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

More documents

Recommendations

Info

0.1, and soil 1.0. There is also an emission of 4 mol/h. Calculate the fugacity concentrations, persistence amounts and outflow rates. I = E + GACBA + GWCBW = 4 + 1000 ¥ 0.01 + 1 ¥ 1 = 15 mol/h SGZ = 1000 ¥ 4 ¥ 10–4 +1 ¥ 10–1 = 0.5 f = I/ SGZ = 30 Pa CA = 0.012 CW = 3 CS = 30 mol/m3 mA = 120 mW = 300 mS = 30 M (total) = 450 mol GACA = 12 GWCW = 3 GSCS = 0 Total = 15 = I mol/h t = 450/15 =30 h In this example, the total amount of material in the system, M, is 450 mol. The inflow rate is 15 mol/h, thus the residence time or the persistence of the chemical is 30 hours. This proves to be a very useful time. Note that the air residence time is 10 hours, and the water residence time is 100 hours; thus, the overall residence time of the chemical is a weighted average, influenced by the extent to which the chemical partitions into the various phases. The soil has no effect on the fugacity or the outflow rates, but it acts as a “reservoir” to influence the total amount present M and therefore the residence time or persistence. 6.2.3 D values The group G Z, and other groups like it, appear so frequently in later calculations that it is convenient to designate them as D values, i.e., ©2001 CRC Press LLC G Z = D mol/Pa h The rate, N mol/h, then equals D f. These D values are transport parameters, with units of mol/Pa h. When multiplied by a fugacity, they give rates of transport. They are thus similar in principle to rate constants, which, when multiplied by a mass of chemical, give a rate of reaction. Fast processes have large D values. We can write the fugacity equation for the evaluative environment in more compact form, as shown below: f = I/(D AA + D AW) = I/SD Ai where D AA = G AZ A, D AW = G WZ W, and the first subscript A refers to advection. Recalculating Example 6.1, Therefore, D AA = 0.4 and D AW = 0.1 and SD Ai = 0.5
©2001 CRC Press LLC f = 15/0.5 = 30 and the rates of output, Df, are 12 and 3 mol/h, totaling 15 mol/h as before. It is apparent that the air D value is larger and most significant. D values can be added when they are multiplied by a common fugacity. Therefore, it becomes obvious which D value, and hence which process, is most important. We can arrive at the same conclusion using partition coefficients, but the algebra is less elegant. Note that how the chemical enters the environment is unimportant, all sources being combined or lumped in I, the overall input. This is because, once in the environment, the chemical immediately achieves an equilibrium distribution, and it “forgets” its origin. 6.2.4 Advective Processes In an evaluative environment, there are several advective flows that convey chemical to and from the environment, namely, 1. inflow and outflow of air 2. inflow and outflow of water 3. inflow and outflow of aerosol particles present in air 4. inflow and outflow of particles and biota present in water 5. transport of air from the troposphere to the stratosphere, i.e., vertical movement of air out of the environment 6. sediment burial, i.e., sediment being conveyed out of the well mixed layer to depths sufficient that it is essentially inaccessible 7. flow of water from surface soils to groundwater (recharge) It also transpires that there are several advective processes which can apply to chemical movement within the evaluative environment. Notable are rainfall, water runoff from soil, sedimentation, and food consumption, but we delay their treatment until later. In situations 1 through 4, there is no difficulty in deducing the rate as GC or Df, where G is the flowrate of the phase in question, C is the concentration of chemical in that phase, and the Z value applies to the chemical in the phase in which it is dissolved or sorbed. For example, aerosol may be transported to an evaluative world in association with the inflow of 10 12 m 3 /h of air. If the aerosol concentration is 10 –11 volume fraction, then the flowrate of aerosol G Q is 10 m 3 /h. The relevant concentration of chemical is that in the aerosol, not in the air, and is normally quite high, for example, 100 mol/m 3 . Therefore, the rate of chemical input in the aerosol is 1000 mol/h. This can be calculated using the D and f route as follows, giving the same result. If Z Q = 10 8 , then f = C Q/Z Q = 100/10 8 = 10 –6 Pa D AQ = G QZ Q = 10 ¥ 10 8 = 10 9
Page 1 and 2:
McKay, Donald. "Front matter" Multi
Page 3 and 4:
Multimedia Environmental Models The
Page 5 and 6:
hensive, and reliable, and they hav
Page 7 and 8:
Chapter 1 Introduction Chapter 2 So
Page 9 and 10:
McKay, Donald. "Introduction" Multi
Page 11 and 12:
It is now evident that our task is
Page 13 and 14:
McKay, Donald. "Some Basic Concepts
Page 15 and 16:
give the derived units directly wit
Page 17 and 18:
Energy (joule, J) The joule, which
Page 19 and 20:
particles (aerosols), or biota in w
Page 21 and 22:
Worked Example 2.1 A three-phase sy
Page 23 and 24:
(i) What is the concentration (C) i
Page 25 and 26:
Answer ©2001 CRC Press LLC 5.1 kg,
Page 27 and 28:
or or When t is zero, C is zero, th
Page 29 and 30:
What is the absolute minimum piscic
Page 31 and 32:
©2001 CRC Press LLC C 1 = C O/(1 +
Page 33 and 34:
containing nonequilibrium quantitie
Page 35 and 36:
1. Fallout of chemical from air to
Page 37 and 38:
validated using real environments.
Page 39 and 40:
©2001 CRC Press LLC CHAPTER 3 Envi
Page 41 and 42:
of other, somewhat similar or homol
Page 43 and 44:
Table 3.2 List of Chemicals Commonl
Page 45 and 46:
elatively high concentrations. This
Page 47 and 48:
exists between toxicologists and ch
Page 49 and 50:
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 and 102: Although it may appear environmenta
Page 103 and 104: Figure 5.4 Illustration of quantita
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: This enables us to conceive of, and
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 and 186:
ates can thus be used to estimate m
Page 187 and 188:
Figure 7.9 Combination of D values
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
Page 211 and 212:
mean. For chemical between depths o
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
Page 219 and 220:
are similar to those described by M
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
Page 231 and 232:
iomagnification is more significant
Page 233 and 234:
An alternative and more elegant met
Page 235 and 236:
8.11.2 Model of a Chemical Evaporat
Page 237 and 238:
Paterson et al. (1991), and Hung an
Page 239 and 240:
8.14.1 Introduction ©2001 CRC Pres
Page 241 and 242:
mated again in mg/day. Food, the ot
Page 243 and 244:
models. Most interest is in LRT in
Page 245 and 246:
available from the University of To
Page 247 and 248:
McKay, Donald. "Appendix" Multimedi
Page 249 and 250:
©2001 CRC Press LLC
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?