Variations In PAM Effectiveness As An Erosion Control Method In Texas Coastal Soils As a Function of Soil Chemical Properties.

Texas has some of the highest coastal erosion rates in the country.  Erosion rates on coastal barrier islands are particularly high.  Erosion of barrier islands threatens ecologically sensitive coastal wetland habitat, and lessens the islands’ ability to protect the coast from the impact of major storms.  Polyacrylamide polymers have been used effectively in agricultural settings, but have rarely been used in coastal environments.  The polyacrylamide polymers sold commercially for wind or water erosion control is typically an anionic copolymer with roughly 15–40% of the acrylamide chain segments replaced by an acrylic acid group, and a molecular weight between 3 and 25 million.  The natural soil texture, structure, organic matter content and high salinity of coastal soils is far different from the conditions encountered in agricultural fields.   

We hypothesize that soil-polymer interaction for soils with high surface energy, such as smectite or soils with high level of transition metal or organic coatings will be dominated by dipole-dipole interactions, and ionic interactions.  While polymer-soil interactions for soils of low surface energy, such as kaolinite or soils with high concentrations of silica or quartz, would be dominated by non-ionic and low dipole moment interactions.   In soils of low surfaced energy, where entropic effects play a significant role in soil-polymer interaction is seems probable that a non-ionic polymer would be more effective than the anionic polymers typically used in erosion prevention applications.

In an effort to evaluate the potential for PAM usage as an erosion prevention tool, these hypothesis were tested by performing a series of flocculation tests using an polyacrylamide polymers with both pure minerals and natural soils, and subsequently comparing these results to measured surface energy values.  In addition laboratory flume tests were done to measure erosion on soils following polymer application.