Introduction
We have seen that consuming fossil fuels probably influences (or will influence) world climate. This is not the only way the Earth is being affected by burning fossil fuels; we will consider here other ways the atmospheric chemistry is being altered. Alternative energy sources have their own specific environmental problems which will also be described.
Atmospheric Pollutants
Historically, the main air pollution problem in both developed and rapidly industrialising countries has typically been high levels of smoke and sulphur dioxide emitted following the combustion of sulphur-containing fossil fuels such as coal, used for domestic and industrial purposes. These days, the major threat to clean air is now posed by traffic emissions. Petrol and diesel-engine motor vehicles emit a wide variety of pollutants, principally carbon monoxide (CO), oxides of nitrogen (NOx), volatile organic compounds (VOCs) and particulate matter (PM10), which have an increasing impact on urban air quality. In addition, pollutants from these sources may not only prove a problem in the immediate vicinity of these sources, but can be transported long distances.
Photochemical reactions resulting from the action of sunlight on nitrogen dioxide (NO2) and VOCs, typically emitted from road vehicles, lead to the formation of ozone. Ozone is a secondary pollutant, which often impacts rural areas far from the original emission site as a result of long-range transport.
In all except worst-case situations, industrial and domestic pollutant sources, together with their impact on air quality, tend to be steady or improving over time. However, traffic pollution problems are worsening world-wide.
Because of their potential impacts on human health, welfare and the natural environment, ambient concentrations for a number of these pollutants are measured continuously at a wide range of rural and urban locations throughout the UK.
A list of the principle pollutants produced by industrial, domestic, and traffic sources are shown in Fig. 1. A detailed description and sources, and potential effect on health/environment can be viewed at [https://uk-air.defra.gov.uk/assets/documents/What_are_the_causes_of_Air_Pollution.pdf]
Main principle pollutants;
- Sulphur dioxide
- Nitrogen oxides
- Particular matter (PM10, PM2.5 and PM1)
- Ozone and volatile organic compounds
- Toxic Organic Micro-Pollutants (TOMPS)
- Benzene
- 1,3-Butadiene
- Carbon monoxide
- Lead and heavy metals
Figure 1: List of the principle pollutants produced by industrial, domestic, and traffic means. (Owen Inger - Gray, Lews Castle College)
Fossil fuels cause other environmental problems as well. It is difficult to achieve complete combustion and soot is often released into the atmosphere.
Soot is what gives smoke its colour and is mostly made up of tiny particles of carbon. The particles form in the yellow part of a flame and are carried into the atmosphere, but they will always return to the ground to cause breathing and other health related problems, as well as forming unsightly deposits blackening buildings facades (Fig. 2).
The main sources of air pollution;
A stationary source of air pollution refers to an emission source that does not move, also known as a point source. Stationary sources include factories, power plants, and dry cleaners. The term area source is used to describe many small sources of air pollution located together whose individual emissions may be below thresholds of concern, but whose collective emissions can be significant.
A mobile source of air pollution refers to a source that is capable of moving under its own power. In general, mobile sources imply “on-road” transportation, which includes vehicles such as cars, sport utility vehicles, and buses. In addition, there is also a “non-road” or “off-road” category that includes gas-powered lawn tools and mowers, farm and construction equipment, recreational vehicles, boats, planes, and trains.
An agricultural source arise from operations that raise animals and grow crops, which can generate emissions of gases and particulate matter.
Figure 2: Soot deposit on a building. [Webster, R.G.M et al. 1992 ‘Stonecleaning in Scotland - Research Report to Historic Scotland and Scottish Enterprise’, Masonry Conservation Research Group, Gilcomston Litho, Aberdeen] (Public Domain)
Activity 1
- What is smog?
- How is the air quality measured?
Solution
a.
Smog is a fusion of the words Smoke and Fog and is a associated with the burning of fossil fuels. In the past, smog from coal burning was common and was composed mainly of carbon particles and sulphur dioxide and could cause death. In some cities the problem was so bad the burning of coal was banned. Now smog is less obvious but pervasive and is more likely caused by emissions from car exhausts. This type of smog consists mostly of soot particles, carbon monoxide and ozone. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulates. Man-made smog is derived from coal combustion emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.
b.
Air quality is a measure of how clean or polluted the air is. Monitoring air quality is important because polluted air can be bad for our health—and the health of the environment.
Air quality is measured with the Air Quality Index, or AQI. The AQI works like a thermometer that runs from 0 to 500 degrees. However, instead of showing changes in the temperature, the AQI is a way of showing changes in the amount of pollution in the air. The AQI is calculated based on the average concentration of a particular pollutant measured over a standard time interval (e.g. 24 hours for most pollutants, 8 hours for carbon monoxide and ozone).
An AQI under 50 means that the air quality is good. At this low AQI level, a person can spend time outdoors and air pollution will pose very little risk to their health. As the AQI number increases, the greater the level of air pollution and the greater the health concern. (See the chart below for a summary of the AQI levels of health concern.)
|
Air Quality Index Levels of Health Concern |
Numerical Value | Meaning |
| Good | 0 to 50 | air quality is considered satisfactory, and air pollution poses little or no risk. |
| Moderate | 51 to 100 | Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. |
| Unhealthy for Sensitive Groups | 101 to 150 | Members of sensitive groups may experience health effects. the general public is not likely to be affected. |
| Unhealthy | 151 to 200 | Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects. |
| Very Unhealthy | 201 to 300 | Health alert: everyone may experience more serious health effects |
| Hazardous | 301 to 500 | Health warnings of emergency conditions. The entire population is more likely to be affected. |
Environmental Pollution
Significant environmental damage accompanies the extraction and transportation of fossil fuels. Oil is moved around the world by sea in tankers, and some super tankers are capable of conveying 2 million barrels of oil, more than the daily consumption of the UK at about 1.5 million barrels. Ships of this size are vulnerable to damage and accidents release oil into the marine environment. The effect of oil spills is often disastrous to wildlife. Seabirds get covered in heavy oil and drown, water is polluted, light is blocked from the sea and gas exchange is prevented.
Environmental pollution is defined as “the contamination of the physical and biological components of the earth/atmosphere system to such an extent that normal environmental processes are adversely affected.” [Environmental Management, 2017.]
Environmental pollution is the build-up and accumulation of toxic heavy metals in the air, water, and land that reduce the ability of the contaminated sites to support life. The rise in human population density and anthropogenic activity has led to degradation of the Earth’s surface through misuse of environmental resources and improper disposal of wastes. In addition, the advancements in science and technology as well as the increase in industry have led to an increase in the dumping of wastes, ranging from raw sewage to nuclear waste, into the environment, which poses a serious problem for the survival of humanity.
Probably the worst disaster (but not the most oil) was when the Exxon Valdez tanker struck a reef off Alaska in 1989 releasing 11 million gallons of oil into the sea (Fig. 4). Half a million seabirds are believed to have died as a result. The clean up operation cost Exxon Mobil over $2 billion.
Figure 4: The Exxon Valdez vessel oil spill [source (CC4.0)]
Oil spills are cleaned by a variety of methods: booms round up the floating oil; skimming the oil off the surface; absorbing the oil; burning the oil; using solvents and detergents; dredging heavy oil off the sea floor; the use of digestive micro organisms.
A direct result of the Exxon Valdez disaster is that all tankers must be double-hulled in U.S. waters by 2015 and in European waters by 2010. A double hull makes an oil leak less likely when the outer skin is breached.
There have also been serious accidents in UK waters. The Torrey Canyon in 1967 and the Sea Empress in 1996 (though there have also been significant leaks from North Sea oil rigs and wells).
The 2010 Deepwater Horizon oil spill in the Gulf of Mexico (fig. 5) has been described as the worst environmental disaster in the United States, releasing about 4.9 million barrels (210 million US gal; 780,000 m3) of crude oil making it the largest marine oil spill. Both the spill and the clean-up efforts had effects on the environment. Most of the impact was on the marine species. Eight U.S. national parks were threatened and more than 400 species that live in the Gulf islands and marshlands are at risk.
Figure 5: Deepwater Horizon on fire with support vessels [source]
Figure 6: The Deepwater Horizon oil rig burns and collapses into the Gulf of Mexico. [source] (US DOD, public domain)
About eight percent, or about one of every 13 barrels of the Deepwater Horizon-spilled oil that reached the ocean surface, eventually made its way into airborne organic particles small enough to be inhaled into human lungs, and some of those particles likely reached the Gulf coast when the winds were blowing toward the shore. Over the course of the spill, the total mass of organic particles formed from evaporating surface oil was about ten times bigger than the mass of soot from all the controlled burns. Controlled burns are used to reduce the size of surface oil slicks and minimize impacts of oil on sensitive shoreline ecosystems and marine life.
The organic particles formed in the atmosphere from hydrocarbons that were released as surface oil evaporated, and they got bigger as they travelled in the plume. The atmospheric plume was about 30 kilometres wide (about 18.5 miles) when it reached the coast.
Ann M. Middlebrook, scientist at NOAA ESRL’s Chemical Sciences Division (CSD) and lead author of the study said;
"We could see the sooty black clouds from the burning oil, but there’s more to this than meets the eye. Our instruments detected a much more massive atmospheric plume of almost invisible small organic particles and pollutant gases downwind of the oil spill site."
Activity 2
When you think of environmental pollution, it typically comes in seven different types. These include air, water, land, radioactive, thermal, light, and sound pollution. Explore the definition and causes of each type of pollution.
Solution
- Air Pollution
Air pollution is when noxious gases and chemicals get suspended in air. These pollutants can go up in the atmosphere and infect our clouds creating acid rain, or they can just hang out like smog does and make it harder for people to breathe.
- Water Pollution
Humans need water to survive. That is a fact. However, waste and chemicals can get thrown into waterways. This is called water pollution. Not only can they affect fish and other marine life, when pollutants get into the water, they have a devastating effect on the water cycle. Natural causes of water pollution include algae blooms and volcanos.
- Land Pollution
Land pollution happens when the soil gets contaminated by fertilizers or chemicals being dumped. The pollution in the land can seep into the ground water or run into lakes and streams creating a vicious pollution cycle.
- Radioactive Pollution
When you think of radioactive pollution, you might think of Chernobyl or Fukushima. Both of these nuclear power plants used fission of radioactive materials, uranium and plutonium, to create electricity, and both failed. Their failure led to toxic chemicals and radiation being leaked out into the environment, which is radioactive pollution.
- Noise Pollution
Noise pollution is caused by loud noises that can hurt the human ears. Types of noise pollution can include explosions, jet engines, and even concerts (if you are nearby). Noise pollution is dangerous because it can cause hearing loss.
- Light Pollution
Have you ever noticed that in a big city with a lot of lights, it is impossible to see the stars? Well, the cause is using vase numbers of electric lights to light up the sky. While lights are great for helping us to see at night, too many lights cause light pollution blocking out the night sky. Light pollution can also be harmful to animals as the lights of big cities can confuse migrating birds.
- Thermal Pollution
While most pollution types are straightforward, thermal pollution is a bit tricky. Many times, nuclear power plants and factories use water for cooling. However, if they put that warmed up water back into the environment, it impacts the fish and wildlife because it has less oxygen content. This is called thermal pollution. Thermal pollution can be caused by natural forces too like soil erosion giving water more sunlight.
Safe Energy Sources?
Although a count of immediate fatalities is a reasonable way of measuring the safety of most energy sources, this criterion is not necessarily applicable to nuclear energy. The nature of radiation is that it does not kill instantly (or obviously) but will induce DNA mutations that can sometimes result in the subject developing cancer. The effect is cumulative in the sense that prolonged exposure or higher energy radiation increases the risk.
The Chernobyl nuclear disaster in 1986 occurred when the core overheated and a resulting (non-nuclear) explosion sent radioactive material into the air (Fig. 7). It subsequently came back to the ground as fallout or contamination. In the actual event 30 people died, but many millions of people throughout Europe have been exposed to radioactive dust and gas. It is difficult to gauge the overall consequences of the explosion because there is no clear way of distinguishing cancers caused by this event from those with other causes. The UN estimate that 4,000—9,000 people throughout Europe have died or will die of cancer as a result, though a statistical analysis does not back these figures up and only 28 people are definitely known to have died since as a result of the accident.
In spite of the apparent low number of fatalities, the lives of hundreds of thousands of people were affected through displacement from the contaminated surroundings, and the worry from fear of the consequences of radiation exposure. Nuclear power therefore poses a greater threat to the population and the environment than might be apparent from bare statistics.
Figure 7: The fallout from Chernobyl 7 days after the accident. Used under Fair dealing: [source:BBC]
Shown in Fig. 8, the New Safe Confinement (NSC) is a structure built to confine the remains of the number 4 reactor. The structure also encloses the temporary Shelter Structure (sarcophagus) that was built around the reactor immediately after the disaster. The New Safe Confinement is designed to prevent the release of radioactive contaminants, protect the reactor from external influence, facilitate the disassembly and decommissioning of the reactor, and prevent water intrusion for the next 100 years.
Figure 8 Chernobyl Nuclear reactor enclosed within the dome of the
New Safe Confinement to protect the environment from further damage in 2017.
[source (CC BY-SA 4.0)]
Hydroelectricity is a renewable source of energy that supplies 20% of the world’s electricity. The power is obtained by damming fast-moving rivers to build up a head of water. As the water is contained, it floods the area behind the dam. This means a lot of land may be lost and many people displaced during project construction (Fig. 9). Downstream, a dam will severely disrupt a river ecosystem. Dams can also fail catastrophically with flooding and loss of life.
Figure 9: Derwent and Ashopton were villages 'drowned' in 1944 when the Ladybower Reservoir in Derbyshire, England was created.
[source (public domain)]
Large wind turbines would seem to be an effective way of generating clean energy, but they too are not without environmental problems. Construction and siting can release huge quantities of carbon dioxide into the air, particularly on peat subsoil which is also vulnerable to movement and subsidence. Turbines can be noisy and, for some people, are visually unappealing, and can adversely affect tourism. Offshore wind farms in shallow waters can affect fishing.
Many of the large areas free from development and habitation in the UK are in that state because of conservation measures to protect wildlife, but they are obvious targets for large wind farm developments because of the need for a lot of space away from populated areas. This results in conflict between planners and conservationists on the basis of damage to important habitats and the death of birds and other wildlife.
Activity 3
A large concern with nuclear power is disposing the waste material. Discuss methods of disposal?
Solution
- Radioactive wastes are stored so as to avoid any chance of radiation exposure to people, or any pollution.
- The radioactivity of the wastes decays with time, providing a strong incentive to store high-level waste for about 50 years before disposal.
- Disposal of low-level waste is straightforward and can be undertaken safely almost anywhere.
- Storage of used fuel is normally under water for at least five years and then often in dry storage.
- Deep geological disposal is widely agreed to be the best solution for final disposal of the most radioactive waste produced.
Most low-level radioactive waste (LLW) is typically sent to land-based disposal immediately following its packaging for long-term management. This means that for the majority (~90% by volume) of all of the waste types produced by nuclear technologies, a satisfactory disposal means has been developed and is being implemented around the world.
For used fuel designated as high-level radioactive waste (HLW), the first step is storage to allow decay of radioactivity and heat, making handling much safer. Storage of used fuel may be in ponds or dry casks, either at reactor sites or centrally.
Intermediate-level radioactive waste (ILW) that contains long-lived radioisotopes is also stored pending disposal in a geological repository.
The table below provides commonly accepted disposal options.
| Option | Suitable waste types | Examples |
| Near-surface disposal at ground level, or in caverns below ground level (at depths of tens of metres) | LLW and short-lived ILW |
|
| Deep geological disposal (at depths between 250m and 1000m for mined repositories, or 2000m to 5000m for boreholes) | long-lived ILW and HLW (including used fuel) |
|
List of other disposal options;
- Near-surface disposal
- Deep geological disposal
- Mined repositories
- Deep boreholes
- Multinational repositories
- Interim waste storage and transport
- Storage ponds
- Dry storage
- Multi-purpose canisters
- Storage casks and systems
Other proposed options;
- Long-term above ground storage
- Disposal in outer space
- Rock melting
- Disposal at subduction zones
- Sea disposal
- Sub-seabed disposal
- Disposal in ice sheets
- Deep well injection (liquid)
Accepting Compromise
We have seen there appears to be no way of generating power in the quantity needed in the world today without some impact on people and the environment. This should come as no surprise—we are consuming fossil fuel at a rate thought to be over 100 times as fast as it was originally produced.
The idea of a future where we somehow harvest sufficient energy without affecting the planet is probably fantasy (Fig. 10), unless there comes along a dramatic scientific breakthrough. Until then we have to recognise that there will have to be some trade-offs. Energy production comes at a cost and the people benefiting and those adversely affected are not necessarily going to be the same people. It is guaranteed the environment will suffer as usual.
The sensible approach is to try to reduce consumption and to look at the detail of each method of producing, distributing and using energy and consider where existing efficiencies can be improved. Alternative/renewable technologies should be adopted where this is justified and not merely on a matter of principle. By adopting this approach, the release of carbon dioxide may be reduced to a level that is ‘safe’ for the planet without the population succumbing to economic chaos.
Figure 10: This graphic by Allan Faustino is a metaphor for the quest to strive to produce and use only clean energy (the unicorn). The effort might ultimately be futile. [source]. used under fair dealing.
One of the main problems in evaluating technologies and their environmental and economic effects is that everything is so deeply interlinked and knock-on effects must be accounted for. This is clearly illustrated in the decision to encourage motorists to switch from diesel to biodiesel (Fig. 11), and the concept of carbon trading. These ideas were advocated for the best of motives, but may instead result in overall damage to the environment.
There are concerns regarding increased resource consumption. The greater the population, the more will be each person’s individual contribution to carbon dioxide emissions, ultimately leading to anthropogenic global warming. Average land area available per person will become smaller. Waste generation problems will jack up. Children also tend to consume more air, water and food in their early developmental stages. They thus will have higher exposure to various pollutants and degraded environments from the early part of their lives.
There are disagreements regarding the severity of this global issue. But due to increased homogenisation and communication within people, the topics of overpopulation and ethics of procreation are being widely challenged.
The major question here is; Could climate change affect human evolution?
Figure 11: The life cycle of biodiesel [source]. used under fair dealing.
The reason why climate change could reduce racial differences is that it will trigger massive migrations. In recent decades the world has become more urbanized, with people moving into large cities in coastal areas. But as polar ice melts and sea levels rise, large numbers of people will be forced to flee the coasts. And as droughts become more common and more severe, people living in more arid areas will have to move to places with more reliable sources of water.
One consequence of large-scale migrations is what biologists call gene flow, a type of evolution caused by the blending of genes between populations. When people from different populations mate and reproduce, their combined genes intermingle in their children. That can lead to combinations of traits not seen in either parent or in the populations they come from.
Furthermore, our digestive systems will evolve in response to shifts in food availability and changing diets will also trigger changes in our microbiomes.
Activity 4
Does human population growth have an impact on climate change? Explain?
Solution
No doubt human population growth is a major contributor to global warming, given that humans use fossil fuels to power their increasingly mechanized lifestyles. More people means more demand for oil, gas, coal and other fuels mined or drilled from below the Earth’s surface that, when burned, spew enough carbon dioxide (CO2) into the atmosphere to trap warm air inside like a greenhouse.
Population growth is important because it affects the Earth's ability to withstand climate change and absorb emissions, such as through deforestation as land is converted for agricultural use to feed a growing human population.
Currently, around 7.9 billion people live on our planet and scenarios for the future show a plausible range from 8.5 to over 12 billion before the population will level off or start to decline, depending on the future course of fertility and mortality. These people will also have to cope with the consequences of climate change that may be in the range of 1.5 °C to more than 3 °C, depending on the scale of mitigation efforts.
Below is a graph comparing the increase of world population to the amount of carbon dioxide released. It can be seen there is a relationship between the two and that they increase together.
Figure 12 Graphs comparing world population to world carbon dioxide emissions. (Source, UN 2017, Public Domain)
If you have enjoyed this topic and wish to read further, more notes can be found by following the link below. You will require Microsoft Publisher to open the file: