Environmental Fate of 1,2,3,4,7-Pentachlorodibenzo-p-Dioxin in a Canadian Prairie Soil

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Abstract
The fate of 1,2,3,4,7-pentachlorodibenzo-p-dioxin (P5CDD) was studied in a Canadian prairie soil under field conditions by applying 14C-labelled P5CDD to a series of soil microplots and sampling the 0–2 and 2–5 cm depths over a period of 2 years. Analysis by HPLC-LSC revealed that, although P5CDD dissipated from the plots with a half-life of approximately 1.1 y, leaching and biodegradation were unable to account for the observed losses. Only 1.3% of the applied 14C-P5CDD appeared in the 2–5 cm depth at 639 days indicating minimal leaching during the course of the experiment. Furthermore, since only 0.9% of the applied radiolabel appeared as extractable degradation products at day 639, biodegradation was not an important loss pathway for P5CDD in soil. Nonextractable 14C, representing an irreversibly bound fraction of P5CDD, stabilized at approximately 10% leaving roughly 70% of the radiolabel unaccounted for at day 639. The observed losses are attributed to volatilization of parent P5CDD from the soil plots.