THE EFFECTS OF SEDIMENT CONTACT TIME ON K-OC OF NONPOLAR ORGANIC CONTAMINANTS

Mobility of nonpolar organic contaminants depends upon partitioning be tween sediment solids and interstitial water. The objective of this st udy was to measure the constancy of K-oc values for polychlorinated bi phenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs) over time. Two PCBs and one PAH were incubated and sampled periodically over a 6 month period. Results demonstrated that as time of contact increased, the value of K-oc increased, reflecting a decrease in the truly disso lved contaminant concentration in the interstitial water. The data als o showed a marked dependence of K-oc on the source of organic carbon a nd a 2 to 17 fold deviation of measured K-oc values from values predic ted by empirical relationships. Therefore, empirical data may be the o nly truly reliable alternative for determining mobility potential of t hese contaminants.