Atmospheric deposition, afforestation and water quality at Loch Dee, S.W. Scotland

Abstract

This work describes an investigation of the factors governing the water quality in three upland streams at Loch Dee, S.W Scotland. Particular emphasis is placed on the factors affecting streamwater acidification in the short and medium time scales. The streams are differentiated from one another by the land-use employed in each of the stream catchments. The details of both the site and methods of data collection are described. Variations in both bulk precipitation and streamwater chemistry are examined at the weekly scale in order to determine the factors regulating streamwater chemistry. The 5 factors are; atmospheric deposition, weathering rates, biological production and consumption, ion-exchange and catchment hydrology. A more detailed examination of one of the processes (ion-exchange) is undertaken at both the catchment and laboratory scale. The data show that short-term streamwater acidification can be induced by ion-exchange of H+ for Na+ in the catchment soils following precipitation inputs heavily laden with sea-silts. The role of hydrology in determining streamwater acidity over storm periods is also considered using a time-series model. The model indicates that significant differences exist between the 3 catchments hydrology in terms of the duration and timing of acidic episodes in the streams.