wAbstract
@High phosphorus (P) in surface drainage water from agricultural
and urban runoff is the main cause of eutrophication within aquatic
systems in South Florida, including the Everglades. While primary
sources of P in drainage canals in the Everglades Agricultural
Area (EAA) are from land use application of agricultural chemicals
and oxidation of the organic soils, internal sources from canal
sediments can also affect overall P status in the water column.
In this paper, we evaluate P release and equilibrium dynamics
from three conveyance canals within the EAA. Incubation and flux
experiments were conducted on intact sediment cores collected
from four locations within the Miami, West Palm Beach (WPB), and
Ocean canal. After three continuous exchanges, Miami canal sediments
reported the highest P release (66}37 mg m-2) compared
to WPB (13}10 mg m-2) and Ocean (17}11 mg m-2)
canal over 84 days. Overall, the P flux from all three canal sediments
was highest during the first exchange. Miami canal sediments showed
the highest P flux (2.4}1.3 mg m-2 day-1)
compared to WPB (0.83}0.39 mg m-2 d-1) and
Ocean canal sediments (0.98}0.38 mg m-2 day-1).
Low P release from WPB canal sediments despite having high TP
content could be due to carbonate layers distributed throughout
the sediment column inhibiting P release. Equilibrium P concentrations
estimated from the sediment core experiment corresponded to 0.12}0.04
mg L-1, 0.06}0.03 mg L-1, and 0.08}0.03
mg L-1 for Miami, WPB, and Ocean canal sediments, respectively,
indicating Miami canal sediments behave as a source of P, while
Ocean and WPB canal sediments are in equilibrium with the water
column. Overall, the sediments showed a significant positive correlation
between P release and total P (r=0.42), Feox
(r=0.65), and Alox (r=0.6) content of sediments.
The contribution of P from the three main canals sediments within
the EAA boundary corresponded to a very small portion of the total
P load existing the EAA. These estimates, however, only take into
consideration diffusive fluxes from sediments and no other factors
such as canal flow, bioturbation, resuspension, and anaerobic
conditions.
Keywords: Everglades Agricultural Area; Sediments; Canal; Phosphorus;
Equilibrium; Incubation; Releasex
1. Introduction
2. Materials and methods
@2.1. Sediment sampling and analyses
@2.2. Sediment core incubation
@2.3. P-flux estimation
@2.4. Estimation of EPCw using sediment core
incubation
3. Results and discussion
@3.1. Phosphorus release from canal sediments
@3.2. Phosphorus flux
@3.3. Equilibrium phosphorus concentration (EPCw)
@3.4. Sediment physico-chemical properties and P release
4. Conclusions
Acknowledgments
References