Mg-Rich Minerals in Sediment and Suspended Particulates of Lake Okeechobee and Tributaries in the Northern Everglades: Implications for TurbidityWillie HarrisSoil and Water Science Department, University of FloridaOther contributors: Matt Fisher, Rocky Cao, Todd Osborne, Rex EllisAcknowledgments: Ramesh Reddy, Woody Dierberg, John White, Tom James
Determine if mineral components of sediments in Lake Okeechobee and water conveyances of N. Everglades also occur as suspended sediment and hence constitute potential abiotic contributors to turbidity.
Mission from God
Summary of Results:
Lake sediment clay: sepiolite, smectite, dolomite, calcite, kaolinite, palygorskite.
Lake sediment silt: Dominated by carbonates and/or quartz; smaller amounts of Ca phosphates and sepiolite.
Lake suspended solids: Similar to sediment, except smectitemore prevalent.
Everglade samples (sediment and suspended solids): calcite, dolomite, palygorskite, aragonite, quartz, sepiolite
Blue: contain Mg
Orange: commonly contain some Mg
SEM secondary image
EDS elemental dot maps
Discrete Ca-P phases commonly observed
Chemical properties of Mg-bearing minerals
M = exchangeable cations; can range from 0.2 to 0.6.
Physical properties of Mg-bearing minerals
From U. S. Geological Survey Open-File Report 01-041
Solids data for samples we collected
Effect of pH
Effect of ionic strength
Effect of cation valence
Upper - hydrated Na, a monovalent cation
Middle - hydrated Ca, a divalent cation
Lower - "specifically adsorbed" Al, trivalent
Mystery and importance of provenance.
Mud mineralogy similar to that for geologic phosphate deposits. Might mud have accumulated by stream transport from these deposits?
Torry Muck has sepiolite and smectite.
Prevalent to S and E of Lake Okeechobee
From EVERGLADES AGRICULTURAL AREA SOIL SUBSIDENCE AND LAND USE PROJECTIONS, Dr. George Snyder,
Prepared December, 2003
Cox, S., D. Lewis, S. McCollum, M. Bledsol, and R. Marrotte. 1988. Subsidence study of the Everglades Agricultural Area. USDA, SCS, Greenacres, FL. pp. 25.
(No divine revelation forthcoming)
A mystery that cries for a solution
• Reciprocal of double layer thickness:
K = A z [n0 / εkT]1/2
where: K = reciprocal of double layer thickness
A = a constant
z = counter ion charge
n0 = electrolyte conc
ε = dielectric constant of solvent
T = temperature (Kelvin)