Atmospheric Chemistry
Posted by Alex
• • Full article
Atmospheric Composition
Atmospheric Gases |
Name |
Formula |
Concentration |
Lifetime |
| Nitrogen |
N2 |
78.1% |
|
| Oxygen |
O2 |
20.9% |
|
| Argon |
Ar |
0.9% |
|
| Carbon Dioxide |
CO2 |
394 ppm |
30-100 years |
| Water Vapor |
H2O |
5-50,000 |
10 days |
| Neon |
Ne |
18 |
|
| Helium |
He |
5 |
|
| Methane |
CH4 |
1.7 |
10 years |
| Krypton |
Kr |
1.1 |
|
| Stratospheric Ozone |
O3 |
500 ppb |
|
| Hydrogen |
H2 |
500 |
5 years |
| Nitrous Oxide |
N2O |
300 |
100 years |
| Xenon |
Xe |
90 |
|
| Carbon Monoxide |
CO |
50 |
3 months |
| Tropospheric Ozone |
O3 |
10 |
20 days |
| CFC-12 |
CF2Cl2 |
500 ppt |
150 years |
| Carbonyl Sulfide |
OCS |
500 |
2 years |
| CFC-11 |
CFCl3 |
250 |
75 years |
| Hydrogen Peroxide |
H2O2 |
100 |
1 day |
| Formaldehyde |
CH2O |
100 |
10 days |
| Terpene |
C10H16 |
100 |
10 hours |
| Isoprene |
C5H8 |
100 |
5 hours |
| Carbon Tetrachloride |
CCl4 |
100 |
30 years |
| Methylchloroform |
CH3CCl3 |
65 |
7 years |
| Nitrogen Oxides |
NOx |
10 |
1 day |
| Ammonia |
NH3 |
10 |
5 days |
| Sulfur Dioxide |
SO2 |
10 |
5 days |
| Dimethyl Sulfide |
CH3SCH3 |
10 |
1 day |
| Carbon Disulfide |
CS2 |
1 |
1 month |
| Hydrogen Sulfide |
CS2 |
1 |
5 days |
| Hydroperoxyl Radical |
HO2 |
1 |
1 second |
| Hydroxyl Radical |
OH- |
0.1 |
1 second |
|
Residence Time |
\[ \tau = \frac{A}{F} \ \left[ \frac{Capacity}{Flux} \right] \]
|
Mixing Ratio (ppb) |
\[ MR = \frac{n_i}{n_{tot}-n_i} \ \frac{mol}{mol} \]
|
Volume Mixing Ratio (ppbv) |
\[ VR = \frac{V_i}{V_{tot}-V_i} \ \frac{m^3}{m^3} \]
|
| |
Gas Laws
Dalton's Law |
\[ p_{tot} = p_1 + p_1 + p_1 + \cdots + p_n \equiv \sum_{i=1}^{n} p_i \]
|
Boyle's Law |
\[ p_1V_1 = p_2V_2 \]
|
Charles's Law |
\[ \frac{V_1}{T_1} = \frac{V_2}{T_2} \]
|
Gay-Lussac's Law |
\[ \frac{p_1}{T_1} = \frac{p_2}{T_2} \]
|
Avogadro's Law |
\[ \frac{V_1}{n_1} = \frac{V_2}{n_2} \]
|
Ideal Gas Law |
\[ pV = nR^*T \]
\[ pV = Nk_BT \]
|
| |
Chemical Reactions
Reaction Types |
\[ \Delta H_{reaction}^{\ominus} > 0 \ \ \ (Endothermic) \]
\[ \Delta H_{reaction}^{\ominus} < 0 \ \ \ (Exothermic) \]
|
Hess's Law |
\[ \Delta H_{reaction}^{\ominus} = \sum \Delta H_{f\ (products)}^{\ominus} - \sum \Delta H_{f\ (reactants)}^{\ominus} \]
|
Arrhenius Equation |
\[ k_b = A \exp \left( \frac{-E_a}{RT} \right) \]
|
Unimolecular Reaction |
Example |
Rate |
Lifetime |
| A → B+C |
\[ r = -\frac{d[A]}{dt} = k_u[A] \] |
\[ \tau_u = \frac{1}{k_u} \] |
|
Bimolecular Reaction |
Example |
Rate |
Lifetime |
| A+B → C+D |
\[ r = -\frac{d[A]}{dt} = k_b[A][B] \] |
\[ \tau_b = \frac{1}{k_b[B]_0} \] |
|
Termolecular Reaction |
Example |
Rate |
Lifetime |
| A+B+m → C+D+m |
\[ r = -\frac{d[A]}{dt} = k_b[A][B][m] \] |
\[ \tau_t = \frac{1}{k_t[B]_0[m]} \] |
|
General Reaction |
Example |
Rate |
Lifetime |
| aA + bB → cC + dD |
\[ r = -\frac{1}{a} \frac{d[A]}{dt} = k[A]^a[B]^b \] |
\[ \tau = \frac{1}{k[B]_0^b} \] |
|
Steady State |
\[ \frac{d[A]}{dt} = 0 \]
|
| |
Photochemistry
Photochemical Processes |
|
Reaction |
Example |
Luminescence |
\[ A^* \to A + h\nu \] |
Bleach |
Non-Radiative Deactivation |
\[ A^* \to A + \Delta H \] |
Sunscreen |
Ionization |
\[ A^* \to A^+ + e^- \] |
Scanner |
Energy Transfer |
\[ A^* + B \to A + B^* \] |
Plastics |
Isomerization |
\[ A^* \to B \] |
Vitamin D Synthesis |
Addition |
\[ A^* + B \to A + B^* \] |
Fungicide |
Photodissociation |
\[ AB^* \to A + B \] |
Ozone |
|
Tropospheric Ozone |
\[ NO_2 + h\nu \xrightarrow{\lambda<420} NO + O\left( ^3P \right) \]
\[ O_2 + O\left( ^3P \right) \xrightarrow{M} O_3 \]
|
Stratospheric Ozone |
\[ O_2 + h\nu \xrightarrow{\lambda<240} 2O\left( ^3P \right) \]
\[ O_2 + O\left( ^3P \right) \xrightarrow{M} O_3 \]
|
| |
Gas Constants
Universal Gas Constant |
\[ R^* = 8.314 \ \frac{J}{mol\ K} \]
\[ R^* = 0.082 \ \frac{L\ atm}{mol\ K} \]
|
Gas Constant (Dry) |
\[ R_{d} = 287 \ \frac{J}{kg\ K} \]
|
Gas Constant (Moist) |
\[ R_{v} = 461.5 \ \frac{J}{kg\ K} \]
|
| |
Physical Constants
Avogadro's Number |
\[ N_A = 6.022\times 10^{23} \ \frac{molec}{mol} \]
|
Air Concentration |
\[ n_{air} = 2.46\times 10^{25} \ \frac{molec}{m^3} \]
|
Density of Air |
\[ \rho_{air} = 1.2 \ \frac{kg}{m^3} \]
|
Density of Fresh Water |
\[ \rho_{fresh} = 1000 \ \frac{kg}{m^3} \]
|
Density of Seawater |
\[ \rho_{sea} = 1025 \ \frac{kg}{m^3} \]
|
Density of Ice |
\[ \rho_{ice} = 917 \ \frac{kg}{m^3} \]
|
Boltzmann's Constant |
\[ k_{B} = 1.381\times 10^{-23} \ \frac{J}{K} \]
|
Molecular Weight of Air |
\[ M_{d} = 28.97 \ \frac{g}{mol} \]
|
Molecular Weight of Water |
\[ M_{v} = 18.02 \ \frac{g}{mol} \]
|
Specific Heat Capacity |
\[ c_{v} = 717 \ \frac{J}{kg\ K} \]
\[ c_{p} = 1004 \ \frac{J}{kg\ K} \]
|
| |
Latent Heat
Latent Heat of Vaporization |
\[ L_{v} = 2.50\times 10^{6} \ \frac{J}{kg} \]
|
Latent Heat of Sublimation |
\[ L_{s} = 2.83\times 10^{6} \ \frac{J}{kg} \]
|
Latent Heat of Fusion |
\[ L_{f} = 0.33\times 10^{6} \ \frac{J}{kg} \]
|
| |
Solubility
pH Equation |
\[ pH = -log_{10} \left[ H^+ \right] \]
|
Henry's Law |
\[ \frac{\left[ A\left(l\right) \right]}{\left[ A\left(g\right) \right]} = H_A^*RTL \]
|
| |
Air Quality
Air Quality Index |
Color |
Condition |
8-hr O3
(ppb) |
24-hr PM2.5
(μg/m3) |
24-hr CO
(ppm) |
|
Good |
0 - 59 |
0.0 - 15.4 |
0.0 - 4.4 |
|
Moderate |
60 - 75 |
15.5 - 35.4 |
4.5 - 9.4 |
|
USG |
76 - 95 |
35.5 - 65.4 |
9.5 - 12.4 |
|
Unhealthy |
96 - 115 |
65.5 - 150.4 |
12.5 - 15.4 |
|
Very Unhealthy |
116 - 374 |
150.5 - 250.4 |
15.5 - 30.4 |
|
Hazardous |
N/A |
250.5+ |
30.5+ |
|
Sources of OH- |
Photolysis of O3:
|
\[ \begin{aligned} &O_3 + h\nu \xrightarrow{\lambda<320} O \left( ^1D \right) + O_2 \\ &O \left( ^1D \right) + H_2O \to 2OH^- \end{aligned} \] |
Photolysis of CH2O:
|
\[ \begin{aligned} &CH_2O + h\nu \xrightarrow{\lambda<330} O H^- + HCO^- \\ &HCO^- + O_2 \to CO + HO_2^- \\ &H^- + O_2 \to HO_2^- \\ &HO_2^- + NO \to NO_2 + OH^- \end{aligned} \] |
Photolysis of H2O2:
|
\[ H_2O_2 + h\nu \xrightarrow{\lambda<360} 2OH^- \] |
Photolysis of HONO:
|
\[ HONO + h\nu \xrightarrow{\lambda<400} OH^- + NO \] |
|
Stratospheric Reactions |
Ox Cycle:
(Chapman Cycle)
|
\[ \begin{aligned}
&O_2 + h\nu \xrightarrow{\lambda<240} 2O\left( ^3P \right) \\
&O_2 + O\left( ^3P \right) \xrightarrow{M} O_3 \\
&O_3 + h\nu \xrightarrow{\lambda<320} O_2 + O\left( ^1D \right) \\
&O_3 + O\left( ^3P \right) \to 2O_2 \end{aligned} \] |
HOx Cycle:
|
\[ \begin{aligned}
&H_2O + O\left( ^1D \right) \to 2OH^- \\
&O_3 + OH^- \to HO_2 + O_2 \\
&O_3 + HO_2 \to OH^- + 2O_2 \\
&HO_2 + OH^- \to H_2O + 2O_2 \end{aligned} \] |
NOx Cycle:
|
\[ \begin{aligned}
&N_2O + O\left( ^1D \right) \to 2NO \\
&NO + O_3 \to NO_2 + O_2 \\
&NO_2 + h\nu \xrightarrow{\lambda<420} NO + O\left( ^3P \right) \\
&NO_2 + O\left( ^3P \right) \to NO + 2O_2 \end{aligned} \] |
NOx Reservoir Species:
|
\[ \begin{aligned}
&NO_2 + OH^- \to HNO_3 \ \ \ (day) \\
&NO_2 + O_3 \to NO_3 + O_2 \ \ \ (night) \\
&NO_2 + NO_3 \to N_2O_5 \end{aligned} \] |
|
CFC Reactions |
Gas-Phase Reactions:
|
\[ \begin{aligned}
&CF_2Cl_2 + h\nu \xrightarrow{\lambda<260} Cl + CF_2Cl \\
&Cl + O_3 \to ClO + O_2 \\
&ClO + O\left( ^3P \right) \to Cl + O_2 \end{aligned} \] |
Multi-Phase Reactions:
|
\[ \begin{aligned}
&Cl + HO_2 \to HCl + O_2 \\
&ClO + OH^- \to HCl + O_2 \\
&ClO + NO_2 \to ClONO_2 \\
&ClONO_2 + HCl \xrightarrow{surface} Cl_2 + HNO_3 \\
&Cl_2 + h\nu \xrightarrow{\lambda<350} 2Cl \end{aligned} \] |
|
Tropospheric Reactions |
ROx Cycle:
|
\[ \begin{aligned}
&RH + OH^- \to R + H_2O \\
&R + O_2 \xrightarrow{M} RO_2 \end{aligned} \] |
HOx Cycle:
|
\[ \begin{aligned}
&CO + OH^- \to H + CO_2 \\
&H + O_2 \xrightarrow{M} HO_2 \\ \\
&CH_4 + OH^- \to CH_3 + H_2O \\
&CH_3 + O_2 \xrightarrow{M} CH_3O_2 \\
&CH_3O_2 + NO \xrightarrow{M} CH_3O + NO_2 \\
&CH_3O + O_2 \xrightarrow{M} CH_2O + HO_2 \end{aligned} \] |
NOx Cycle:
|
\[ \begin{aligned}
&NO + RO_2 \to NO_2 + RO \ \ \ (day) \\
&NO_2 + h\nu \xrightarrow{\lambda<420} NO + O\left( ^3P \right) \\
&O_2 + O\left( ^3P \right) \xrightarrow{M} O_3 \\ \\
&NO + O_3 \to NO_2 + O_2 \ \ \ (night) \\
&NO_2 + h\nu \xrightarrow{\lambda<420} NO + O\left( ^3P \right) \\
&O_2 + O\left( ^3P \right) \xrightarrow{M} O_3 \end{aligned} \] |
Combustion:
|
\[ \begin{aligned}
&O_2 \xrightarrow{heat} 2O\left( ^3P \right) \\
&N_2 + O \xrightarrow{heat} NO + N \\
&N + O_2 \xrightarrow{heat} NO + O\left( ^3P \right) \end{aligned} \] |
|
Volatile Organic Compounds |
|
General Formula |
Example |
Alkane |
\[ R-H \] |
\[ CH_4 \ \ (methane) \] |
Alkene |
\[ R_2C=CR_2 \] |
\[ C_2H_4 \ \ (ethylene) \] |
Alkyne |
\[ RC=CR \] |
\[ C_2H_2 \ \ (acetylene) \] |
Aromatic |
\[ C_6R_6 \] |
\[ C_6H_6 \ \ (benzene) \] |
Alcohol |
\[ R-OH \] |
\[ CH_3OH \ \ (methanol) \] |
Aldehyde |
\[ R-CHO \] |
\[ CH_2O \ \ (formaldehyde) \] |
Ketone |
\[ RCOR \] |
\[ (CH_3)_2CO \ \ (acetone) \] |
Peroxides |
\[ R-OOH \] |
\[ H_2O_2 \ \ (h.\ peroxide) \] |
Organic Acid |
\[ R-COOH \] |
\[ CH_2O_2 \ \ (formic\ acid) \] |
Organic Nitrate |
\[ R-ONO_2 \] |
\[ CH_3NO_3 \ \ (methyl\ nitrate) \] |
Alkyl Peroxy Nitrate |
\[ RO_2-NO_2 \] |
\[ CH_3O_2NO_2 \ \ (methyl\ p.) \] |
Peroxy Acyl Nitrate |
\[ RO_2-NO_2 \] |
\[ C_2H_3NO_5 \ \ (PAN) \] |
Alkyl Radical |
\[ R\cdot \] |
\[ CH_3\cdot \ \ (methyl\ r.) \] |
Acyl Radical |
\[ RC\cdot O \] |
\[ CH_3C\cdot=O \ \ (acetyl\ r.) \] |
Alkoxy Radical |
\[ RO\cdot \] |
\[ CH_3O\cdot \ \ (methoxy\ r.) \] |
Peroxy Radical |
\[ RO_2\cdot \] |
\[ CH_3O_2\cdot \ \ (methylperoxy\ r.) \] |
Biogenic |
\[ C_5H_8 \] |
\[ C_{10}H_{16} \ \ (\alpha -pinene) \] |
|
Particle Sizes |
Aitkin |
Large |
Giant |
| \[ r<0.1 \] |
\[ 0.1 < r < 1 \] |
\[ r>1 \] |
Nuclei |
Accumulation |
Coarse |
| \[ r<0.1 \] |
\[ 0.1 < r < 2.5 \] |
\[ r>2.5 \] |
|
| |