Sorption of trichloroethene onto stylolites

Batch and double reservoir diffusion cell experiments are used to investiga te sorption of trichloroethene onto stylolites. Stylolites are common featu res in carbonate rock formations, and might contain high amounts of organic matter. Due to the hydrophobic character of TCE, its transport in fracture d carbonate aquifers could be significantly affected due to these aforement ioned features. No research has been carried out to evaluate the impact of stylolites on organic pollutant transport. The main objectives of this expe rimental research are to verify TCE sorption onto stylolites, and to derive sorption and diffusion parameters describing the solute/rock interaction. Test results show that stylolites from the Lockport Formation in Southern O ntario, Canada contain significant amounts of organic carbon. Discrepancies are noted between carbon analyzer data and estimates from batch experiment s and these might be due to TCE sorption also onto a clay mineral phase in stylolites or due to selective sampling. Adsorption and desorption behavior of TCE is investigated in specially designed double reservoir diffusion ce lls made out of stainless steel and Teflon. Three semi-analytical solutions for one-dimensional, reactive tracer migration through a porous medium are derived and used to evaluate TCE time-concentration profiles. Experimental data can best be modeled using a kinetic Langmuir sorption formulation wit h a maximum sorption capacity of 1.3 to 4.6 mu g/g and a kinetic sorption c onstant of 4 x 10(-7) to 5 x 10(-7) l/mg s(-1). TCE desorption into the exi t reservoir is found to be a very slow kinetic process. No retardation is o bserved during TCE migration through a clay and organic matter free dolosto ne sample. TCE seems not to interact with calcareous mineral phases and mov es conservatively. Bromide diffusion curves yield geometry factors (gamma) for dolostone ranging between 0.05 and 0.13. From this study it can be conc luded that TCE sorption is of importance when modeling TCE migration in fra ctured, stylolitic limestone aquifers where diffusion into the rock matrix takes place. Temporal TCE storage in rock matrix stylolites and fracture wa ll stylolites has to be taken into consideration when evaluating actions of remediation at organic spill sites. (C) 1999 Elsevier Science B.V. All rig hts reserved.