Equilibrium sorption of tributyltin chloride (TBT) was measured on selected estuarine and freshwater sediments. Isotherms from 24-h equilibrations were linear, with sorption coefficients between 1.1 x 10' and 8.2 x lo3 L/kg. The similarity of sorption and desorption coefficients for these sorbates showed that TBT sorption is reversible. Sorption coefficients decreased with increasing salinity and varied by a factor of 2 over the salinity range 0 to 34%0. Desorption kinetics indicated an initial fast rate followed by a slower rate of desorption, similar to published data for metal ions and hydrophobic organic molecules on sediments. Water and sediment concentrations of TBT at locations in the Chesapeake Bay system were used to calculate apparent sorption coefficients, which generally agreed with laboratory-measured sorption coefficients. Exceptionally high apparent sorption coefficients were found near areas of high vessel activity and may be due to TBT paint chips in the sediment.
Degradation rates of benzene, p-xylene, naphthalene, and o-dichlorobenzene have been measured in a heterogeneous, unconfined aquifer during a pulse injection experiment at Columbus Air ForceBase, Columbus, Mississippi. Dissolved oxygen in the pulse plume maintained aerobic conditions. Degradation kinetics calculated from the complete field data set were approximately first order with the following rate constants: benzene, 0.0070 d-l; p-xylene, 0.0107 d -•; naphthalene, 0.0064 d -l; and o-dichlorobenzene, 0.0046 d-1. Reaction rates were also calculated from a near-field subset of the data using a model based on the hydrologic characteristics of the aquifer. Shapes of the degradation rate curves were consistent with microbial degradation processes. Maximum degradation rates obtained are presumed to be characteristic of the microbial population metabolism. Carbon 14-1abeled p-xylene was included in the injection solution to permit detection of degradation products. This technique is suggested for future field experiments, because it distinguishes solute degradation from solute losses by sorption and evaporation and allows mass balance to be demonstrated throughout the course of the reaction in the aquifer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.