UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd ...

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(CEC) of the soils. Such an anomaly may have resulted from precipitation reactions brought about by high initial lead concentrations used in these experiments (20 to 830 mg/l). Lead adsorption characteristics of 7 alkaline soils from India were determined by Singh and Sekhon (1977). The authors concluded that soil clay, organic matter, and the calcium carbonate influenced lead adsorption by these soils. However, the initial lead concentrations used in these experiments ranged from 5 to 100 mg/l, indicating that in these alkaline soils the dominant lead removal mechanism was quite possibly precipitation. In another adsorption study, Abd-Elfattah and Wada (1981) measured the lead adsorption behavior of 7 Japanese soils. They concluded that soil mineral components which influenced lead adsorption ranged in the order: iron oxides>halloysite>imogolite, allophane>humus, kaolinite>montmorillonite. These data may not be reliable because high lead concentrations (up to 2,900 mg/l) used in these experiments may have resulted in precipitation reactions dominating the experimental system. Anionic constituents, such as phosphate, chloride, and carbonate, are known to influence lead reactions in soils either by precipitation of minerals of limited solubility or by reducing adsorption through complex formation (Rickard and Nriagu, 1978). A recent study by Bargar et al. (1998) showed that chloride solutions could induce precipitation of lead as solid PbOHCl. Presence of synthetic chelating ligands such as ethylenediaminetetraacetic acid (EDTA) has been shown to reduce lead adsorption on soils (Peters and Shem, 1992). These investigators showed that the presence of strongly chelating EDTA in concentrations as low as 0.01 M reduced K d for lead by about 3 orders of magnitude. By comparison quantitative data is lacking on the effects of more common inorganic ligands (phosphate, chloride, and carbonate) on lead adsorption on soils. A number of adsorption studies indicate that within the pH range of soils (4 to 11), lead adsorption increases with increasing pH (Bittel and Miller, 1974; Braids et al., 1972; Griffin and Shimp, 1976; Haji-Djafari et al., 1981; Hildebrand and Blum, 1974; Overstreet and Krishnamurthy, 1950; Scrudato and Estes, 1975; Zimdahl and Hassett, 1977). Griffin and Shimp (1976) also noted that clay minerals adsorbing increasing amounts of lead with increasing pH may also be attributed to the formation of lead carbonate precipitates which was observed when the solution pH values exceeded 5 or 6. Solid organic matter such as humic material in soils and sediments are known to adsorb lead (Rickard and Nriagu, 1978; Zimdahl and Hassett, 1977). Additionally, soluble organic matter such as fulvates and amino acids are known to chelate soluble lead and affect its adsorption on soils (Rickard and Nriagu, 1978). Gerritse et al. (1982) examined the lead adsorption properties of soils as a function of organic matter content of soils. Initial lead concentrations used in these experiments ranged from 0.001 to 0.1 mg/l. Based on adsorption data, the investigators expressed K d value for a soil as a function of organic matter content (as wt.%) and the distribution coefficient of the organic matter. The data also indicated that irrespective of soil organic matter content, lead adsorption increased with increasing soil pH (from 4 to 8). In certain soils, lead is F.3
also known to form methyl- lead complexes (Rickard and Nriagu, 1978). However, quantitative relationship between the redox status of soils and its effect on overall lead adsorption due to methylation of lead species is not known. Tso (1970), and Sheppard et al. (1989) studied the retention of 210 Pb in soils and its uptake by plants. These investigators found that lead in trace concentrations was strongly retained on soils (high K d values). Lead adsorption by a subsurface soil sample from Hanford, Washington was investigated by Rhoads et al. (1992). Adsorption data from these experiments showed that K d values increased with decreasing lead concentrations in solution (from 0.2 mg/l to 0.0062 mg/l). At a fixed pH of 8.35, the authors found that K d values were log-linearly correlated with equilibrium concentrations of lead in solution. Calculations showed that if lead concentrations exceeded about 0.207 mg/l, lead-hydroxycarbonate (hydrocerussite) would probably precipitate in this soil. The K d data described above are listed in Table F.1. F.2.0 Approach The initial step in developing a look-up table consisted of identifying the key parameters which were correlated with lead adsorption (K d values) on soils and sediments. Data sets developed by Gerritse et al. (1982) and Rhoads et al. (1992) containing both soil pH and equilibrium lead concentrations as independent variables were selected to develop regression relationships with K d as the dependent variable. From these data it was found that a polynomial relationship existed between K d values and soil pH measurements. This relationship (Figure F.1) with a correlation coefficient of 0.971 (r 2 ) could be expressed as: K d (ml/g) = 1639 - 902.4(pH) + 150.4(pH) 2 The relationship between equilibrium concentrations of lead and K d values for a Hanford soil at a fixed pH was expressed by Rhoads et al. (1992) as: K d (ml/g) = 9,550 C -0.335 where C is the equilibrium concentration of lead in µg/l. The look-up table (Table F.2) was developed from using the relationships F.1 and F.2. Four equilibrium concentration and 3 pH categories were used to estimate the maximum and minimum K d values in each category. The relationship between the K d values and the 2 independent variables (pH and the equilibrium concentration) is shown as a 3-dimensional surface (Figure F.2). This graph illustrates that the highest K d values are encountered under conditions of high pH values and very low equilibrium lead concentrations and in contrast, the lowest K d values are encountered under lower pH and higher lead concentrations. The K d values listed in the look-up table encompasses the ranges of pH and lead concentrations normally encountered in surface and subsurface soils and sediments. F.4 (F.1) (F.2)
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United States Office of Air and Rad
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NOTICE The following two-volume rep
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This publication is the result of a
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TO COMMENT ON THIS GUIDE OR PROVIDE
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CONTENTS NOTICE ...................
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Concentrations Extractable Iron Con
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Appendix A - Acronyms and Abbreviat
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Figure E.1. Variation of K d for Cr
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Table 5.16. Uranium(VI) aqueous spe
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Table H.3. Simple and multiple regr
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1.0 Introduction The objective of t
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discussed. The geochemical modeling
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2.0 The K d Model The simplest and
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track many more parameters and some
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of interest. The retardation factor
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(e.g., soil). An increasing body of
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complexation constants for the cont
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the soil column. Additionally, the
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Element Table 5.2. Concentrations o
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5.2.3 Aqueous Speciation Cadmium fo
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5.2.4 Dissolution/Precipitation/Cop
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cadmium, indicating that cadmium an
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5.2.6.2.2 Limits of K d Values with
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organic chelates (e.g., EDTA). Init
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(tarapacaite) in chromium sludge fr
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K d). Soils containing Mn oxides ox
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Table 5.7. Estimated range of Kd va
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most common valence state of lead e
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Table 5.8. Lead aqueous species inc
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Under reducing conditions, galena (
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C Adsorption of lead increases with
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(Choppin, 1983). Plutonium hydrolyt
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Table 5.10. Plutonium aqueous speci
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5.6.5 Sorption/Desorption Plutonium
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content in the system. Additionally
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much greater concentrations. Thus,
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exchanged which they attributed to
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up tables was based in part on thei
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organic complexes likely predominat
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Thorium undergoes hydrolysis in aqu
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The distribution of thorium aqueous
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from about 10 -8.5 mol/l (0.0007 mg
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Based on the assumptions and limita
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5.10 Tritium Geochemistry And K d V
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uranium. Uranium(VI) species domina
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gives 0.1 to 10 µg/l as the range
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mineral in reducing ore zones (Fron
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Percent Distribution 100 80 60 40 2
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5.11.6 Partition Coefficient, K d ,
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No attempt was made to statisticall
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Table 5.18. Selected chemical and t
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Another objective of this report is
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6.0 REFERENCES Adriano, D. C. 1992.
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Bensen, D. W. 1960. Review of Soil
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Metals by Geomedia. Variables, Mech
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EPA (U.S. Environmental Protection
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Griffin, R. A., A. K. Au, and R. R.
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+ Keeney-Kennicutt, W. L., and J. W
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Mattigod, S. V., A. L. Page, and I.
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Oscarson, D. W., and H. B. Hume. 19
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Relyea, J. F. and D. A. Brown. 1978
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Schultz, R. K., R. Overstreet, and
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Szalay, A. 1964. “Cation Exchange
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Yariv, S., and H. Cross. 1979. Geoc
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APPENDIX A Acronyms, Abbreviations,
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PC Personal computers operating und
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A.3.0 List of Symbols and Notation
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APPENDIX B Definitions
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Clay Content - particle size fracti
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Polynuclear Species - an aqueous sp
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C.1.0 Background Appendix C Partiti
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Cadmium K d Table C.2. Correlation
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C.3.0 Data Set for Soils Table C.4
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Cd K d (ml/g) Clay Cont. (wt%) pH C
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Page 163 and 164: Cd K d (ml/g) Clay Cont. (wt%) pH C
Page 165 and 166: Cd K d (ml/g) Clay Cont. (wt%) pH C
Page 167 and 168: D.1.0 Background Appendix D Partiti
Page 169 and 170: A second data set (see Section D.4)
Page 171 and 172: Table D.3. Correlation coefficients
Page 173 and 174: By transposing the CEC and cesium K
Page 175 and 176: Table D.6. Cesium K d values measur
Page 177 and 178: eported in Table D.8 are described
Page 179 and 180: a 1 b 1 Range of Solution Cs Concen
Page 181 and 182: Figure D.4. Generalized cesium Freu
Page 183 and 184: Table D.10. Estimated range of K d
Page 185 and 186: D.3.0 K d Data Set for Soils and Pu
Page 187 and 188: Cesium Kd (ml/g) Clay (wt.% ) Mica
Page 193 and 194: Cesium K d (ml/g) Clay (wt%) Mica (
Page 195 and 196: Bruggenwert, M. G. M., and A. Kamph
Page 197 and 198: Shiao, S. Y., P. Rafferty, R. E. Me
Page 199 and 200: E.1.0 Background Appendix E Partiti
Page 201 and 202: chromium-reductive soils may stem f
Page 204 and 205: E.2.0 Approach The approach used to
Page 206 and 207: Table E.3. Estimated range of K d v
Page 208 and 209: Table E.4. Data from Rai et al. (19
Page 210 and 211: E.4.0 References Davis, J. A. and J
Page 212 and 213: APPENDIX F Partition Coefficients F
Page 216 and 217: Table F.1. Summary of K d values fo
Page 218 and 219: Figure F.2. Variation of K d as a f
Page 220 and 221: F.4.0 References Abd-Elfattah, A.,
Page 222 and 223: APPENDIX G Partition Coefficients F
Page 224 and 225: A number of investigators have exam
Page 226 and 227: pH value, which is typical of the m
Page 228 and 229: These significant reductions in ads
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Page 234 and 235: Table G.2. Regression models for pl
Page 236 and 237: G.4.0 References Barney, G. S. 1984
Page 238 and 239: Nelson, D. M., R. P. Larson, and W.
Page 240 and 241: APPENDIX H Partition Coefficients F
Page 242 and 243: 1.6 ml/g for a measurement made on
Page 244 and 245: Figure H.1. Relation between stront
Page 246 and 247: Figure H.2. Relation between stront
Page 248 and 249: H.2.4 Approach Figure H.4. Relation
Page 250 and 251: A second look-up table (Table H.5)
Page 252 and 253: Sr K d (ml/g) Clay Content (%) pH C
Page 254 and 255: Sr K d (ml/g) Clay Content (%) pH C
Page 256 and 257: Sr K d (ml/g) Clay Conten t (%) pH
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Konishi, M., K. Yamamoto, T. Yanagi
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APPENDIX I Partition Coefficients F
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descriptive statistics of the thori
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Figure I.1. Linear regression betwe
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The look-up table (Table I.5) for t
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Thorium K d (ml/g) pH Clay (wt.%) C
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Rai, D., A. R. Felmy, D. A. Moore,
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J.1.0 Background Appendix J Partiti
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J.2.2 Uranium K d Studies on Soils
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Washington. The studies included an
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and then decreases with increasing
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Kd (ml/g) 100,000 10,000 1,000 100
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papers. Warnecke et al. (1984) indi
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Anderson et al. (1982) summarize an
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McKinley and Scholtis (1993) compar
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In a similar comparison of sorption
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J.3.1 K d Values as a Function ff p
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discussed, and one would have to ma
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al., 1992; and others). These refer
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· Manskaya et al. (1956) studied a
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concentrations of humic acid, there
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pH U Kd (ml/g) Clay Cont. (wt.%) CE
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J.6.0 References Ames, L. L., J. E.
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Erikson, R. L., C. J. Hostetler, R.
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R. C. Ewing. Materials Research Soc
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Sheppard, M. I., and D. H. Thibault
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Yamamoto, T., E. Yunoki, M. Yamakaw
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