ESS chap.6 Atmospheric systems and societies

Atmosphere

gases that surround the earth’s surface and are retained by the gravitational field

roles of the atmosphere

• provides a shield from meteorites

• protects us from harmful sun radiation

• moderates and stabilizes our climate (temperature with greenhouse gases)

• source of the oxygen we breathe and the carbon dioxide plants use for photosynthesis

how is the atmosphere connected to other Earth systems?

• litoshpere

• hydrosphere

• biosphere

through biogeochemical cycles (carbon cycle)

structure of the atmosphere

• multiple layers with varying pressure and temperature : troposphere + stratosphere + mesosphere + thermosphere

sunlight is higher at the tropics than polar regions → temperature differences that drive air movement and circulation

• atmospheric circulation : distributes and spread heat and polllutants (turns local issues into global problems)

Earth’s initial condition

• 4.6 billion years ago

• extremely hot, volcanic activity and radioactive decay

• environment not suitable for life

Eras

Hadean era

• from 4.6 to 4 billion years ago

• after greek god Hades - “hellish” conditions

• ended with the Earth’s cooling that allowed water vapor to condense and form oceans

Archean era

• from 4 to 2.5 billion years ago

• cyanobacteria changed oxygen levels (increase)

Proterozoic era

• from 2.5 billion to 542 million years ago

• increase of oxygen levels - decrease of carbon dioxide levels

• formation of the ozone → more complex organisms (eukaryotes) and movement of life from oceans to land

composition of the atmosphere

early atmosphere

• hydrogen and helium

• escaped due to solar winds and weak magnetic field

today

• nitrogen (78%)

• oxygen (21%)

• argon, carbon dioxide, water vapor and other gases (1%)

birth of life

• 3.8 billion years ago

• anaerobic bacterias (methane-producing prokaryotes)

stratosphere

• 10-50km

• temperature at -60°C

• air is dry

• winds and temperature increase with height

• ozone layer

Albedo effect

The albedo effect is about how much sunlight a surface reflects. Bright surfaces, like ice and snow, reflect most sunlight, keeping things cooler. Darker surfaces, like oceans or forests, absorb more sunlight, making things warmer. When ice melts and exposes darker surfaces, more heat is absorbed, which can make the planet warm up faster.

High albedo effect = cool temperatures

Low albedo effect = warm temperatures

Troposhere

• less than 10km

• where we live

• air gets cooler as you go higher

• contains most of the atmosphere’s air, clouds, weather system

what is solar radiation made up of?

• visible light

• ultraviolet light

• infrared heat

greenhouse gas effect diagram

atmospheric system model

where is ozone located?

lowest part of the stratosphere - good ozone

troposphere - bad ozone

highest concentrations of ozone are located above Antarctica

chemical composition of ozone

3 atoms of oxygen

role of the ozone

filters and protects from harmful UV lights (that damage living tissue)

allows UVA (wrinkles) and UVB (skin cancer) but blocks UVC (destroys DNA)

What are some ODS (ozone-depleting substances)?

• CFCs (chlorine, fluorine, carbon) - found in aerosols and plastic

• halons - found in fire extinguishers

What are the effects of ODS?

• increased skin cancer, cataracts, immune issues

• ecosystem harm

the Montreal protocol

WHEN - 1987, then 1992 ( new amendment in Copenhagen)

WHY - reduce ozone-depleting substances/protect the ozone layer/propose alternatives

WHO - all 198 UN member countries

Chemical processes: how CFCs destroys ozone

1 molecule of CFC = 1 atoms of carbon + 2 atoms of fluorine + 2 atoms of chlorine

• UV light breaks down the molecule and releases chlorine atoms

• chlorine atom (Cl) + ozone (O3) → oxygen (O2) + chlorine monoxide (ClO)

• chlorine atom is regenerated in another reaction and can repeat the process

What is photochemical smog and how does it form?

a mixture of pollutants that are formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react to sunlight, creating a brown haze above cities

Primary pollutant

air pollutants which are directly emitted from their source

examples

• carbon monoxide

• water vapour

• sulfur dioxide

• nitrogen oxide

Secondary pollutant

pollutants formed when primary pollutants react with UV light in the atmosphere

• acid rain

• tropospheric ozone

Catalytic converter

reduce the amount of nitrogen oxide released by cars

What are the impacts of the smog?

• pollution

• irritated eyes

• lung cancer

Industrial smog

caused by smoke and sulfur dioxide emissions mixing with fog

In December 1952, London experienced industrial smog over four days, contributing to around 4,000 deaths.

What is acid deposition?

result of primary pollutants of sulfur dioxide (SO2) and nitrogen oxides (NOx) reacting with water in the atmosphere to form secondary pollutants of sulphuric acid and nitric acid respectively

it can be :

• Wet deposition occurs when pollutants are incorporated into the clouds or falling raindrops, resulting in acidified rain or snow.

• Dry deposition occurs when atmospheric pollutants are removed by gravity or direct contact under dry conditions

Causes of acid deposition

composition of fossil fuels

Effects of acid rain

Direct effects

• degradation of coniferous forest

• Ocean acidification

• degradation of rivers and lakes

• degradation of buildings made of limestone and marble

Indirect effects

• dissolve aluminium in the soil which is then leached out

• nutrients and minerals are leached out (dissolved)

→ impacts plant growth as they lack aluminium, nutrients, and minerals

pH

acid - between 0 and 7

neutral = water - 7

alkaline - between 7 and 14

rain is usually between 5 and 6 (presence of carbonic acid = CO2 + H2O): when the acidity is lower than 5, it is considered acid rain

Role of lichen

indicator species - only grows in non-polluted environments

dies as pollution level rise

Solutions and management of acid rain

transboundary issue but not as much as climate change

tools used to reduce acid deposition

• policies/legislation (regulations)

• changing human behaviors (reducing emissions of sulfur dioxide)

• economic instruments (e.g. tax on polluting cars)

• technology

UN Geneva Convention - 1979

Volatile Organic Compounds (VOCs)

include methane or ethane

they enter photochemical reactions and contribute to the formation of photochemical smog along with hydrocarbons and nitrogen oxides.

Liming

when limestone is used in lakes and rivers to reduce the acidity (but expensive and local – treats the symptom not the cause)