McKay, Donald. "Front matter" Multimedia Environmental Models ...

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5.4.9 Quantitative Structure Property Relationships An invaluable feature of many series of organic chemicals is that their properties vary systematically, and therefore predictably, with changes in molecular structure. This relationship is illustrated for the chlorobenzenes in Figure 5.4. Figure 5.4A is a plot of log subcooled liquid solubility versus chlorine number from 0 (benzene) to 6 (hexachlorobenzene), which shows the steady drop in solubility as a result of substituting a chlorine for a hydrogen. The magnitude is a decrease in log solubility of about 0.65 units (factor of 4.5) per chlorine. Vapor pressure (Figure 5.4B) behaves similarly, with a drop of 0.72 units (factor of 5.2). K OW (Figure 5.4C) shows an increase of 0.53 units (factor of 3.4). The Henry’s law constant (Figure 5.4D) decreases by 0.16 units (factor of 1.4). These plots are invaluable as a method of interpolating to obtain values for unmeasured compounds. They provide a consistency check for newly reported data. They form the basis of estimation methods in which these properties are calculated for a variety of atomic and group fragments. An extension of the QSPR concept is to use the same principles to correlate and estimate toxicity. This is referred to as a quantitative structure activity relationship or QSAR. The best environmental example is the correlation of fish toxicity data expressed as a LC50 (µmol/L) versus K OW as obtained by Konemann (1981). ©2001 CRC Press LLC log (1/LC50) = 0.87 log K OW – 4.87 This and other correlations have been reviewed and discussed by Veith et al. (1983), Kaiser (1984, 1987), Karcher and Devillers (1990), and Abernethy et al. (1986, 1980). The fundamental relationship expressed by this correlation is best explained by an example. Consider two chemicals of log K OW 3 and 5. The LC50 values will be 182 and 3.3 µmol/L, a factor of 55 different. If the target site is similar to octanol in solvent properties, and equilibrium is reached, then the concentrations at the target site will be the product LC50 ¥ K OW or 182,000 and 330,000 µmol/L, only a difference of a factor of 1.8. The chemical of lower K OW appears to be less toxic (it has a higher LC50) when viewed from the point of view of water concentration. When viewed from the target site concentration, it is slightly more toxic. The chemicals in the correlation display similar toxicities when evaluated from the target site concentrations. The correlation therefore expresses two processes, partitioning and toxicity, with most of the chemical-to-chemical variation being caused by partitioning difference. Such chemicals are referred to as narcotics in which the effect seems to be induced by high lipid concentrations. 5.4.10 Summary The key properties of a pure substance for our purposes are its vapor pressure (i.e., its solubility in air), its solubility in water, its solubility in octanol, and the three partition coefficients K AW, K OW, and K OA. The magnitudes of these quantities are controlled by vapor pressure and activity coefficients.
Figure 5.4 Illustration of quantitative structure property relationships for benzene and the chlorobenzenes showing the systematic changes in properties with chlorine substitution. ©2001 CRC Press LLC
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McKay, Donald. "Front matter" Multi
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Multimedia Environmental Models The
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hensive, and reliable, and they hav
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Chapter 1 Introduction Chapter 2 So
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McKay, Donald. "Introduction" Multi
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It is now evident that our task is
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McKay, Donald. "Some Basic Concepts
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give the derived units directly wit
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Energy (joule, J) The joule, which
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particles (aerosols), or biota in w
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Worked Example 2.1 A three-phase sy
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(i) What is the concentration (C) i
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Answer ©2001 CRC Press LLC 5.1 kg,
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or or When t is zero, C is zero, th
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What is the absolute minimum piscic
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©2001 CRC Press LLC C 1 = C O/(1 +
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containing nonequilibrium quantitie
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1. Fallout of chemical from air to
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validated using real environments.
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©2001 CRC Press LLC CHAPTER 3 Envi
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of other, somewhat similar or homol
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Table 3.2 List of Chemicals Commonl
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elatively high concentrations. This
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exists between toxicologists and ch
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determine priority. This is a subje
Page 51 and 52: Another important classification of
Page 53 and 54: Figure 3.1 (continued) ©2001 CRC P
Page 55 and 56: Table 3.5 (continued) dichlorometha
Page 57 and 58: Table 3.5 (continued) total PCB 326
Page 59 and 60: Figure 3.2 Plot of log K AW vs. log
Page 61 and 62: chlorofluoro compounds are very sta
Page 63 and 64: 3.3.2.7 Arsenic Compounds Arsenic,
Page 65 and 66: McKay, Donald. "The Nature of Envir
Page 67 and 68: Figure 4.1 Evaluative environments.
Page 69 and 70: are subject to two important deposi
Page 71 and 72: metals and organic chemicals from w
Page 73 and 74: carbon figure for deeper sediments
Page 75 and 76: flows. The quality of this groundwa
Page 77 and 78: Table 4.2 Evaluative Environments A
Page 79 and 80: McKay, Donald. "Phase Equilibrium"
Page 81 and 82: Figure 5.1 Some principles and conc
Page 83 and 84: likely using an equilibrium criteri
Page 85 and 86: Another useful quantity is the rati
Page 87 and 88: experimentally, but not directly, u
Page 89 and 90: ©2001 CRC Press LLC 5.3 PROPERTIES
Page 91 and 92: 1.0. This, then, is the fugacity or
Page 93 and 94: where ©2001 CRC Press LLC pH is -l
Page 95 and 96: In terms of solubilities, S iA and
Page 97 and 98: The temperature coefficient is the
Page 99 and 100: (1982), Baum (1997) and Leo (2000).
Page 101: Although it may appear environmenta
Page 105 and 106: 5.5 ENVIRONMENTAL PARTITION COEFFIC
Page 107 and 108: C S = K PC W benzene = 1.1 ¥ 0.001
Page 109 and 110: Mackay (1986), in an attempt to sim
Page 111 and 112: Compartment Definition of Fugacity
Page 113 and 114: high concentration in the fish, but
Page 115 and 116: heat capacity of 0.38 J/g°C requir
Page 117 and 118: Therefore, ©2001 CRC Press LLC f =
Page 119 and 120: ©2001 CRC Press LLC Z T = S(V i/V
Page 121 and 122: ©2001 CRC Press LLC air Z = P S /R
Page 123 and 124: Table 5.1 Table 5.1 Summary of Defi
Page 125 and 126: Figure 5.7 Fugacity form 1 for dedu
Page 127 and 128: Calculate the following physical-ch
Page 129 and 130: ©2001 CRC Press LLC CHAPTER 6 Adve
Page 131 and 132: that all water will spend 100 days
Page 133 and 134: This enables us to conceive of, and
Page 135 and 136: ©2001 CRC Press LLC f = 15/0.5 = 3
Page 137 and 138: D AS dominates. A residence time of
Page 139 and 140: and Therefore, ©2001 CRC Press LLC
Page 141 and 142: eaction situation in which there is
Page 143 and 144: The rate constants in each case are
Page 145 and 146: ©2001 CRC Press LLC 1/t O = SD Ai/
Page 147 and 148: e achieved in 10 days. Detractors o
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Page 151 and 152: to Zepp and Cline (1977) for the or
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©2001 CRC Press LLC 6.7 LEVEL II C
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Figure 6.3 Fugacity Level II calcul
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McKay, Donald. "Intermedia Transpor
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Figure 7.1 Illustration of nonequil
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5. Diffusion within soils, and from
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sionally, the term flux rate is use
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©2001 CRC Press LLC N = ABDC/ Dy m
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no currents or eddies. In practice,
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diffusivity, and some unknown layer
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where ©2001 CRC Press LLC X = y/ U
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fraction of the total volume that i
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Figure 7.6 Mass transfer at the int
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partition coefficient. The signific
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and the series retains a similar ra
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ments of resuspension rates are par
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Figure 7.8 Movement of air phase (k
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ates can thus be used to estimate m
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Figure 7.9 Combination of D values
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Figure 7.10 Four-compartment Level
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Table 7.2 Order of Magnitude Values
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Unlike the Level II calculation, it
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Figure 7.12 Sample Level III output
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McKay, Donald. "Applications of Fug
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applications. Citations are given t
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Another approach is to employ Monte
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LEVEL1B A six-compartment Level I p
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Figure 8.1 Air-water exchange proce
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The total rates of transfer are thu
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Figure 8.2 Chemical transport and t
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mean. For chemical between depths o
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8.5.2 Process Description The water
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learn the benefits of using fugacit
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where Figure 8.5 QWASI model: stead
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are similar to those described by M
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C F ª Z Ff W ª 1.608 mol/m 3 ª 4
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y Mackay et al. (1983), and an appl
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accordingly, but the final solution
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Figure 8.10 Fish bioaccumulation pr
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The nature of the processes control
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iomagnification is more significant
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An alternative and more elegant met
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8.11.2 Model of a Chemical Evaporat
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Paterson et al. (1991), and Hung an
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8.14.1 Introduction ©2001 CRC Pres
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mated again in mg/day. Food, the ot
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models. Most interest is in LRT in
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available from the University of To
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McKay, Donald. "Appendix" Multimedi
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©2001 CRC Press LLC
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