Explanatory model for the occurrence of iron and manganese in the groundwater in Umeälvsåsen

Abstract

High concentrations of iron and manganese are common substances in Swedish groundwater that require treatment before use in drinking water. Elevated concentrations of these elements have been detected by Ramboll in Umeälvsåsen, a glaciofluvial esker in northern Sweden, which is under consideration as a future groundwater source. This thesis aims to identify the underlying causes of the elevated concentrations and develop an explanatory model applicable to similar projects. The study combined theoretical background with site-specific data to establish theories of potential underlaying causes. Verification of theories was made using statistical analysis, laboratory testing, and GIS-based spatial analyses. The findings indicate a strong correlation between wetlands and high iron and manganese concentrations, supporting the hypothesis of hydraulic connectivity between wetlands and groundwater. Additionally, lower groundwater velocity and deeper wells were found to significantly influence groundwater geochemistry. The results did not support other potential explanations, such as seasonal variability or the presence of organic lenses. The proposed model emphasizes the importance of early stage hydrogeochemical assessments and provides a methodological framework for identifying underlying contamination sources in future groundwater projects. These insights contribute to more effective planning and management of groundwater resources in glaciofluvial deposits, avoiding problems with iron and manganese.