Volatile loss of PCB Aroclors from subaqueous sand

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 degrees 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 PCBs and other hydrophobic compounds from wet soils and sediments may be rapid and substantial. Further work is needed to elucidate the implications for analytical procedures, remedial actions, and the global mass balance of PCBs.