1、Designation: C1733 10Standard Test Method forDistribution Coefficients of Inorganic Species by the BatchMethod1This standard is issued under the fixed designation C1733; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONAs an aqueous fluid migrates through geologic media, certain reactions occur that are dependentupon the chemistry of th
3、e fluid itself and upon the chemistry and geochemistry of other fluids and solidphases with which it comes in contact. These geochemical interactions affect the relative rates at whichchemical species in the migrating fluid (such as ions) travel with respect to the advancing front ofwater. Processes
4、 of potential importance in retarding the transport of chemical species in the migratingfluid (movement of species at velocities less than the ground-water velocity) include ion exchange,adsorption, complex formation, precipitation (or coprecipitation, for example Ba2+and Ra2+co-precipitating as the
5、 sulfate), oxidation-reduction reactions, and precipitate filtration. Partitioningmay be caused by processes that include adsorption, precipitation, and coprecipitation that cannot bedescribed easily by equations and, furthermore, these solute removal mechanisms may not instanta-neously respond to c
6、hanges in prevailing conditions and may not be entirely reversible.An empirical ratio known as the distribution coeffcient (Kd) is defined as:Kd5Mass of solute on the solid phase per unit mass of solid phaseMass of solute in solution per unit volume of the liquid phaseand has been used to quantify t
7、he collective effects of these processes for the purpose of modeling(usually, but not solely, applied to ionic species). The distribution coefficient is used to assess thedegree to which a chemical species will be removed from solution (permanently or temporarily) as thefluid migrates through the ge
8、ologic medium; that is, the distribution coefficient is used to calculate theretardation factor that quantifies how rapidly an ion can move relative to the rate of ground-watermovement.This test method is for the laboratory determination of the distribution coefficient (Kd), which maybe used by qual
9、ified experts for estimating the retardation of contaminants for given undergroundgeochemical conditions based on a knowledge and understanding of important site-specific factors. Itis beyond the scope of this test method to define the expert qualifications required, or to justify theapplication of
10、laboratory data for modeling or predictive purposes. Rather, this test method isconsidered as simply a measurement technique for determining the degree of partitioning betweenliquid and solid, under a certain set of conditions, for the species of interest.Justification for the distribution coefficie
11、nt concept is generally acknowledged to be based onexpediency in modeling-averaging the effects of attenuation reactions. In reference to partitioning insoils, equilibrium is assumed although it is known that this may not be a valid assumption in manycases.The distribution coefficient (Kd) for a spe
12、cific chemical species may be defined as the ratio of themass sorbed per unit of solid phase to the mass remaining per unit of solution, as expressed in theabove equation. The usual units of Kdare mL/g (obtained by dividing g solute/g solid by g solute/mLsolution, using concentrations obtained in ac
13、cordance with this test method).Major difficulties exist in the interpretation, application, and meaning of laboratory-determineddistribution coefficient values relative to a real system of aqueous fluid migrating through geologicmedia (1)2. The distribution coefficient or Kdconcept is based on an e
14、quilibrium condition for givenreactions, which may not be attained in the natural situation because of the time-dependence orkinetics of specific reactions involved. Also, migrating solutions always follow the more permeablepaths of least resistance, such as joints and fractures, and larger sediment
15、 grain zones. This tends to1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.allow less time for reactions to occur and less sediment surface exposure to the migrating solution, andmay preclude the attainment of local chemical equilibr
16、ium.Sorption phenomena also can be strongly dependent upon the concentration of the species of interestin solution. Therefore, experiments performed using only one concentration of a particular chemicalspecies may not be representative of actual in situ conditions or of other conditions of primary i
17、nterest.Similarly, experimental techniques should consider all ionic species anticipated to be present in amigrating solution, in order to address competing ion and ion complexation effects, which maystrongly influence the sorption of a particular species.Sorption can be strongly controlled, by pH.
18、Therefore, in situ pH, especially of groundwater, shouldbe considered in determinations of Kd. Values of pH must be determined, preferably in the field whenmaterials are sampled and must be carefully determined in the laboratory procedure. Other in situconditions (for example, ionic strength, anoxic
19、 conditions, or temperature) could likewise haveconsiderable effect on the Kdand need to be considered for each situation.Site-specific materials must be used in the measurement of Kd. This is because the determined Kdvalues are dependent upon rock and soil properties such as the mineralogy (surface
20、 charge andenergy), particle size distribution (surface area), and biological conditions (for example, bacterialgrowth and organic matter). Special precautions may be necessary to assure that the site-specificmaterials are not significantly changed prior to laboratory testing. This may require refri
21、geration orfreezing of both soil and water samples. Chemical means of preservation (such as addition of acid togroundwater) will cause changes in sample chemistry and must be avoided.The choice of fluid composition for the test may be difficult for certain contaminant transportstudies. In field situ
22、ations, the contaminant solution moves from the source through the porousmedium. As it moves, it displaces the original ground water, with some mixing caused by dispersion.If the contaminant of interest has a Kdof any significant magnitude, the front of the zone containingthis contaminant will be co
23、nsiderably retarded. This means that the granular medium encountered bythe contaminant has had many pore volumes of the contaminant source water pass through it. Theexchange sites achieve a different population status and this new population status can control thepartitioning that occurs when the re
24、tarded contaminant reaches the point of interest. It is recommendedthat ground water representative of the test zone (but containing added tracers) be used as contactliquid in this test; concentrations of potential contaminants of interest used in the contact liquid shouldbe judiciously chosen. For
25、studies of interactions with intrusion waters, the site-specific ground watermay be substituted by liquids of other compositions.The distribution coefficient for a given chemical species generally assumes a different value whenconditions are altered. Clearly, a very thorough understanding of the sit
26、e-specific conditions thatdetermine their values is required if one is to confidently apply the Kdconcept to migration evaluationand prediction.The most convenient method of determining Kdis probably the batch method (this test method), inwhich concentrations of the chemical species in solid and liq
27、uid phases, which are in contact with oneanother, are measured. Other methods include dynamic column flow-through methods usingcontinuous input of tracer or pulsed input. In the field, a dual tracer test can be conducted using aconservative (nonsorbing) tracer and one that does sorb; from the differ
28、ence in travel times of the twotracers, Kdcan be calculated.In summary, the distribution coefficient, Kd, is affected by many variables, some of which may notbe adequately controlled or measured by the batch method determination. The application ofexperimentally determined Kdvalues for predictive pu
29、rposes must be done judiciously by qualifiedexperts with a knowledge and understanding of the important site-specific factors. However, whenproperly combined with knowledge of the behavior of chemical species under varying physicochemi-cal conditions of the geomedia and the migrating fluid, distribu
30、tion coefficients can be used forassessing the rate of migration of chemical species through a saturated geomedium.1This test method is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.07 on Waste Materials.Current edition approv
31、ed Oct. 1, 2010. Published October 2010. DOI: 10.1520/C173310.2The boldface numbers in parentheses refer to a list of references at the end of this standard.C1733 1021. Scope1.1 This test method covers the determination of distribu-tion coefficients of chemical species to quantify uptake ontosolid m
32、aterials by a batch sorption technique. It is a laboratorymethod primarily intended to assess sorption of dissolved ionicspecies subject to migration through pores and interstices ofsite specific geomedia. It may also be applied to other materialssuch as manufactured adsorption media and constructio
33、nmaterials.Application of the results to long-term field behavioris not addressed in this method. Distribution coefficients forradionuclides in selected geomedia are commonly determinedfor the purpose of assessing potential migratory behavior ofcontaminants in the subsurface of contaminated sites an
34、d wastedisposal facilities. This test method is also applicable to studiesfor parametric studies of the variables and mechanisms whichcontribute to the measured distribution coefficient.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thi
35、sstandard.1.3 This standard does not purport to address all of thesafety concerns, 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-bility of regulatory limitations prior to use.2. Re
36、ferenced Documents2.1 ASTM Standards:3D422 Test Method for Particle-Size Analysis of SoilsD1293 Test Methods for pH of WaterD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD2488 Practice for Description and Identification of Soils(Visual-Manual Pr
37、ocedure)D3370 Practices for Sampling Water from Closed ConduitsD4319 Test Method for Distribution Ratios by the Short-Term Batch Method4D4448 Guide for Sampling Ground-Water MonitoringWellsD5730 Guide for Site Characterization for EnvironmentalPurposes With Emphasis on Soil, Rock, the Vadose Zoneand
38、 Ground Water3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 distribution coeffcient, Kd, nthe concentration of aspecies sorbed on a solid material, divided by its concentrationin solution in contact with the solid, under constant concentra-tion conditions, as follows:Kd5Mass
39、of solute on the solid phase per unit mass of solid phaseMass of solute in solution per unit volume of the liquid phase(1)3.1.1.1 DiscussionBy constant concentration conditions,it is meant that the Kdvalues obtained for samples exposed tothe contact liquid for two different time periods (at least on
40、eday apart), other conditions remaining constant, shall differ bynot more than the expected precision for this test method. It isconvenient to express Kdin units of mL(or cm3) of solution pergram of geomedia.3.1.2 species, nspecific form of an element defined as toisotopic composition, electronic or
41、 oxidation state, complex ormolecular structure, or combinations thereof (2).3.1.3 tracer, nan identifiable substance, such as a dye orradioactive isotope, that can be followed through the course ofa mechanical, chemical, or biological process.4. Significance and Use4.1 The distribution coefficient,
42、 Kd, is an experimentallydetermined ratio quantifying the distribution of a chemicalspecies between a given fluid and geomedium sample undercertain conditions, including the attainment of constant aque-ous concentrations of the species of interest. The Kdconcept isused in mass transport modeling, fo
43、r example, to assess thedegree to which the movement of a species will be delayed byinteractions with the geomedium as the solution migratesthrough the geosphere under a given set of undergroundgeochemical conditions (pH, temperature, ionic strength, etc.).The retardation factor (Rf) is the ratio of
44、 the velocity of thegroundwater divided by the velocity of the contaminant, whichcan be expressed as:Rf5 1 1 rb/ he! Kd(2)where:rb= bulk density of the porous medium (mass/length3) andhe= effective porosity of the medium (unitless) expressedas a decimal.4.2 Because of the sensitivity of Kdto site sp
45、ecific condi-tions and materials, the use of literature derived Kdvalues isstrongly discouraged. For applications other than transportmodeling, batch Kdmeasurements also may be used, forexample, for parametric studies of the effects of changingchemical conditions and of mechanisms related to the int
46、erac-tions of fluids with geomedia.5. Apparatus5.1 Laboratory Ware (plastic bottles, centrifuge tubes, opendishes, pipettes) cleaned in a manner consistent with theanalyses to be performed and the required precision. Whereplateout may have significant effect on the measurement,certain porous plastic
47、s should be avoided and the use of FEPTFE-fluorocarbon containers is recommended.5.2 Centrifuge, capable of attaining 1400 g, or filteringapparatus.5.3 Filters, filtration apparatus, including syringe filters,capable of removing particles of $0.45 micrometers. Filtermedia should be selected to not s
48、orb species of interest underthe experiment conditions. Sorption has been observed on filtermedia composed of certain materials (3).5.4 Laboratory Shaker/Rotator, ultrasonic cleaner (op-tional).3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at s
49、erviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.C1733 1035.5 Environmental Monitoring Instruments, a pH meter,conductance meter, and thermometer.5.6 Analytical Balance capable of measuring to 0.01g.5.7 Appropriate Equipment, necessary to replicate in situconditions within the laboratory apparatus.5.8 Analytical Instrumentation, appropriate for determina-tion of the concentration of major constituen
