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A Case Study of a Chemical Spill: Polychlorinated Biphenyls (PCBs): 3. PCB Sorption and Retardation in Soil Underlying the Site
Author(s) -
Anderson Michael R.,
Pankow James F.
Publication year - 1986
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr022i007p01051
Subject(s) - sorption , silt , environmental chemistry , partition coefficient , chemistry , polychlorinated biphenyl , soil contamination , volatilisation , soil water , environmental science , adsorption , soil science , chromatography , geology , organic chemistry , paleontology
Condie silt from near a polychlorinated biphenyls (PCBs) and chlorinated benzenes spill site was studied with respect to the sorption and predicted retardation of these compounds. The soil organic carbon fraction ( f oc ) of the silt was measured to be 0.0036 ± 0.00088. The sorption partition coefficient ( K p ′ milliliters/gram) values were: 2,2′,5,5′‐tefrachlorobiphenyl (4‐PCB), 5000; 2,2′,4,5,5′‐pentachlorobiphenyl (5‐PCB), 9400; and 2,2′,4,4′,5,5′‐hexachlorobiphenyl (6‐PCB), 26,000. The direct measurement of the K p values allowed an improved estimation of sorption over that possible with the measured f oc and the available literature K oc data. Mean transport retardation factors ( R ) for 4‐PCB, 5‐PCB, and 6‐PCB in saturated silt were calculated to be 2.7 E + 04, 5.0 E + 04, and 1.4 E + 05, respectively. This implies that dissolved PCBs will move only very slowly through unfractured Condie silt. Since the K p values of the PCBs were not affected when 20 mg/L of 1,2,4‐trichlorobenzene was added to the aqueous phase, PCB transport at the site will not be accelerated by the presence of the chlorinated benzenes. Therefore if fractures are not present in the silt in its middle and lower levels, then there is little chance that the PCBs pose a threat to the underlying Regina aquifer system. R values predicted for 1,2,4‐trichlorobenzene and 1,2,4,5‐tetrachlorobenzene were 120 and 600, respectively; they may also not pose an immediate threat to the underlying aquifer if fractures are absent.