TEMPERATURE-DEPENDENT SORPTION OF NAPHTHALENE, PHENANTHRENE AND PYRONE TO LOW ORGANIC-CARBON AQUIFER SEDIMENTS

Sorption experiments were conducted with naphthalene, phenanthrene, an d pyrene on low organic carbon sediments at 4 and 26 degrees C using b atch and column techniques. Experimental controls ensured the absence of biologic and photolytic activity and colloid-free solution supernat ants. Equilibrium distribution coefficients (K-d) increased 1.1-1.6 ti mes with a decrease in temperature of 22 degrees C. Fraction instantan eous sorption (A values did not change significantly with a decrease i n temperature of 22 degrees C. Desorption rate constants (k(2)) decrea sed 1.2-2.6 times with a decrease in temperature of 22 degrees C. Time s 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 aque ous phase and small amounts of organic matter(f(oc) = 0.02%) on the se diments. The temperature dependence of K-d and k(2) may be small as co mpared to the effects of heterogeneities in field-scale aquifer system s. Thus, thermal gradients may not be of major importance in most satu rated subsurface regimes when predicting solute transport. However, aq uifer remediation pump-and-treat times could be decreased because incr eased temperature decreases both retardation and tailing.