Occurrence of acidic groundwater in precambrian crystalline bedrock aquifers, Southwestern Sweden

Abstract

The pH and alkalinity of groundwater from 7651 wells drilled in the Precambrian crystalline bedrock of southwestern Sweden has been evaluated. The wells are generally less than 100 m deep. Analytical results were collected from different laboratories and authorities in the region. In areas with thin soil cover or coarse-grained deposits overlying the bedrock, alkalinity is normally less than 100 mg HCO3 L−1. Below the marine limit, where clayey sediments predominate, alkalinity sometimes even exceeds 200 mg HCO3 L−1. When comparing pH and alkalinity of groundwaters from Quaternary deposits with bedrock groundwaters, the latter always have higher pH and alkalinity values. The most acidic bedrock groundwaters are found in small areas close to the city of Goteborg due to additional factors of high acid loadings, high groundwater discharge and thin soil layers.