HR: 1400h
AN: H33B-05    [Abstracts]
TI: Diffusion of Nutrients in an Isolated Wetland Resulting From Shallow Pore Water Gradients Affected by Antecedent Soil Conditions.
AU: * Bhadha, J H
EM: jango@ufl.edu
AF: University Of Florida, Department of Soil & Water Science, 2169, McCarty Hall (A)., Gainesville, Fl 32611, United States
AU: Jawitz, J W
EM: jawitz@ufl.edu
AF: University Of Florida, Department of Soil & Water Science, 2169, McCarty Hall (A)., Gainesville, Fl 32611, United States
AU: Dunne, E J
EM: ejdunne@ufl.edu
AF: University Of Florida, Department of Soil & Water Science, 2169, McCarty Hall (A)., Gainesville, Fl 32611, United States
AU: Perkins, D B
EM: dbperkins@ufl.edu
AF: University Of Florida, Department of Soil & Water Science, 2169, McCarty Hall (A)., Gainesville, Fl 32611, United States
AB: Historically sequestered nutrients in wetland soils may be gradually released to the water column through the process commonly referred to as internal loading. The watershed for Lake Okeechobee, FL (USA) is heavily agricultural and excess nutrients in this area are drained to the Lake by ditches and canals. Formerly isolated, wetlands in this area have also been extensively ditched and drained. In this study, diffusive fluxes of nutrients were calculated using Fick's First Law from shallow pore water gradients, and later compared to fluxes measured by an incubated laboratory experiment on 10-cm intact soil cores from the same sites. Three intact soil cores from a wetland located on an operational beef farm were used to measure total phosphorus (TP), along with soil properties such as porosity, bulk density, and pH. Simultaneously, pore water concentrations of total organic carbon (TOC), total Kjeldahl nitrogen (TKN), and soluble reactive phosphorus (SRP) were also measured at the same three sites for a period of twelve months, and compared to surface water concentrations during flooded periods. A strong correlation between concentration gradients in pore water SRP and those observed in soil TP, suggests that shallow pore water concentrations reflect antecedent soil conditions. If this is true, then fluxes associated with diffusion and advection could greatly affect the total ground water fluxes across the soil-water interface. Fickian diffusive fluxes, estimated six times over a twelve month sampling period, were found to vary between 7-38 mg.m^-2.d^-1 for TOC, 1-18 mg.m^-2.d^-1 for TKN, and 0.04-0.86 mg.m^-2.d^-1 for SRP. While factors such as wetland stage and hydroperiod may have affected the fluxes, it is ultimately the concentration gradients across the soil-water interface that drives diffusive fluxes.
DE: 1830 Groundwater/surface water interaction
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: 2007 Joint Assembly