Sorption of fulvic acid on aluminum oxide and desert soil

Abstract

Four batch and four column experiments were conducted to investigate the sorption of salicylic acid onto aluminum oxide. Nine column experiments were performed using fulvic acid as a sorbate, and aluminum oxide and a desert soil with a low fraction organic carbon (f(OC)) ( 0.009 percent) as sorbents. Batch experiments provided estimates of partition coefficient that were eight to ten times larger than column estimates. A two-site kinetic model was used to interpret the observed tailing of breakthrough curves. Kp estimates for fulvic acid on desert soil ranged from 3 to 23 cm³/g. The time scale of the desorption reaction is 12 days. The majority of the sorption sites appear to be kinetically controlled. Results suggest that recharge of untreated Central Arizona Project water through desert washes will remove only 10-15 percent of the fulvic acid present after two void volumes have infiltrated. This may eventually contaminate existing groundwater supplies with trihalomethane precursors.