Contaminant transport and mass transfer to runoff including infiltration

Abstract

Experiments were conducted in a flume (3.0 meter long, 0.3 meter wide by 0.3 meter deep) to examine chemical loss to surface runoff. The bottom of the flume was made of a perforated steel plate, which allowed infiltration to occur during the runoff event. Three experiments were conducted. The objective of the first experiment was to introduce a calcium chloride solution as surface flow into the flume which was pre-saturated with calcium bromide. This experiment allowed the transfer of chemicals from soil to runoff to be examined. The second experiment was the reverse of the first experiment, i.e. the soil was saturated with calcium chloride and the surface flow contained calcium bromide. This experiment was done to examine chemical transport from runoff to the soil. In the last experiment, the soil was saturated with a mixture of calcium bromide, sodium benzoate, and pentafluorobenzoic acid (PFBA), and the surface flow contained calcium chloride. The sodium benzoate was chosen to examine biodegradation. The PFBA and bromide, both non-reactive tracers, have different aqueous diffusion coefficients. The results obtained for these two were compared to help determine if the mass transfer in the soil mainly is due to flow, or if diffusion contributes. With this research it has been shown that there are several factors influencing chemical loss to runoff infiltration, biodegradation, and there are also suggestions that there is transfer due to diffusion processes.