PCB mixtures in surface deposits composed of core sand and ash from an aluminum foundry are enriched (3.6-9.4) in chlorine percentage relative to deeper horizons. The deeper materials closely match (R-2 = 0.902-0.962) Aroclor 1248, the aroclor used on-site and recovered from the floor inside the foundry (R-2 = 0.998). This similarity suggests the more deeply buried PCBs have been stable and immobile for a 20-40 yr period. Chlorine enrichment upward is interpreted as the result of volatilization of lower and orthochlorinated congeners from surficial materials during repeated water evaporation. These results suggest surficial deposits contaminated by PCBs may be a significant source of lower ortho-chlorinated PCB congeners to the atmosphere and that buried PCBs can remain unchanged for decades. Comparison with sediments contaminated with Aroclor 1248 and known to have undergone anaerobic microbial dechlorination, indicates that Aroclor 1248 can be transformed to PCB mixtures enriched or depleted in chlorine by environmental processes. References: 20
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