Production vs. solubility in controlling runoff of DOC from peat soils – The use of an event analysis

This study considers a detailed record of dissolved organic carbon (DOC) runoff from two small peat-covered catchments in the North of England in order to understand the whether DOC runoff is limited by its solubility or by its production. The study characterises each runoff event from the two catchments in terms of their: initial flow, pH, conductivity, DOC; humification ratio; and the changes in these variables over the event. The event analysis uses multiple and logistic regression approaches to show that: (i) runoff events showed both increases and decreases in DOC; and (ii) time between events was found to be significant in controlling DOC flux and/or concentration in both study catchments. The study implies that a dominant control on DOC concentration in runoff is the amount of flow through the peat soil and that the rate of release is fast upon the time scale considered by this experiment (approximately <8 h). Diffusion is the limiting process on DOC in runoff for times up to 2 days. The rate of production of DOC only becomes important at time scales of more than this.