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Mineralization and Volatilization of Polychlorinated Biphenyls in Sludge‐amended Soils
Author(s) -
Fairbanks B. C.,
O'Connor G. A.,
Smith S. E.
Publication year - 1987
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1987.00472425001600010004x
Subject(s) - volatilisation , environmental chemistry , sewage sludge , soil water , loam , chemistry , mineralization (soil science) , calcareous , sewage , environmental science , environmental engineering , soil science , geology , organic chemistry , paleontology
Abstract Polychlorinated biphenyls (PCBs) are toxic organics of concern limiting the reuse of sewage sludge on agricultural lands. The mineralization and volatilization of PCBs ( 14 C‐Aroclor 1254) were monitored for 240 d in three calcareous soils from New Mexico, amended or unamended with sewage sludge. Two first‐order rate constants were used to describe both processes and to compare treatment effects of sludge addition, PCB concentration (5, 50, 500 mg/kg), soil textural class, and length of sludge incubation with soils prior to experimentation. Total loss of PCBs ranged from 8 to 33%. Fifty and 95% disappearance times ranged from 2.5 to 5.9 yr and 6.1 to 26.3 yr, respectively. Treatment effects on total loss closely paralleled those of volatilization. Volatilization of organics ranged from 5 to 31%, and was the major means of loss of 14 C in unamended soils and all 500 mg PCB/kg treatments. Volatilization, and thus environmental transport, was decreased by sludge addition. Exposure of the soil to sludge prior to experimentation had no effect on volatilization when compared to fresh sludge additions. Carbon‐14‐organic volatile loss was greater in two sandy loams than in a clay soil. Comparing PCB concentrations, volatilization was generally greatest at 50 mg/kg and least at 500 mg/kg, with comparatively smaller differences between 5 and 50 mg/kg. Degradation of 14 C‐Aroclor 1254 to 14 CO 2 ranged from 1 to 11%. Overall, 14 CO 2 evolution, and thus detoxification increased with sewage sludge addition and decreased with increasing PCB concentration. Mineralization exceeded volatilization in sludge‐amended soils at 5 mg PCBs/kg. During the first 60 d of incubation, previous exposure of the soil to sewage sludge increased mineralization in the 5 and 50 mg PCB/kg treatments. In no case did sewage sludge additions increase the environmental hazard of Aroclor 1254 in these soils.