Document jN9O1BD95a1ojB5D5GM5GnoN

AdsorptionofFC 95 and FC 143 on Soil(Note:the3M Env. Lab summary istitledS:ummary of the Soil Adsorptionstudyof the Potassium Saltof Perfluorooctanesulfonaiccid,7/22/98) SOIL ADSORPTION TEST SUBSTANCE Identity:Perfluorooetanesulfonamtaey; alsobe referretdo as PFOS or FC-95. (I-Octanesulfonaiccid,1.1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8heptadecafluorop-o,tassiumsaltC,AS # 2795-39-3) Remarks field: The testsubstanceisa whitepowder of uncharacterizepdurity.Thistestingisbeing repeated percurrentproceduresand bestavailablepractices. METHOD Method: Adsorption-Desorptiosntudyusingthe approach recommended by the U.S.EPA forpesticidreegistration GLP (Y@N): No Year (study performed): 1978 Statisticamlethods: Statisticaanlalysisand plottinogfthedata was done withtheMINITAB package ofthe3M TRAC computer service. Temperature: 16-19"C Stock and testsolutionpreparation: Test solutionswere made by dilutinagstocksolutioonf 14C_IabelePdertluorooctanesulfonatTeh.e type of solventused tomake thestocksolutionisnotnoted,nor istheactivity ofthe radio-labeletdestsubstance. Remarks field: The Bdllsandy loam soilwas characterizeads having 57% sand,36% silt7,% clay,2.5% organicmatter,1.5% organiccarbon, withpH 6.5and cationexchange capacityof 15.3meq./l00 gms. Standardsolutionosfthe 14C-labeledcompound were prepared inD.I. water atconcentrationosf282 mg/L, 158 mg/L, 90 m'@g/L5,1 mg./L,and 28 mg/L. Twenty-fivmel ofeach solutiownas shaken m(itdhuplicate5 gram samples ofthesoilina 50 ml polypropylenecentrifugteubesfor24 hours on a wristshakeratroom temperature(16-19'3C). Desorptionextractiownere performedVithD.I.water aftertheadsorption phase oftheexperiment.The samples from theadsorptionand desorptionexperimentswere centrifugeidndividualalty5000 rpm for10 minutes,afterwhich,threealiquotosfeach supernatantsolutiownere preparedforscintillatcioounnting.From the raw countingdata,compound concentrationwsere calculatefdorallofthesupernatantsolutions. RESULTS K: 0.99(N=1). K,,,:66* Remarks field: The lineasrhapeoftheadsorptioinsotherms indicatedthatperfluorooctanesulfonaatdesorptionon soilwould be independent ofconcentration. * The studyreporthad calculateda soil/organiccarbon partitioning coefficienotf45. Afterreview,itwas determinedthatthe value should have been 66 based on the formula(K. = K'x 100/1.5(%organiccarbon); K'= (x/m)/C.). CONCLUSIONS The studysubstance isexpected toexhibithighmobilityinthe kindofsoil testedand would move withthe groundwater. Submifter: 3M Company, EnvironmentalLaboratory,P.O. Box 33331, St.Paul,Minnesota,55133 DATA QUALITY Reliability:Klimischranking2. This studylacksdetailon the stock solutionand the purityofthe radio-labeletdestsubstance.Additionally, some calculationhsave questionablereliability. REFERENCES 3M TechnicalReport madsorptionof FC 95 and FC 143 on Soil."S.K. Welsh, Project9970612633 Fate of Fluorochemicals,Report No. 1,Feb. 27,1978 OTHER Last changed: 5/2/00 SUMMARY OF THE SOEL ADSORPTION STUDY OF THE POTASSIUM SALT OF PERFLUOROOCTANESULFONIC ACID Introduction Soiladsorption-desorptsitoundieswere conductedto indicatethe mobilityof potassiumperfluorooctanesulfoniantae sandy loam soil.The approachused was that recommended by theU.S.EnvironmentalProtectioAngency forpesticidreegistration. Materialsand Methods The Brillsandy loam soilwas charactmizedas having 57% sand,36% silt7,% clay,2.5% organicmatter,1.5% organiccarbon,with pH 6.5 and cationexchangl-c-capacitoyf 15.3meq./lOOgms. Standardsolutionsof the "C4abeled compound were preparedinD.I.wateratconcentrationosf 282 mg/l,158 mg/l,90 mg/l,51 mg/l,and 28 mg/l. Twenty-fiveml ofeach solutiownas shakenwith duplicat5e gram samplesof thesoilin a 50-mlpolypropylenecentriffitguebesfor24 hourson a wristshakeratroom temperatur(e16-19"C). Desorptionextractionwsere performedwith D.I.water afterthe adsorptionphase of the experiment The samplesfi-omthe adsorptionand desorptionexperimentswere centdfugedindividuallayt5000 rpm for 10 minutes,afterwhich,threealiquotosf each supernatanstolutionwere preparedforscintillaticoonunting.From theraw counting data,compound concentrationwsere calculatefdorallofthesupernatantsolutions. Resultsand Discussion The linearshape of the adsorptionisothermsih'dicatetdhat potassium pm-fluorooetanesulfonaadtseorptionon soilwould be independentof concentration.A soiladsorptiocnoefficien(tK)of 0.99indicatetdhatthiscompound would be mobilein thiskindof soiland would move withthegroundwater. A soilorganiccarbonpartitionicnogefficie(nYtj was calculateidnthisreportto be 45. However, aftercloserexaminationtheK. valueshouldbe 66 (Kw = 100 * K (1.5% organiccarbon)).Again,thisvalueindicatehsighnjobifitiynthiskindofsoil. July22, 1998 MICHIGAN STATE UNIVERSITY DEPA"MU4T OF CITOP MD SOIL SCENCES nm@ff & SOM SCMr4CFS SUMDLNR, Xay 19, 1993 L'TSTLAr4SINri- MICMGAN 4s&24.1325 Dr. Robert D. Howell 3M Company 3H Center, Bldg. 2-3E-09 St. Paul, HN 55144-1000 Dear Dr. Howell: Enclosed are my review comments regarding the nine 3M Techuicial Reports, recommendationsfor improving the quality of the individualstudies, and some recommendationsfor future research. Please review this information and let me know if I can be of any further assistance. I do have interest in submittinga research proposal to 3H in accordance with the recommendationsfor future research. Perhaps we could discuss this further. I enthusiasticallsyupportyour effortsto obtain information on the environmentalfate and behavior of the 3M products. Xy consultingfee for the work performed to date is $3,200.00(three and one half days for review of materialsand preparationof reportsplus one half day consultationwith Dr.,,@ell at MSU, at $800.00 per day). Sincerely StepihenA. Boyd, P Professor MSU is AhWwwOm Actio*lEqudO"ortanitylmsanaion Review of TechnicalReport Summary Adsorptionof FC 95 and FC 143 inSoil Materialand Methods Should giverecoveriesofcompounds -inblank(no-soile)xperiments.Statesthatpolypropylene sorbslessthan glasson polyethyleneb,ut doesn'tgivea numericalvalue. The largeheadspace(25 mi ina 50 tube)isundesirablea;ny lossesofthe "'C-Ltbd,e.g.,from volatilizatioornstickingto the tube,willinflattehesorptioncoefficienstincethe method calculatetshe amount sorbedby differencbeetween the initiaalnd finalequilibriumsolution concentrationsA.lso the 24 hour mixingperiodseems arbitrary.Were experimentsdone for differenpteriodsof time toestablisthhatequilibriumwas reachedwithin24 hours? Detailson the stocksolutionarelacking.What solventwas used and what is the specific activitaynd radjoCheMiCaplurityof the14C_FC 95. The ideaof usinga cottonswab afterthedrainingstepisunusual.Hopefullythisdi soilas wellas water. Ite - 20% or lessdecreaseinsoluteconcentratiodnue l@@ as high as I'dliketosee it. A 50% or greaterdecreasewould be better. This sectiongenerallylacksdetailthatwould normallybe requiredfor IL) viove n't Resultsand Discussion The linearitoyf theisothermhas been shown over theconcentratiornange us Zell demonstratethattheentireisothermislinear,thelinearitmyust extendto equi concentrationtshatapproach thewater solubilitoyf thecompound. Do you kno% -.Y of FC95 or FC 143: If not,how were the'uu'daslolutionconcentrationsseleemd@i The sorptioncoefflcien(tK) of FC 95 appearsto be about I as indicated.The organicmatter normalizedsorptiocnoefficie(nKt. = K/f.) isK. = 1/0.025= 40, or logK. = 1.6.-7%s isa soilsorptioncoefficienitntermediatbeetween benzene and toluene.Itwould to examine some additionasloilsto confirmthisK. value. Generally,theK. convergewithina factorof 2 to3 fordifferenstoils.This would increasemy coi accuracyof the one measured value. I've spotchecked the soilconcentrationosf FC-95 for both the sorptiona experimentsand I get essentialltyhe same values.ne calculationlsook good. Ile K valuesforFC 143 islower thanFC 95 indicatintghatitprobablyhas a solubility7.le hystersiisnthedesorptionisothermissurprisinga,nd hasbeen ovi The sorptionisothermislinearindicatinag singlesorptiveprocess.The conclusionregarcang "duw differenbtindingmechanisms ...with strongerbindingathigherconcentmtionsand the converseatlower concenftadons*isvery speculativbeased on the singleexperiment. Ifone examines column I "Amount Desorbed as a Percentof Amount Adsorbed" thevaluesrange from 26 to212 percents,o it'sprettyinconclusiven.ere isa fairlgyood discussioonf hysteresiisn J.Environ.Qual. 12:325-330by Kosldnenand Cheng who observedthisphenomena forthe weak acidpesticid2e,4,5-T.The causesof hysteresiasre variedand complicatedand may includemicrobialdegradatioonf thecompound duringdesorptiona,nd changesin thephysical and/orchemicalpropertieosf thesou-solutiosnystem.For example,desorptionusingdistilled water(asisthecasehere)couldresultin soildispersiosno that-aclearsupernatanstolution couldnotbe obtained.Thiscan causequenchingofradioactiviitnysolutioannd otherproblems leadingtoerror. Ile "materiablalance"as presentedinthereportisa littlmeisleading.To obtaina material balanceyou shouldmeasuretheamount of '4C-activiitnysoilattheend of theexperiment,and add ittothemeasured solutiocnoncentrations. GeneralComments. The Yu.valuescalculatehdere use an organiccarboncontentof 2.2% whereas thevaluestatedin theMaterialsand Methods is1.5%? The watersolubilitaireescitedas 300 mg/L forPC 95 and > 20g/L forPC 143. Surelythe lattevralueiswrong. Ifthesolubilitaireestrulythatdifferenth,enthesorptivperoperties shouldbe vastlydifferenwth,ich theyarenot. IfFC143 has a solubiliotfy >20,000 mg/L, thenI would expectno sorption.This valuemust be erroneous. Recommendations: 1. ObtainingK, K.. valueson additionasloils.DetermineifX. isrelativecloynstant. 2. Obtaina truemass balanceby measuring"C-activitiyn soiland solutiopnhase. 3. Interpredtesorptiodnatamore cautiously. 4. Get correctvalueof watersolubiliotfyPC 143. lie -F 7-11-A TECHNICAL REPORT SUMMARY Date 2/27/78 TO: TECHNICAL COMMUNICATIONS CENTER - 201-2CN F- (Important- ifreportisprintedon both si@ ofpoper,wnd tviocopiesto TCC.) Division Project EE & PC Fate of Fluotochemicals ...... Report TVtVe Adsorption of FC 95 and FC 143 on soil To oqq D. L. Bacon Author(s) Steohen K. Welsh Notebook Reference #40673, f.47704 57 @k SECURITY 10, 0 Opion. lcompany Confkle@titi) Closed jpocialAuthorization) 3PA CHEMICAL REGISTRY KEYWORDS: (Selecttornu from 3M Thesaurus. t other &Wlicawe CURRENT OBJECTIVE: To obtain an indication'of FC 9S-*andFC 143 mobility in sandy loam soil. EE & PC Div. Fluorochemical Soil Adsorption Mobility REPOR* ABSTRACT- 1200-250 words) This ebmae't infomation iscmanbu@ by theTachnkal Conumniw'tions Center to alert3M'ors 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.' Ads.orption-desorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubility*data can provide such information. The adsorption coeffiorits for FC 95 and"FC 143 were determined to be 6.99 and 0.38, respectively. For FC 9S 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. :nformationLiaison nitials; C:3 EW 2 CONCLUSIONS Adsorption coefficient for FC 9S and FC 143 were 0.99 and 0.39, respectively. For FC 95, adsorption and desorption could be described by a sin9'le valued functionwhile for FC 143, they could not, Considering adsorption coefficients,desorptioncharacteristicsand water solubilities9. both compounds would be judged mobile in the sandy loam soil used in this study. INTRODIJCTION As a part of the Fate of FluorochemicalsProject, an indication.of mobility of FC 9S and FC 143 in sandy loam soil was desired. Adsorptiondesorption experiments (after Davidson, 1976, and Hamaker, 197S) along with water solubilitydata can provide this indicatignof 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 loan soil (57% sand, 36% silt, 7% clay, 2.5% organic matter, l.S% organic carbon, with pH 6.S and C.E.C. of 15.3,meq./lOOg) were shaken with 2S ml of solution in SO ml. poly- propylene centrifugetubes for 24 hours on a wrist actioltshaker at.room temp. (16-190C). Polypropylenetubes 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 14 C-labeled FC 95.were 282 mg/l., IS8 mg/l., 90 mg/l.io Sl mg/l., 28 mg/l., (100%, S6%, 32%, 18%, 10%, 1% of stock). Concentrations of 14 C-labeled FC 143 were S23 mg/l., 293 mg/l., 167 mg/l., 94 mg/l., 52 ing/l., and 5.2 mg/l. 3 After shaking the initial solutionsas well as the three desorpiion extractions with deionized water, the samples ?gerecentrifuged at 5000 rpm for 10 min., and three aliquots of each supernatantsolution were taken for scintillationcounting. After the adsorption step, 22.5 ml of solution were recovered. Therefore, it was assumed that 2.5 al of liquid remained with the'soil in each step and this-amount was accounted for in the desorption calculat:*Lons (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,l'iquidwe.reput into the tubes. In the FC 14.3experiment, 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, disintegrationsper minute (DPN).and FC 95 and FC 143 concentrations were calculated for all of the supernatant ,solutions.. Statisticalanalysis 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 9S 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/a a KC1IN, 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 4 that FC 95 adsorption on soil ivouldbe independent of concentration. The low adsorptioncoefficient (K=0.99) indicated that FC 95 would be mobile, i.e., it would move readily with the ground water through this sandy loan soil. TABLE I A InitialFC 95 Conc., mg/l 282.2 158.0 90.0 Si.0 28.0 2.8 FC 95 ADSORPTION DATA Equil. Conc., C. mg/l. 233.9 134.2 76.9 42.0 22.1 2.0 Removed A-BBY So" 7-A-x 'Do 17.1 is.1 14.6 17.8 21.1 27.0 D Total PC 95 .In InitialSolln (A x 0.025 liters) 7.0500 3.9S 00 2.2SOO 1.2750 0.7001) 0.0700 E Total FC 95 in golln at Equil., mg (B x 0.025 liters) S. 84 7.1;0 3.3SSDO 1.922SO I.DSOOO 0.55250 d.osoo6 F FC 95 Adsorbed on'Soil. xim, lig/g (D-E) x 10 UK/MR 5 1 Soil 240.8 1l@9.0 6@.7. 45 3 29:S 3.8 Desorption data for FC 9S 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 singie-valued function with desorptioncoefficients,Kt, equaling the adsorptioncoefficient, K. s 240 A 180 -r4 120 0 0 V) 60 0 0 A A B A Regression Eqn.: Y -0.29 + 0.99 x R-Squared'- 0.98S' A --Ar-tualData Points B Predicted Y values 60 iio 180 240 300 Equil. Conc., C, mg/l FI.GURE I PC 9S Adsorption Isotherm Thisi along -withthe observation that approximately all of the adsorbed FC 9S.was subsequently desorbed (TABLE Ii, Co'lummH) . in4kcated that binding forces were weak and would be another indicaiionof high mobility of FC 9s. @aterial balance data for FC.9S'are presented in TABLE III and these data indicate that all of the chemical was accounted for throughout the exp eriment. 6 A Equil. Conc. in Solution, C, mg/l. 233.900 134.200 76..900 .42.000 22.100 2.000 TABLE II FC 95 DESORPTION ISOTHERM DATA* Equil. Conc. in First Desorption mg/l. c Equil. Conc. in Second Desorption -Big/I. S2.7000 30.3000 18.3000 9.6000 S.3000 0.6.000 14.9000 9.0000 S.3000 2.9000 1.7000 0.2000 D Equil. Conc. in Third Desorption mg/l. S.20000 2.80000 i.9oooo 1.06000 0.60000 0.10000 E Amount -Adsorbed on Soil, .X/m pa/g (Column F, TABLE 1) 240.800 119.000 65.700 45.300 29.SDO 3.800 F Amount on Soil After First Desorption, ug/g 67.6000 19.4SOO 3.3000 13.2000 11.4-000 1.7000 G Amount-on Soil After @econd Desorption, lig/g 12.0000 -14.9000 -16.7000 -2.OSOO 4.7000 0.9000 H Amount oh Soil After Third Desorption, ug/g -9.1500 -2S.8000 -23.gSbO. -2.0000 2.2SOO 0.4SOO *ColuiinsP, G, and H were calculated in the same way as Column P, TABLE I, with correction for the amount of FC 9S in the 2.S ml of solutioriremaining from the previous step in each case (See Materials and Methods Section.) 'Ads@oArdpstoiropntion Isso4therm ---------- --------- --------IZO. ------------------o?4u. FIGURE 2 FC 95 DESORPTION DATA POINTS AND ADSORPTION ISOTHERM LO 9-656 caft oi- "a cam Cll- CAI to $mum" cme (AIVUA FIGURE 3 ADSORPTION AND DESORPTION ISOTHERMS FOR FLUOMETURON ON COBB SAND. SOLID AND BROKEN LINES ARE BEST FIT FOR ADSORPTION AND DESORPTION, RESPECTIVELY. (From Davidson, 7 TABLE III FC 9S Material Balance* A Total Initial FC 95 in Solution, mg. (Column D, TABLE I)'- 7.OSOOO 3.95000 2..25000 1.27SOO' 0.7000 0.0700, B FC 95 in Solution at Equil., mg. (Column E, TABLE ii S.847SO 3.35500 1.992SO I.OSOO 0.552SO O.OSO,60 c FC 9S on soil at Equil., mg. LA - B) 1.20250 o.s9soo 0.327SO 0.22SO 0.147SO 0.02000 D -Amount Removed by First Desorption,mg. 0.864500 0.497750 0.311000 0.159000 0.090soo O..Ollsoo G Total Amount Des.orbed by Three Desorptions, mg -(DtE+F) 1.2483 0.7240 ..0.4473 0.2350 .0.1363 0.0178 E F Amount Removed by Amount Removed by Second DesorEtion, mg.. Thi-rdDesorption, mg. 0.278000 0.1717SO 0.100000 0.055750 0.0.33SOO 0.004000 O.lOS750 O.OS4SOO 0.0362SO 0.0202SO 0.0122SO 0.0022SO H Amount Remaining on Soil After 3*Desorptions,'mg. (C G) I Amount Desorbed as Percent of Amount Adsorbed (G/C x 100) -0.4S7SO -0.12900 -0.1197S -0.01000 O.il2SO 0.002250 103.805 121.681 13@&.56S 164.444 92.373 88.7SO .*Columns D, E, and F were obtained by first calculatingthe amount (mg) of FC-95 in 27.5 mi (2S ml added plus 2.S ml remaining from previou'sstep) of solution in each respective step and then subtractingthe amount (mg) in the 2.S ml of solution remaining from the previous step. 9 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 9S with K=0.38 and N=I. Regression analyses were not performed on the desorption isotherms, however, the graphed data (FIGURE 4) indicated that adsorption and desorption could not be described by a single-valued function. That is, the KI and Ni values for desorption would not be the same as K and N for adsorption. Subjective evaluation would indicate that the desdrptiolicoefficients.. would be much smaller than the adsorption coefficient, K, at solution concentrations greater than about 2S mg/l, 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 2S mg/l., 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 way indicate a tendency for FC 143 to be immobile at high concentrations, it would be quit.emobile 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% ii@sorption (last column in TABLE VI) were erratic, in general, the data indicated that all of the FC 143 was accounted for throughout the experiment. TABLE IV FC 143 Adsorption Data A Initial FC.143 Conc.j mg/j. B Equil. Cone., co us/l. 522.5 292.6 167.2 94.151.3 5.2 .485.8 279.1 160.3 92.2 49.9 5.1 c z Removed By Soil A -B -A x 100) 7.. 0 4 .6 4.1 2.0 4.5 1.9 D Total Ft 143 Total FC 143 in in Initial Solln, Sol'n at Equil., mg (A x 0.025 liters) (-Bx 0.025 liters) 13.0625 7.3150 .4.1800 2.3525 1.3075 O.i3O'o 12.1450 6.9775 4.0075 2.3050 1.2475 0.1275 F F@ 143 Adsorbed on Soil, r (D-E) X 10 ug/g 183.5 67.5 34.5 -'12.0 0.5 10 .'TABLE v FC 143 Desorption Isotherm Data* A. B Equil. Conc. in Solution, Ci Equil. Conc. in first Desorption Solution, mg/l. BTable IV) 485.i600 279.'100 160.300 92.200 49.900 5.100 47..6000' @8.8000 17.2000 10.7000 6.1000 0.6000. c D Equil. Conc. Equil. Conc. in Second Desorp- in Third Desorptiati tion Solution, mikli. solution, =A/j. 6.80000 4.80000 3.40000 2'.00000 0.80000 0.10000 3.50000 2.90000 2.00000 6.50000 0.20000 o.oiDO6 E F G Amount Adsorbed Amount on Soil on Soil, x/m, After First besorp- ug/$. . ug/i (ColuimnF. TABLE IV) -Aion Amount on Soil After Second Desorppg/g tion Amount on Soil After Third DesorpUg/g tion. 183.500 67.500 34.500 9.50'0 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 *Colum'nsF, 0, and B were calcuuted in the same way.'@"'Colimn P. TABLE IV with correctionfor.the amount of FC 143 in the 2.5 &1 of solutionremaining from the previous step in each case (See Materials and Methods Section). 200 ISO B 106 so 0 A B E 0 A 2A B A A c Y -16.3 + 0.39 X R-SQUARED 009.36 -50 0 100 200 300 400 Soo Equil. Cone.,. C, mg/l FIGURE 4 FC 143 ADSORPTION AND DESORPTION ISOTHERMS Solid line is best fit adsorption isotherm. Dotted lines are estiviated.@desorption isotherms. A's are adsor*ption isother'mdata points. B, C, DilE, and F are desorption data points for the respective concentrations. GENERAL COMMENTS The FC 95 and FC 143 adsorption coefficients fr.oa"thesee-Veriments may be converted to the analogous constants based on soil organic.'earbon content Koct with the equation Koc n 160 K/(% organic carbon) giving a Koc 6.f45 for FC 95 a:nd17 for FC 143 (2.2% organic carbon for this soil). Comparing these values to those in TABLE VII, it can be seen that PC 95 and PC 143 are at the low end of the spectrum, again indicating high mobility of these compounds. F,l 12 TABLE VI PC 143 T@ATERIAL BALANCE* A Total FC 143 Initiallyin Solution mg. (Column D, Table IV) 13..0625 7.31SO 4.1800 2.3S2S 1.30@S 0.1300 D Amount RemoVed by First Desorption, mg. 0.09450 0.0832S OiO7225 6.0637$ 0.0430.0 0.00375 G Total Amount Desorbed by Thiee .bes.orptions,mg (D+E+F). 0.2416 0.2120 0.1693 0 .'0l08 O.OS35 0.0050 FC 143 in Solution at Equil., mg. (Column E, TABLE IV) 12.1450 @.'977S 4.007S 2.30SO 1.247S 0.127S E Amount Removed by Second Desorption, mg. 0.06800 6.06100. O.OSOSO 0.0282S 0.00675 0.0012S H Axmnt Remaining on Soil After 3 Desorptions, mg. __LC G 0.676750 0.12SSOO 0.0032SO -0.6532SO 0.0067SO -0.00252S c FC 143 on Soil at Equil., mg. (A - B) .0.917S 0.337S 0.172S 0.0475 0.0600 0.002S F Amount Removed by.. Third Desorption, mg. 0.0792SO 0.0667SO 0.046500 0.008750 0.003SOO' 0.00002S I Amount De'sorbed.as percent of Amount Adsorbed (G/C x 100) 26.349 62.8is 98.116 212.105 89.7SO 201.000 *Columns D, E, and F were obtained by first calculatingthe amount (mg) of PC 243 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. 13 TABLE VII Comparison of AdsorptionCoefficients fdr a SelectedGroup of Pesticides (Hamaker and 7bompson, 1972) Che*mical Koc (mobile) ChIOTamben 12.8 (FC 143 - - - - - - - - - 17) 2,4-D 32 (PC 95 - - - - - - - - - -45) Propham si @gromacil 71 monuron 83 Sinazine 13S Propazine lS2 .[)ichlbbenil 164 @*'razine 172 oloropropham 24S Prometone 300 Ametr)m 380 D3'Luron 485 Prometryne 513 Chloroxuron 4,986 Paraquat 20,000 (iiiriobilDIeY)T 243,000 The small amounts adsorbed and ease of desorption is consistentwith'the relatii,elhyigh watersolubilityof FC 9S (300 mg@k) and FC 143 26 i/l.) and with th6.*chanicanlature of the molecules - organic salis which ionize in aqueous solution: c 8F'17S03-e C7Fl@C02-N"4* FC 95 FC 143 )7! 14 Terms DPM - Disintegrations per minute C -- Concentrationof chemical in solution at equilibrium x/m - Concentration of chemical adsorbed on soil at equilibrium R2 Coefficientof determination K Adsorptioncoefficient KI Desorptioncoefficient N - Exponential term in Freundlich Equation- Ni - Exponential term for desorption equation Koc A4sorptioncoefficient based on soil organic carbon content References -bavidson,J. M., et. al., 1975, Use of Soil Parameters for Describing Pesticide Movement Through SoLls..U. S. EPA, EPK-660/2-75-,009. Davidson, J. "M.',1976, 'Wert'icalMovesent and Distribution of Organics in Soils.."presented at.-Symposiumon Noiibibloi)'.cTarlansport and Tiansformationof Pollutants on Land and Water, at National Bureau of Standifds, Gaithersburg, MD., !Ey 11-1371-976. Hamaker, J. W. and J. M. Thompson, 1972. "AdsorptioT?in Organic Chemicals in the Soil Environment. C. A. I. Goring and J. W. Hamaker. (ads.).-Marcel Dekker, Inc., N. Y. Hamaker,J. W., 1975, ."Interpretationof Soil Leaching Experiments," in Chemicals, Human-Health and the Environment, A Collection of Dow Scientific Papers, Vol. 1, Dow Chemical USA, Midland, Mich. 48640 ST@ - Attachedarecomments on the3M TechnicalReport "AdsorptionofFC 95 and FC 143 on SoiL SY, WeJsh, Project9970612633 FateofFluomehenimL% Report No. 1,Feb.27, 1978" made by ProfessorStephenA. Boyd, Mcbigan StateUniversityd,atedMay 19,1993. Review ofTechnicalReport Summary Adsorptionof PC 95 and PC 143 inSoil Materialand Methods Should giverecoverieosf compounds -inblank (no-soile)xperiments.Statesthatpolypropylene sorbslessthanglasson polyethyleneb,ut doesn'tgivea numericalvalue. The largeheadspace(25 ml in a 50 tube)isundesirablea;ny lossesof the14C-label,e.g.,from vol;ltilizn@toir stieldngto the tube,willinflattehe sorptioncoefficienstincethe method calculatetshe amount sorbedby differencbeetween the initiaalnd finalequilibriumsolution concentrationsA.lso the24 hour mixingperiodseems arbitrary.Were experimentsdone for differenpteriodsof time toestablisthhatequilibriumwas reachedwithin24 hours? Detailson the stocksolutionare lacking.What solventwas used and what is the specific activitaynd radiochemicaplurityof the"IC-FC 95. The ideaofusinga cottonswab afterthedmining stepisunusual:Hopefullythisdidn'tremove soflas wellas water-.Ile - 20 % or lessdecreasein soluteconcentratiodnue tosorptionisn't as highas I'dEke totm it.A 50% or greaterdecreasewould be better. This sectiongenerallylacksdetailthatwould normallybe requiredforpublication. Resultsand Discussion The linearitoyf theisothermhas been shown over theconcentratiornangeused. However, to demonstratethattheentireisothermislinear,thelinearitmyust extendto equilibriumsolution concentrationtshatapproachthewatersolubilitoyfthecompound. Do you )mow thesolubility of FC95 or FC143: Ifnot,how were theinitiaslolutionconcentrationsselected? lle sorptioncoefficie(nKt) of PC 95 appearstobe about I as indicated.The organicmatter normalizedsorptiocnoefficie(nKt. = K/fj isK. = 1/0.025= 4R,orlogK. = 1.6.This isa soilsorptioncoefficienitntermediatbeetween benzene and toluene.Itwould be worthwhile to examine some additionasloilsto confirmthisK. value. Generally,theK. valuesshould convergewithina hcwr of 2 to3 fordifferenstoils.This would increasemy confidenceinthe accuracyof theone measured value. I'vespot'checkedthe soilconcentrationosf FC-95 for both the sorptionand desorption experimentsand I getessentialltyhe same values. The calculationlsook good. The K valuesforPC 143 islower thanPC 95 indicatintghatitprobablyhas a higherwater solubilityT.he hystersiisnthedesorptionisothermissurprisinga,nd has been over-interpreted. The sorptionisothermislinearindicatinag singlesorptiveprocess.The conclusionregarding *threedifferenbtindingmechanisms ...withstrongerbindingathigherconcentrationasnd the converseatlower concentrationsi"svery speculativbeased on thesingleexperimenl Ifone examines column I 'Amount Desoibed asa Percentof Amount Adsorbed" thevaluesrangefrom 26 to212 percent,so it'sprettyinconclusiven.ere isa fairlygood discussioonf hysteresiisn J. Environ.Qual. 12:325-330by Kosidnenand Cheng who observedthisphenomena forthe weak acidpesticid2e,4,5-T. The causesof hystereeiasre variedand complicatedand may includemicrobialdegradationof thecompound duringdesorption,and changes in thephysical and/orchemicalpropertieosf theso*il-solutsiyosntem. For example,desorptionusingdistilled water (asisthecasehere)couldresultin soildispersionso thata clearsupernatantsolution could not be obtained.Miis can causequenchingofradioactivitiyn solutioannd otherproblems leadingto error. Ile "matmw balance"as presentedin thereportisa littlmeisleading.To obtaina material balanceyou shouldmeasure the amount of "IC-activiitnysoilattheend of theexperiment,and add ittothe measured solutionconcentrations. GeneralComments. Ile K,. valuescalculatehdere use an organiccarbon contentof 2.2% whereas the value statedintheMaterialsand Methods is 1.5%? ne watersolubilitaireescitedas 300 mg/L forFC 95 and >'20g/L forFC 143. Surelythe LiV= valueiswrong. Ifthesolubilitiaerse trulythatdifferenit,hen the sorptiveproperties shouldbe vastlydifferentw,hich theyare not. IfFC143 has a solubilitoyf .>20,000 mg/L, thenI would expectno sorption.This valuemust be erroneous. Recommendations: 1. ObWning K, K. valueson additionasloils.DetermineifK. isrelativecloynstnt. 2.' Obtaina truemass balanceby measuting "'C-activitiyn soiland solutionphase. 3. Interpredtesorptiondatamore cautiously. 4. Get coned valueof water solubiliotfyFC 143. Form 6747 11 A TECHNICAL REPORT SUMMARY Date 2/27/78 TO: TECHNICAL COMMUNICATIONS CENTER - 201-2CN (importa-tiItfreporitsprilnedon bo&'sideosfpaperw,nd twocopiestoTCC.) DivWon Project Report Title To EE & PC Fate of Fluorochemicals . Adsorption of FC 9S and FC 143 on soil. t.Numbw 0222 Project Numbw 9970612633 ROPO" Number AuthorW Notebook Stephen K. Welsh werice SY-LJ SECURITY )o. #40673, #47704 open . I cloud (C4wnpnyConfidential)(SpeciAaulthorintion) 3M CHEMICAL* REGISTRY KEYWORDS: .'(Seletaornufrom3M Thmurus. Suggest other applicabtloerml) CURRENT OBJECRIVE: To obtain an indication of FC 9S and VC EnVloyoo Numberis) 73583 'ga-oTpa-"-* including Coversh"t 14 Now ChemicalRseported 13 yo El No 143 mobility in sandy loam EE & PC - Div. Fluorochemical Soil Adsorption Niobility soil. REPORT A13STRACT: (2DO-250 words) This abmact information b distributedby the Technical Communications Conteirto &Is" 3M'ersto ConWany 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-desorpt ion experiments (after Davids;n, 1976, and HamakeT, 1975) along with water solubility data can provide such'information. The adsorption coeffi%nts for FC 9S and--FC143 were determined to be 0.99 and 0.38, respectively. For FC 9S adsorption and desorption could be described by a'single valued fupction 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. lnformbtionLiaison. 2 CONCLUSIONS Adsorption coefficien.tfor FC 9S'and FC 143 were 0.99 and 0.38, respectively. For FC 95, adsorption and desorption could be described by a single valued functionwhile for FC 143, they could not, Considering adsorptioncoefficients,desorption characteristics and water solubilities, both compounds would be judged mobile in the sandy loam soil used in this study. INTROIXJCTION As a part of the Fate of Fluorochemicals Project, an indicationof. mobility of FC 95 and FC 143 in sandy loam toil was:desired. Adsorptiondesorption experiments (after Davidson, 1976, and Hamaker, 1975) along with water solubilitydata can provide this indicatign of mobility. This approach is used by the U. S. EPA in pesticide registration requirements. MATERIALS AND METHODS Duplicate S-g samples of air-dried Brill sandy loam soil (S7% sahd, 36% silt, 7% clay, 2.S% organic matter, 1.5% organic carbon, writhpH 6.S and C.E.C. of IS,.3meq./lOOg) were shaken with 2S ml of solution in SO ml.'poly-propylenecentrifuge tubes for 24 hours on a wrist act'l@bsnhaker.at room temp. (16-190C). Polypropylene tubes were used because they were found in separate experiments (3M Tech Notebook #470673, 'C. H. Schrandt) to absorb less FC 9S and PC 143 than glass or polyethylene tubes. Solutionswere made by diluting a stock solution of each chemical. Concentrations of 14C-labeled FC 9S were 282 mg/l., 158 mg/l., 90 mg/l., Sl mg4l., 28 mg/l., (100%, S6%, 32%, 18%, 10%, 1% of stock). Concentrations of 14C'-labeledFC 143 were S23 mg/l., 293 mg/l., 167 mg/l., 94 mg/l., S2 mg/l.,, and 5.2 mg/l. 3 After shaking the initial solutions as well as the three '@esorption extractions with deionized water, the samples Were centrifuged at SOOO rpm for 10 min., and three aliquots of each supernatant solution were taken for scintillationcounting. After the adsorption step, 22.5 ml of solution were recovered. Therefore, it was assumed that 2.S 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 9S experiment, the supernatant.liquid was simply drained off at each step and the next 2S ml of liquid were* put into the tubes. In the FC 143".e#eriment, the supernatant' liquid remaining after the draining step was absorbed with a cotton swab before putting the @ext 2S ml of liquid into the tubes. The procedures for the FC 9S and FC 143 experiments were recorded in 3H 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 3K 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 m KC1IN, it could be seen that the adsorption coefficient, X, equaled 0.99 and the exponent, N, equaled one. The linear shape of the adsorption isotherms (N=l) indicated 4 that FC 95 adsorption on soi.1would be independent of concentration. The low adsorption coefficient (K=0.99) indicated that FC 95 would be m*obile, i.e., it would move'readilywith the ground water through this sandy loam soil. TABLE I A Initial FC 9S Cone., mg/l 282.2 158.0 90.0 Si.0 28.0 2.8 FC 95 ADSORPTION DATA B Equil. Cone., C, mg/l. 233.9 134.2 76.9 42.0 22.1 2.0 c Removed A4 By Soil x 100 17.1 IS.1 14.6 17.8 21.1 27.0 D Total FC 9S In InitialSolln (A x 0.025 liters) 7.OSOO 3.9SOO .2.2500 1.27SO 0.7000 0.0700 E F Total FC 95 inSolln at gquil*.,mg (B x 0.02S liters). .5.84 7.r%n 3.35SOO 1.92250 1.OSOOO O.SS2SO O.OSOOO FC 95 Adsorbedon Soil, xim, ug/g. (D-E) x 10 ut/mg 5 & Soi I 240.8 11-9.0 'i@S.7 4S.3 29.S 3.8 Desorption'data for FC 9S are shown in TABLE II and FIGURE 2. For comparison, 'desorptionisotherms 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,KI, equaling the adsorption coefficient, K. 240 :L ra 180 120 60 0 0 A AA B A Regression Eqn.: Y -0.29 + 0.99 X R-Squared - 0.98S A - Actual Data Points* B - Predicted Y Values 60 120 180 240 300 Equil. Conc., C, mg/l FIGURE -1 FC 9S Adsorption Isotherm This, along with the observation that approximately all of the adsorbed FC 95 was subsequently desorbod (TABLE II, Column H) indi@catedthat. binding forces were weak and 'wouldbe another indication of high mobility of FC 95. Maierial balance data for FC.9S are presented in TABLE III and these data indicate that all of the chemical was accounted for throughout the experiment. 6 A Equil. Conc. in Solution, C, mg/l. 233.900 134.200 76.900 42.000 22.100 2.000 TABLE II FC 9S.DESORPTION.'ISOTtIERN DATA* B Equil. Conc. in First Desorption mg/l. c Equil. Conc. in Second Desorption mg/l. 52.7000 30.3000 18.3000 9.6000 S.3000 0.6000 14.9000 9.0000 S.3000 2.9000 1.7000 0.2000 D Equil. Conc. in Third Desorption mg/l.- 5.20000 2.80000 1.80000 1.00000 0.60000 0.10000 E @mount Adsorbed on Soil, x/m ug/g ,'ColumnF, TABLE I) 240.800' 119.000 65.700 45.300 29.500 3.800 AmDunt on Soil After First Desorption, ug/g 67.6000 19.4500 3.3000 13.2000 11.4000 1.7000 G Amount on Soil After Second DesoEBtion, lig/g 12.0000 -14.9000 -16.7000 2.0500 4.7000 0.9000 H Amount on Soil After Third Desorption, ug/g -9.1soo -25.8000 -23.9500 -2.0000 2.2500 0.4SOO *Columns F, G, and H were calculated in the same way as Column F,'TABLE -I with correction for the amount of FC 9S in the 2.S ml of solution remaining from the.previous step in each case (See Mat.erialsand Methods Section.) 140.-o 0. c AMsdosroprtpiotnion Issiotherm, to z s-cmem 20634 CO" Ito. E4u. too. FIGURE 2 FC 9S DESORPTION DATA POINTS AND ADSORPTION ISOTHERM cuoi io SOLUTM CONC 10 fwot=P) ADSORPTION FLUOMETURON FIGURE 3 AND DESORPTION ISOTHERMS FOR ON COBB SAND. SOLID AND BROKEN .-@^-r%VrTr%Lt ALIN 7 TABLE III FC 9S Material Balance* A Total Initial* FC 9S in Solution, mg. (Col@= D-;-TABLE I)'. 7.OSDOO 3.95000 2.2SO00 1.27SOO 0.7000 0.0700, B FC 9S in Solution at Equil., mg. '(Column E, TABLE I) 5.847SO 3.35SOO 1.99250 1.OSOO O.SS250 0.05000 c FC 9S 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-.Ollsoo G Total Amount Desorbed by Three Desorptions, mg -(D+E+F) 1.2483 0.7240 0.4473 0.2350 0.1363 0.0178 E F Amount Removed by Amot&t Removed by Second Desorption, mg.. Third Desorption, mg. 0.278000 0.1717SO 0.100000 0.055750 0.033SOO 0.004000 O.lOS750 0.054500 0.036250 0.020250 0.0122SO 0.0022SO H Amount Remaining on Soil After 3 Desorptions,mg. (C G) Amount Desorbed as Percent of Amount Aas'orbed (G/C x 100). -0.457SO -0.12900 -0.1197S -0-01000 0.11250 0.0022SO 103.805 1.2-1.681 ii6.S6S 104.444 92.373 88.750 *Columns D, E, and F were obtained by first calculatingthe amount (mg) of FC-9S in 27.S ml (2S ml added plus 2.5 ml remaining from previous step) of solution in each respective step and then subtracting the amount (mg) in th6 2.S ml of solution remaining from the previous step. 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 9S with K-0.38 and Nal. Regression analyses were not performed on the desorption isotherms, however, the graphed data (FIGURE 4) indicated that adsorption and de sorption could not be described by a single-valued function. That is, the KI and N' values for desorption would not be the same as K and N for adsorption. Subjective evaluation would indicate that the desorption coefficients x I , would be much.smaller than the adsorption coefficient, K, at solution concentrations greater than about 25 mg/l, since the slope of 'th6 adsorption isotherm was much greater than the slop46s of the'4#soTption isotherms in this range. At -solution concentrations less than 25 mg/l., 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 quitb.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% deiorption (last column in TABLE VI) were erratic, in general, the data indicated that all of the FC 143 was accounted for throughout the experiment. 9 TABLE IV PC 143 Adsorption Data A Initial PC 143 Cone.0 Be/le B. Equil. Conc., C, ms/l. 522.5 292.6 167.2-- 944-1., .52.3 5.2 485.8 279.1 160.3 92.2 49.9 5.1 c Z Removed By Soil A - B x 100) A 7.0 4.6 4.1 2.0 4.5 1.9 D E Total PC 143 Total PC 143 in in InitialSol'n, Sol'n at Equil., mg mg (A x 0.025 liters) (B x 0.025 liters) 13.0625 7.3150 4.1800 2.3525. I.3075' 0.1300 12.1450 6.9775 .4.0075 2.3050 1.2475 0. 1275' FG 143 Adsorbed on Soil, g/ g (D-t) X'170__ug/a 5 a So 1j. 183.5 67.5 -,U.5 :-9.5 12.0 0.5 10 TABLE V FC 143 Desorption Isotherm Data* A Equil. Conc. in Solution, C, ux/l (Column B.Table 485.800 279.100 160.300 92.200 49.900 5.100 B Equil. Conc. in first Desorption Solution, na/l. 47.6000. 28.8000 17.2000 10.7000 6.1000 0.6000 c D* Equil. Conc. in Second Desorption Soluticin,as/l. Equil. Cone. in Third Desorption solution, mg/j. 6.80000 4.80000 3.40000 2.00000 0.80000 o.ioooo 3.50000 2.90000 2.00000 0.50000 0.20000 0.01000 E Amount Adsorbed on Soil, X/M, (Column@F, TABLE Amount on Soil After First besorp- ---Uon 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 G Amount on Soil Af ter Second Desorp- tion H Amount on Soil After Third Desorpug/g tion' 151.000 38'.650 9.950 -8.900 2.050 -0.500 135.150 25.100 0.650 -10.650 1.350 -a.505 *Columns F, C, and R vere calculated in the same way as Column'F, TABLE IV vith correction for the amount of FC 143 in the 2.5 al of solution remaining from the previous step in each case (See Materials and Methods Section). 200 iso B 100 so C----- A 0 B E 0 A 0 2A B A A c Y - -16.3 + 0. 38*X R-SQUARED 0.936 -so 0 100 200 300 400 Soo Equil. Conc., C, mg/l FIGURE 4 FC 143 ADSORPTION AND DESORPTION ISOTHERMS Solid line is best fit adsorptionisotherm. Dotted lines are estkmated 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-9S and..FC143 adsorption coefficients from these experiments may be converted to the analogous constants based on soil organic carbon colaten;Koc , with the equation kocm 100K/(% organic*carbon) giving' a Koc of 4S for FC 9S and 17 for FC 143 (2.2% organic carbon for this soil)i 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. 12 VI FC 143 MATERIAL BALANCE* .A Total FC 143 Initiallyin Solution Mg-* (-ColumnD,-Table IV)- 13.062S 7.31SO 4.1800 2.352S 1.307S 0.1300 D Amount Removed by First Desorption, Mg- 0.09450 0.0832S O.-'07@25 0.06375 0.04300 0.0037S G Total Amount.Deso-rbed by Thiee Desorptions, mg (D+E+P) 0.2418 0.2120 0.1693 0.1008 0.053S 0.0050 B FC 143 in Solution at Equil.*,Mg. (Column E, TABLE IV) 12.1450 6.977S 4.007S 2.30SO 1.247S 0.127S E Amount Removed by Second Desor2tion, mg. 0.06800 0.06100. 0.05050 0.02825 0.0067S 0.0012S H Amount Remaining on Soil After 3 Desorp-, tions, mg. (C - G 0.676750 0.125500 0.0032SO -0.053250 0.0067SO -OiOO252S c FC 143 on Soil at Equil., mg. (A B) 0.9175 0.337S 0.172S. 0.0475 0.0600 0.002S F Amount Removed by Third Desorption, mg. 0.0792SO 0.0667SO 0.046SOO 0.0087SO 0.003500 0.00002S I Amount Desorbed as percent of Amount Adsorbed (G/C x 100) 26.349 62.91S 98.116 212.10S 88.750 201.000 *Columns D, E, and F were obtained by first calculatingthe amount (Mg) of FC 243 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.S mi of solution remaining from the previous step. 13 TABLE VII Comparison of Adsorption Coefficients for a Selected Group of Pesticides (liamakerand Thompson, 1972) Chenical Koc (mobile) Chloramben 12.9 (FC 143 - - - - - - - - - 17) 2,4-D 32 (FC 95 :--- - - - - - - - -4S) Prophan si BTomacil 71 Monuron 83 Simazine 135 Prbpazine @152 Dichlobenil Atrazine Chloropropham Prometone Ametryn Diuron Prometryne 164 172 24S 300 380 48S 513 t Chloroxu"n 4,986 F H 12 2. OW Paraquat 20,000 (immob'3*.leD)DT 243,000 The small'amountsadsorbed and ease of desorption is consistent with the relativelyhigh water solubilityof FC 9S (300 mg/@) and It 143 (>20 g/l.) and with the eltemicalnature of the molecules - organic salts which ionize in aqueous solution: C F %so 8 17 3 C7FisCO2 NH4* FC 95 FC 143 14 Terms DPM Disintegrationsper minute C Concentrationof chemical in solution at equilibrium x/m - Concentrationof chemical adsorbed on soil it equilibrium R2 - Coefficientof determinati6n K. - Adsorption coefficient KI - Desorption coefficient N - Exponential term in Freundlich Equation N' - Exponential term for desorption equation Koc - Adsorptioncoefficient based on soil organic carbon content References Davidson,-J.M., et. al., 1975, Use of Soil Parameters for Describing Oesticide 'Movement Through SFil-s U. S. EPAT EPA-6-6-072-75-009. Davidson, J. M , 1976, "Vertical Movement and Distrii"butioonf.Organics in Soils,"presented at Sympos* on Nonbiological Transport and Transformation of Pollutants on--LandZO Water, at National Bureau of Standards, Gaithersburg, MD., May 11-13, 1976. Hamaker, J. W. and J. M. Thompson, 1972. 'uAdsorptioT?in Organic Chemicals in the Soil Environment. C. A. I. Goring and J. W. Hamaker, (eds.-Y.Marcel Dekker, Inc., N. Y. Hamaker, J. W., 197S, "Interpretation of Soil Leaching Experiments," in Chemicals, Human Health and the Environment, A Collection of Dow Scientiric Papers Vol. 1, Dow Chemical USA, Midland, Mich. 48640