ESS topic 6

Primary pollutants

Pollutants that are put directly into the air by human or natural activity. E.g. carbon dioxide, sulfur, nitrates, etc.

Secondary pollutants

Pollutants that form from chemical reactions that occur when primary pollutants come in contact with other primary pollutants or with naturally occuring substances, such as water vapor or sunlight.

Tropospheric ozone

An example of a secondary pollutant. It is formed when oxygen molecules react with oxygen atoms that are released from nitroxen dioxide, in the presence of sunlight.

This pollutant is highly reactive and damages plants, irritates eyes, and creates respiratory illnesses. Tropospheric ozone is the main pollutant in smog.

Photochemical smog

Air pollution by a mixture of smoke and fog, mainly consisting of tropospheric ozone. Often present in large cities like London and Beijing.

The frequency and severity of smog depends on climate, population density, fossil fuel use, and it can be caused by deforestation and burning as well.

Thermal inversion

A condition that occurs when there is a lack of air movement so that warm air traps cool air. This causes concentrations of air pollutants to build up near the ground instead of being dissipated by regular air movements. Smog is associated with this.

Pollution management strategies for smog

- Altering human activity to consume less fossil fuels. E.g. purchasing energy-efficient technologies, using public transportation or walking and cycling.

- Regulating and reducing the release of pollutant. E.g. taxing air plane tickets or having governmental regulations.

- Preventing emissions by e.g. using catalytic converters on car exhausts to clearn primary pollutants.

- Regulating fuel quality which is done by governments.

- Clean-up strategies, like reforestation and re-greening.

Economic losses due to air pollution

- Decrease in tourism.

- The cost of clean-up strategies.

- Decreased worker productivity.

- Decreased crop productivity.

- The costs of healthcare.

- The costs of replacing materials.

Acid deposition

Sulfur oxides (SO2) and nitrogen oxides (NOx), emitted by burning fossil fuels, enter the atmosphere where they combine with oxygen and water to form sulfuric acid and nitric acid-and return to Earth's surface.

Dry deposition

A form of acid deposition in which dry, sulfate-containing particles settle out of the air.

Wet deposition

A form of acid deposition in which acid falls to Earth as precipitation, rain, snow, mist, hail. E.g. acid rain.

Acid rain

Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.

Characteristics of an acidified lake

- Impoversihed species structure.

- Visibility several times greater than normal.

- White moss spreading across the bottom of the lake.

- Increased levels of dissolved metals like copper, zinc, and aluminium. The metals more available to animals in that state.

Indirect toxic effects of acid deposition

As acidification increases, there is increased solubility of certain metals. E.g. aluminium is more soluable when pH is below 4.5. This affects for example fish.

Indirect nutrient effects of acid deposition

- There are studies showing that high levels of aluminium in water can cause Alzheimer's disease for humans.

- People can also be seriously affected by digesting fish that have accumalted high levels of mercury.

- Increasing acidity leads to falling numbers of fungi, bacteria, and earthworms.

Human distribution of acid deposition

- Acidification is largely due to human activity (surprise, surprise).

- Many countries produce pollutants, but then deposit them far away from their point of origin.

- A lot of countries in Europe, including the Southern half of Sweden and Norway, are the main regions of acidic deposition.

Natural distribution of acid deposition

- Bog moss secretes acid.

- Litter from conifers is acidic and hard to break down.

- Volcanoes produce a lot of sulfur and nitrogen dioxide. This can lead to a lot of acid rain, like it did in Montserrat in 1995, destroying a cloud forest and a lake.

- Some environments are able to neutralize the effects of acid rain, while some are very sensitive to it. Chalk and limestone are good at it, while granite is not at all resistant to it.

Methods for preventing acid deposition

- Reducing use of fossil fuel (requires government inititative for large effects).

- Reduce the number of private cars on roads and increase the amount of people using public transport.

- Switching to low sulfur fuel.

- Removing sulfur before combustion.

- Reducing sulfur oxides released on combustion by FBT or FGD. These methods are expensive, but very effective. Wet scrubbing, spray dry scrubbing, and scrubbing with a sodium sulfite solution.

- Burning coal in the presence of crushed limestone in order to reduce the acidification process.

- Removing sulfur from waste gases after combustion.

- Allowing decomposition of plants to return nutrients to the soil and offset the acidification process.

Clean up and restoration strategies for acid deposition

- Spreading ground limestone, aka liming, in acidified lakes. It's expensive and has to be done several times to be effective. It enables fish and aquatic plants to keep living in the lake.

- Recolonizing damaged systems.

However, an important aspect of these methods is that they're only short-term solutions. If the emissions of sulfur and nitrogen dioxide aren't stopped, the problems will remain.

Earth's atmosphere

A mixture of gases (nitrogen, oxygen, CO2, water vapor, etc) that surrounds the planet. It's a dynamic system with inputs, outputs, flows, and storages which have undergone changes throughout time.

The hydrosphere

All the water at and near the surface of the Earth, 97% of which is in oceans.

The cryosphere

Frozen water on Earth, ice sheets, glaciers, and snow.

The biosphere

The parts of Earth in which life exists including land, water, and the atmosphere.

What does the atmosphere consist of?

Nitrogen makes up 78%, 21% oxygen, and remaining 1% is carbon dioxide, water vapor and other gases.

The ozone layer

Protective layer in atmosphere that shields Earth from UV radiation.

Thermosphere

4th layer of the atmosphere, 80-100 km. It is a virtual vaccuum and there's a rise in absorbed energy because of the short wave radiation.

Mesosphere

3rd layer of the atmosphere, 50-80 km. Temperatures decrease here because there's a lower density which prevents the absorption of energy.

Stratosphere

2nd layer of Earth's atmosphere, 17-50 km. The ozone layer is located here. This area has no dust or water vapor and it's hot there.

Troposphere

1st layer of the atmosphere, 0-17 km. This is where we live and where weather processes happen.

Greenhouse gases (GHGs)

Gases that trap heat and contribute to global warming, such as carbon dioxide, methane, nitrous oxide, and water vapor.

Global warming/climate change

An increase in the average temperature of the Earth's atmosphere.

Human activities and GHGs

Human activities have increased the amount of GHGs in the atmosphere, mainly by burning fossil fuels. Here are some examples:

- Burning fossil fuels (coal, oil, gas) which releases CO2 into the atmosphere.

- Deforestation affects CO2 levels.

- Increased cattle farming which has lead to a rise in methane levels.

- Rice farming also contribtues to increased methane levels.

- Agricultural fertilizers have lead to higher nitrous oxide concentrations when the fertilizers break down.

Clouds

They're formed of millions of tiny water droplets held in suspension. Most of them form in the troposphere and they play a great role in the albedo affect. There are many different types of clouds, varying in height and form/shape.

The albedo effect

The positive feedback loop in which an increase in the Earth's temperature causes ice to melt so more radiation is absorbed by the Earth's surface leading to further increases in temperature.

The greenhouse effect

A natural and necessary process in which GHGs allow short-wave radiation to pass through the atmosphere, but trap a percentage of the outgoing long-wave radiation. It increases global temperatures by about 33C, which allows life on Earth.

However, this effect can and has been enchanced or accelerated because of anthropogenic causes.

UV radiation

Rays given off by the sun that create warmer temperatures, but overexposure can lead to e.g. cancer.

Ozone

A gas molecule that is made up of three oxygen atoms that exists in a small amount in the atmosphere. It has an important role there because it absorbs UV radiation.

UV radiation and ozone

Some UV radiation from the Sun is absorbed by stratospheric ozone causing ozone molecules to break apart. Under normal conditions, the ozone molecules reform.

Ozone-depleting substances (ODSs)

There are a number of human activities that decrease the levels of ozone in the atmosphere, which means that more UV radiation is let through. Halogenated organic gases, like CFCs, are used in aerosols, gas-blown plastics, pesticides, flame retardants, and refrigerants.

Chloroflurocarbons (CFCs)

Halogenated compounds that contribute to the depletion of the atmospheric ozone layer.

The ozone hole

A thinning of stratospheric ozone that varies from place to place and over the course of a year. E.g. each Spring in Antarctica there is a huge reduction in stratospheric ozone.

Effects of UV radiation on living creatures

- UV-B is the most harmful wavelengths of UV radiation.

- Overexposure for humans can lead to eye damage, sunburn, and skin cancers. It can also damage the immune system.

- Phytoplankton are very sensitive to UV-B radiation and can be severely damged by it.

- Other animals can suffer similarly to humans.

- Plants can also be damaged by UV-B.

Reducing ODSs

- Recycling refrigerants.

- Developing alternatives to gas-blown particles, halogenated pesticides, propellants, and aerosols.

- Developing non-propellant alternatives.

- The United Nations Environment Programme (UNEP) plays a key role in providing information, and creating and evaluating international agreements for the protection of stratospheric ozone.

The phase-out of methyl bromide

Methyl bromide (MeBr) is an odourless, colourless gas that has been used as a soil pesticide to control pests across a wide range of agricultural sectors. However, this pesticide is an ozone depleting substance and so its production and import to USA and Europe was phased out in 2005. It was replaced by non-chemical alternatives like crop rotation and grafting.

Black market for ODSs

- There is a huge black market for ODSs.

- ODS substitutes are more expensive than CFCs.

- It is also costly to update equipment to enable use of alternative chemicals.

- The lifetime of CFC-containing equipment is long.

- Penalties in many countries for ODS smuggling is small.

The Montreal Protocol on Substances that Deplete the Ozone Layer

- Formed in 1987.

- An international agreement for the reduction of use of ODCs signed under the direction of UNEP.

- National governments who complied with the agreement made national laws and regulations to decrease the consumption and production of halogenated organic gases such as CFCs.

MEDCs vs LEDCs on ODSs

Many LEDCs have complained about the regulations on ODSs as they claim that those substances could help the country grow economically. For MEDCs it's not really a big problem.