchange. The high temporal variation in groundwater chemistry directly corresponded to groundwater recharge. With an increase in groundwater recharge, KMnO4 consumption, EC, alkalinity and Ca concentrations also increased in most wells, while Fe, Al, Mn and SO4 were occasionally increased during the spring after snowmelt under specific geological conditions. Based on the future climate scenarios, precipitation in the Hanko area is expected to increase and the Baltic Sea level to rise. This could cause increased recharge of the aquifer from surface water, but also some seawater intrusion due to the sea-level rise and storm surges, as well as increased groundwater abstraction. An increase in the concentrations of some dissolved elements and changes in groundwater geochemistry along the coastline can be expected in the future. Thus, in coastal aquifers with low hydraulic gradients, the hydrogeochemistry should be used to confirm the intrusion of seawater. The PCA and HCA multivariate statistical approaches are useful tools to extract the main components that are able to identify the vulnerable areas of the aquifer impacted by natural or human activities, either on regional or site-specific scales. The integration of PCA and HCA with conventional classification of groundwater types, as well as with the hydrogeochemical data, provided an understanding of the complex groundwater flow systems, supporting aquifer vulnerability assessment and groundwater management in the future. The degree of groundwater vulnerability in the Hanko aquifer has been greatly impacted by seasonal variations in groundwater recharge during the year, and will also vary depending on climate change variability in the long term. The potential for high groundwater vulnerability to contamination from sources on the ground surface occurs during the period with a high groundwater recharge rate after snowmelt, while high vulnerability to seawater intrusion could occur when there is a low groundwater recharge rate in the dry season. This thesis study highlighted the importance of the integration of groundwater vulnerability assessment methods for shallow, unconfined, low-lying coastal aquifers from a comparison of three intrinsic vulnerability mapping methods: the AVI, a modified version of SINTACS and the GALDIT method. The modified SINTACS could be used as a guideline for groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow, unconfined, low-lying coastal aquifers under future climate change.
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The groundwater geochemistry of the coastal aquifer in Hanko is very similar to that of inland shallow aquifers generally in Finland, where the groundwater is mainly of the Ca–HCO3 type, with low dissolved element concentrations, low pH and alkalinity, and low Ca and Mg concentrations due to rapid percolation or the short residence time. The stable isotopes δ2H and δ18O clearly suggest that the Hanko aquifer recharges directly from meteoric water (snowmelt and rainfall), with minor or insignificant contributions from the Baltic Sea and surface water. However, the geochemistry of the groundwater suggests sulphate reduction in the mixed zone between freshwater and seawater, indicating that local seawater intrusion may temporarily take place, although the contribution of seawater was found to be very low. Further inland, the influence of surface water could be observed from higher levels of KMnO4 consumption in wells near the lake above the aquifer. The findings also demonstrated that the use of stable isotopes δ2H and δ18O alone to identify seawater–aquifer interaction is not sufficient to determine the rate of water exchange. The high temporal variation in groundwater chemistry directly corresponded to groundwater recharge. With an increase in groundwater recharge, KMnO4 consumption, EC, alkalinity and Ca concentrations also increased in most wells, while Fe, Al, Mn and SO4 were occasionally increased during the spring after snowmelt under specific geological conditions. Based on the future climate scenarios, precipitation in the Hanko area is expected to increase and the Baltic Sea level to rise. This could cause increased recharge of the aquifer from surface water, but also some seawater intrusion due to the sea-level rise and storm surges, as well as increased groundwater abstraction. An increase in the concentrations of some dissolved elements and changes in groundwater geochemistry along the coastline can be expected in the future. Thus, in coastal aquifers with low hydraulic gradients, the hydrogeochemistry should be used to confirm the intrusion of seawater. The PCA and HCA multivariate statistical approaches are useful tools to extract the main components that are able to identify the vulnerable areas of the aquifer impacted by natural or human activities, either on regional or site-specific scales. The integration of PCA and HCA with conventional classification of groundwater types, as well as with the hydrogeochemical data, provided an understanding of the complex groundwater flow systems, supporting aquifer vulnerability assessment and groundwater management in the future.
The degree of groundwater vulnerability in the Hanko aquifer has been greatly impacted by seasonal variations in groundwater recharge during the year, and will also vary depending on climate change variability in the long term. The potential for high groundwater vulnerability to contamination from sources on the ground surface occurs during the period with a high groundwater recharge rate after snowmelt, while high vulnerability to seawater intrusion could occur when there is a low groundwater recharge rate in the dry season. This thesis study highlighted the importance of the integration of groundwater vulnerability assessment methods for shallow, unconfined, low-lying coastal aquifers from a comparison of three intrinsic vulnerability mapping methods: the AVI, a modified version of SINTACS and the GALDIT method. The modified SINTACS could be used as a guideline for groundwater vulnerability assessment of glacial and deglacial deposits in inland aquifers, and in combination with GALDIT, it could provide a useful tool for assessing groundwater vulnerability to both contamination from sources on the ground surface and to seawater intrusion for shallow, unconfined, low-lying coastal aquifers under future climate change.