Introduction to Soil Chemistry

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142 extraction taining one to several percent water. The soil is weighed and extracted as if it were dry (see Chapter 4, Section 4.13.1). It must be kept in mind that under these conditions the extractant will pick up and in some cases become saturated with water that will need to be removed before proceeding with the analysis. Another approach is to add an inorganic drying agent such as anhydrous sodium sulfate to the moist or wet soil. This latter approach is limited by the contact between the drying agent and the soil.Although adding a drying agent to soil will remove some water, it cannot be expected to remove all water. Thus, even in this case the extractant will contain some water after extraction and may need to be dried before analysis can be undertaken. Because even air dry soil will have a variable amount of water, analytical results are reported on the bases of the dry weight of soil taken. This procedure is described in Chapter 4 and expressed in equations (4.3) and (4.4). After extraction organic solvents can be dried using a number of common drying agents. Usually these are inorganic salts that react with water in a solvent and become hydrated. Not all drying agents are suitable for all solvents or solvents containing certain functional groups; thus care must be taken in selecting the drying agent. Common drying agents and their characteristics are listed in Table 7.2 [20]. Drying conditions are specific for specific extractions procedures, and thus the extraction method used will determine the drying required for the method used. 7.6. EXTRACT ANALYSIS Extracts may be analyzed using by colorimetry, spectroscopy (Chapter 8), chromatography, or a combination of chromatography and spectroscopy (Chapter 9). Spectroscopic, chromatographic, and chromatographic/mass spectroscopic analysis will most often be carried out directly on the clean, dry extract. 7.7. CONCLUSIONS A variety of methods, both physical and chemical, are used to separate components of interest from the soil matrix.This is usually accomplished using one of a number of different procedures, solvents, and solutions. Once isolated, the extracted component will be cleaned by one of several purification procedures that may also result in concentration. In other cases the extractant will be concentrated after the cleanup process is completed. In many instances one of the most important contaminants to remove will be water. Once cleaned, the extract may be analyzed by a wide variety of spectrophotometric and chromatographic methods.
ibliography 143 PROBLEMS 7.1. What type of extractant would you chose to extract the following compounds from soil? Explain the rationale for your choice. (a) LiCl (b) CH 3CH 2OH (c) CH 3(CH 2) 10CH 3 7.2. List the different “grades” of water available and describe how they are different and what residual materials they might contain. 7.3. A 100-g soil sample from the field was dried overnight at 105°C and later was found to have a weight of 95g. Calculate the percent moisture on a dry-weight bases [see Chapter 4, equations (4.3) and (4.4)]. 7.4. A researcher develops an extraction–cleanup procedure using a sandy soil. The procedure works well and is reported in the literature. Another researcher uses the same procedure on a clayey soil and an organic soil and obtains very poor, inconsistent results. What factors might account for these results? (You might want to use information from previous chapters to help answer this question.) 7.5. Describe in detail two extraction procedures applied to soil. (You might want to consult some of the references in the bibliography to answer this question.) 7.6. Describe two cleanup methods and list the advantages and disadvantages of each. 7.7. Explain why drying soil is both an important and a difficult procedure. Explain why all nonaqueous soil extracts may need to be dried. (You will need to consult previous chapters to answer this question.) 7.8. Can solid-phase extraction be used to concentrate an extract? 7.9. Using alcohol in ether as an example, explain why the stabilizers added to solvents may cause a problem in an extraction procedure. 7.10. What are the similarities between hexanes and petroleum ether? How do their characteristics affect chromatographic analysis? (You might want to consult Chapter 9 in answering this question.) BIBLIOGRAPHY Chulsung K, Lee Y, Ong SK. Factors affecting EDTA extraction of lead form leadcontaminated soils. Chemosphere 51:845–853, 2003.
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Introduction to Soil Chemistry Anal
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CHEMICAL ANALYSIS A SERIES OF MONOG
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Copyright © 2005 by John Wiley & S
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CONTENTS PREFACE xiii CHAPTER 1 SOI
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contents ix 4.14. Conclusion 89 Pro
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contents xi CHAPTER 10 SPECIATION 1
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xiv preface Moisture levels can cha
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CHAPTER 1 SOIL BASICS I MACROSCALE
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soil basics i 3 Mollisol Ap 0 - 17.
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soil basic i 5 Spodosol Oi 0 - 2.5
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horizonation 7 or basic.Thus, the t
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horizonation 9 Table 1.2. Major-Min
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peds 11 As would be expected, only
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peds 13 Figure 1.7. Peds isolated f
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P soil color 15 B P = pores B = bri
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soil naming 17 Under most condition
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soil chemistry, analysis, and instr
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ibliography 21 thus increased oxida
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CHAPTER 2 SOIL BASICS II MICROSCOPI
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O O Si O O d - d H H + d + O soil s
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d - Si O O O Al O O H d+ O O HO OH
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O HO O O O HO O O Si O Al O Si O O
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soil solids 31 the name taken from
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onding considerations 33 The two op
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surface features 35 Because differe
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energy considerations 37 side-by-si
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In Figure 2.5 the path to the right
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H O H H O C Na +- O O H H O H H O H
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eferences 43 2.7. Explain how the r
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CHAPTER 3 SOIL BASICS III THE BIOLO
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animals 47 C Figure 3.2. An ant col
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plants 49 Grasses and other similar
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plants 51 Rhizosphere Figure 3.4. I
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microorganisms 53 Table 3.1. Design
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microorganisms 55 microaerophilic,
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ioorganic 57 activity may be increa
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organic compounds 59 and may contai
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organic compounds 61 Table 3.3. Fun
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R 2C R organic compounds 63 O C - O
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analysis 65 3.7.1. Analysis for Ani
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problems 67 oxide by components in
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eferences 69 6. Bais HP, Park S-W,
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CHAPTER 4 SOIL BASICS IV THE SOIL A
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water 73 The soil atmosphere also c
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D C water 75 B Figure 4.3. A wide-d
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compounds in solution 77 tion is li
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+ NH4 + NH4 H H O + NH4 H H H + NH
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organic ions in solution 81 consequ
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distribution between soil solids an
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oxidative and reductive reactions i
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measuring soil water 87 soil is rep
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problems 89 blocks, and thermocoupl
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Page 112 and 113: 94 electrical measurements Figure 5
Page 114 and 115: 96 electrical measurements 1200 100
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Page 128 and 129: 110 electrical measurements Science
Page 130 and 131: 112 titrimetric measurement pH 13 1
Page 132 and 133: 114 titrimetric measurement Table 6
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Page 138 and 139: 120 titrimetric measurement Soil Sa
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Page 142 and 143: 124 titrimetric measurement - + X +
Page 144 and 145: 126 titrimetric measurement REFEREN
Page 146 and 147: 128 extraction Organic compounds, i
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Page 150 and 151: 132 extraction All nonaqueous solve
Page 152 and 153: 134 extraction Table 7.2. Character
Page 154 and 155: 136 extraction Figure 7.3. Solution
Page 156 and 157: 138 extraction Figure 7.5. A microw
Page 158 and 159: 140 extraction serious interference
Page 162 and 163: 144 extraction Cohen DR, Shen XC, D
Page 164 and 165: 146 extraction ultrasound; Applicat
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Page 168 and 169: 150 spectroscopy Incident X-rays q
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Page 193 and 194: CHAPTER 9 CHROMATOGRAPHY Chromatogr
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eferences 193 U.S. Environmental Pr
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196 speciation - Al H 2 O K H2O H2O
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198 speciation to consider all poss
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200 speciation many more species th
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202 speciation atomic absorption is
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204 speciation Table 10.2. Common O
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206 speciation reflecting the titra
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208 speciation Some oxyanions are s
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210 speciation 13. Wang J, Ashley K
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212 index Bioreactor, 124 Bioremedi
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214 index Gas chromatograph-mass sp
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216 index Path length, 159 Ped(s),
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218 index TMS, see Tetramethylsilan
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Vol. 34. Neutron Activation Analysi
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Vol. 117 Applications of Fluorescen
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