Factors affecting the retention of dissolved organic carbon in upland soils
The aim of this thesis was to investigate soil and environmental factors which influence the adsorption of DOC in upland, moorland soils. In Chapter 1 climate change, the greenhouse effect and the global carbon cycle are discussed briefly. A more detailed discussion of carbon cycling in the plant-soil-water system focuses on DOC retention in podzols and the review concludes with a summary of the aims of this thesis. A peaty podzol has greater potential to retain DOC than the other major soil types within the Glen Dye catchment, N.E. Scotland. Retention of DOC by physico-chemical surface interactions occurred in the mineral horizons of the soil where locally high concentrations of amorphous Fe and Al were present. Laboratory experiments using potassium hydrogen phthalate as a source of DOC showed that DOC retention is favoured by longer contact times between soil and solution. Net retention of DOC in the podzol profile is decreased by increasing the solution pH and by repeated wetting/drying and freezing/thawing cycles. As temperature and reaction time increased, respiration becomes more important as a mechanism for depleting solution phthalate DOC concentrations. Annual fluxes of DOC in precipitation, podzolic O, E and Bs soil horizon solution and stream water were estimated for the Burn of Waterhead catchment to be 35, 121, 83, 37 and 48 kg C ha-1yr-1 respectively. The DOC fluxes and the concentrations of related elements varied seasonally, with the largest DOC fluxes produced in the autumn and lowest in the summer. The annual DOC flux from the Burn of Waterhead was lower than fluxes from other catchments at Glen Dye. Results from the field site supported laboratory experimental results which suggested that climate change will result in an increase in the DOC flux from results which suggested that climate change will result in an increase in the DOC flux from peaty podzolic soil.