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Project ID:2006WA147B

Title: Transport of Colloids in Soils Studied by Geocentrifuge Techniques

Project Type: Research

Start Date: 03/01/2006

End Date: 02/28/2007

Congressional District: Washington, 5th District

Focus Categories: Hydrology, Methods, Groundwater

Keywords: colloids, particles, transport, pathogens

Principal Investigators: Flury, Markus (Washington State University); Sharma, Prabhakar (Washington State University)

Federal Funds: $23,000

Non-Federal Matching Funds: $46,000

Abstract: Pharmaceuticals, pathogens, pesticides, and heavy metals often move through soils by the process of colloid or colloid-facilitated transport. Colloids are commonly defined as particles less than 10 micrometer in diameter that can remain suspended in aqueous solution for considerable amounts of time. Pharmaceuticals, pesticides, and heavy metals are prone to attach to colloids in soils, and pathogenic microorganisms are considered colloids themselves. It is therefore important to understand the mechanisms of colloid transport in soils. In this proposal we focus on the understanding of fundamental mechanisms of colloid transport in soils. Recently, advanced experimental tools to study colloid transport have become available. We propose to use one of these tools, geocentrifuge techniques, to study colloid transport. Geocentrifuges are particularly useful to study transport processes in soils, because the flow rates, which are inherently slow is soils, can be sped up considerably. However, it is expected that there is a critical centrifugal acceleration, beyond which colloid behavior becomes unrepresentative compared to normal gravity.

The overall goal of this proposal is to test the suitability of geocentrifuges to study colloid transport in soils. Specifically, we address the following objectives:

  1. Determine critical centrifugal accelerations as a function of colloid specific density under unsaturated flow conditions.
  2. Determine the effect of surface properties on colloid transport in geocentrifuges.
  3. Examine colloid mobilization as a function of centrifugal acceleration.

This study combines colloid transport theory with laboratory experimentation. We have developed a theoretical framework to describe colloid transport in geocentrifuges, and will further develop this theory. We will rigorously test the theory by a series of geocentrifuge experiments. Colloid filtration experiments will be carried out with representative soil colloids under different centrifugal accelerations. We will experimentally determine critical accelerations, above which colloid transport will be altered compared with normal gravity. The results of this project will advance our fundamental understanding of colloid transport in soils. We will systematically test the use of geocentrifuges to study colloid transport. As geocentrifuges are powerful tools to study transport processes in soils, the results of this study provide the basis for successful application of this technique for studying colloidal transport processes.

Progress/Completion Report, PDF

U.S. Department of the Interior, U.S. Geological Survey
Maintained by: John Schefter
Last Updated: Thursday, January 03, 2008
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