Experimental determination of 1,4-dioxane sorption in glacial sediments

Abstract:

Despite its widespread occurrence and recognition as an emerging groundwater contaminant of concern, the sorptive behavior of 1,4-dioxane on natural sediments remains poorly characterized. Physicochemical properties, such as its miscibility in water and low K_ow, may limit 1,4-dioxane sorption in natural systems. Nevertheless, accurate distribution coefficients for commonly occurring sediments are needed to predict 1,4-dioxane migration rates and model solid phase storage capacity in aquifers. Reported empirical 1,4-dioxane retardation factors range from 1.0 to 1.6, implying linear isotherm K_d values of 0.0 to 0.10 cm³/g, highlighting the large uncertainty in 1,4-dioxane sorption behavior.

The objective of this study is to quantify 1,4-dioxane sorption isotherms for homogeneous materials frequently found within Pleistocene glacial sediments. Sorption isotherms were developed in a series of ongoing bench top batch experiments utilizing homogeneous illite, kaolinite, bentonite (montmorillonite), silica (Ottawa sand), and calcite and dolomite powders across 1,4-dioxane concentrations ranging from 100 to 10,000 µg/L (ppb). Nanopure water matrices were buffered with sodium bicarbonate to a pH of 8.3 and an ionic strength of 0.043. Aqueous samples were prepared using a frozen micro-extraction technique, and analysed for equilibrium 1,4-dioxane concentrations using a Thermo Scientific Triple Quad GC/MS-SRM. Preliminary results indicate quantifiable sorption to the homogeneous materials as well as heterogeneous glacial sediments comprised of similar mineralogies. K_d values derived from these experiments can be used to estimate sorbed dioxane mass in a variety of sediments contaminated with 1,4-dioxane.