A series of experiments were conducted to measure the rate of volatile loss of PCBs from subaqueous quartz sand spiked with Aroclors 1242, 1248, 1254, and 1260 under laboratory conditions (20 °C, 25% relative humidity). Volatilized PCBs were trapped on Florisil columns attached to a 1.5-L evaporation chamber through which 1.2 L/min of filtered air was drawn for a 24-h period. PCB losses ranged from 20 to 65% and were inversely correlated with the chlorine percentage of the aroclors (R 2 = 0.97). Congeners with the fewest number of chlorines in each aroclor were preferentially lost. In comparison, sediment from a Federal Superfund site along the St. Lawrence River, originally contaminated with Aroclor 1248, lost 19% of its PCB total during a similar experiment. Several orthochlorinated congeners, produced by anaerobic biodegradation, were preferentially lost, and four of these (2/2; 2/6; 2; 26/2) accounted for >55% of the total loss. This work suggests that under certain conditions the volatile loss of PCB...