Document rxRD07Gva5XoEjrGX1q6VMa1a

BACK TO MAIN SOIL ADSORPTION TEST SUBSTANCE Identity: Perfluorooctanesulfonate; may also be referred to as PFOS or FC-95. (1Octanesulfonic acid, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluoro-, potassium salt, CAS # 2795-39-3) Remarks: The test substance is a white powder. Sample was re-crystalized from a production lot of FC-95. Purity determined to be 97.9% by LC/MS, 1H-HMR, 19F-NMR and elemental analyses techniques. METHOD_____________________________________________________ Method: Based on OECD 106 GLP (Y/N): Yes Year completed: 2001 Statistical methods: Statistical analysis and plotting of the data was done according to OECD Method 106 using Microsoft Excel. Temperature: Room Temperature (19-30C) Stock and test solution preparation: The test concentrations and conditions were determined in a Preliminary experiment. For the definitive experiment, test solutions were made by diluting a stock solution of un-radiolabeled Perfluorooctanesulfonate to a final test substance concentration of approximately 0.5 mg/L in aqueous 0.01 M CaCl2. Soil Class Soil Characteristics: C la y Loam Source Lot Number P h y s ic a l Description % O rganic C a rb o n % Sand % Silt % Clay CEC (m eq/100g) Agvise Laboratories, Northwood, ND 00-2407 Agvise Laboratories, Northwood, ND 00-2404 1.00 mm air- 1.00 mm air- dried, 0-6" deep dried, 0-6" deep 2.6% 4.9% 16% 39% 22% 50% 62% 54.5 11% 23.9 pH in 0.01 M C a C l2 7.2 7.4 1 Value is for pH in water not pH in 0.1M CaCl2 Clay Loam Agvise Laboratories, Northwood, ND 00-2405 1.00 mm airdried, 0-6" deep 2.6% 21% 46% 33% 24.7 6.0 Sandy Loam Agvise Laboratories, Northwood, ND 99-2564 R iv e r Sedim ent Agvise Laboratories, Northwood, ND 00-2046 1.00 mm air- 1.00 mm air- dried, 0-6" deep dried, 0-6" deep 2.8% 1.3% 58% 39% 22% 42% 20% 19% 23.3 17.5 7.81 7.7 Dom estic S lu d g e NIST, from Denver, CO POTW 2781 200 mesh, oven-dried, sterilized Not analyzed Not analyzed Not analyzed Not analyzed Not analyzed Not analyzed BACK TO MAIN Test Conditions: Adsorption Kinetics: Replicate study samples containing the soils (or sediments or sludges) were equilibrated by shaking for at least 12 hours at room temperature with 0.01 M CaCl2. Study samples were dosed with the test substance at approximately 0.5 mg/L and placed on an orbital shaker. Replicate sets of these study samples were removed at designated time points throughout a 48 hour time period. Study samples were then prepared and analyzed for the target analyte. The adsorption kinetics were determined using this data. The last set of study samples (48 hour) were saved and used for the desorption kinetics portion of the method. Desorption Kinetics (One concentration): After the adsorption kinetics experiment, the 48 hour study samples were centrifuged and the aqueous phase removed. The volume of solution removed was replaced by an equal volume of 0.01 M CaCl2 without test substance. The new mixture was agitated until the desorption equilibrium was reached. During a 48-hour period, at defined time intervals, small aliquots of the aqueous phase were removed and analyzed for the target analyte. The desorption kinetics were determined using this data. RESULTS_______________________________________________________ Soil Type Clay Clay Loam Sandy Loam River Sediment Domestic Sludge Adsorption Kinetics of PFOS, 1:5 Soil:Solution Ratio, 48 Hour Time Point A verage Distribution c o e ffic ie n t, Kd, L/g Percentage of O rg a n ic C a rb o n in S o il A verag e O rganic Carbon norm alized Adsorption C o e ffic ie n t, Koc, L/g 0.0183 2.6 70.4 0.00972 2.6 37.4 0.0353 2.8 126 0.00742 1.3 57.1 < 0.120 Not available Not calculable All matrices adsorbed the test substance strongly. The sludge demonstrated very strong adsorption (>96%) and PFOS was not detected in the extracts. The data indicate that adsorption occurred within the first few hours of exposure and the test substance concentration did not vary significantly after 16 hours. Apparent Desorption Kinetics of PFOS, 1:5 Soil:Solution Ratio, 48 hour Time Point Soil Type D e so rp tio n C o effic ie n t, K des, L/g Barnes Loam 0.0000471 Clay Loam 0.0000158 Clay 0.0000349 River Sediment 0.0000100 Domestic Sludge < 0.000237 BACK TO MAIN The test substance was poorly desorbed from the soil/sediment/sludge matrices during the 48hour study period. The river sediment displayed the most desorption at 39% after 48 hours. The sludge samples did not desorb a detectable amount of test substance. Desorption that did occur was accomplished rather quickly; after the 8 hour time point the test substance concentration did not vary significantly. Adsorption Isotherms Soil type Log KadsF Kads^CO Clay -1.2515 0.0560 Clay Loam -1.3762 0.0421 Sandy Loam -1.0369 0.0919 River Sediment -2.0261 0.0094 Domestic Sludge -1.246 0.0568 (1) Freundlich adsorption coefficient Regression constant, 1/n 0.884 0.841 0.829 0.989 1.2581 Regression Constant, n 1.13 1.19 1.21 1.01 0.795 . Desorption Isotherms Soil Type Log K desF KdesF(1) C la y -0.653 Clay Loam -1.084 Sandy Loam -0.981 River Sedim ent -1.41 Dom estic Sludge 1.47 (1) Freundlich desorption coefficient 0.222 0.082 0.104 0.039 29.5 Regression Constant, 1/n 0.935 0.954 1.01 1.02 0.327 Regression Constant, n 1.07 1.05 0.988 0.984 3.06 Freundlich adsorption isotherms relate the amount of test substance adsorbed on the soil to the amount present in the aqueous solution at equilibrium. The values calculated for the regression constant indicate that the data obtained for the test substance over two orders of magnitude is slightly non-linear. CONCLUSIONS Perfluorooctanesulfonate (PFOS) appeared to adsorb strongly to all of the soil/sediment/sludge matrices tested. PFOS would not be considered to be qualitatively mobile as per OECD Guideline106 (1/21/00) as the Kd values are > 1 mL/g. The test substance, once adsorbed, does not desorb readily, even when extracted with an organic solvent. In either case, adsorption or desorption, an equilibrium is achieved in less than 24 hours, with substantial adsorption (>50%) occurring in some of the time 0 samples after approximately 1-minute of contact. The test substance exhibited low mobility in all of the adsorbants tested. The shape of the PFOS adsorption isotherm (H-type) indicates a very strong chemical/adsorbent interaction. Because PFOS is a strong acid, it likely forms strong bonds with soils, sludge and sediment via the mechanism of chemisorption. BACK TO MAIN Submitter: 3M Company, Envi ronmental Laboratory, P.O. Box 33331, St. Paul, Minnesota, 55133 DATA QUALITY___________________________________________ Reliability: Klimisch ranking 1. REFERENCES 3M Technical Report "Soil Adsorption/Desorption Study of Potassium Perfluorooctanesulfonate (PFOS)". Mark E. Ellefson, Project Number E00-1311, Final Report Completion Date June 4, 2001. OTHER Last Changed: June 27, 2001