The chemistry of groundwater has been altered to a large degree through the influence of human activities. Addition of acids through precipitation and dry deposition, nitrogen from agriculture and sewage systems, and chloride from deicing are quantitatively the most important sources. In this paper the chemical characteristics of groundwater are discussed for a crystalline bedrock area located above the highest marine shoreline in southern Sweden. The aim of the study is to establish the background levels for the main chemical constituents in these waters. Focusing on sulphate and chloride, contributions from deposition are evaluated and a comparison with surface water chemistry is performed. Approximately 50% of the base cations in the lakes with extremely low alkalinity originate directly from deposition, while the corresponding figure for lakes with higher, though still low alkalinity, is approximately 39%, and for shallow wells the figure is 36%. There is evidence that the lakes receive water from a shallower depth than the shallow wells, but both groups receive the base cations mostly from the exchange store, or from weathering where the alkalinity produced is consumed by acid inputs. Deposition levels of sulphate and chloride are better approximated by lake water than by groundwater.

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