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  • Electron donor limitations reduce microbial enhanced trichloroethene DNAPL dissolution: a flux-based analysis using diffusion-cells.

Electron donor limitations reduce microbial enhanced trichloroethene DNAPL dissolution: a flux-based analysis using diffusion-cells.

Chemosphere (2012-12-12)
Jo Philips, Roeland Van Muylder, Dirk Springael, Erik Smolders
ABSTRACT

Electron donor limitations likely reduce microbial enhanced trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) dissolution. This study quantitatively examined the relation between the DNAPL dissolution enhancement and the electron donor supply rate. An experiment used diffusion-cells with a 5.5 cm central sand layer, separating a DNAPL layer from an aqueous top layer. Top layers were amended with different concentrations of formate (0-16 mM). The TCE DNAPL dissolution rate increased from no enhancement compared to abiotic dissolution without formate, to a 2.4 times dissolution enhancement with 16 mM formate amended to the top layer. With 2, 4 and 8 mM formate amended the top layer, the TCE diffusion flux out of the DNAPL layer equaled the formate diffusion flux out of the top layer, which illustrates their stoichiometric interdependence under electron donor limiting conditions. In contrast, with 16 mM formate amended to the top layer, the TCE diffusion flux was lower than the formate diffusion flux, demonstrating that the dechlorination kinetics limited the DNAPL dissolution enhancement. The DNAPL dissolution flux under electron donor limiting conditions was readily predicted from the electron donor concentration in the top layer.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Trichloroethylene, JIS special grade, ≥99.5%
Supelco
Trichloroethylene solution, certified reference material, 5000 μg/mL in methanol
Supelco
Trichloroethylene, analytical standard, stabilized with 30 – 50 ppm Diisopropylamine
Sigma-Aldrich
Trichloroethylene, anhydrous, contains 40 ppm diisopropylamine as stabilizer, ≥99%
Sigma-Aldrich
Trichloroethylene, ACS reagent, ≥99.5%