Characterization of mass transfer of lower chlorinated benzenes from contaminated sediment into water

Abstract

Mass transport of chlorinated benzenes as found at the Petro-Processors of Louisiana, Inc. (PPI) Superfund site was characterized for a range of flow rates in small streams. At this site hazardous waste was historically disposed of in unengineered pits. Hexachlorobenzene and lesser chlorinated degradation products were found among other compounds. As waste was being disposed into unengineered pits, it seeped to lagoons and sediments of Baton Rouge Bayou (BRB), which flows through and nearby the former disposal areas. Characterization of the transport and fate of chlorobenzenes at PPI is an integral part of the Monitored Natural Attenuation (MNA) remedy currently underway. Laboratory experimental results and mathematical model predictions of the flux of 1,3-dichlorobenzene (1,3-DCB) from sediments into water are presented. 1,3-DCB was studied as individually and as part of a mixture of four contaminants with 1,2-DCB, chlorobenzene (MCB) and trichlorobenzene (TCB).Surficial sediments were collected, spiked with contaminants and leached to determine flux over time. Two advection–dispersion models were tested and the effect of low, cycling and fast stream flow on the contaminant flux was assessed. Model results suggest that tortuosity and effective diffusivity are related effective system predictors and descriptors. Statistical analysis supports the models’ predictive capabilities.