Materials To Remedy
Environmental Pollutions
Graduate Course (445.686)
Seoul National University, 2008/1
Chapter 1. Environmental Chemistry
• Complications in the use of units for the concentration of the composition
- ppm (parts per million)(cf. ppt, ppb): g of solutes per million milliliters of solution
=
E.g. 10 ppm aq. NH4OH
=10 mgNH4+L-1 = 10 x 10-3 gNH4
+L-1
=10 x 10-3/18.0 molNH4+L-1
= 5.56 x 10-4 mol NH4+L-1
1.1 Environmental composition: Aqueous solutions
11 or mgLmLg
Chapter 1. Environmental Chemistry
E.g. 10 ppm aq. NH4OH
= 5.56 x 10-4 mol NH4+L-1
= 5.56 x 10-4 mol NO3-L-1 (1:1 conversion)
= 5.56 x 10-4 x 62 x 103 mg NO3-L-1
= 34 ppm NO3-
( is due to molar mass difference between NH4+ and NO3
-)
= 34 mgNO3-L-1 =34 x 14/62 mgNL-1
= 7.7 mgNL-1 = 7.7 ppm(this is one way of avoiding complication abovementioned)
1.1 Environmental composition: Aqueous solutions
Chapter 1. Environmental Chemistry
• If molar concentration units are used, there will never be any confusion.
• Another limitation of ‘parts per…’:
they give no indication of the concentration of the reactive groups
E.g. Assumption : TOC in a forest stream = 9.0 mgCL-1
COOH/g of humic material in water = 4 mmolg-1
Carbon contents in humic material = 50 %
Then,
TOC = 9 x 10-3 x 100/50 g humic material/ L water
= 9 x 10-6 x 100/50 g humic material/L
x 4 x 10-3 mol COOH/g humic material
= 8 x 10-3 mol COOH/L water
1.1 Environmental composition: Aqueous solutions
Chapter 1. Environmental Chemistry
• Mass fraction of various kinds are used for solids without any ambiguity.
E.g. global avg. conc. of Fe: 4.1 wt%
V: 160 g/g = 160 ppm.
1.1 Environmental composition: Solids
1.1 Environmental composition: Gases
•Molar fraction or percentage conc. (usu. mixing ratio) are used for
gases. vol. fraction partial pressure
•For gases at low conc., ‘parts per…’ family of units is frequently used.
E.g. ppmv (parts per million by volume)
•Mass/vol, moles/vol, molecules/vol. are frequently used.
E.g. O2 in air, mixing ratio = 20.95% = 9.35 x 10-3 mol/L = 0.299 g/L
Chapter 1. Environmental Chemistry
• In many cases, the species distribution of the species, particularly
existing in more than one form is more important.
E.g. carbonate species and mercury in water
1.1 Environmental composition: Species distribution
a: oceans with 0.56 mol/L Cl- content
b: well water with 2.7 x 10-4 mol/L Cl-
Chapter 1. Environmental Chemistry
•Four principal compartments of the environments
-The atmosphere (the gaseous environment)
-The hydrosphere (the liquid, essentially aqueous environment)
-The terrestrial (solid) environment
-The biosphere (the living environment)
E.g. Water cycle
1.2 Chemical Processes
Since all processes are at steady state,
the residence time of water in the atmosphere
can then be determined by
days 6.90262.0
kgy 1096.4
kg 103.1
out)or (in flux
atmosphere in theamount statesteady
timeresidence
1-17
16
y
Chapter 1. Environmental Chemistry
• Human activity effects on the natural processes
E.g. The Bhopal disaster in India (3 December, 1984)
- massive release of methyl isocyanate (CH3-N=C=O) gas from the storage
tank
- killed 3,000 persons, 300,000 persons affected by exposure
- MIC is a starting material for carbaryl that is carbamate pesticide
- Usu. stored under refrigeration in an underground
- Causes: technological problems (T) + human activity factors (H)
T: failure of cooling unit, leakage of water into the tank, loss of nitrogen
pressure above the MIC, failure of safety device, etc.
H: political, organizational, and human factors, etc.
1.3 Anthropogenic (human) effects
Chapter 2. The earth’s atmosphere
• Major components: following mixing ratios are const. up to an altitude of
ab. 80 km due to the kinetic energy of gas molecules, being sufficiently
big enough to overcome any gravitational forces
2.1 Regions of the atmosphere: General Introduction
Avg. molar mass of the
atmosphere,aM
196.28
222222
-
COCOArArOONNa
gmol
fMfMfMfMM
Total mass of the atmosphere
Earth) theof (radius m1037.6
ms81.9 Pa,101325
kg105.27
kg]in [4
6
2-0
18
20
r
gP
g
rPM atm
Chapter 2. The earth’s atmosphere
• Four sections of the atmosphere: depending on the T change direction,
troposphere (대류권), stratosphere (성층권), mesosphere (중간층),
thermosphere (열권)
Pressure changes with altitude
RTghM
haePP /0
h=altitude in meter
Ph=pressure at given altitude in Pa
2.1 Regions of the atmosphere: General Introduction
Chapter 2. The earth’s atmosphere
• In thermosphere (열권) : nearly vacuum at ab. the altitude of 100 km
• For one photon,
• For 1 mol of photons,
2.1 Regions of the atmosphere: Chemical composition
J/photon 100.2
m 10100
ms 100.3Js106.6
18
9-
-1834
hcE
kJ/mol 1200106.0100.2 2318 E
kJ/mol 945H 2Nnm) 126( N 0
2 h
kJ/mol 498H 2Onm) 240( O 0
2 h
kJ/mol 1500H e Nnm) 80( N 0-
22 h
kJ/mol 1310H eOnm) 91( O 0- h
• In mesosphere (중간층): some amount of O3 that absorbs solar radiation
OOnm) 320230( O **
23 h
Chapter 2. The earth’s atmosphere
2.1 Regions of the atmosphere: The troposphere
• Convection currents and winds cause constant movement of the air
Chapter 2. The earth’s atmosphere
2.2 Reactions and calculations in atmospheric chemistry:
Thermodynamic calculations
• For
• At 25 C, : uneasy reaction at R.T.
• At 1500 C (I.e. in a cylinder of an internal combustion engine at the time of
ignition),
• Then the equilibrium constant is
• Since , if after complete burning, in the
compressed cylinder gas at 2500 C, then after some reaction between O2 and N2
(meaning the loss of partial pressure, x, of each)
• if x650 kPa, then
• Therefore, PNO=2x=1.4 kPa I.e. NO ratio in hot cylinder =
)( NO2)(O)(N 22 ggg
kJ/mol1.173)55.86(22 00 fGG
kJ/mol 2.111)2(2 0000
)(
0
2773 22 ONNONOf SSSTHG
0080.082.42773//314.8
/111200ln
0
P
TP K
KKmolJ
molJ
RT
GK
)/)(/(
)/(00
20
22PPPP
PPK
ON
NOP kPa 0.1 kPa, 650
22 ON PP
0080.0)0.1)(650(
4 2
xx
x66.002.52.54 2 xxx
ppmv 2200ppmv10kPa650
kPa 4.1 6
Chapter 2. The earth’s atmosphere
2.2 Reactions and calculations in atmospheric chemistry:
Kinetic calculations
• For the reverse reaction of
• At 25 C, if atmospheric conc. of NO=100 ppbv
• Then the initial rate of decomposition of NO at R.T. is
• The half-life, : 1028 times longer than the age of the
Earth
• This means there should be other reactions must be involved in controlling
the atmospheric conc. of NO -> Think what?
/mol/sm 106.2 )( NO2)(O)(N 3/1021.36
222
4 Tekggg
mol/s/m 103.4 341
2
k
sNOk i /mol/m 102.7][ 3522
2
yNOk
ti
38
2
2/1 108.1][
1
Chapter 2. The earth’s atmosphere
2.2 Reactions and calculations in atmospheric chemistry:
Photochemical reactions
• For , reaction rate=
• Since the production rxn=consumption rxn,
• Therefore
ONOh 2NO
][]][[ 212 NOfNOROOk
1
22 ][
][
][
f
ROOk
NO
NO
][ 21 NOf
2.2 Reactions and calculations in atmospheric chemistry:
Reactions involving free radicals
OH2OHO
OOO
OOO
ONONO
2
3
**
23
32
2
h
MM
h