Distribution, sources and behavior of 1,4-dioxane and glymes in the aquatic environment
The research focuses on investigation of six hydrophilic ethers: ethyl tert-butyl ether (ETBE), 1,4-dioxane, monoethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), and tetraethylene glycol dimethyl ether (tetraglyme) with respect to their distribution and behaviour in the environment.
The selected ethers are highly miscible in water and have Henry’s law constants ranging from 1.04×10-14 to 1.64×10-3 atm x m3 x mol-1 ensuring low volatility from aqueous solutions. Based on their octanol-water partition coefficient (log Pow= - 1.03 to 1.92) they exert negligible potential for bioaccumulation and are only weakly retarded by sorption to soil particles or suspended solids. Therefore, the main target compartment of ETBE, 1,4-dioxane and glymes is presumed to be the hydrosphere. Moreover their physiochemical properties combined with their low biodegradability imply difficult removal from water and wastewater, which greatly increases the potential for surface-, groundwater and drinking water contamination. Ethers chosen for this study are solvents with a broad scope of industrial applications. 1,4-dioxane is used as a processing solvent in the production of adhesives, paint strippers, dyes, degreasers, fabric cleaners, paper, electronics and many more. It is also formed as an undesired by-product in industrial processes, such as synthesis of polyester and ethoxylation. Ethyl tert-butyl ether (ETBE) is a fuel oxygenate used in numerous countries as an antiknock agent and to enhance fuel combustion. In German, replacement of ETBE by ethanol as fuel additive is continuously increasing since 2007. Glycol dimethyl ethers (glymes) are saturated polyethers, commonly used as reaction solvents in the area of pharmaceutical or specialty chemical production. They also find widespread use in the manufacturing of products such as printing inks, paints and coatings, adhesives, batteries, break fluids, and many other sectors.
Solid phase extraction in combination with GC/MS-SIM was validated for the six hydrophilic ethers [Stepien and Püttmann, 2013]. The method was successfully applied to various environmental samples.
Samples from the surface water, groundwater, bank filtration sites (drinking water) and sewage treatment plants (STPs) are being collected at several locations in Germany and Poland.
Ongoing studies and results
Initially, spot samplings of seven water bodies in Germany were done to determine the occurrence of the selected contaminants. These and further samplings revealed a ubiquitous presence of 1,4-dioxane in many surface water samples including rivers Main, Rhine and Oder. The widespread sampling campaign of the Oder River showed significant concentrations of triglyme and tetraglyme (>100 ng/L). Their possible sources in the Oder River are currently investigated. Moreover, all of the glymes were present at various locations in the Rhine River above their detection limit (ranging between 12-44 ng/L). Results of the bank filtration and groundwater studies from the Oderbruch area show that 1,4-dioxane and glymes are not readily biodegradable and, therefore persist in the anoxic environment. Currently samples from other sites that produce drinking water from bank filtration are investigated for the occurrence and removal of the six hydrophilic ethers. Additionally, samples from the STPs are being collected, in order to determine the contribution of wastewater to surface water loading with 1,4-dioxane and glymes.
Stepien DK, Püttmann W. Simultaneous determination of six hydrophilic ethers at trace levels using coconut charcoal adsorbent and Gas Chromatography/Mass Spectrometry. Anal Bioanal Chem. 2013; 405: 1743-1751