Sorption experiments were conducted with naphthalene, phenanthrene, and pyrene on low organic carbon sediments at 4 and 26 ??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 ??C. Fraction instantaneous sorption (F) values did not change significantly with a decrease in temperature of 22 ??C. Desorption rate constants (k2) decreased 1.2-2.6 times with a decrease in temperature of 22 ??C. Times to equilibrium were at least 40 h. The magnitude of observed K(d) and k2 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 k2 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.
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Temperature-dependent sorption of naphthalene, phenanthrene, and pyrene to low organic carbon aquifer sediments