1、Designation: E 1195 01Standard Test Method forDetermining a Sorption Constant (Koc) for an OrganicChemical in Soil and Sediments1This standard is issued under the fixed designation E 1195; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for determiningthe partitioning of organic chemicals between
3、 water and soil orsediment. The goal is to obtain a single value which can beused to predict partitioning under a variety of environmentalconditions from the measurement of sorption coefficients forspecific solids.1.2 Sorption represents the binding process of chemicals tosurfaces of soils or sedime
4、nts through chemical, or physical, orboth interactions.1.3 The sorption of nonpolar organic chemicals, and tosome extent polar organic chemicals, is correlated with theorganic carbon content of the sorbing solid. Charged inorganicand organic molecules may behave differently, and some otherproperty,
5、such as, cation exchange capacity, clay content, ortotal surface area of sorbing solids, may influence sorption.Hydrous metal oxides of iron and aluminum may significantlyaffect sorption in sediments. In order to provide a sorptioncoefficient that is useful for a wide range of soils andsediments, th
6、e coefficient is based on organic carbon content.This approach, however, will not apply to all chemicals or allsoils and sediments. In cases where it does not apply, theinvestigator may need to seek other methods of relatingsorption to the properties of the chemical, soil, or sediment.1.4 It is poss
7、ible that, in addition to organic carbon, sorptionis correlated with the total surface area of sorbing solids. Thismay be particularly important with solids having organiccarbon contents so low that sorption to inorganic surfaces issignificant in comparison to sorption by organic material. Insuch a
8、case, inclusion of the total surface area into the sorptioncalculation may be useful. For further information on thissubject see Ref (1).21.5 Equilibrium sorption coefficients are determined. It isrecognized that equilibrium conditions do not always exist inenvironmental situations, but sorption equ
9、ilibria values arenecessary for making generalizations about environmentalpartitioning.1.6 Studies are conducted preferably with an analytical ortechnical-grade chemical. Mixtures are used only if analyticalmethods allow measurement of individual components ofinterest in the mixture. Good laboratory
10、 procedures must befollowed to ensure validity of the data.1.7 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bi
11、lity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 421 Practice for Dry Preparation of Soil Samples forParticle-Size Analysis and Determination of Soil Con-stantsD 422 Test Method for Particle-Size Analysis of SoilsD 1193 Specification for Reagent WaterD 4129 Te
12、st Method for Total and Organic Carbon in Waterby Oxidation Coulometric Detection2.2 Other standards:OECD Test Guideline 10643. Terminology Definitions3.1 sorption distribution coeffcient (Kd)the concentrationof chemical sorbed by solids, in g/g, on an oven-dry solidsweight basis divided by the conc
13、entration of chemical in thewater, in g/g, at equilibrium.3.2 organic carbon normalized sorption constant (Koc)thesorption distribution coefficient, Kd, normalized to the relativeorganic carbon content (fraction) of the solid oc (Koc= kd/%OC 3 100).1This test method is under the jurisdiction of ASTM
14、 Committee E47 onBiological Effects and Environmental Fate and is the direct responsibility ofSubcommittee E47.04 on Environmental Fate of Chemical Substances.Current edition approved Oct. 10, 2001. Published November 2001. Originallypublished as E 1195-87. Last previous edition E 1195-87 (Reapprove
15、d 1993)e1.2The boldface numbers in parentheses refer to the list of references at the end ofthis test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the sta
16、ndards Document Summary page onthe ASTM website.4Available from the Organization for Economic Co-Operation and Delevopment2, rue Andr Pascal F-75775 Paris Cedex 16 France.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of
17、Test Method4.1 The sorption coefficient of a chemical is measured byequilibrating an aqueous solution containing an environmen-tally realistic concentration of the chemical with a knownquantity of soil or sediment. After reaching equilibrium, thedistribution of chemical between the water and the sol
18、ids ismeasured by a suitable analytical method. If appropriate for thetest material, sorption constants are calculated on the basis ofthe organic carbon content of the solids. In addition toreporting single values for each solid, the sorption constantsfrom all solids are averaged and reported as a s
19、ingle value.5. Significance and Use5.1 Sorption data are useful for evaluating the migratorytendency of chemicals into the air, water, and soil compart-ments of our environment. They can be used in the predictionor estimation of volatility from water and soil, concentration inwater, leaching through
20、 the soil profile, run-off from landsurfaces into natural waters, and biological availability. Addi-tional information concerning testing to determine sorptioncoefficients can be found in OECD test Guide 106 (7).5.2 This test method assumes that sorption of at leastnonpolar organic chemicals is main
21、ly influenced by the organicmatter of the soil or sediment solids. There is ample evidencein the literature to support this assumption, and the user of thistest method should refer to Ref. (2) for more information onthis subject. Organic carbon content is chosen as the basis forsorption instead of o
22、rganic matter content. This is becauseorganic carbon values generally are measured directly byanalytical methods. Organic matter may be estimated bymultiplication of the organic carbon values by a somewhatarbitrary constant of 1.7 (3). This test method is based on theassumption that all of the mater
23、ial sorbed to the solids isreversibly bound. The analyses described herein assume equi-librium between the liquid and solid concentrations of the testcompound. In some cases, there may be a fraction of thecompound that is irreversibly bound to the solids. For thesecases, the measurements made by the
24、 test may not reflect a true“equilibrium”. The irreversible sorption phenomena has beenextensively documented and the reader is referred to (9), (10)and (8) for more discussion on this topic.5.3 A sorption constant is obtained and is essentially inde-pendent of soil properties other than organic car
25、bon. This valueis useful because, once it is determined, the sorption distribu-tion characteristics for any solid can be estimated based on itsorganic carbon content.5.4 This test method is designed to evaluate sorption atenvironmentally relevant concentrations as a function of or-ganic carbon conte
26、nt of different soil and sediment solids.Therefore, the number of different solids is emphasized in theprocedure rather than the number of chemical concentrationsstudied with each solid. In general, one concentration isemployed since the test method assumes that at low solutionconcentrations, sorpti
27、on isotherms approximate linearity andsorbed concentrations do not exceed typical environmentalloading. Errors arising from concentration effects at lowenvironmental concentrations usually are less than the varia-tion existing between different solids, when dealing withsorption trends in a general m
28、anner. Therefore, the initialconcentration of the test chemical in solution should not exceed0.5 of its water solubility.5.5 As an option, a procedure is given for determiningconcentration effects on sorption. This is because high concen-trations may be present in certain environmental situations;su
29、ch as landfills and spills. This procedure should be done atfour concentrations over a hundred fold concentration range(for example, 0.1, 0.5, 2, and 10 ppm initial solution concen-tration). If low solubility presents analytical difficulties, solu-tion concentrations should range over at least one o
30、rder ofmagnitude. The Freundlich equation is an appropriate expres-sion of these effects:Ca5 KCs1/n(1)where:Ca= chemical adsorbed, oven-dry solids weight, g/g,K = sorption coefficient,Cs= solution concentration at equilibrium, g/g, and1/n = exponent.5.5.1 A log plot of the Freundlich equation yields
31、 thefollowing linear relationship:log Ca5 log K 1 1/n log Cs(2)6. Apparatus6.1 High-Speed Temperature Controlled Centrifuge, ca-pable of removing particles 0.1-m radius from solution.Details of centrifugation techniques are given in the Proceduresection.6.2 Centrifuge Tubes, capable of withstanding
32、high speedand made of glass, metal, or other suitable material whichminimizes adsorption of the test chemical to its surface. Thetubes should be capped with TFE-fluorocarbon or aluminum-lined screw caps.6.3 Analytical Instrumentation, suitable for measuring theconcentration of the test chemical in s
33、olids and water.6.4 Laboratory Oven, capable of maintaining a temperatureof 103 to 110C. The oven is used for determining the moisturecontent of soils or sediments.7. Reagents and Materials7.1 Analytical or technical grade chemical of known purityshould be used. If available, all reagents shall conf
34、orm to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society.5Radiolabeled test materials ofknown radio-purity or nonlabeled test materials of knowncomposition are suggested.7.2 Purity of WaterReagent water shall conform to Speci-fication D 1193 for Type IV grade
35、water.8. Sampling, Test Specimens, and Test Units8.1 Use soils or sediments, or both, varying in organiccarbon content, pH, and texture or particle-size distribution.5“Reagent Chemicals,American Chemical Society Specifications,”Am. Chemi-cal Soc., Washington, D.C. For suggestions on the testing of r
36、eagents not listed bytheAmerican Chemical Society, see “Reagent Chemicals and Standards,” by JosephRosin, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”E1195012Four to seven different samples are recommended. Record theirhistory, if available, description, and site loc
37、ation.8.2 Collect soil samples in containers lined with polyethyl-ene bags. Collect from the top 6 in. of the soil profile andbefore storing, screen through a 2-mm sieve. Store at 4C.Store and handle the soil samples at the moisture content attime of collection. If initial moisture content is too hi
38、gh forsatisfactory screening, partially dry the soil samples, by expos-ing to air for brief periods. When using air-dried soil samples,longer sorption equilibrium times may be required to allow theorganic matter to become thoroughly wetted.8.2.1 Determine the soil pH, particle-size distribution, and
39、organic carbon content for each soil sample. Cation or anionexchange capacity may be needed for charged molecules.Refer to Ref (3) for measurement methods.8.2.2 Determine the moisture content on a soil specimenallowing sorption to be based on oven-dried solids weight.Discard the soil specimen after
40、determining the moisturecontent.8.3 Sediment samples from aquatic systems should not beair-dried or frozen prior to use. Collect sediment samples witha suitable grab or coring device and, if not used immediately,store in a suitable bottle at 4C for periods up to 10 days.Minimal sediment characteriza
41、tion should include organiccarbon content and particle-size distribution. Work with ionsand molecules having functional groups capable of ionizingcan be aided by characterization of redox potential, pH, andcation or anion exchange capacity of the sediments.8.3.1 Measurement of sorption properties of
42、 anoxic sedi-ments, usually characterized by the presence of a hydrogensulfide odor, requires strict adherence to oxygen exclusionduring a test. Admission of even small amounts of oxygen tothe diluted sediments suspension will allow oxidation offerrous iron with a concomitant precipitation of ferric
43、 hydrox-ide, which is a highly efficient scavenger for many dissolvedconstituents. However, when the primary area of concern in theaquatic system is aerobic, conduct the test under a normal airatmosphere using well-aerated sediments. For further informa-tion consult Ref (4).8.4 Base the solids conte
44、nt (or conversely, water content) ofthe soil or sediment specimen on the oven-dry weight (24 hdrying at 103 to 110C). Only in the case of very dilutesediment suspensions (0.1 % solids or less) are dry-weightcorrections for dissolved inorganic and organic species re-quired. Do not reuse in any sorpti
45、on measurement the speci-mens used for this dry-weight solids determination.8.5 Combustion is the preferred measurement method fororganic carbon, using the procedures described in Test MethodD 4129 or other similar procedures.8.6 Determine the particle-size distribution by a combina-tion of sieving
46、and sedimentation. The fractions are gravel (2mm), sand (2.0 to 0.05 mm), silt (0.05 to 0.002 mm), and clay(0.1-m radiusand 2.65-g/cm3density from solution:t 52.22 3 1010r/min!ln Rb/Rt(10)where:t = seconds,r/min = revolutions per minute,Rt= distance from center of centrifuge rotor to top ofsolution
47、in centrifuge tube, cm, andRb= distance from center of centrifuge rotor to bottomof centrifuge tube, cm.11.2 This assumes spherical particles and:t 5 9/2Fnv2r2prp2r!Gln Rb/Rt! (11)where:v2= 4p2r/min!3600,rp= particle radius = 1 3 105cm,n = viscosity of water at 25C = 8.95 3 103g/s cm,rp= particle de
48、nsity = 2.65 g/cm3, andr = density of water = 1.0 g/cm3.In general practice double the calculated times to ensurecomplete separation.11.3 Moisture percentage of solids:M 5A 2 B! 100B(12)where:M = moisture percentage,A = sample wet weight, g, andB = sample oven-dry weight, g.11.4 Oven-dry solids weig
49、ht in wet solids sample:B 5A1 1 M/100(13)where:B = oven-dry solids weight, g,A = sample wet weight, g, andM = moisture percentage.11.5 Total water present:WT5 WA1 A 2 B! (14)where:WT= total quantity of water, mL,WA= volume of water added, mL,A = wet weight of solids, g, andB = oven-dry weight of solids, g.FIG. 2 Relationship Between Water to Soil Ratios and KdatVarious Percentages of Sorbed MaterialE119501511.6 Total chemical in water:T 5 WT! CS! (15)where:T = total quantity of chemical left in water, g,WT= total quantity of water, mL, andCs= concentration
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