Transport of barrel and spherical shaped colloids in unsaturated porous media.
Model colloids are usually spherical, but natural colloids have irregular geometries. Transport experiments of spherical colloids may not reflect the transport characteristics of natural colloids in porous media. We investigated saturated and unsaturated transport of colloids with spherical and angular shapes under steady-state, flow conditions. A pulse of negatively-charged colloids was introduced into a silica sand column at three different effective water saturations (Se = 0.31, 0.45, and 1.0). Colloids were introduced under high ionic strength of [106]mM to cause attachment to the secondary energy minimum and later released by changing the pore water to low ionic strength. After the experiment, sand was sampled from different depths (0, -4, and -11 cm) for scanning electron microscopy (SEM) analysis and colloid extraction. Water saturation affected colloid transport with more retention under low than under high saturation. Colloids were retained and released from a secondary energy minimum with more angular-shaped colloids being retained and released. Colloids extracted from the sand revealed highest colloid deposition in the top layer and decreasing deposition with depth. Pore straining and grain-grain wedging dominated colloid retention.
Department of Crop, Soil & Environmental Sciences, Auburn University, Auburn, AL 36849, United States; Department of Crop & Soil Sciences, Washington State University, Pullman, WA 99164 and Puyallup, WA 98371, United States. Electronic address: knappi@auburn.edu.
Thorsten
T
Knappenberger
Department of Crop & Soil Sciences, Washington State University, Pullman, WA 99164 and Puyallup, WA 98371, United States. Electronic address: agrscar@ku.ac.th.
Surachet
S
Aramrak
Department of Crop & Soil Sciences, Washington State University, Pullman, WA 99164 and Puyallup, WA 98371, United States. Electronic address: flury@wsu.edu.
Markus
M
Flury
D003102:Colloids / Q000032:analysis* / Q000737:chemistry*; D062070:Hydrology / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D009994:Osmolar Concentration; D016062:Porosity; D012822:Silicon Dioxide; D014867:Water / Q000032:analysis
D003102:Colloids; D014867:Water; D012822:Silicon Dioxide
Barrels; Colloid shape; Colloids; Spheres; Unsaturated transport