Geology

What contributed towards earth's secondary atmosphere?

(After magma ocean cooled) Continued to cool. Three processes: Outgassing of bombarding meteorites Outgassing of earth's interior (main one) Photochemical reactions involving atmospheric gases and UV radiation from the Sun

Photochemical reactions

1. Dissociation of water vapor to hydrogen and oxygen with hydrogen escaping into space 2. Newly formed oxygen reacted with methane to form carbon dioxide and water 3. Oxygen also reacted with ammonia to form nitrogen and water

A single chlorine atom can react with how many ozone molecules?

10,000

Troposphere

18km at equater, 8km at poles 80-90% of mass of atmosphere Heated at bottom, rising air cools Cause out weather

How much has the average global ozone concentrations declined since 1980s?

3%

Mesosphere

50km-80km Temperature cools at higher altitudes

What does the D layer do?

Absorb AM radio waves disappears at night

What caused photochemical smog?

Advent of automobile

What caused oxygen in atmosphere to increase over time?

Aerobic bacteria ~2 billion years ago Stratospheric ozone layer began developing 400 million years ago

Major sources of CFC

Air conditioning and refrigeration Product of foam Aerosol sprays Solvents in electronics industry

Ancient photosynthetic cyanobacteria:

Appeared ~3.6 billion years ago Released oxygen as byproduct into oceans and atmosphere

What has doubled since 1980

Asthma prevalence

Thermosphere

Beyond 80km Low pressures (.005mb) Temperature increases upward because solar wind Near poles, earth's magnetic field concentrations with solar wind to form auroras

What do E and F layers do?

Bounce waves back to earth

What layers compose the ionosphere?

D, E, F

Why does temperature cool at higher altitudes in mesosphere?

Decreasing influence of ozone Does not absorb any significant portion of solar radiation

Particulate matter

Diverse mixture of fine particles: Haze Smoke Dust

What causes formation of antarctic ozone hole?

During antarctic spring, sunlight provides energy to drive photochemical reactions: melting of polar clouds released trapped compounds compounds take part in chemical reactions that lead to ozone destruction

Photochemical dissociation hypothesis

Early atmosphere contained abundant methane, ammonia, water vapor Early atmosphere exposed to ultraviolet light from sun No ozone layer back then, so ultraviolet light reached surface of early earth

Homosphere

Earth's surface to 80km Atmospheric pressure decreases with height Uniform blend of gases Mostly nitrogen and oxygen

Gravity's effect on outgassing 4.4 BY ago

Held heavier gases (H2O, CO2, and N2) near earth's surface forming secondary atmosphere Lighter ones like H2 and He escaped into space

Modern atmosphere's chemical regions

Heterosphere Homosphere

Causes of ozone depletion

High-energy particles from solar flares and sunspots bombard our atmosphere Volcanic gases and ash particles react with ozone to break it down Release of CFC's into the atmosphere

Anthropogenic Pollution

Human-caused air pollution most prevalent in urbanized regions

What interactions with solar wind cause temperature to increase upward in thermosphere?

Ionization of atmospheric gases increases with sunlight at night shortwave radio waves bounce off ionosphere

What did earth's primary (first) atmosphere after accretion consist of?

Mainly hydrogen captured from the solar nebula by Earth's gravity Bombarding meteorites contributed additional gases: water vapor, carbon monoxide, methane, ammonia

Boundaries between temperature layers

Mesopause Stratopause Tropopause

Troposphere atmospheric components

Natural and human-caused variable gases, particles, and other chemicals Aerosols like soot produced dimming of sunlight reaching earth's surface by 4-8% Estimated 4.3 million killed by air pollution worldwide

What forms ozone in the stratosphere?

Natural processes

What months are depletion of Arctic ozone detected in northern hemisphere?

November and April

Ozone formation

O-O bond of oxygen molecule broken by uv light Formed O atom reacts with O2 and forms ozone

Heterosphere

Outer - 80km above surface less than 0.001% of atmosphere's mass gases not evenly mixed

What has been decreasing in the atmosphere since early 60s?

Ozone levels From September to November Hole grown enormously Hole covers area three times larger than US

Air pollution

Particulates and aerosols: small particles of dust, soon suspended pollution Combustion of fossil fuels Power and industrial plants Photochemical smog from interaction between sunlight and combustion products Industrial smog

Major air pollutants in photochemical smog

Peroxyacetyl nitrate (PAN) damages plants Ground-level ozone Nitrogen dioxide interacts with water vapor to produce nitric acid

Two sources of free oxygen in earth's early atmosphere

Photochemical dissociation Ancient photosynthetic cyanobacteria

What destroys ozone?

Photolysis - if O-O bond split by sunlight Formed O atom reacts with another ozone molecule and forms two oxygen molecules O2

Montreal Protocol signed by 24 nations

Pledged to reduce CFCs by 1999 CFC has now been phased out Ozone layer expected to recover in coming decades due to CFC decline Antarctic ozone not expected to return to 1980 global levels until 2050 and completely eliminated by 2065

Where has significant thinning of the ozone layer occurred?

Polar regions over last few decades

What happens during the antarctics winter?

Polar stratospheric clouds form under dark, extremely cold conditions Westerly winds circulate around continent creating atmospheric container (vortex) that traps and chills air Low temperatures form cloud particles that trap compounds

Clean Air Act

Reductions in carbon monoxide nitrogen oxides volatile organic compounds particulate matter lead Political debate

What is the beneficial influence of ozone (trace gas) on incoming radiation?

Stratospheric ozone protects us from incoming uv radiation from the sun

What caused earth to blow most of the primary atmosphere back into space?

The mars-sized object ~4.5 BY ago

Atmospheric layers based on temperature

Thermosphere Mesosphere Stratosphere Troposphere

Straosphere

Tropopause to 50km above earth Warmer going up because absorbs UV light from Sun to produce ozone

What is mostly absorbed by ozone layer?

UV radiation

Sources of Carbon dioxide in troposphere

Volcanism Weathering and erosion Respiration Burning of fossil fuels

What caused early oceans 4.4 billion years ago?

Water vapor condensing from cooling atmosphere raining down onto surface

Natural Factors Affecting Air pollution

Winds Local and Regional Landscapes Temperature inversion

Photochemical dissociation

all methane and ammonia converted to carbon dioxide and nitrogen Excess oxygen started to accumulate as more water dissociated

CFC

chlorine-flourine-carbon detected in stratosphere 1974

Winds

gather and move pollutants can be from one country to another affection international relations

Photochemical smog

results from interaction of sunlight with combustion products in automobile exhaust (nitrogen oxides and VOCs)

Local and regional landscapes

surrounding mountains, hills can form barriers to air movement volcano eruptions can erupt particulates into atmosphere and lead to acid rain