|Title||Case study of steady oxygen concentration gradients in a groundwater plume from a highway infiltration basin|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Authors||Ostendorf DW, Park C, Rotaru C, Pereira MS|
|Journal||Journal of Environmental Engineering|
|Keywords||Case studies, Dissolved oxygen, groundwater pollution, Highways and roads, Infiltration, Runoff, Stormwater management|
We measure and model the steady transport of specific conductivity and dissolved oxygen through a groundwater plume from a highway infiltration basin in southeastern Massachusetts. Specific conductivity is treated as a conservative surrogate for runoff contamination, and the data calibrate a 0.27-m vertical dispersivity αα of the aquifer and the bottom streamline elevation of the plume, which falls to an 8-m depth below the water table. The dissolved oxygen degrades as a first order reactant in the plume to levels below 1 mg/L, with a decay constant λλ of 0.12 day−10.12 day−1 . The latter may be attributed in part to the historical use of an alternative de-icing agent calcium magnesium acetate on the highway, since acetate is a readily biodegradable substrate for microorganisms. The calibrated kinetics suggest that plume microbes and geochemistry degrade oxygen over two orders of magnitude faster than their ambient groundwater counterparts, which impose a linear decrease of dissolved oxygen concentration below the plume. Simulations suggest that the anoxic groundwater plume extends 1,600 m downgradient of the infiltration basin, a distance that will shorten by an order of magnitude if salt is used exclusively to de-ice the highway.