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

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Time (second or hour, s or h) The standard unit of a second (s) is inconveniently short when considering environmental processes such as flows in large lakes when residence times may be many years. The use of hours, days, and years is thus acceptable. We generally use hours as a compromise. Concentration The preferred unit is the mole per cubic metre (mol/m3) or the gram per cubic metre (g/m3). Most analytical data are reported in amount or mass per litre (L), because a litre is a convenient volume for the analytical chemist to handle and measure. Complications arise if the litre is used in environmental calculations, because it is not coherent with area or length. The common mg/L, which is often ambiguously termed the “part per million,” is equivalent to g/m3. In some circumstances, the use of mass fraction, volume fraction, or mole fraction as concentrations is desirable. It is acceptable, and common, to report concentrations in units such as mol/L or mg/L but, prior to any calculation, they should be converted to a coherent unit of amount of substance per cubic metre. Concentrations such as parts per thousand (ppt), parts per million (ppm), parts per billion (ppb), and parts per trillion (also ppt) should not be used. There can be confusion between parts per thousand and per trillion. The billion is 109 in North America and 1012 in Europe. The air ppm is usually on a volume/volume basis, whereas the water ppm is usually on a mass/volume basis. The mixing ratio used for air is the ratio of numbers of molecules or volumes and is often given in ppm. Concentrations must be presented with no possible ambiguity. Density (kg/m3) This has identical units to mass concentrations, but the use of kg/m3 is preferred, water having a density of 1000 kg/m3 and air a density of approximately 1.2 kg/m3. Force (newton, N) The newton is the force that causes a mass of 1 kg to accelerate at 1 m/s2. It is 105 dynes and is approximately the gravitational force operating on a mass of 102 g at the Earth’s surface. Pressure (pascal, Pa) The pascal or newton per square metre (N/m 2 ) is inconveniently small, since it corresponds to only 102 grams force over one square metre, but it is the standard unit, and it is used here. The atmosphere (atm) is 101325 Pa or 101.325 kPa. The torr or mm of mercury (mmHg) is 133 Pa and, although still widely used, should be regarded as obsolescent. ©2001 CRC Press LLC
Energy (joule, J) The joule, which is one N-m or Pa-m3, is also a small quantity. It replaces the obsolete units of calorie (which is 4.184 J) and Btu (1055 J). Temperature (K) The kelvin is preferred, although environmental temperatures may be expressed in degrees Celsius, °C, and not centigrade, where 0°C is 273.15 K. There is no degree symbol prior to K. Frequency (hertz, Hz) The hertz is one event per second (s–1). It is used in descriptions of acoustic and electromagnetic waves, stirring, and in nuclear decay processes where the quantity of a radioactive material may be described in becquerels (Bq), where 1 Bq corresponds to the amount that has a disintegration rate of 1 Hz. The curie (Ci), which corresponds to 3.7 ¥ 10 10 disintegrations per second (and thus 3.7 ¥ 10 10 Bq), was formerly used. Gas Constant (R) This constant, which derives from the gas law, is 8.314 J/mol K or Pa-m3/mol K. An advantage of the SI system is that R values in diverse units such as cal/mol K and cm3·atm/mol K become obsolete and a single universal value now applies. 2.2.1 Prefices The following prefices are used: Note that these prefices precede the unit. It is inadvisable to include more than one prefix in a unit, e.g., ng/mg, although mg/kg may be acceptable, because the base unit of mass is the kg. The equivalent µg/g is clearer. The use of expressions such as an aerial pesticide spray rate of 900 g/km2 can be ambiguous, since a kilo(metre2) is not equal to a square kilometre, i.e., a (km) 2. The former style is not permissible. ©2001 CRC Press LLC Factor Prefix Factor Prefix 101 102 103 106 109 1012 1015 1018 deka da 10–1 hecto h 10–2 kilo k 10–3 mega M 10–6 giga G 10–9 tera T 10–12 peta P 10–15 exa E 10–18 deci d centi c milli m micro m nano n pico p femto f atto a
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: give the derived units directly wit
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
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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
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©2001 CRC Press LLC f = 15/0.5 = 3
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D AS dominates. A residence time of
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and Therefore, ©2001 CRC Press LLC
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eaction situation in which there is
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The rate constants in each case are
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©2001 CRC Press LLC 1/t O = SD Ai/
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e achieved in 10 days. Detractors o
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sulfate to sulfide or by dechlorina
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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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