Atmospheric deposition effects on the chemistry of a stream in Northeastern Georgia

A modeling study of the Allt a Mharcaidh catchment in the Cairngorm region of Scotland has been undertaken to investigate long term trends in acidification and model sensitivity to soil physical and chemical characteristics. The MAGIC model (Model of Acidification of Groundwater In Catchments) is used to demonstrate that the sulphate adsorption ability of the soil and quality and quantity of rainfall inputs have significant effects on model output. Optimal weathering rates and predicted present day ion concentrations in streamwater compare well with measured and observed values. The analysis shows that the catchment has become progressively acidified since pre-industrial times but major changes in stream acidity have yet to occur.