Nonequilibrium sorption of organic chemicals by low organic-carbon aquifer materials

The objective of the work reported herein was to investigate nonequilibrium sorption of four representative organic chemicals by five aquifer materials comprised of low organic carbon (i.e., less than 0.1%). The results of miscible displacement experiments were analyzed using a one-dimensional advective-dispersive transport model, wherein sorption is considered instantaneous for a fraction of the sorbent and rate-limited for the remainder. An inverse correlation between the desorption rate constant and the equilibrium sorption constant was evident. It appears that all five aquifer materials exhibited similar nonequilibrium behavior, which suggests that the sorbent has only a secondary effect on the nature of nonequilibrium sorption. In addition, the data obtained for the aquifer materials were similar to data obtained for sorbents of higher organic-carbon contents.