Document LJNLOOMVd8dRpXzxzkraR0NvX

Attachment to Letter to C. Auer Dated May 4, 2000: Environmental Studies on Perfluorooctanesulfonates (Post-1975) AR3&-O055 Physical/chemical Properties T itle Laboratory or A uthor D eterm ination o f the M elting Point/M elting R a n g e o f P F O S ; Boiling W ildlife /' Point (N ot C onducted) International, Ltd. Determination of the V ap or Pressure of P F O S Using the Spinning Wildtifg,-- ^ 2 Rotor G uage Method International, Ltd. PFOS: Determ ination of the n-O ctan ol/W ater Partition Coefficient,^ W ildlife y by the Shake Flask M ethod - A N on-G LP Feasibility Study i p ^ ^ Support o f W ildlife International, Ltd. Project N u m b e r4 T C -1 0 8 International, Ltd. Com pletion D a te __ Robust Sum m aries, Final R eport, Protocol 5/5/99 Robust Sum m ary, Final R eport, Protocol 2/11/00 Robust Sum m ary, Feasibility Study 1 3M/W ildlife International, Ltd., U of Trent f- D eterm ination of the W a tp rS o lu b ility of P F O S by the S h ake Flask Method s' W ildlife International, Ltd. c-Technical R e p p rt' Solubility M easu rem en ts on F C -9 5 3M Env. Lab y Solubility Estim ate of F C -95 by use of Xertex T O C Analyzer Xertex, 3M Env. Lab 3/19/99 4 /2 6 /0 0 2/6/81 6/29/82 Robust Sum m ary, Letter Report Robust Sum m ary. Final R eport, Protocol B rief Robust Sum m ery, critique from Endw in T u c ke r (3 /1/9 3), Final Report Brief robust sum m ary, fetter report Environmental Fate and Transport Title Adsorption of FC 95 and F C 143 on Soil (Note: the 3M Env. Lab I sum m ary is titled: S u m m ary of th e Soil Adsorption study of the Potassium Salt of Perfluorooctanesulfonic acid, 7/22/98) FC-95/Photolysis Study Using Sim ulated Sunlight. (Note: the 3M Env. Lab sum m ary is titled: sum m ary o f Photolysis Study Using Simulated Sunlight on the Potassium Salt of Perfluorooctanesulfonic acid) Biodegradation Studies o f Fluorocarbons (8/1 2 /7 6 ) report and Biodegradation Studies o f Fluorocarbons - III (7/1 9 /7 8 ) report. (Note: both reports sum m arized with one robust sum mary) B O D /C O D results for F C -94-X (Li salt of P FO S) i B O D /C O D results for F C -9 9 (D EA salt of P FO S) Transport betw een environm ental com partm ents (fugacity (. m odeling) included in letter from Don M ackay on the air/w ater partitioning coefficient calculations A nalysis for fluorochem icals in Bluegill fish. Laboratory or A u th o r 3M Env. Lab 3M Env. Lab 3M Env. Lab Pace Analytical 3M Env. Lab DMER 3M Env. Lab Com pletion D ate Type 2/27/78 Robust Sum m ary, 3M Env. Lab Sum m ary, C om m ents from S tephen A. Boyd from M S U , Final R eport 1/9/79 Robust Sum m ary, 3M Env. Lab Sum m ary, Final Report 8/12/1976, 7/19/78 Brief R obust Sum m ary, 2 Final R e p o rts 3/30/94 6 /8 /7 9 Com puter-generated S um m ary o f Testing R esults Robust Sum m ary and final R eports No date Robust Sum m ary, letter report 5/17/79 Robust Sum m ary. Technical R eport 000172 ENVIRONMENTAL FATE AND TRANSPORT This section presents inform ation and test results from abiotic, and biotic degradation and soil adsorption studies. D egradation studies include hydrolysis, photolysis, and biodegradation. M uch of this w ork is in progress w ith final rep o rts scheduled fo r th e J u n e to August, 2000 timeframe. As these studies progress, there are certain key findings th at can be presented as prelim inary results: 1. T here has been no indication th a t perfluorooctanesulfonate undergoes any degradation from hydrolysis, photolysis, or biodegradation mechanisms. 2. In all hydrolysis and photolysis studies, perfluorooctanesulfonate has not been detected as a degradation product in any conclusive experiment. This prelim inary finding calls into question the assum ption of expected degradation of other fluorochemicals to perfluoroctanesulfonate. 3. In the studies focused on hydrolysis of fluorochemical polymers th at form the structure of the specific industrial and consumer products, it has been determ ined th at these m aterials are relatively stable in the environment. For example, the following half-lives are estimated for various polymers: POLYMER H A L F -L IF E Acrylate and ester 1-5 years Polyethylene glycol based 3-50 years U reth an e >500 years For hydrolysis to occur, polymers m ust be subjected to an aqueous environment, w hich is not expected to occur in a m unicipal o r in d u strial landfill. 4. Relative to photolysis, the current data suggests a hypothesis th at these m aterials will photolyze to carboxylate structures. These structures have much different properties then sulfonates in th at they are much less bioaccum ulative in ecological species. A dditional discussion of these results and ongoing studies will be presented in subsequent submissions and reports. 000173 SOIL ADSORPTION T E S T SUBSTANCE__________________________________________________ Identity: Peilluorooctanesulfonate; may also be referred to as PFO S or FC-95. (1-Octanesulfonicacid, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8heptadecafluoro-, potassium salt, CAS # 2795-39-3) Remarks field: The test substance is a white powder of uncharacterized purity. This testing is being repeated per current procedures and best available practices. METHOD M ethod: Adsorption-Desorption study using the approach recommended by the U.S. E P A fo r pesticide registration GLP (Y/N): No Y ear (study performed): 1978 Statistical methods: Statistical analysis and plotting of the data was done with the MINITAB package of the 3M TRAC computer service. Tem peratu re: 16-19C Stock and test solution preparation: Test solutions were made by diluting a stock solution of 14C-labeled Perfluorooctanesulfonate. The type of solvent used to make the stock solution is not noted, nor is the activity of the radio-labeled test substance. Rem arks field: The Brill sandy loam soil was characterized as having 57% sand, 36% silt, 7% clay, 2.5% organic matter, 1.5% organic carbon, with pH 6.5 and cation exchange capacity of 15.3 m eq./100 gms. Standard solutions of the 14C-labeled compound were prepared in D.l. water at concentrations of 282 mg/L, 158 mg/L, 90 mg/L, 51 mg/L, and 28 mg/L. Twenty-five ml of each solution was shaken with duplicate 5 gram samples of the soil in a 50 ml polypropylene centrifuge tubes for 24 hours on a wrist shaker at room temperature (16-19C). Desorption extraction were performed with D.l. water after the adsorption phase of the experiment. The samples from the adsorption and desorption experiments were centrifuged individually at 5000 rpm for 10 minutes, after which, three aliquots of each supernatant solution were prepared for scintillation counting. From the raw counting data, compound concentrations were calculated for all of the supernatant solutions. RESULTS 000174 K: 0.99 (N=1) Koc: 66* R em arks field: The linear shape of the adsorption isotherms indicated that perfluorooctanesulfonate adsorption on soil would be independent of concentration. * The study report had calculated a soil / organic carbon partitioning coefficient of 45. After review, it was determined that the value should have been 66 based on the formula (Koc = K' x 100/1,5(% organic carbon); K' = (x/m)/Ce). CONCLUSIONS The study substance is expected to exhibit high mobility in the kind of soil tested and would move with the groundwater. Subm itter: 3M Company, Environmental Laboratory, P.O. Box 33331, St. Paul, Minnesota, 55133 DATA QUALITY____________________________________________________ Reliability: Klimisch ranking 2. This study lacks detail on the stock solution and the purity of the radio-labeled test substance. Additionally, some calculations have questionable reliability. R EFER ENC ES___________________________________________________ 3M Technical Report "Adsorption of FC 95 and FC 143 on Soil." S.K. Welsh, Project 9970612633 Fate of Fluorochemicals, Report No. 1, Feb. 27,1978 O TH ER ________________________________________ ^ _________________ Last changed: 5/2/00 000175 SUMMARY OF THE SOIL ADSORPTION STUDY OF THE POTASSIUM SALT OF PERFLUOROOCTANESULFONIC ACID Introduction Soil adsorption-desorption studies were conducted to indicate the mobility o f potassium perfluorooctanesulfonate in a sandy loam soil. The approach used was that recommended by the U.S. Environmental Protection Agency for pesticide registration. Materials and Methods w The Brill sandy loam soil was characterized as having 57% sand, 36% silt, 7% clay, 2.5% organic matter, 1.5% organic carbon, with pH 6.5 and cation exchange capacity o f 15.3 meq./lOOgms. Standard solutions o f the ,4C-labeled compound were prepared in D.I. water at concentrations o f 282 m g/1,158 m g/1,90 m g/1,51 mg/1, and 28 mg/1. Twenty-five m l o f each solution was shaken w ith duplicate 5 gram samples o f the soil in a 50 ml polypropylene centrifuge tubes for 24 hours on a wrist shaker at room temperature (16-19 C). Desorption extractions were performed with D.I. water after the adsorption phase of the experiment. The samples from the adsorption and desorption experiments were centrifuged individually at 5000 rpm for 10 minutes, after which, three aliquots o f each supernatant solution were prepared for scintillation counting. From the raw counting data, compound concentrations were calculated for all o f the supernatant solutions. Results and Discussion The linear shape o f the adsorption isotherms indicated that potassium perfluorooctanesulfonate adsorption on soil would be independent o f concentration. A soil adsorption coefficient (K) o f 0.99 indicated that this compound would be mobile in this kind o f soil and would move with the groundwater. A soil organic carbon partitioning coefficient (K^) was calculated in this report to be 45. However, after closer examination the K, value should be 66 (K*. = 100 * K / (1.5% organic carbon)). Again, this value indicates high mobility in this kind o f soil. 000176 July 22,1998 MICHIGAN STATE UNIVERSITY DEPARTMENT OF CROP AND SOIL SCIENCES PLANT & SOIL SCIENCES BUILDING M a y 19, 1993 EAST LANSING MICHIGAN 48824-1325 Dr. Robert D. Howell 3M Company 3M Center, Bldg. 2-3E-09 St. Paul, M N 55144-1000 Dear Dr. Howell: Enclosed are my review comments regarding the nine 3M Technicial Reports, recommendations for improving the quality of the individual studies, and some recommendations for future research. Please review this information and let me know if I can be of any further assistance. I do have interest in submitting a research proposal to 3M in accordance with the recommendations for future research. Perhaps we could discuss this further. I enthusiastically support your efforts to obtain information on the environmental fate and behavior of the 3M products. My consulting fee for the work performed to date is $3,200.00 (three and one half days for review of materials and preparation of reports plus one half day consultation with Dr. well at MSU, at $800.00 per day). 4a aamm 1mm Stephen A. Boyd, Pi Professor MSU is an Affirmativ* Actiou/Equai Opportunity Institution 000177 Review o f Technical Report Summary Adsorption of FC 95 and FC 143 in Soil Material and Methods Should give recoveries of compounds in blank (no-soil) experiments. States that polypropylene sorbs less than glass on polyethylene, but doesn't give a numerical value. The large headspace (25 ml in a 50 tube) is undesirable; any losses o f the l4C-label, e.g., from volatilization or sticking to the tube, will inflate the sorption coefficient since the method calculates the amount sorbed by difference between the initial and final equilibrium solution concentrations. Also the 24 hour mixing period seems arbitrary. Were experiments done for different periods o f time to establish that equilibrium was reached within 24 hours? Details on the stock solution are lacking. What solvent was used and what is the specific activity and radiochemical purity of the WC-FC 95. The idea o f using a cotton swab after the draining step is unusual. Hopefully this soil as well as water. The ~20% or less decrease in solute concentration due as high as I 'd like to see it. A 50% or greater decrease would be better. nove -n't This section generally lacks detail that would normally be required for A > Results and Discussion ^ cr The linearity of the isotherm has been shown over the concentration range us demonstrate that the entire isotherm is linear, the linearity must extend to equi concentrations that approach the water solubility of the compound. Do you knov of FC95 or FC143: If not, how were the initial solution concentrations selected'* .j The sorption coefficient (K) of FC 95 appears to be about 1 as indicated. The organic matter normalized sorption coefficient ( K . = K /foJ is = 1/0.025 = 40, or log = 1.6. This is a soil sorption coefficient intermediate between benzene and toluene. It would to examine some additional soils to confirm this K, value. Generally, the K^, converge within a factor of 2 to 3 for different soils. This would increase my coi accuracy of the one measured value. I 've spot checked the soil concentrations of FC-95 for both the sorption a experiments and I get essentially the same values. The calculations look good. The K values for FC 143 is lower than FC 95 indicating that it probably has a solubility. The hystersis in the desorption isotherm is surprising, and has been ov< The sorption isotherm is linear indicating a single sorptive process. The conclusion regarding "three different binding mechanisms ... with stronger binding at higher concentrations and the converse at lower concentrations" is very speculative based on the single experiment. If one examines column I "Amount Desoibed as a Percent of Amount Adsorbed" the values range from 000178 26 to 212 percent, so it's pretty inconclusive. There is a fairly good discussion o f hysteresis in J. Environ. Qual. 12:325-330 by Koskinen and Cheng who observed this phenomena for the weak acid pesticide 2,4,5-T. The causes of hysteresis are varied and complicated and may include microbial degradation of the compound during desorption, and changes in the physical and/or chemical properties of the soil-solution system. For example, desorption using distilled water (as is the case here) could result in soil dispersion so that a clear supernatant solution could not be obtained. This can cause quenching of radioactivity in solution and other problems leading to error. The "material balance" as presented in the report is a little misleading. To obtain a material balance you should measure the amount o f ,4C-activity in soil at the end o f the experiment, and add it to the measured solution concentrations. General Comments. The K*. values calculated here use an organic carbon content o f 2.2% v ` whereas the value stated in the Materials and Methods is 1.5%? The water solubilities are cited as 300 mg/L for FC 95 and > 20g/L for FC 143. Surely the latter value is wrong. If the solubilities are truly that different, then the sorptive properties should be vastly different, which they are not. If FC143 has a solubility of >20,000 mg/L, then I would expect no sorption. This value must be erroneous. Recommendations: 1. Obtaining K, values on additional soils. Determine if is relatively constant. 2. Obtain a true mass balance by measuring ,4C-activity in soil and solution phase. 3. Interpret desorption data more cautiously. 4. Get correct value o f water solubility o f FC 143. 000179 ?r 'forjk C747 11-A TECHNICAL REPORT SUMMARY Data 2/27/78 TO: TECHNICAL COMMUNICATIONS CENTER - 201-2CN (Im portant - I f report sp rin ted on both sides o f paper, send tw o copies to TCC J Division Project Report fitte TO Aurhorls) EE 8 PC Fate of Fluorochemicals Adsorption of FC 95 and FC 143 on soil D. L. Bacon Stephen K. Welsh Notebook Reference #40673, #47704 c c n ia iT V W sttuuHi n f ^ Opn. (Company Confidential) wClooswed .special Authorization) 3M CHEMICAL ^ REGISTRY ^ ! r'f*+- I -1 KEYWORDS: (Select terms from 3M Thesaurus. Suggest other applicable terms.) CURRENT OBJECTIVE: To obtain an indication of FC 95- and FC 143 mobility in sandy loam EE 8 PC - Div. Fluorochemical ,) Soil Adsorption Mobility soil. REPO RT ABSTRACT: (20O-2S0 words) This abstract information is distributed by the Technical Communications Center to alert 3M 'eri to Company R&D. As a part of the Fate of Fluorochemicals Project, an indication of mobility of FC 95 and FC 143 in sandy loam soil was desired. Adsorption-desorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubility data can provide such information. Cid The adsorption coeffi/erits for FC 95 and^FC 143 were determined to be 0.99 and 0.38, respectively. For FC 95 adsorption and desorption could be described by a single valued function while for FC 143, they could not. Based on these data, both compounds would be judged mobile in the sandy loam soil used in this study. J Information Liaison . Initials: 000180 CONCLUSIONS if Adsorptiori coefficient for FC 95 and FC 143 were 0.99 and 0.38, respectively. For FC 95, adsorption and desorption could be described by a single valued function while for FC 143, they could not, Considering adsorption coefficients, desorption characteristics and water solubilities, both compounds would be judged mobile in the sandy loam soil used in this study. INTRODUCTION As a part of the Fate of Fluorochemicals Project, an indication of mobility of FC 95 and FC 143 in sandy loam soil was desired. Adsorptiondesorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubility data can provide this indicatipn of mobility. This approach is used by the U. S. EPA in pesticide registration requirements. MATERIALS AND METHODS Duplicate 5-g samples of air-dried Brill sandy loam soil (57% sand, 36% silt, 7% clay, 2.5% organic matter, 1.5% organic carbon, with pH 6.5 and C.E.C. of 15.3 meq./lOOg) were shaken with 25 ml of solution in 50 ml. poly propylene centrifuge tubes for 24 hours on a wrist action, shaker at room temp. (16-19C). Polypropylene tubes were used because they were found in separate experiments (3M Tech Notebook #470673, C. H. Schrandt) to absorb less FC 95 and FC 143 than glass or polyethylene tubes. Solutions were made by diluting a stock solution of each chemical. Concentrations of 14C-labeled FC 95 were 282 mg/1., 158 mg/1., 90 mg/1., 51 mg/1., 28 mg/1., (100%, 56%, 32%, 18%, 10%, 1% of stock). Concentrations of 14C-labeled FC 143 were 523 mg/1., 293 mg/1., 167 mg/1., 94 mg/1., 52 mg/1., and 5.2 mg/1. oooisi After shaking the initial solutions as well as the three desorption extractions with deionized water, the saaples fere centrifuged at 5000 rpm for 10 min., and three aliquots of each supernatant solution Were taken for scintillation counting. After the adsorption step, 22.5 ml of solution were recovered. Therefore, it was assumed that 2.5 ml of liquid remained with the soil in each step and this amount was accounted for in the desorption calculations (see Results ahd Discussion section). In the FC 95 experiment, the supernatant liquid was simply drained off at each step and the next 25 ml of liquid were put into the tubes. In the FC 143 experiment, the supernatant liquid remaining after the draining step was absorbed with a cotton swab before putting the next 25 ml of liquid into the tubes. The procedures for the FC 95 and FC 143 experiments were recorded in 3M Technical Notebook #40673, p. 49 and p. 51, respectively. From the raw counting data, disintegrations per minute (DPIjQ and FC 95 and FC 143 concentrations were calculated for all of the supernatant solutions. Statistical analysis and plotting of the data was done with the MINITAB package of the 3M TRAC computer service. RESULTS AND DISCUSSION FC 95 Adsorption data for FC 95 are presented in TABLE I and FIGURE 1. Comparing the regression equation of the adsorption isotherm (FIGURE 1) x/m = -0.29 + 0.99C with the Freundlich equation x/m * KC1^ 1, it could be seen that the adsorption coefficient, K, equaled 0.99 and the exponent, N, equaled one. The linear shape of the adsorption isotherms (N=l) indicated 00018 '> '.vV ' 4 that FC 95 adsorption on soil would be independent of concentration. The low adsorption coefficient (K=0.99) indicated that FC 95 would be mobile, i.e., it would move readily with the ground water through this sandy loam soil. TABLE I FC 95 ADSORPTION DATA Initial FC 95 Cone., mg/1 B Equil. Cone., C, mg/1. % Removed By Soil ^ x 100 ) 282.2 158.0 90.0 51.0 28.0 ) 2.8 233.9 134.2 76.9 42.0 22.1 2.0 17.1 15.1 14.6 17.8 21.1 27.0 D Total FC 95 In Initial Sol'n (A x 0.025 liters) 7.0500 3.9500 2.2500 1.2750 0.7000 0.0700 E Total FC 95 in Sol'n at Equil., mg (B x 0.025 liters) 5.84750 3.35500 1.92250 1.05000 0.55250 0.05000 F FC 95 Adsorbed on Soil, x/m, ug/g fCD-E) x 105 yg/mg . *________5 g Soil J 240.8 119.0 65.7 45.3 29.5 3.8 Desorption data for FC 95 are shown in TABLE II and FIGURE 2. For comparison, desorption isotherms for the pesticide fluometuron are given in FIGURE 3. For.clarity FC 95 desorption isotherms are not drawn in FIGURE 2. However, all of the data points lie very close to the adsorption isotherms i indicating that adsorption and desorption could be described by a single-valued function with desorption coefficients, k ' equaling the adsorption coefficient, K. 0 0 0 1 S 3 S Adsorbed on Soil, x/m, ug/g. FIGURE .1 FC 9S Adsorption Isotherm ?. This, along with the observation that approximately all of the adsorbed FC 95 was subsequently desorbed (TABLE II, Column H) indicated that binding forces were weak and would be another indication of high mobility of FC 95. Material balance data for FC 95 are presented in TABLE III and these data indicate that all of the chemical was accounted for throughout the experiment. 000154 .. V_ 6 A Equil. Cone, in Solution, C, mg/1. 233.900 134.200 76.900 42.000 22.100 2.000 TABLE II FC 95 DESORPTION ISOTHERM DATA* B Equil. Cone, in First Desorption mg/1* C Equil. Cone, in Second Desorption mg/1. 52.7000 30.3000 18.3000 9.6000 5.3000 0.6000 14.9000 9.0000 5.3000 2.9000 1.7000 0.2000 D Equil. Cone. in Third Desorption mg/1. 5.20000 2.80000 1.80000 1.00000 0.60000 0.10000 E Amount Adsorbed on Soil, x/m yg/g (Column F, TABLE I) 240.800 119.000 ) 65.700 45.300 . 29.500 ' 3.800 F Amount on Soil After First Desorption, yg/g 67.6000 19.4500 3.3000 13.2000 11.4000 1.7000 G - Amount on Soil After Second Desorption, yg/g 12.0000 -14.9000 -16.7000 2.0500 4.7000 0.9000 H Amount on Soil After Third Desorption, yg/g -9.1500 -25.8000 -23.9500 -2.0000 2.2500 0.4500 Columns F, G, and H were calculated in the same way as Column F, TABLE I with correction for the amount of FC 95 in the 2.5 ml of solution remaining from the previous step in each case (See Materials and Methods Section.) A iSO. IS O . -- - -- * -- ------------. 4M. 5C>(>. FIGURE 2 FC 95 DESORPTION DATA POINTS AND ADSORPTION ISOTHERM FIGURE 3 ADSORPTION AND DESORPTION ISOTHERMS FOR FLUOMETURON ON COBB SAND. SOLID AND BROKEN LINES ARE BEST FIT FOR ADSORPTION AND DESORPTION. RESPECTIVELY. fFrom Davidson. TABLE III FC 95 Material Balance* A Total Initial FC 95 in Solution, mg. (Column D, TABLE I) 7.05000 3.95000 2.25000 1.27500 0.7000 0.0701 B FC 95 in Solution at Equil., mg. (Column E, TABLE I) 5.84750 3.35500 1.99250 1.0500 0.55250 0.05000 C FC 95 on soil at Equil., mg. (A - B) 1.20250 0.59500 0.32750 0.2250 0.14750 0.02000 D Amount Removed by First Desorption, mg. 0.864500 0.497750 0.311000 0.159000 0.090500 0.011500 EF Amount Removed by Amount Removed by Second Desorption, mg.. Third Desorption, mg. 0.278000 0.171750 0.100000 0.055750 0.033500 0.004000 0.105750 0.054500 0.036250 0.020250 0.012250 0.002250 G Total Amount Desorbed by Three Desorptions, mg (D+E+F) 1.2483 0.7240 0.4473 0.2350 0.1363 0.0178 H Amount Remaining on Soil After 3 Desorptions, mg. (C - G) -0.45750 . -0.12900 -0.11975 -0.01000 0.11250 0.002250 I Amount Desorbed as Percent of Amount Adsorbed (G/C x 100) 103.805 121.681 136.565 104.444 92.373 88.750 `Columns D, E, and F were obtained by first calculating the amount (mg) of FC-95 in 27.5 ml (25 ml added plus 2.5 ml remaining from previous step) of solution in each respective step and then subtracting the amount (mg) in the 2.5 ml of solution remaining from the previous step. 000186 FC 143 Data for FC 143 are presented in TABLE IV and TABLE V and in FIGURE 4. The adsorption isotherm indicated FC 143 nobility similar to that of FC 95 with K=0.38 and N=l. Regression analyses were not performed on the desorp tion isotherms, however, the graphed data (FIGURE 4) indicated that adsorption and desorption could not be described by a single-valued function. That is, the K1 and N 1 values for desorption would not be the same as K and N for adsorption. Subjective evaluation would indicate that the desorption coefficient! K1, would be much smaller than the adsorption coefficient, K, at solution concentrations greater than about 25 mg/1, since the slope of the adsorption isotherm was much greater than the slopes of the desorption isotherms in this range. At solution concentrations less than 25 mg/1., the desorption coefficients would appear to be much greater than the adsorption coefficient. From this it would appear that two or three different binding mechanisms -were involved with stronger binding occuring at the higher concentrations and the converse at lower concentrations. While this may indicate a tendency for FC 143 to be immobile at high concentrations, it would be quite mobile in any situations involving low concentrations. Material balance data for FC 143 are presented in TABLE VI. While the two concentrations resulting in 212%and 201% desorption (last column in TABLE VI) were erratic, in general, the data indicated that all of the FC 143 was accounted for throughout the experiment. 0001S7 TABLE IV FC 143 Adsorption Data A Initial FC 143 Cone.i mg/l. B Equil. Cone., C, mg/l. 522.5 292.6 167.2 .94.1'. 52.3 5.2 485.8 279.1 160.3 92.2 49.9 5.1 C X Removed By Soil ( x 100) 7.0 4.6 4.1 2.0 4.5 1.9 D Total FC 143 in Initial Sol'n, mg (A x 0.025 liters) E Total FC 143 in Sol'n at Equil., mg (B x 0.025 liters) F FG 143 Adsorbed on Soil, */m, yg/g CD-E) X 103 yg/rc 1 .... 5 e SoilJ 13.0625 7.3150 4.1800 2.3525 1.3075 0.130 12.1450 6.9775 4.0075 2.3050 1.2475 0.1275 183.5 67.5 34.5 x9.5 12.0 0.5 000188 10 TABLE V EC 143 Desorption Isotherm Data* AB Equil. Cone. In Solution, C, mg/1 Equil. Cone. in first Desorption Solution, mg/1. (Column B,Table IV) 485.800 279.100 160.300 92.20 49.900 5.100 47.6000 28.8000 17.2000 10.7000 6.1000 0.6000 CD Equil. Cone. Equil. Cone. in Second Desorp- in Third Desorption tion Solution, mg/1. solution, mg/1. 6.80000 4.80000 3.40000 2.00000 0.80000 0.10000 3.50000 2.90000 2.00000 0.50000 0.20000 0.01000 EF GH Amount Adsorbed .Amount on Soil on Soil, x/m, After First Oesorp- Wt/JB. H8/g_______ tion (Column F. TABLE IV) Amount on Soil Amount on Soil After Second Desorp- After Third Desorp- Ug/g tion u s Zb ___ 183.500 67.500 34.500 9.500 12.000 0.500 164.600 50.850 20.050 -3.250 3.400 -0.250 151.000 38.650 9.950 -8,900 2.050 -0.500 135.150 25.100 0.650 -10.650 1.350 -0.505 Columns F, G, and H were calculated In the same way'ns Column F ( TABLE IV with correction for the amount of FC 143 In the 2.5 ml of solution remaining from the previous step In each case (See Materials and Methods Section). 000159 11 Equil. Cone., C, mg/1 FIGURE 4 FC 143 ADSORPTION AND DESORPTION ISOTHERMS Solid line is best fit adsorption isotherm. Dotted lines are estimated desorption isotherms. A's are adsorption isotherm data points. B, C, D; E, and F are desorption data points for the respective concentrations. GENERAL COMMENTS The FC 95 and FC 143 adsorption coefficients from these experiments may be converted to the analogous constants based on soil organic carbon content Kqc> with the equation KQC *= 100 K/(% organic carbon) giving a Kqc of 45 for FC 95 and 17 for FC 143 (2.2% organic carbon for this soil). Comparing these values to those in TABLE VII, it can be seen that FC 95 and FC 143 are at the low end of the spectrum, again indicating high mobility of these compounds. 000190 .-; ; a.,'.f i1-! i' ,'-t.'. '5v, t'i-ivV-jriV,: ,>-.'.-. -: 12 TABLE VI FC 143 MATERIAL BALANCE* A Total FC 143 Initially in Solution mg. (Column D, Table IV) 13.0625 7.3150 4.1800 2.3525 1.3075 0.1300 D Amount Removed by First Desorption, mg. 0.09450 0.08325 0.07225 - .06375 0.04300 0.00375 G Total Amount Desorbed by Three Desorptions, mg (D+E+F) 0.2418 0.2120 0.1693 0.1008 0.0535 0.0050 B FC 143 in Solution at Equil., mg. (Column E, TABLE IV) C FC 143 on Soil at Equil., mg. (A - B) 12.1450 6.9775 4.0075 2.3050 1.2475 0.1275 E Amount Removed by Second Desorption, mg. 0.06800 0.06100 0.05050 0.02825 0.00675 0.00125 H Amount Remaining on Soil After 3 Desorptions, mg. (C - G ) 0.676750 0.125500 0.003250 -0.053250 0.006750 -0.002525 0.9175 0.3375 0.1725 0.0475 0.0600 0.0025 F Amount Removed by Third Desorption, mg 0.079250 0.066750 0.046500 0.008750 0.003500 0.000025 I Amount Desorbed as percent of Amount Ad sorbed (G/C x 100) 26.349 62.815 98.116 212.105 88.750 201.000 Columns D, E, and F were obtained by first calculating the amount (mg) of FC 143 in 27.5 ml (25 ml added plus 2.5 ml remaining from previous step) of solution in each respective step and then subtracting the amount (mg) in the 2.5 ml of solution remaining from the previous step. 000191 13 ' TABLE VII Comparison of Adsorption Coefficients for a Selected Group of Pesticides (Hamaker and Thompson, 1972) Chemical KQC (mobile) Chloramben 12.8 (FC 1 4 3 ................ 17) 2,4-D 32 (FC 95 ................. 45) Propham 51 Bromacil 71 Monuron 83 Simazine 135 ...Propazine 152 Dichlobenil 164 ` Atrazine 172 Chloropropham 245 Prometone 300 Ametryn 380 Diuron . 485 Prometryne 513 Chloroxuron 4,986 Paraquat 20,000 (immobile) DDT 243,000 The small amounts adsorbed and ease of desorption is consistent with the relatively high water solubility of FC 95 (300 mg/1) and Be 143 (>2(j g/1.) and with the.chemical nature of the molecules - organic salts which ionize in aqueous solution: C8F17S03 K FC 95 C7F15C02 NH4* FC 143 J 000192 14 Terms DPM - Disintegrations per minute C -Concentration of chemical in solution atequilibrium x/m -Concentration of chemical adsorbed on soil at equilibrium _ Coefficient of determination K - Adsorption coefficient i K' -Desorption coefficient N -Exponential term in Freundlich Equation N' - Exponential term for desorption equation Kqc - Adsorption coefficient based on soil organic carbon content References Davidson, J. M., et. al., 1975, Use of Soil Parameters for Describing Pesticide Movement Through Soils, U. S. EPA, EPA-660/2-75-009. Davidson, J. M., 1976, "Vertical Movement and Distribution of Organics in Soils," presented at Symposium on Nonbiblogical Transport and Transformation of Pollutants on Land and Water, at National Bureau of Standards, Gaithersburg, MD., May 11-13, 1976. Hamaker, J. W. and J. M. Thompson, 1972. 11Adsorption1*in Organic Chemicals in the Soil Environment. C. A. I. Goring and J. W. Hamaker (eds.) Marcel bekker, Inc., N. Y. Hamaker, J. W., 1975, "Interpretation of Soil Leaching Experiments," in Chemicals, Human Health and the Environment, A Collection of Dow Scienti fic Papers, Vol. 1, Dow Chemical USA, Midland, Mich. 48640 000193 Attached are comments on the 3M Technical Report "Adsorption o f FC 95 and FC 143 on Soil. S.K. Welsh, Project 9970612633 Fate o f Fluorochemicals, R eport N o. 1, Feb. 2 7 ,1 9 7 8 " m ade by Professor Stephen A. Boyd, Michigan State University, dated May 19,1993. 000194 Review o f Technical Report Summary Adsorption o f FC 95 and FC 143 in Soil M aterial and Methods Should give recoveries o f compounds in blank (no-soil) experiments. States that polypropylene sorbs less than glass on polyethylene, but doesn't give a num erical value. T he large headspace (25 ml in a 50 tube) is undesirable; any losses o f the 14C-label, e .g ., from volatilization or sticking to the tube, will inflate the sorption coefficient since the method calculates the amount sorbed by difference between the initial and final equilibrium solution concentrations. Also the 24 hour mixing period seems arbitrary. W ere experiments done for different periods o f time to establish that equilibrium was reached within 24 hours? Details on the stock solution are lacking. W hat solvent was used and what is the specific activity and radiochemical purity o f the 14C -FC 95. T he idea o f using a cotton swab after the draining step is unusual: Hopefully this didn't rem ove soil as well as water.... The --20% or less decrease in solute concentration due to sorption isn't as high as I 'd like to see it. A 50% o r greater decrease would be better. This section generally lacks detail that would normally be required for publication. Results and Discussion The linearity o f the isotherm has been shown over the concentration range used. However, to demonstrate that the entire isotherm is linear, the linearity must extend to equilibrium solution concentrations that approach the water solubility of the compound. Do you know the solubility o f FC95 or FC143: If not, how were the initial solution concentrations selected? T he sorption coefficient (K) o f FC 95 appears to be about 1 as indicated. The organic matter normalized sorption coefficient (K ^ = K /foJ is = 1/0.025 = 40, o r log = 1.6. This is a soil sorption coefficient intermediate between benzene and toluene. It would be worthwhile to examine some additional soils to confirm this value. Generally, the K, values should converge within a factor of 2 to 3 for different soils. This would increase my confidence in the accuracy o f the one measured value. I 've spot checked the soil concentrations o f FC-95 fo r both the sorption and desorption experiments and I get essentially the same values. The calculations look good. T he K values for FC 143 is low er than FC 95 indicating that it probably has a higher w ater solubility. The hystersis in the desorption isotherm is surprising, and has been over-interpreted. The sorption isotherm is linear indicating a single sorptive process. The conclusion regarding "three different binding mechanisms ... with stronger binding at higher concentrations and the converse at lower concentrations" is very speculative based on the single experiment. If one examines column I "Amount Desorbed as a Percent o f Amount Adsorbed" the values range from 000195 26 to 212 percent, so it's pretty inconclusive. T h ere is a fairly good discussion o f hysteresis in J. Environ. Qual. 12:325-330 by Koskinen and Cheng who observed this phenomena for the weak acid pesticide 2,4,5-T. The causes o f hysteresis are varied and complicated and may include microbial degradation o f the compound during desorption, and changes in the physical and/or chemical properties of the soil-solution system. F or example, desorption using distilled w ater (as is the case here) could result in soil dispersion so that a clear supernatant solution could not be obtained. This can cause quenching o f radioactivity in solution and other problems leading to error. T h e ''m aterial balance" as presented in the report is a little misleading. T o obtain a m aterial balance you should measure the amount o f I4C-activity in soil a t the a id o f the experim ent, and add it to the measured solution concentrations. General Comments. The K* values calculated here use an organic carbon content o f 2.2% whereas the value stated in the Materials and M ethods is 1.5% ? T he water solubilities are cited as 300 m g/L for FC 95 and > 20g/L for F C 143. Surely the latter value is wrong. If the solubilities are truly that different, then the sorptive properties should be vastly different, which they are not. If FC143 has a solubility o f > 2 0 ,0 0 0 m g/L, then I would expect no sorption. This value must be erroneous. Recommendations: 1. Obtaining K, values on additional soils. D eterm ine if is relatively constant. 2. Obtain a true mass balance by measuring 14C-activity in soil and solution phase. 3. Interpret desorption data more cautiously. 4. Get correct value o f water solubility of FC 143. 000196 r ft ' Form 6747 11 A TECHNICAL REPORT SUMMARY O at* 2/27/78 TO: TECHNICAL COMMUNICATIONS CENTER - 201-2CN (Im portant - I f report sprinted on both sides o f paper, send two copies to T C C .) Division . Proiact RaportTitia To EE PC Fate of Fluorochemicals Adsorption of FC 95 and FC 143 on soil Dapt.Numbar 0222 ProjactNumbar 9970612633 AaportNumbar 1 Authorial Stephen K. Welsh Notabook Rafaranco #40673, #47704 SECURITY ^ O Opan (Company Confidantial) J Closad (Special Authorization) 3M C H E M IC A L 'w REG ISTR Y ^ Em ploya# N um b tr(i) 73583 No, ofPagasIncludingCovarahaat 14 New Chemicals Reported Yes QNo KEYWORDS: . (Select terms from 3 M Thesaurus. Suggest other applicable terms.) CURRENT OBJECTIVE: To obtain an indication of FC 95 and *FC 143 mobility in sandy loam soil. EE 8 PC - Div. Fluorochemical Soil Adsorption Mobility REPO RT ABSTRACT: (20 0-250 words) This abstract info rm ation is distributed by the Technical Comm unications Center to alert 3M `ars to Company R & O .. As a part of the Fate of Fluorochemicals Project, an indication of mobility of FC 95 and FC 143 in sandy loam soil was 'desired. Adsorption-desorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubility data can provide such information. The adsorption coeffi%nts for FC 95 and'FC 143 were determined to be 0.99 and 0.38, respectively. For FC 95 adsorption and desorption could be described by a'single valued function while for FC 143, they could not. Based on these data, both compounds would be judged mobile in the sandy loam soil used in this study. Information Liaison 1Initial . 000197 2 CONCLUSIONS Adsorption coefficient for FC 95 and FC 143 were 0.99 and 0.38, respectively. For FC 95, adsorption and desorption could be described by a single valued function while for FC 143, they could not, Considering adsorption coefficients, desorption characteristics and water solubilities, both compounds would be judged mobile in the sandy loam soil used in this study. INTRODUCTION As a part of the Fate of Fluorochemicals Project, an indication of mobility of FC 95 and FC 143 in sandy loam soil was'desired. Adsorptioni desorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubility data can provide this indication of mobility. This approach is used by the U. S. EPA in pesticide registration requirements. MATERIALS AND METHODS Duplicate 5-g samples of air-dried Brill sandy loam soil (57% sahd, 36% silt, 7% clay, 2.5% organic matter, 1.5% organic carbon, with pH 6.5 and C.E.C. of 15.3 meq./lOOg) were shaken with 25 ml of solution in 50 ml.'poly- propylene centrifuge tubes for 24 hours on a wrist action shaker at room temp. (16-19C). Polypropylene tubes were used because they were found in separate experiments (3M Tech Notebook #470673, C. H. Schrandt) to absorb less FC 95 and FC 143 than glass or polyethylene tubes. Solutions were made by diluting a stock solution of each chemical. Concentrations of 14C-labeled FC 95 were 282 mg/1., 158 mg/1., 90 mg/1., 51 mg/1., 28 mg/1., (100%, 56%, 32%, 18%, 10%, 1% of stock). Concentrations of 14C-labeled FC 143 were 523 mg/1., 293 mg/1., 167 rag/1., 94 mg/1., 52 mg/1., and 5.2 mg/1. 000198 3 After shaking the initial solutions as well as the three desorption extractions with deionized water, the sauries H'ere centrifuged at 5000 rpm for 10 min., and three aliquots of each supernatant solution were taken for scintillation counting. After the adsorption step, 22.5 ml of solution were recovered. Therefore, it was assumed that 2.5 ml of liquid remained with the soil in each step and this amount was accounted for in the desorption calculations (see Results and Discussion section). In the FC 95 experiment, the supernatant liquid was simply drained ** off at each step and the next 25 ml of liquid were put into the tubes. In the FC 143 experiment, the supernatant liquid remaining after the draining step was absorbed with a cotton swab before putting the next 25 ml of liquid into the tubes. The procedures for the FC 95 and FC 143 experiments were recorded in 3M Technical Notebook #40673, p. 49 and p. 51, respectively. From the raw counting data, disintegrations per minute (DPM) and FC 95 and FC 143 concentrations were calculated for all of the supernatant solutions. Statistical analysis and plotting of the data was done with the MINITAB package of the 3M TRAC computer service. RESULTS AND DISCUSSION FC 95 Adsorption data for FC 95 are presented in TABLE I and FIGURE 1. Comparing the regression equation of the adsorption isotherm (FIGURE 1) x/m * -0.29 + 0.99C with the Freundlich equation x/m = K C ^ N, it could be seen that the adsorption coefficient, K, equaled 0.99 and the exponent, N, 0 0 0 1 9 equaled one. The linear shape of the adsorption isotherms (N=l) indicated 4 that FC 95 adsorption on soil would be independent of concentration. The low adsorption coefficient (K=0.99) indicated that FC 95 would be mobile, i.e., it would move readily with the ground water through this sandy loam soil. TABLE I FC 95 ADSORPTION DATA A Initial FC 95 Cone., mg/1 282.2 158.0 90.0 51.0 28.0 2.8 D Total FC 95 In Initial Sol'n (A x 0.025 litersi 7.0500 3.9500 2.2500 1.2750 0.7000 0.0700 B Equil. Cone., C, mg/1. 233.9 134.2 76.9 42.0 22.1 2.0 E Total FC 95 in Sol'n at Equil;, mg (B x 0.025 liters) 5.84750 3.35500 1.92250 1.05000 0.55250 0.05000 C % Removed By Soil c ^ x 100) -- *-----17.1 15.1 14.6 17.8 21.1 27.0 .l' * i F Vi - FC 95 Adsorbed on Soil, x/m, yg/g f (D-E) x 103 vR/rng . 5 g Soil 240.8 1*9.0 65.7 45.3 29.5 3.8 Desorption data for FC 95 are shown in TABLE II and FIGURE 2. For comparison, desorption isotherms for the pesticide fluometuron are given in FIGURE 3. For clarity FC 95 desorption isotherms are not drawn in FIGURE 2. However, all of the data points lie very close to the adsorption isotherms indicating that adsorption and desorption could be described by a single-valued function with desorption coefficients, K' equaling the adsorption coefficient, 000200 Adsorbed on Soil, x/m, ug/g. 5 FIGURE J. FC 95 Adsorption Isotherm This, along with the observation that approximately all of the adsorbed FC 95 was subsequently desorbed (TABLE II, Column H) indicated that binding forces were weak and would be another indication of high mobility of FC 95. Material balance data for FC 95 are presented in TABLE III and these data indicate that all of the chemical was accounted for throughout the experiment. 000201 6 A Equil. Cone, in Solution, C, mg/1. 233.900 134.200 76.900 42.000 22.100 2.000 TABLE II FC 95 DESORPTION ISOTHERM DATA* B Equil. Cone, in First Desorption mg/I. C Equil. Cone, in Second Desorption mg/1. 52.7000 30.3000 18.3000 9.6000 5.3000 0.6000 14.9000 9.0000 5.3000 2.9000 1.7000 0.2000 D Equil. Cone, in Third Desorption mg/1. 5.20000 2.80000 1.80000 1.00000 0.60000 0.10000 E \mount Adsorbed on Soil, x/m yg/g Column F, TABLE I) 240.800 119.000 65.700 45.300 29.500 3.800 F Amount on Soil After First Desorption, yg/g . 67.6000 19.4500 3.3000 13.2000 11.4000 1.7000 G> Amount on Soil After Second Desorption, yg/g 12.0000 -14.9000 -16.7000 2.0500 4.7000 0.9000 H Amount on Soil After Third Desorption, yg/g -9.1500 -25.8000 -23.9500 -2.0000 2.2500 0.4500 *Columns F, G, and H were calculated in the same way as Column F,'TABLE I with correction for the amount of FC 95 in the 2.5 ml of solution remaining from the previous step in each case (See Materials and Methods Section.) -ro. -------------------*----------------------------- #< I6 . 4M. * 160. >00. FIGURE 2 FC 95 DESORPTION DATA POINTS AND ADSORPTION ISOTHERM coneSOUiTlON O o f l* 8) 000202 FIGURE 3 ADSORPTION AND DESORPTION ISOTHERMS FOR FLUOMETURON ON COBB SAND. SOLID AND_BROKEN 7 TABLE III FC 95 Material Balance* A Total Initial' FC 95 in Solution, mg. [Column D-; TABLE I)' 7.05000 3.95000 2.25000 1.27500 0.7000 0.0700* B FC 95 in Solution at Equil., mg. (Column E, TABLE I) 5.84750 3.35500 1.99250 1.0500 0.55250 0.05000 C FC 95 on soil at Equil., mg. (A - B) 1.20250 0.59500 0.32750 0.2250 0.14750 0.02000 D Amount Removed by First Desorption, mg. 0.864500 0.497750 0.311000 0.159000 0.090500 0-:011500 E -F Amount Removed by Amount Removed by Second Desorption, mg.. Thirt# Desorption, mg. 0.278000 0.171750 0.100000 0.055750 0.033500 0.004000 0.105750 0.054500 0.036250 0.020250 0.012250 0.002250 G Total Amount Desorbed by Three Desorptions, mg (D+E+F) 1.2483 0.7240 0.4473 0.2350 0.1363 0.0178 H Amount Remaining on Soil After 3 Desorptions, mg. (C - G) -0.45750 -0.12900 -0.11975 -0.01000 0.11250 0.002250 I Amount Desorbed as Percent of Amount Adsorbed (G/C x 100)_ 103.805 121.681 136.565 104.444 92.373 88.750 *Columns D, E, and F were obtained by first calculating the amount (mg) of FC-95 in 27.5 ml (25 ml added plus 2.5 ml remaining from previous step) of solution in each respective step and then subtracting the amount (mg) in th 2.5 ml of solution remaining from the previous step. 000203 8 FC 143 Data for FC 143 are presented in TABLE IV and TABLE V and in FIGURE 4. The adsorption isotherm indicated FC 143 mobility similar to that of FC 95 with Ks0.38 and N=l. Regression analyses were not performed on the desorp tion isotherms, however, the graphed data (FIGURE 4) indicated that adsorption and desorption could not be described by a single-valued function. That is, the K' and N' values for desorption would not be the same as K and N for adsorption. Subjective evaluation would indicate that the desorption coefficients K*, would be much smaller than the adsorption coefficient, K, at solution concentrations greater than about 25 mg/1, since the slope of the adsorption isotherm was much greater than the slopes of the desorption isotherms in this range. At solution concentrations less than 25 mg/1., the desorption coefficients would appear to be much greater than the adsorption coefficient. From this it would appear that two or three different binding mechanisms were involved with stronger binding occuring at the higher concentrations and the converse at lower concentrations. While this may indicate a tendency for FC 143 to be immobile at high concentrations, it would be quite, mobile in any situations involving low concentrations. Material balance data for FC 143 are presented in TABLE VI. While the two concentrations resulting in 212%and 201% desorption (last column in TABLE VI) were erratic, in general, the data indicated that all of the FC 143 was accounted for throughout the experiment. 000204 9 TABLE IV FC 143 Adsorption Data A Initial FC 143 Cone., mg/1. 522.5 292.6 167.2 94 1 52.3 5.2 B Equil. Cone., C, mg/1. 485.8 279.1 160.3 92.2 49.9 5.1 C Z Removed By Soil ( -- ~ - x 100) . 1 7.0 *4.6 4.1 2.0 4.5 1.9 D Total FC 143 in Initial Sol'n, mg (A x 0.025 liters) E Total FC 143 in Sol'n at Equil., mg (B x 0.025 liters) F FG 143 Adsorbed on Soil, x/m, pg/g ,(D-E) X-10* pg/mg % ^ . 5 ir Soil-' 13.0625 7.3150 4.1800 2.3525 1.3075 0.1300 12.1450 6.9775 4.0075 2.3050 1.2475 0.1275 183.5 67.5 .34-5 ^ 9.5 12.0 0.5 000205 10 TABLE V FC 143 Desorption Isotherm Data* AB Equil. Cone, in Solution C, mg/1 Equil. Cone. in first Desorption Solution, mg/1. (Column B(Table IV) 485.800 279.100 160.300 92.200 49.900 5.100 47.6000 28.8000 17.2000 10.7000 6.1000 0.6000 EF Amount Adsorbed Amount on Soil on Soil x/m After First Desorp- pg/s Ug/g_______ tion (Column F. TABLE IV) 183.500 67.500 34.500 9.500 12.000 0.500 164.600 50.850 20.050 -3.250 3.400 -0.250 CD Equil. Cone. Equil. Cone. in Second Desorp- in Third Desorption tion Solution, mg/1. solution mg/1. 6.80000 4.80000 3.40000 2.00000 0.80000 . 0.10000 ;* * \t G 3.50000 2.90000 2.00000 0.50000 0.20000 0.01000 H Amount on Soil Amount on Soil After Second Desorp- After Third Desorp- Vg/g tion us/g tion 151.000 38.650 9.950 -8.900 2.050 -0.500 135.150 25.100 0.650 -10.650 1.350 -0.505 Columns F, G, and H were calculated in the same way as Column F, TABLE IV with correction for the amount of FC 143 in the 2.5 ml of solution remaining from the previous step in each case (See Materials and Methods Section). 000206 Adsorbed on Soil, x/ra, ug/g. 11 Equil. Cone., C, mg/1 FIGURE 4 FC 143 ADSORPTION AND DESORPTION ISOTHERMS Solid line is best fit adsorption isotherm. Dotted lines are estimated desorption isotherms. A's are adsorption isotherm data points. B, C, D, E, and F are desorption data points for the respective concentrations. GENERAL COMMENTS The FC 95 and FC 143 adsorption coefficients from these experiments may be converted to the analogous constants based on soil organic carbon content K^, with the equation kQC * 100 K/(% organic carbon) giving a Kqc of 45 for FC 95 and 17 for FC 143 (2.2% organic carbon for this soil); Comparing these values to those in TABLE VII, it can be seen that FC 95 and FC 143 are at the low end of the spectrum, again indicating high mobility of these compounds. 000207 12 'TABLE VI FC 143 MATERIAL BALANCE* A Total FC 143 Initially in Solution mg. (Column D, Table IV) 13.0625 7.3150 4.1800 2.3525 1.3075 0.1300 D Amount Removed by First Desorption, mg. 0.09450 0.08325 0.07225 0.06375 0.04300 0.00375 G Total Amount De sorbed by Three Desorptions, mg (D+E+F)_______ 0.2418 0.2120 0.1693 0.1008 0.0535 0.0050 B FC 143 in Solution at Equil., mg. (Column E, TABLE IV) C FC 143 on Soil at Equil., mg. (A - B) 12.1450 6.9775 4.0075 2.3050 1.2475 0.1275 E 0.9175 0.3375 0.1725 0.0475 0.0600 0.0025 * ` F Amount Removed by Amount Removed by Second Desorption, mg. Third Desorption, mg. 0.06800 0.06100. 0.05050 0.02825 0.00675 0.00125 0.079250 0.066750 0.046500 0.008750 0.003500 0.000025 H Amount Remaining on Soil After 3 Desorp tions, mg. 1C - G )__________ I Amount Desorbed as percent of Amount Ad sorbed (G/C x 100) 0.676750 0.125500 0.003250 . -0.053250 0.006750 -0.002525 26.349 62.815 98.116 212.105 88.750 201.000 *Columns D, E, and F were obtained by first calculating the amount (mg) of FC 143 in 27.5 ml (25 ml added plus 2.5 ml remaining from previous step) of solution in each respective step and then subtracting the amount (mg) in the 2.5 ml of solution remaining from the previous step. 000208 13 TABLE VII Comparison of Adsorption Coefficients for a Selected Group of Pesticides (Hamaker and Thompson', 1972) Chemical KQC (mobile) (immobile) Chloramben 12.8 (FC 143 ........ ------ 17) 2,4-D 32 (FC 95 .---------........ 45) Propham 51 Bromacil 71 Monuron 83 Simazine 135 Propazine 152 Dichlobenil 164 Atrazine 172 Chloropropham 245 Prometone 300 Ametryn 380 Diuron 485 Prometryne 513 Chloroxuron 4,986 Paraquat 20,000 DDT 243,000 The small amounts adsorbed and ease of desorption is consistent with the relatively high water solubility of FC 95 (300 mg/I) and Ffc 143 (>20 g/1.) and with the chemical nature of the molecules - organic salts which ionize in aqueous solution : C8F1?S03 K FC 95 C7F15C02 ^ 4 FC 143 000209 14 / Terms DPM - Disintegrations per minute C - Concentration of chemical in solution at equilibrium x/m - Concentration of chemical adsorbed on soil at equilibrium r2 _ Coefficient of determination K - Adsorption coefficient K' - Desorption coefficient N - Exponential term in Freundlich Equation : ' li N* - Exponential term for desorption equation Kq C - Adsorption coefficient based on soil organic carbon content References Davidson, J. M., et. al., 1975, Use of Soil Parameters for Describing Pesticide Movement Through Soils, U. S. EPA, EPA-660/2-75-009. Davidson, J. M., 1976, "Vertical Movement and Distribution of Organics in Soils," presented at Symposium on Nonbiological Transport and Transformation of Pollutants on -Land and' Water, at National Bureau of Standards, Gaithersburg, MD., May 11-13, 1976. Hamaker, J. W. and J. M. Thompson, 1972. "Adsorption" in Organic Chemicals in the Soil Environment. C. A. I. Goring and J. W. Hamaker* (eels.). Marcel Dekker, Inc., N. Y. Hamaker, J. W., 1975, "Interpretation of Soil Leaching Experiments," in Chemicals, Human Health and the Environment, A Collection of Dow Scienti fic Papers, Vol. 1, Dow Chemical USA, Midland, Mich. 48640 000210