The rapid underground dissolution of gypsum, and the evolution of the gypsum karst in Lithuania and England, results in subsidence problems which can make construction difficult. The natural dissolution yields sulphate-rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants.In the north of Lithuania gypsum karst is developed in Devonian gypsum. Here the towns of Biržai, Pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged. The majority of the potable water in these areas is derived from groundwater abstracted from sandstone sequences that underlie the gypsum. In Lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst. These measures include environmentally-friendly farming, restrictions on land use and exclusion zones around subsidence hollows.In England subsidence caused by the dissolution of Permian gypsum has caused severe problems in the vicinity of the town of Ripon. Numerous buildings have been damaged and new sites are difficult to develop. Here formal planning regulations have recently been introduced to help to mitigate against the worst effects of subsidence resulting from gypsum dissolution.
Groundwater utilization and groundwater quality vary in the Baltic and Nordic countries mainly because of different geological settings. Based on the geology, the countries were treated in the following three groups: (1) Fennoscandian (Finland, Sweden, and Norway) countries, (2) Denmark and Baltic (Estonia, Latvia, and Lithuania) countries, and (3) Iceland. Most of the utilized groundwater resources are taken from Quaternary deposits, but Denmark and the Baltic countries have in addition, important resources in Phanerozoic rocks. The groundwater quality reflects the residence time of water in the subsurface and the chemical composition of the geological formations. Concentrations of ions in the Fennoscandian bedrock are elevated compared to Iceland, but lower than in Denmark and the Baltic countries. Compared to groundwater in the bedrock, groundwater in Quaternary deposits has usually lower concentrations of dissolved minerals. Unconfined Quaternary aquifers are vulnerable to contamination. Examples from Denmark and the Baltic countries illustrate challenges and successful effects of mitigation strategies for such aquifers related to agricultural application and management of nitrogen. Confined and deeper groundwater is better protected against anthropogenic contamination, but water quality may be affected by harmful compounds caused by geogenic processes (namely, sulfide, arsenic, fluoride, and radon).
For the present study, geochemical ages were derived from radiocarbon and radiokrypton age calibration with groundwater chemical contents (Na+, K+, Mg2+, Ca2+, Cl−, SO42−, HCO3−). Geochemical ages may fill the dating gap (40–150 ka) between the isotope techniques mentioned. A case study of groundwater in the Baltic Artesian Basin has involved geochemical age calibration, data filtering (such as regional subdivision of the basin for more accurate results) and geochemical dating of groundwater of unknown age. Various approaches to interpretations of geochemical age results could be used. Bicarbonate and sulphate are sensitive to the hydrochemical environment and should be omitted from geochemical age calculations. Modern fresh groundwater samples should also be excluded from calibration in order to obtain more reliable trend lines. Calcium-sodium cation exchange occurs in deep aquifers and may be used for geochemical age determination of fossil groundwater.
<p>45 Geological Survey Organisations (GSOs) from 32 European countries developed an ERA-NET Co-Fund Action: Establishing the European Geological Surveys Research Area to deliver a Geological Service for Europe (GeoERA). The GeoEra project HOVER (<strong>H</strong>ydrogeological processes and Geological settings <strong>over </strong>Europe controlling dissolved geogenic and anthropogenic elements in groundwater of relevance to human health and the status of dependent ecosystems) aims to gain understanding of the controls on groundwater quality across Europe using the combined expertise and data held by member states. Objectives of the HOVER work package 7 (WP7) are i) review of existing index methods for assessing the vulnerability of the upper aquifer to pollution and selection of the methods to be applied at the pilot and pan-EU scale, ii) compilation and harmonization of input data sets required for assessing vulnerability, and iii) assessment of aquifer vulnerability to pollution (both in maps and 2-d schematic cross sections).</p> <p>The selected methodology adopted in this project is DRASTIC, which will be applied in ten pilot areas and at the pan-European scale. In karst regions, however, the COP method will be applied in the pilots. This is accompanied with comparisons with the outcomes of existing national vulnerability assessments. It is anticipated to validate the resulting vulnerability maps at the pilot level using available groundwater nitrate contamination information.</p>
The qualitative status of groundwater is often underestimated. This is because distinguishing trends of hydrogeochemistry variation linked to anthropogenic pressure from natural trends in groundwater is challenging. The study aims to evaluate the effect of the natural processes on the limits of temporal variability of the natural background level (NBL) in springs draining aquifer units with different vulnerabilities. Shallow groundwater samples of eighteen natural springs were investigated. Statistical analysis and geochemical modelling were used. The results showed that the natural temporal variability limits of HCO3−, Na+, K+, Cl− and SO42− in high vulnerability aquifers were narrower than in moderate and low vulnerability aquifers. This pattern was determined by the stronger buffering effect of carbonate equilibrium, sulphate reduction, and dilution processes on the variation of these major ions in high vulnerability aquifers. Meanwhile, natural temporal variability limits of TDS, Ca2+ and Mg2+ in high vulnerability aquifers were wider than in moderate and low vulnerability aquifers. This pattern was related to the stronger buffering effect of ion exchange on the variability limits of Ca2+ and Mg2+ in springs of moderate and low vulnerability aquifer units than the buffering effect of weaker carbonate dissolution and higher dilution intensity on the variability limits of Ca2+ and Mg2+ in springs of high vulnerability aquifer. The results of this research could be helpful for the reasonable integrated management and effective protection of groundwater resources.
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