Investigation of Colloid Transport under Unsaturated Steady Flow Conditions Using a Geocentrifuge

• Applicant: Dr. Thorsten Knappenberger
• Subject Area: Soil Sciences
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 164643073

• Final Report Year: 2014

Final Report Abstract

I found out that background noise from silica sand has a significant impact on spectrophotometry measurements. However, spectrophotometer measurements are often used in column studies with soil and sands and therefore it is important to assess and understand the error sources and how to avoid them. I have designed a new column effluent setup that minimized measurement errors. I also incorporated these findings into my results to guarantee state of the art methods. I overall designed a new column experimental setup specially for the use in geocentrifuges. In my centrifuge experiments I found out that colloid transport is affected by both, the water content and the pore water velocity. My results clearly show that the water content is the more important one. However, it is still not well understood how colloids interplay with the air-water interface. It is known that colloids attach to the air-water interface and that this attachment very strong but there is still debate about the mechanisms. Future research will have to focus in these attachment mechanisms and the importance of transient vs. steady state flow.

Publications

• 2011: Using a Geocentrifuge to Study Colloid Transport in Unsaturated Porous Media. ASA, CSSA, and SSSA Annual Meetings, San Antonio, Texas, USA
  Knappenberger, T., M. Flury, E.D. Mattson, J.B. Harsh, F. Zang, G. Gee, and P. Lichtner
  
• 2012: Identifying the role of flow rate and water content in colloid transport in unsaturated porous media. In: Geophysical Research Abstracts Vol. 14, EGU2012-524
  Knappenberger, T., M. Flury, E.D. Mattson, J.B. Harsh, F. Zang, G. Gee, and P. Lichtner
  
• 2013: Impact of water content and pore water velocity on transport of colloids in unsaturated porous media. ASA, CSSA, and SSSA Annual Meetings, Tampa, Florida, USA
  Knappenberger, T., M. Flury, E.D. Mattson, J.B. Harsh
  
• 2014: Does Water Content or Flow Rate Control Colloid Transport in Unsaturated Porous Media? Environmental Science and Technology 48(7),3791–3799
  Knappenberger, T., M. Flury, E.D. Mattson, and J.B. Harsh
  (See online at https://doi.org/10.1021/es404705d)