Effects of Hydrology and Temperature on Dissolved Organic Matter Mobilization and Transport within forest soils
Abstract
Dissolved organic matter (DOM) in soils plays an important role in surface water and groundwater quality. Higher concentrations of DOM may enhance the transport of nutrients and associated pollutants to freshwaters and coastal zones. The primary purpose of this study is to investigate the influences of temperature and hydrologic factors on the mobilization and transport of DOM in unsaturated soils. Laboratory columns were packed with soils taken from the Harvard forest in Petersham, MA. Unsaturated flow conditions were maintained by applying suction to the bottom of the soil columns. Columns packed with topsoil (A horizon) were irrigated by series of rainfall events using the same total volume of artificial rain water. The experiments were distinguished on the basis of the period of time between successive rainfall events and the rainfall intensity. In all experiments, DOM (measured by dissolved organic carbon) concentration peaked simultaneously with the passage of wetting front and then rapidly declined as flow stabilized during each rainfall event. In all cases, DOC concentrations declined with successive rainfall events. The results show greater DOM mobilization under rainfall with lower intensity. The interruption interval between successive rainfall events also significantly affected the DOM leaching. Higher DOC concentrations were observed within treatments with longer interruption intervals. The leached DOM was also characterized by UV absorbance, fluorescence spectroscopy in the emission mode, and additional spectroscopic-based indices, such as the humification index. Ongoing experiments are focusing on the transport and adsorptive fractionation of DOM in subsoils (B horizon). The effects of flow rate and temperature on these processes are being investigated. The information gained will provide insight into predicting the environmental fate of DOM-associated pollutants and in understanding the mechanisms that govern DOM mobilization and transport in soils.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H33F1074X
- Keywords:
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- 0486 Soils/pedology (1865);
- 1806 Chemistry of fresh water;
- 1831 Groundwater quality;
- 1871 Surface water quality;
- 1875 Vadose zone