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 PCBs
and other hydrophobic compounds from wet soils and sedi
ments 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.
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