Influence of soil clay content on dissolved organic matter in stream waters

Abstract

Dissolved organic carbon (DOC) is of major importance for freshwater ecology and water treatment, particularly in Australia. Work comparing two small catchments, one yielding water with high DOC concentrations (Lawless) and the other yielding water with low DOC concentrations (Retreat Valley), is described. Differences between stream DOC concentrations in the two catchments were related to differences between the properties of the catchment soils. The Retreat Valley soils had higher C contents than the Lawless soils, but the C was less soluble, resulting in lower DOC concentrations in soil core leachates. The lower solubility of C in the Retreat Valley soils was the result of a higher clay content and hence a higher surface area for adsorption reactions. The Retreat Valley soils had a higher adsorption capacity for organic matter than did the Lawless soils. The clay contents of soils was found to be an important factor influencing stream DOC concentrations throughout the Mt Lofty Ranges, and the prediction of DOC concentrations in streams on a broad scale is discussed.