EFFECT OF NATURAL DISSOLVED ORGANIC-MATTER FOUND IN GROUNDWATER ON SOIL ADSORPTION AND TRANSPORT OF PENTACHLOROPHENOL

Kinetic, equilibrium, and transport experiments were performed to quantify pentachlorophenol (PCP) adsorption and mobility in water-saturated soil columns. The effect of natural dissolved organic matter (NDOM, <0.1 mg/L or 15 mg/L) found in groundwater was investigated. While the pH was found to greatly affect the adsorption of PCP, the adsorption rate was not affected by NDOM at either pH 5.4 or pH 6.3. For a low concentration range (PCP <0.4 nmol/mL), the effect of NDOM on PCP adsorption isotherms was negligeable at pH 5.2, 5.4, and 6.1. The breakthrough curves (BTCs) obtained from displacement studies were fitted to the analytical solution of a one-dimensional transport model that assumes a linear isotherm. The BTCs (pH 6.2-6.5) showed that NDOM do not affect the retardation factor for PCP. However, PCP adsorption isotherms obtained from a higher concentration range (PCP <3 nmol/mL) showed that NDOM may increase the adsorption of PCP on soil at pH 5.4 and 6.1.