wAbstract
@Internal loading is a critical component of the phosphorus (P)
budget of aquatic systems that can control trophic conditions.
While diffusion across the soil-water interface is generally considered
the dominant process controlling P load to the water column, advection
due to water table fluctuations can also be significant. Our objective
was to evaluate the role of diffusive and advective fluxes in
relation to the total P (TP) loads entering and exiting an impacted
wetland in the Lake Okeechobee drainage basin. The average diffusive
flux of TP was 0.32}0.14 mgm-2day-1 and
occurred for 240 days out of 314, while advective flux was 1.31}4.03
mgm-2day-1 and occurred for only 57 days.
Phosphorus load to the wetland via internal modes was estimated
to be 2.3 and 4.0 gday-1 from diffusion and advection
respectively, accounting for 18 of the total P input, while overland
flow (51) was the major input pathway to the wetland. Ditch flow
and groundwater outflow accounted for 49 (18.0 gday-1)
and 14 (5.0 gday-1) of the total P output, respectively.
This study shows the importance of advective flux in addition
to diffusive flux and that the former should not be neglected
when estimating internal P load of transiently flooded isolated
wetlands. The monthly P budget-based retention and release patterns
were consistent with previous findings, showing that intermittent
flooding and drying cycling significantly reduces the P retention
capacity of a wetland.
Keywords: Phosphorus; Wetlands; Internal loading; Diffusion; Advection;
Pore waterx
1. Introduction
@1.1. Background and motivation
@1.2. Site description
2. Methods
@2.1. Field sampling and analyses
@@2.1.1. Hydrologic monitoring and water budget analysis
@@2.1.2. Surface and pore water sampling
@2.2. Flux calculations
@2.3. Phosphorus budget
3. Results and discussion
@3.1. Wetland hydrography and hydroperiod
@3.2. Pore water phosphorus
@3.3. Fuluxes across the soil-water interface
@@3.3.1. Diffusive flux of P based on Fick's first law
@@3.3.2. Advective flux of P based on groundwater fluctuations
@3.4. Phosphorus budget estimation from May 2005 - March 2006
4. Conclusions
Acknowledgments
References