Environmental Chemistry with Major Issues

Nitrogen and Carbon cycles

SO2, H2S from volcanoes, CO2 from forest fires, NO - NO2 - O3 from lightning

N2 - 78%
O2 - 21%
Ar - 1%
CO2 - 0.03%
And trace amounts of others

Troposphere - 0 to 10km
Stratosphere - 10 to 50km
Mesosphere - 50 to 200km
Thermosphere - above 200km

Contains 80% of total mass and almost all of the water vapor (H20 g)

Temperature decreases

Consists of Nitrogen, Oxygen, and Ozone

Temperature increases due to exothermic reactions

Low concentrations of gases

Temperature decreases

Consists of N2, N, O2

Temperature increases due to bombardment of gas mocs by electrons and protons from the sun

Absorbtion of dangerous photons:
Results in loss of an electron -->
NO + hv --> NO+ + e-

Occurs in the mesosphere and thermosphere

Absorbtion of dangerous photons:
Results in dissociation of moc -->
O2 + hv --> O + O --> O2

Occurs in the mesosphere and thermosphere

Natural process:
O2 + uva 240nm --> O + O
M + O + O2 --> O3 + M

Principle absorber of UV radiation from 240 to 300 nm

Ozone is normally found in the stratosphere but that is where it is being depleted

Ozone reaction with CL atoms formed from UV dissociation of Freons results in: OZONE DEPLETION

Chlorofluorocarbons used in AC, Spray propellants, Foam products

Non-toxic
Non-reactive
Non-flammable

Ultraviolet radiation could break C-Cl bonds in freons:
CFCl3 + uv -->CFCl2 + Cl
or
CF2Cl2 + uv -->CF2Cl + CL

Cl acts as a catalyst for Ozone depletion:
Cl + O3 --> ClO (intermediary) + O2
ClO + O --> Cl + O2
=
O3 + O --> 2 O2

Each Cl can destroy 10^4 to 10^5 O3 molecules

High Altitude Aircraft and Some natural processes produce NO, NO2 which can destroy Ozone:
O3 --> O2 + O
NO + O3 --> NO2 + O2
=
2 O3 --> 3 O2

It was thought that Ozone depletion could have very negative side effects such as skin cancer
Most countries agreed to stop using Freons ( which was Epic)
Believed Ozone problem would fix itself (that has been seen to be true)

In the visible region (400 - 700 nm) is being absorbed by the earth's surface

Earth then radiates energy in the infrared region:

Mean temp of the earth is rising significantly

Some mocs are capable of changing their dipole moments which allows them to absorb infrared light

Causes them to lose heat to the troposphere by collisions

H2O - Atmospheric concentration is constant (raises the temp of the earth and allows it to be habitable) Not a problem

CO2 levels have increased 25% over pre-industrial values

10^10 tons of CO2 generated per year by transportation, power production, industry, and home heating (adds 1 ppm annually to the atmosphere)

CH4, NO2, Freons increase to human activity

Freons are very potent greenhouse gases

Causing weather patters to change

Volcanic eruptions and reduction of CFC's may somewhat offset CO2 affects but only viable solution is decrease of CO2 emissions

about 5.5 - 5.6 because of normal CO2 concentrations in the atmosphere

has a pH below 5.6

SO2 from metal extraction, burning of sulfur containing coal, NO2 and other acid anhydrides can lower pH to 4.3

Covalent oxides react w/ water to produce acids (acid anhydrides)

Toxic to aquatic life and vegetation

Develop practical and inexpensive ways to remove SO2 from effluent gases

Installation of H2SO4 manufacturing facilities near SO2 sources

Primary pollutants - NO, CO, Hydrocarbons (from vehicle exhaust)
result in formation of
Secondary Pollutants - NO2, O3 ( these actually cause smog)

O3 reacts with C==C bonds in rubber, lung tissue, and other biological substances (gasoline)

O3 rxns produce mocs like PAN and various Organic intermediates which form aerosoles (liquid droplets) and scatter sunlight to form Haze

Sunlight is important in the rxns

Cause peak concentrations of smog at certain times of the day

Burning coal produces SO2, Ash, Soot, and CO

SO2 forms H2SO4 which leads to (NH4)2SO4 aerosol which is damaging to lungs

Dec 1952, 4000 to 8000 deaths caused by smog in London

1948, deaths in Donora, PA

Lead to US Clean Air Act