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

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1/k 2 versus K OW to obtain quantities containing k M and k W. Such a plot was compiled by Mackay and Hughes (1984), yielding estimates of the two-resistances expressed as characteristic uptake times. Another example is the penetration of chemicals through the waxy cuticles of leaves in which there are air and wax resistances in series. Kerler and Schonherr (1988) have measured such penetration rates for a variety of chemicals, and Schramm et al. (1987) have attempted to model chemical uptake by trees using this tworesistance approach. A plant’s principal problem in life is to manage its water budget and avoid excessive loss of water through leaves. It accomplishes this by forming a waxy layer through which water has only a very slow diffusion rate. Diffusivities are very low, leading to very low MTCs and D values for water. The plant thus exploits this two-resistance approach to conserve water. If only governments could manage their budgets with the same efficiency! 7.9 COMBINING SERIES AND PARALLEL D VALUES Having introduced these transport D values and shown how they combine when describing resistances in series, it is useful to set out the general flux equation for any combination of transport processes in series or parallel. Each transport process is quantified by a D value (deduced as GZ, kAZ, or BAZ/Y) that applies between two points in space such as a bulk phase and an interface, or between two bulk phases. It is helpful to prepare an arrow diagram of the processes showing the connections, as illustrated in Figure 7.9. Diffusive processes are reversible, so they actually consist of two arrows in opposing directions with the same D value but driven by different source fugacities. When processes apply in parallel between common points, the D values add. An example is wet and dry deposition from bulk air to bulk water. ©2001 CRC Press LLC D TOTAL = D 1 + D 2 + D 3, etc. When processes apply in series, the resistances add or, correspondingly, the reciprocal D values add to give a reciprocal total. 1/D TOTAL = 1/D 1 + 1/D 2 + 1/D 3, etc. An example is the addition of air and water boundary layer resistances, which in total control the rate of volatilization from water. It is possible to assemble numerous combinations of series and parallel processes linking bulk phases and interfaces. These situations can be viewed as electrical analogs, with voltage being equivalent to fugacity, resistance equivalent to 1/D, and current equivalent to flux (mol/h). Figure 7.9 gives some examples. In air-water exchange, there can be deposition by the parallel processes of (1) dry particle deposition, (2) wet particle deposition, (3) rain dissolution, and (4) diffusive absorption-volatilization.
Figure 7.9 Combination of D values and resistances in series, parallel, and combined configurations. The soil-air exchange example involves parallel diffusive transport from bulk soil to the interface in water and air, followed by a series air boundary layer diffusion step. The sediment-water example is similar, having parallel diffusive paths for chemical transport in water and in association with organic colloids. The difficulty is to estimate the diffusivity of the colloids. Even more complex combinations can be compiled for transport processes into and within organisms, this being essentially the science of pharmacokinetics. ©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
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Another important classification of
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Figure 3.1 (continued) ©2001 CRC P
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Table 3.5 (continued) dichlorometha
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Table 3.5 (continued) total PCB 326
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Figure 3.2 Plot of log K AW vs. log
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chlorofluoro compounds are very sta
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3.3.2.7 Arsenic Compounds Arsenic,
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McKay, Donald. "The Nature of Envir
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Figure 4.1 Evaluative environments.
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are subject to two important deposi
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metals and organic chemicals from w
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carbon figure for deeper sediments
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flows. The quality of this groundwa
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Table 4.2 Evaluative Environments A
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McKay, Donald. "Phase Equilibrium"
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Figure 5.1 Some principles and conc
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likely using an equilibrium criteri
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Another useful quantity is the rati
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experimentally, but not directly, u
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©2001 CRC Press LLC 5.3 PROPERTIES
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1.0. This, then, is the fugacity or
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where ©2001 CRC Press LLC pH is -l
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In terms of solubilities, S iA and
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The temperature coefficient is the
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(1982), Baum (1997) and Leo (2000).
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Although it may appear environmenta
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Figure 5.4 Illustration of quantita
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5.5 ENVIRONMENTAL PARTITION COEFFIC
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C S = K PC W benzene = 1.1 ¥ 0.001
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Mackay (1986), in an attempt to sim
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Compartment Definition of Fugacity
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high concentration in the fish, but
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heat capacity of 0.38 J/g°C requir
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Therefore, ©2001 CRC Press LLC f =
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©2001 CRC Press LLC Z T = S(V i/V
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©2001 CRC Press LLC air Z = P S /R
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Table 5.1 Table 5.1 Summary of Defi
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Figure 5.7 Fugacity form 1 for dedu
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Calculate the following physical-ch
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©2001 CRC Press LLC CHAPTER 6 Adve
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that all water will spend 100 days
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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
Page 149 and 150: sulfate to sulfide or by dechlorina
Page 151 and 152: to Zepp and Cline (1977) for the or
Page 153 and 154: ©2001 CRC Press LLC 6.7 LEVEL II C
Page 155 and 156: Figure 6.3 Fugacity Level II calcul
Page 157 and 158: McKay, Donald. "Intermedia Transpor
Page 159 and 160: Figure 7.1 Illustration of nonequil
Page 161 and 162: 5. Diffusion within soils, and from
Page 163 and 164: sionally, the term flux rate is use
Page 165 and 166: ©2001 CRC Press LLC N = ABDC/ Dy m
Page 167 and 168: no currents or eddies. In practice,
Page 169 and 170: diffusivity, and some unknown layer
Page 171 and 172: where ©2001 CRC Press LLC X = y/ U
Page 173 and 174: fraction of the total volume that i
Page 175 and 176: Figure 7.6 Mass transfer at the int
Page 177 and 178: partition coefficient. The signific
Page 179 and 180: and the series retains a similar ra
Page 181 and 182: ments of resuspension rates are par
Page 183 and 184: Figure 7.8 Movement of air phase (k
Page 185: ates can thus be used to estimate m
Page 189 and 190: Figure 7.10 Four-compartment Level
Page 191 and 192: Table 7.2 Order of Magnitude Values
Page 193 and 194: Unlike the Level II calculation, it
Page 195 and 196: Figure 7.12 Sample Level III output
Page 197 and 198: McKay, Donald. "Applications of Fug
Page 199 and 200: applications. Citations are given t
Page 201 and 202: Another approach is to employ Monte
Page 203 and 204: LEVEL1B A six-compartment Level I p
Page 205 and 206: Figure 8.1 Air-water exchange proce
Page 207 and 208: The total rates of transfer are thu
Page 209 and 210: Figure 8.2 Chemical transport and t
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Page 213 and 214: 8.5.2 Process Description The water
Page 215 and 216: learn the benefits of using fugacit
Page 217 and 218: where Figure 8.5 QWASI model: stead
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Page 221 and 222: C F ª Z Ff W ª 1.608 mol/m 3 ª 4
Page 223 and 224: y Mackay et al. (1983), and an appl
Page 225 and 226: accordingly, but the final solution
Page 227 and 228: Figure 8.10 Fish bioaccumulation pr
Page 229 and 230: The nature of the processes control
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Page 233 and 234: An alternative and more elegant met
Page 235 and 236: 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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