High fluoride concentrations in surface water - example from a catchment in SE Sweden

摘要

We studied the fluoride occurrence and its relationship to local geological properties in a small catchment (2700ha) located at the Baltic Sea coast in southeast Sweden. The aim was to investigate the possible impact of a granite intrusion (1.4 ga old Gotemar granite) on the fluoride (F) concentrations in a stream, both on a spatial and temporal scale. This type of anorogenic granite is younger than the surrounding bedrock types and typically recognized by its richness in fluorine. The catchment is dominated by exposed bedrock (51.2%) and a thin till cover (30.3%) and 86 % is covered by coniferous and mixed forest. The intrusion is situated in the lower reaches just north of the main stem. Since the stream, which is perennial, is located in the boreal zone (N 57°) it is recognized by strong discharge fluctuations due mainly to snow melt during spring. Time series of surface water chemistry and discharge have been analyzed and combined with targeted sampling within the catchment.