New Mexico Geological Society Annual Spring Meeting — Abstracts

Surfactants have gained recent attention with regard to their potential use in environmental remediation of soils. The effectiveness and efficiency of using sutfactants for removal of organic or heavy metal contaminants will depend in large part on their impact on soil hydraulic properties. Likewise, surfactants also find their way into the soil environment through application of agrochemicals, municipal waste water effluent, and municipal waste sludge to agricultural fields. Since soil hydraulic properties influence crop productivity, surfactant impacts need to be considered.

Testing was done on two different soils (Teller loam and Slaughterville sandy loam) using four surfactants. Two of the surfactants were cationic (TDTMA-Br and POPMDEA-CI), one was anionic (Na-DBS), and the fourth, nonionic (AE) Sutfactants were applied at concentrations of 0.25%, 0.5% and 10% of dry soil weight. Experiments were conducted under both saturated and unsaturated conditions. Surfactant impacts were investigated with regard to saturated soil . hydraulic conductivity, unsaturated soil moisture diffusivity, moisture profile penetration in unsaturated soil, and evaporation from initially saturated soil.

Falling-head permeability tests on 0.5% and 1.0% surfactant treated soils show POPMDEA-Cl, Na-DBS, and AE to substantially reduce saturated hydraulic conductivity. Reductions in some cases (1.0% POPMDEA-CI:Slaughterville, 0.5% Na-DBS:Slaughterville, and 1.0% Na-DBS:Slaughterville) were three to four orders of magnitude. TDTMA-Br had little effect on saturated soil hydraulic conductivity. Transient horizontal column experiments were used to measure surfactant affects on unsaturated soil moisture diffusivity and moisture profile
penetration in unsaturated soil. To some extent, all four sutfactants altered the diffusivity versus moisture content relationship of the two soils tested. The presence of POPMDEA-CL Na-DBS, and AE significantly reduced moisture profile penetration in both Teller loam and Siaughterville sandy loam columns . A controlled humidity chamber was used to measure evaporation losses from initially saturated soil. Soils treated with 1.0% POPMDEA-Cl, 1.0% Na-DBS, and 1.0% AE exhibited less evaporative loss than either the unaltered soils or the 1.0% TDTMA-Br treated soils. Overall test results indicate that sutfactants can have a considerable influence on soil hydraulic properties. Regardless of purpose, this is something that needs to be contemplated before surfactants are introduced at high concentrations into the soil environment.