U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
  
Organic Carbon Associated With Suspended Silt and Colloid From
the Mississippi River and Some of Its Tributaries, July 1991-May 1992
by
Colleen E. Rostad (USGS, Arvada, Colo.), Stephanie G. Monsterleet
(USGS, Arvada, Colo.), LaDonna M. Bishop (USGS, Arvada, Colo.), and Geoffrey
S. Ellis (USGS, Arvada, Colo.)
Abstract
Suspended silt and colloid samples were collected from 16 sites along
the Mississippi River and from some of its tributaries during July-August
1991, October-November 1991, and April-May 1992 to determine the organic
carbon associated with the suspended matter. Sample collection involved
pumping discharge-weighted volumes of river water from a cross section of
the river into a continuous-flow centrifuge to isolate the suspended silt.
Colloid remaining in the aqueous phase was isolated by ultrafiltration.
This is the first time that the presence of organic carbon associated with
the suspended silt and colloid has been investigated along the entire reach
of the Mississippi River from near Minneapolis, Minnesota, to south of New
Orleans, Louisiana. The organic carbon content associated with the colloids
(4 to 31 percent) was much higher than the organic carbon associated with
the silt (1 to17 percent).
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