Introduction to Soil Chemistry

More documents

Recommendations

Info

156 spectroscopy 8.6. ULTRAVIOLET AND VISIBLE SPECTROSCOPY Information about a soil extract can be obtained from the ultraviolet and visible regions of the spectrum. These are wavelengths ranging within 190–400 and 400–900nm, respectively (wider ranges of wavelengths are available on some instruments). The two regions of the spectrum are used very differently in soil analysis, although they are commonly found together in UV–Vis (ultraviolet–visible) spectrometers. The ultraviolet region can be used to obtain spectra of soil extracts; however, it is most commonly used as a detector for high-performance liquid chromatograph (HPLC). The visible region is used for colorimetric analysis, discussed below. Common solvents, such as water, acetonitirile, and heptane, are transparent over both the ultraviolet and visible regions. Because these represent both hydrophilic and hydrophobic solvents, a very broad range of compounds can be easily analyzed by UV. Adsorption in both regions involves promotion of electrons in double or triple bonds or nonbonding pairs of electrons in elements such as those on oxygen or nitrogen, to higher energy levels. Conjugated double bonds and nonbonding pairs conjugated with double bonds absorb at longer wavelengths than do isolated double bonds or nonbonding electron pairs. The more highly conjugated a system the longer the wavelength of the maximum absorption called the lambda max (l max) (see Figure 8.6). This means that all aromatic compounds have strong ultraviolet adsorption bands as well as terpenes and other conjugated systems. Unconjugated aldehydes, ketones, amides, acids, esters, and similar compounds also have ultraviolet absorptions, although they are not as strong. Any extract of soil containing large amounts of organic matter may have multiple absorption bands in the UV–Vis region of the spectrum. A UV–Vis spectrum of a simple aqueous, low-organic-matter, soil extract is shown in Figure 8.6. As seen in this spectrum, even a simple soil extract can have significant absorptions that can mask other potential absorptions of interest. Absorptions can also result in interferences with an ultraviolet and/or visible determination of a component or the derivative of a component. An interesting application of this region of the spectrum is the determination of nitrate and nitrite in soil extracts. Nitrate is very soluble in water and can be extracted using a simple water extraction procedure. Nitrate absorbs at 210nm and nitrite are 355nm and can be quantified using these absorption maxima (l max). Other materials extracted from soil as noted above, however, can obscure this region, and thus caution must be exercised to determine whether there are any interfering components in the extract [11,12,15–17]. 8.6.1. Ultraviolet Sample Preparation Samples are analyzed dissolved in a solvent, commonly acetonitrile, heptane, hexadecane, or water. A scan of the pure solvent in the sample cell, typically made of quartz (A in Figure 8.7), is first obtained. The dissolved sample is
ABSORBANCE 2.8040 2.2432 1.6824 1.2326 0.56079 ultraviolet and visible spectroscopy 157 0.000 200 300 400 500 600 700 800 WAVELENGTH (nm) Figure 8.6. UV–Vis spectrum of simple deionized water extract of soil. Absorption maximum is indicated by an arrow. Note that the absorbance is above 1, and therefore the solution should be diluted before attempting to interpret the spectrum. C Figure 8.7. Sample holders for various spectrophotometric measurements: (A) UV–Vis cells; (B) infrared attenuated total reflection (ATR) plate and stand—plate is attached to stand behind it when in use; (C) simple KBr pellet maker using the two bolts and the center dye; (D) a sample tube for NMR spectroscopy. B A D
Page 1:
Introduction to Soil Chemistry Anal
Page 4 and 5:
CHEMICAL ANALYSIS A SERIES OF MONOG
Page 6 and 7:
Copyright © 2005 by John Wiley & S
Page 9 and 10:
CONTENTS PREFACE xiii CHAPTER 1 SOI
Page 11 and 12:
contents ix 4.14. Conclusion 89 Pro
Page 13:
contents xi CHAPTER 10 SPECIATION 1
Page 16 and 17:
xiv preface Moisture levels can cha
Page 19 and 20:
CHAPTER 1 SOIL BASICS I MACROSCALE
Page 21 and 22:
soil basics i 3 Mollisol Ap 0 - 17.
Page 23 and 24:
soil basic i 5 Spodosol Oi 0 - 2.5
Page 25 and 26:
horizonation 7 or basic.Thus, the t
Page 27 and 28:
horizonation 9 Table 1.2. Major-Min
Page 29 and 30:
peds 11 As would be expected, only
Page 31 and 32:
peds 13 Figure 1.7. Peds isolated f
Page 33 and 34:
P soil color 15 B P = pores B = bri
Page 35 and 36:
soil naming 17 Under most condition
Page 37 and 38:
soil chemistry, analysis, and instr
Page 39 and 40:
ibliography 21 thus increased oxida
Page 41 and 42:
CHAPTER 2 SOIL BASICS II MICROSCOPI
Page 43 and 44:
O O Si O O d - d H H + d + O soil s
Page 45 and 46:
d - Si O O O Al O O H d+ O O HO OH
Page 47 and 48:
O HO O O O HO O O Si O Al O Si O O
Page 49 and 50:
soil solids 31 the name taken from
Page 51 and 52:
onding considerations 33 The two op
Page 53 and 54:
surface features 35 Because differe
Page 55 and 56:
energy considerations 37 side-by-si
Page 57 and 58:
In Figure 2.5 the path to the right
Page 59 and 60:
H O H H O C Na +- O O H H O H H O H
Page 61 and 62:
eferences 43 2.7. Explain how the r
Page 63 and 64:
CHAPTER 3 SOIL BASICS III THE BIOLO
Page 65 and 66:
animals 47 C Figure 3.2. An ant col
Page 67 and 68:
plants 49 Grasses and other similar
Page 69 and 70:
plants 51 Rhizosphere Figure 3.4. I
Page 71 and 72:
microorganisms 53 Table 3.1. Design
Page 73 and 74:
microorganisms 55 microaerophilic,
Page 75 and 76:
ioorganic 57 activity may be increa
Page 77 and 78:
organic compounds 59 and may contai
Page 79 and 80:
organic compounds 61 Table 3.3. Fun
Page 81 and 82:
R 2C R organic compounds 63 O C - O
Page 83 and 84:
analysis 65 3.7.1. Analysis for Ani
Page 85 and 86:
problems 67 oxide by components in
Page 87 and 88:
eferences 69 6. Bais HP, Park S-W,
Page 89 and 90:
CHAPTER 4 SOIL BASICS IV THE SOIL A
Page 91 and 92:
water 73 The soil atmosphere also c
Page 93 and 94:
D C water 75 B Figure 4.3. A wide-d
Page 95 and 96:
compounds in solution 77 tion is li
Page 97 and 98:
+ NH4 + NH4 H H O + NH4 H H H + NH
Page 99 and 100:
organic ions in solution 81 consequ
Page 101 and 102:
distribution between soil solids an
Page 103 and 104:
oxidative and reductive reactions i
Page 105 and 106:
measuring soil water 87 soil is rep
Page 107 and 108:
problems 89 blocks, and thermocoupl
Page 109:
eferences 91 8. Bohn HL, McNeal BL,
Page 112 and 113:
94 electrical measurements Figure 5
Page 114 and 115:
96 electrical measurements 1200 100
Page 116 and 117:
98 electrical measurements Referenc
Page 118 and 119:
100 electrical measurements Standar
Page 120 and 121:
102 Table 5.1. Ion-Selective Electr
Page 122 and 123:
104 electrical measurements In addi
Page 124 and 125: 106 electrical measurements along w
Page 126 and 127: 108 electrical measurements cools w
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
Page 134 and 135: 116 titrimetric measurement H 3 O +
Page 136 and 137: 118 titrimetric measurement Because
Page 138 and 139: 120 titrimetric measurement Soil Sa
Page 140 and 141: 122 titrimetric measurement 6.6. NI
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
Page 148 and 149: 130 extraction 3. What is the distr
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 160 and 161: 142 extraction taining one to sever
Page 162 and 163: 144 extraction Cohen DR, Shen XC, D
Page 164 and 165: 146 extraction ultrasound; Applicat
Page 166 and 167: 148 spectroscopy although technical
Page 168 and 169: 150 spectroscopy Incident X-rays q
Page 170 and 171: 152 spectroscopy with cellulose or
Page 172 and 173: 154 spectroscopy extract components
Page 176 and 177: 158 spectroscopy placed in the samp
Page 178 and 179: 160 spectroscopy to scratch them. W
Page 180 and 181: 162 spectroscopy Data Concentration
Page 182 and 183: 164 spectroscopy these make analysi
Page 184 and 185: 166 spectroscopy Table 8.1. Importa
Page 186 and 187: 168 spectroscopy nance (NMR) spectr
Page 188 and 189: 170 spectroscopy nitrogen containin
Page 190 and 191: 172 spectroscopy 7. Bernick MB, Get
Page 193 and 194: CHAPTER 9 CHROMATOGRAPHY Chromatogr
Page 195 and 196: Mobile phase in abaybayby abaybayby
Page 197 and 198: gas chromatography 179 Figure 9.3.
Page 199 and 200: gas chromatography 181 Table 9.3. C
Page 201 and 202: gas chromatography 183 Gas tight sy
Page 203 and 204: high-performance liquid chromatogra
Page 205 and 206: thin-layer chromatography 187 They
Page 207 and 208: alization of components on a thin-l
Page 209 and 210: conclusion 191 then a pure sample o
Page 211: eferences 193 U.S. Environmental Pr
Page 214 and 215: 196 speciation - Al H 2 O K H2O H2O
Page 216 and 217: 198 speciation to consider all poss
Page 218 and 219: 200 speciation many more species th
Page 220 and 221: 202 speciation atomic absorption is
Page 222 and 223: 204 speciation Table 10.2. Common O
Page 224 and 225:
206 speciation reflecting the titra
Page 226 and 227:
208 speciation Some oxyanions are s
Page 228 and 229:
210 speciation 13. Wang J, Ashley K
Page 230 and 231:
212 index Bioreactor, 124 Bioremedi
Page 232 and 233:
214 index Gas chromatograph-mass sp
Page 234 and 235:
216 index Path length, 159 Ped(s),
Page 236 and 237:
218 index TMS, see Tetramethylsilan
Page 238 and 239:
Vol. 34. Neutron Activation Analysi
Page 240 and 241:
Vol. 117 Applications of Fluorescen
show all

Introduction to Soil Chemistry

Create successful ePaper yourself

Delete template?

Save as template?