Mobilization Assessment and Possibility of Increased Availability of PAHs in Contaminated Soil Using Column Tests

Abstract

Surfactants are well known to increase solubility/mobility of hydrocarbons and can be used to remediate contaminated water and soil. We wanted to explore if Ivey sol® 106 used at less than the critical micelle concentration (CMC) could effectively mobilize PAH (polycyclic aromatic hydrocarbons) from contaminated soil. The first step was to establish a measurement technique. Hence, a column leaching method was undertaken to investigate mobility of PAH-contaminated soil from a former gaswork facility. The methodology was based on a recycled flow of aqueous solution containing CaCl₂ 0.01M through two different soil columns. In the first column test, the free desorption of hydrocarbons was studied by recycling the solution through the soil column with a peristaltic pump and with a liquid/solid ratio of 2, based on ISO/DIS 18772. The solution was replaced with new solution every three days to aid desorption.

In the second column test, the set-up was similar with the exception of the aforementioned recycling solution. In this case, a second column was filled with a resin, Amberlite XAD-2, which captures PAHs entering the solution through the soil column, cleaning it of hydrocarbons (induced desorption). The results obtained for induced desorption and free desorption with reposition showed that liberation of PAHs in the presence of resins was higher (7%) as opposed to free desorption (below 0.3%). These two experiments demonstrated low mobilization of PAHs.

A third column test was performed using a non ionic surfactant, Ivey-sol® 106, 100 μg g⁻¹ of soil below the CMC in the recycling solution. The introduction of Ivey-sol® 106 at 0.005%w/v increased desorption of PAHs to 32%, thus demonstrating the potential for increased bioavailability of the PAHs for bioremediation of the soil.

Keywords:

• Hydrocarbons
• non-ionic surfactant
• bioremediation

Acknowledgments

This work has been carried out in the framework of a project funded by the Spanish Ministry of Science and Education (Plan Nacional I+D+I, CTM2004-05832-C02-01).

We wish to acknowledge the technical support of J.C. Díaz Reyes and M.L. Sevillano. We also wish to thank the inestimable comments and help of Dr. David Craft.