Temperature-dependent sorption of naphthalene, phenanthrene and pyrone to low organic carbon aquifer sediments

Sorption experiments were conducted with naphthalene, phenanthrene, and pyrene on low organic carbon sediments at 4 and 26 degrees C using batch and column techniques. Experimental controls ensured the absence of biologic and photolytic activity and colloid-free solution supernatants. Equilibrium distribution coefficients (K-d) increased 1.1-1.6 times with a decrease in temperature of 22 degrees C. Fraction instantaneous sorption (A values did not change significantly with a decrease in temperature of 22 degrees C. Desorption rate constants (k(2)) decreased 1.2-2.6 times with a decrease in temperature of 22 degrees C. Times to equilibrium were at least 40 h. The magnitude of observed K-d and k(2) values and the effect of temperature on K-d (e.g., low enthalpy of sorption) are consistent with sorbate partitioning between the aqueous phase and small amounts of organic matter(f(oc) = 0.02%) on the sediments. The temperature dependence of K-d and k(2) may be small as compared to the effects of heterogeneities in field-scale aquifer systems. Thus, thermal gradients may not be of major importance in most saturated subsurface regimes when predicting solute transport. However, aquifer remediation pump-and-treat times could be decreased because increased temperature decreases both retardation and tailing.