IB ESS Topic 6

Why is the atmosphere considered a system?

Why is the atmosphere considered a system?

Because it have inputs, outputs, flows, and storages

Atmospheric Inputs

• Water (evaporation and transpiration)

• CO2, SO4 and NO2 from combustion

• Solar radiation

• oxygen through photosynthesis

• CO2 from respiration

• aerosols

Atmospheric Outputs

• precipitation

• solar radiation

• oxygen for respiration

• CO2 for photosynthesis

Composition of atmosphere

78% Nitrogen, 21% Oxygen, 1% Argon, 0.041% Carbon dioxide

The Silly Monkeys Twirled Endlessly

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Closest layer to the earth

Troposphere (0-10km)

What happens in the troposphere?

Weather, cloud formation, greenhouse effect & biota exists there

Where does temperature decrease with altitude?

The troposphere

What layer comes after the troposphere?

Stratosphere (10-50km)

Where does temperature increase with altitude?

Stratosphere

Which layer contains the ozone layer?

Stratosphere

Albedo effect

• a measure of how much of the sun’s energy is reflected back into space

Cloud influence on temperature

• clouds can reflect incoming sunlight back into space → cooling

• clouds contain water vapour which means they can capture outgoing infrared → warming

Greenhouse Effect

• natural and necessary phenomenon

• Maintains suitable temperature for living organisms

Greenhouse Gases

• Water vapor

• Carbon dioxide

• Methane

• Nitrous oxide

• Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFC)

• Perfluorocarbon

• Sulphur hexafluoride

Oxone Layer

Composed of relatively high concentrations of ozone (3 oxygen molecules)

What does the ozone block?

UVc waves (causes damage to organisms/tissues)

What two types of UV make it through the Ozone?

UVa (causes wrinkles) & UVb (causes skin cancer)

UV radiation also affects other living organisms

• Damage to photosynthetic organisms like phytoplankton (basis of many aquatic food webs)

Increased UV-B exposure

• reduces productivity → which threatens the global food supply

Beneficial Effects of UV

• Stimulates the production of Vit.D in animals

• Treats psoriasis and vitiligo

• Steriliser (water purifier)

What are HOGS

Halogenated Organic Gases

HOGS

Usually stable but break down into halogen atoms (F, Cl, Br, I, At) which are highly reactive

ODS (Ozone-depleting substances)

CFC’s, HCFC's, Halons, Methyl bromide, Nitrogen Oxides

Why does ozone tend to thin out at the poles

• atmospheric circulation results in CFCs accumulating at the poles leading to thinning

• this is seasonal as when the poles don’t have sunlight the photochemical reactions don’t occur leading to the accumulation of CFC and once the sunlight returns it triggers the ozone thinning

EVS - Anthropogenic Destruction of Ozone

• CFCs are found in aerosols, coolants, and cleaners → they destroy ozone

• they prevalence of CFCs resulted in a decrease in the thickness of the ozones layer during the late 20th century

• a ban on CFCs allowed the ozone layer to regain thickness

Sources of CFC’s

fire extinguishers, refrigerators, AC units

Pollution Management Stratagey

“Replace, regulate, and restore”

RRR example

altering the human activity producing pollution (replace), regulate and reduce the pollutants at the point of emission, and clean up and restore

Pollution Management of CFC’s and HOGS - Replace

Replace:

• CFC’s with CO2, propane, or air

• aerosol propellants

• stop using methylbromide pesticides

• don’t use aerosol hair products or deodorant

Pollution of Management CFC’s and HOGS - Regulate

Regulate:

• Require a switch to HCFC’s (less harmful) because they don’t persist as long in the atmosphere

• Create laws to require refrigerators returned to manufacturers to recover harmful materials inside

• Capture CFC’s from scrap cars AC units

Pollution Management of CFC’s and HOGS - Restore

• Remove chlorine from the stratosphere or add ozone (not exactly feasible!)

• Ozone layer is slowly replenishing itself as long as we continue the ban

Legislation at National and International Level to Reduce ODSs

UNEP - United Nations Environment Programme

• Key role in providing info & creating/evaluating international agreements with regard to stratospheric ozone

Montreal Protocol 1987 - facts

• 24 MEDCs met in Montreal

• International agreements on the reduction of ODS use.

• National laws and regulations aimed at reducing consumption of ODS (CFCs in particular)

• precautionary principle

Montreal Protocol 1987 - success

Update on Success:

• 197 countries have signed the Protocol

• 1987 - 1.8 million tonnes of ODSs annually

• 2010 - 45000 tonnes of ODSs

• Finalizing production of HCFCs by 2040

What type of ozone is bad

Tropospheric

Air Pollution

gases, liquids, or solids present in the atmosphere in high enough levels to harm humans, other organisms, or materials

Examples of natural pollution

lightning causes forest fires, volcanic eruptions, etc

EVS - Anthropogenic pollution (…Human-induced pollution)

Harmful for 2 reasons

• they precipitate & settle on Earth

• they alter the chemistry of the atmosphere

Much of the air pollution released by humans is concentrated in densely populated urban areas

Primary pollutant

A pollutant that is emitted directly from a source

• Fossil fuel combustion releases: Soot, CO2, NOx, CO, SO

Secondary Pollutant

a pollutant that is formed when primary pollutants undergo a reaction

Air Pollution & Human Health - Exposure to low levels causes

• Eye irritation

• Inflammation of the respiratory tract

• Immune system suppression

• Development of emphysema & chronic bronchitis

Smog

Air pollution that is localized in urban areas where it reduces visibility

Industrial Smog

• smoke pollution; principal pollutants are sulfur oxides and particulate matter.

• worse in the winter months because of heating needs.

Photochemical Smog

A mixture of ~100 primary and secondary pollutants formed under the influence of sunlight - Ozone is the main pollutant

• NOx + VOC + sunlight = photochemical smog

Photochemical Smog sources

auto exhaust, bakeries, dry cleaners

Photochemical smog effects

injures plant tissues, irritates eyes, aggravates respiratory illnesses

Formation of Tropospheric O3

• Nitric Oxide (NO) reacts with Oxygen gas (O2) to form Nitrogen Dioxide (NO2).

• NO2 is a brown gas that contributes to urban haze

• NO2 absorbs sunlight and dissociates into NO & Oxygen atom.

• Oxygen atom combines with oxygen molecules (O2) to form Ozone (O3).

Effects of Tropospheric Ozone

• Oxidizing agent, damage to plants / phytoplankton, damage to humans & animals

Effects of Tropospheric Ozone - Oxidizing agent

• Degrades building materials

• Degrades rubber & plastics

• Impacts car tire lifetime

• Bleaches fabrics

Effects of Tropospheric Ozone - Damage to plants/phytoplankton

• Degrades chlorophyll (reduces photosynthetic ability and therefore productivity/crop yield ↓)

Effects of Tropospheric Ozone - Damage to humans & animals

• Reduces lung action (trouble breathing, aggravates asthma)

• Decreased immune function

• Eye/Nose/Throat irritation

Photochemical Smog is affected by

Population density, fossil fuel use, climate, and local topography

Temperature inversions

Air near the ground is cooler than the air at higher levels and the polluting gases/particulate matter remain trapped in high concentrations near the ground

Temperature inversions LA

• Located between coast and mountains

• Sunny climate produces a layer of warm dry air at higher elevations

• Upwelling in the ocean produces cool ocean air

• As cool air blows inland, the mountains block movement further and layer of warm dry air overlies cool air at the surface

Deforestation and Photochemical Smog

• NOx can also form from slash and burn deforestation practices.

• Not only does tropical rainforest deforestation cause a significant reduction in biodiversity due to the removal of habitat, it also produces photochemical smog which degrades the existing habitat.

• The soot and ash from the combustion of trees can also lead to industrial smog.

Clean Air Act of 1970

• Authorized EPA to set limits on amounts of air pollutants permitted in the USA.

• Saw a 98% decrease in atmospheric lead → due to switch to unleaded gasoline

• 1990 Amendment:

  • focused on Air Toxics & Motor Vehicle Emissions

  • Pre-1990: only 7 toxic chemicals regulated.

  • Post-1990: regulates 189 toxic chemicals.

• 1997 Amendment:

  • Limited emissions of PM-2.5 due to health concerns

  • Smaller PM can get deeper in lungs and lodge in alveoli, leading to many issues, including cancer

RRR - Photochemical Smog - Altering Human Activity

• Reduce driving through public transportation, carpool, biking. This can be done by redesigning our cities.

• Tax credits/penalties can also encourage less driving or shifts to electric cars.

RRR - Photochemical Smog - Controlling Release of Pollutant

• Installing catalytic converters on vehicles. These devices reduce NOx, CO, and hydrocarbon emissions.

• Enforcing emission standards on vehicles.

RRR - Photochemical Smog - Clean Up and Restoration

• Encourage reforestation as trees can remove and store ozone and photochemical smog in plant tissue. Using vegetation to remove pollutants is termed phytoremediation. Using bacteria to remove pollution is termed bioremediation.

What else can we do - photochemical smog

• Driver Smarter

  • Regular Tune-ups, keep tires properly inflated, drive the speed limit

  • SUVs emit nearly twice the pollution (different federal emissions standards)

  • Consider a hybrid or electric vehicle

• Use small-engine machines correctly

  • Up to 10% of US Hydrocarbon emissions

  • Not regulated the same way as vehicles, so emissions are higher

  • What time of day would be best to use them?

• Use scrubbers & electrostatic precipitators

Acidity

• Rain is naturally slightly acidic pH 5.6

• Caused by carbon dioxide in the air dissolving into the water forming carbonic acid

Acid Rain

• However, when sulfur and nitrogen oxides dissolve in the rain they form sulfuric and nitric acid and can have a very low pH (1-3)

• pH scale is logarithmic, pH1 is x10 more acidic than pH 2, and x100 stronger than pH 3

Acid Deposition

Acidic compounds return to earth as either dry or wet deposition

Dry deposition

• heavier particles

• occurs in 2-3 days

• usually settles near the emission source (ex. Ash)

Wet deposition

• occurs usually 4-15 days after emission

• takes place more distant downwind areas (ex. snow, fog, rain)

Smokestacks

• emit pollutants into the air above inversion layers. This allows for mixing and dispersal by winds

• reduces local air pollution but increases regional air pollution

Effects of acid deposition on environment - direct effects

• Inhibits embryonic development of fish

• Chlorophyll loss & yellowing of tree leaves and buds → diminished growth

• Thinning of cuticle (the waxy coating on needles)

• Symbiotic root microbes killed (i.e. Rhizobium spp. and other beneficial fungi)

Effects of Acid Deposition - Plant Life

• For plants, at first, acid deposition will trigger growth by adding nitrogen and sulfur to soil

• Over time, production will be reduced as deposition does the following

  • Leaches calcium, magnesium and other essential nutrients from soil

• Releases aluminum ions which reduce uptake of nutrients and water

• Dissolves & releases toxic heavy metals such as lead, cadmium, and mercury

• Weakens plants making them more susceptible to disease and pests

Toxic Effects of Acid Deposition on Fish

As pH of water nears 5, certain fish populations begin to disappear

• Below a pH of 5, many populations have disappeared, the benthic zone is covered with undecayed material, and mosses dominate shorelines, choking out other vegetation.

• Below a pH of 4.5, the water is essentially devoid of fish.

• Acid deposition will dissolve aluminum from compounds in the soil.

  • Al disrupts salt, water, and oxygen regulating mechanisms in fish

  • The aluminum will cover the gills of fish, causing asphyxiation.

• Mercury can also be released into streams which bioaccumulates and biomagnifies through food chains.

Effects of acid deposition on environment - toxic effects

• Aluminum (Al) leaches out of soil into streams

• Al disrupts salt, water, and oxygen regulating mechanisms in fish

• Al can also adhere to fish gills, causing suffocation

• Around a pH of 5, fisheries see a decline in populations

• Lichens sensitive to SO2 gases and used as indicator species

Effects of acid deposition on environment - Nutrient effects

• Soil particles can’t retain Ca, Mg, K, and other nutrients in acidic environment, so those nutrients are leached out of soil and not available to trees

• Dissolved Al ions damage root hairs (the smallest roots, which are the most effective at absorbing nutrients), so the trees are unable to absorb as many nutrients

• N-fixing bacteria don’t function as well, so less N is added to soil matrix

Effects of acid deposition on environment

• Damage to human infrastructure:

  • acid rain dissolves limestone structures, especially buildings and statues

Acid deposition is Regional

Acid precipitation falls back to Earth rather than entering stratospheric jet stream

• Most areas are downwind of pollution sources

  • Canadian forests damaged by coal-fired power plants in USA

  • Scandinavian and German forests damaged by British coal plants

Acid Deposition is a

Regional problem that is most serious in mountain top forests, areas with high auto traffic, or areas downwind from industrial centers

Reducing the effects of acid deposition

• Techniques used:

  • Liming lakes to neutralise acidity.

  • Precombustion (before burning) techniques.

  • End of pipe measures (after burning).

Pollution management strategies for acid deposition - Replace/Alter

• Switch to renewable energy sources (reduce fossil fuel use)

• Increase energy efficiency (better light bulbs and appliances)

• More public transportation (fewer automobiles on the road)

• Use low-sulfur fuels

Pollution management strategies for acid deposition - Regulate

• Install ‘scrubbers’ on smokestacks of coal-fired power plants to remove SO2

• Catalytic converters installed on automobiles (required by law in the US, Canada, and Europe)

Pollution management strategies for acid deposition - Restore

• Using limestone or calcium carbonate (CaCO3) can neutralize (buffer) the impact of acids.

• Freshwater ecosystems much more vulnerable

  • Expensive and hard to determine how much to add

Pollution Management: Industrial Smog

Altering Human Activity

• Reduce fossil fuel consumption by encouraging

  • more efficient design and reduction of energy demand.

  • a switch to renewable energy sources/electric vehicles.

  • carpooling/public transportation/biking to remove the number of combustion vehicles.

• Tax credits/penalities to encourage less fossil fuel use.

Controlling Release of Pollutant

• Installing catalytic converters on vehicles. These devices reduce NOx, CO, and hydrocarbon emissions.

• Enforcing emission standards on vehicles.

• Switch to low sulfur fuels.

• Installing scrubbers on power plant/incinerator smokestacks

Clean Up and Restoration

• Encourage reforestation as trees can perform phytoremediation.

• Add lime (crushed limestone) to surface waters with low pH.

• Add hay bale barriers in locations with large amounts of runoff