CARBON CYCLE

Well, while many people in their daily life may never think about how their actions affect the natural phenomena that regulates the temperature they enjoy though the daily increase of individual release of CO2 to the atmosphere, we environmentalist think about it all the time maybe more so because of research and studies but also because we are aware that it is the major driving force for world wide trending issues surrounding CLIMATE CHANGE.

CARBON CYCLE

Carbon is present in all living things and continuously moving among Earth’s lithosphere, hydrosphere, biosphere and the atmosphere in various forms for instance as carbon dioxide (CO2) in the atmosphere, sugar or carbohydrates (CnH2nOn) in living organisms and calcium carbonate (CaCO3) in rocks and minerals, the movement of this carbon among the Earth’s spheres is known as the carbon cycle.

Carbon Cycle

Adopted: http://www.visionlearning.com/en/library/Earth-Science/6/The-Carbon-Cycle/95

This illustrates how much carbon is stored in carbon sinks and how carbon moves among the Earth’s spheres.

The earth has a natural system of balancing CO2 in green plants that play a very significant role in, absorbing carbon dioxide and producing sugars that contain carbon referred to as photosynthesis and animals by eating plants to obtain the energy trapped during the process of photosynthesis, as the animals bodies break down the carbohydrates in the plant tissue, CO2 is released to the atmosphere a process called respiration, CO2 is also released when plants and animals decay.

Different paths of the carbon cycle recycle the element at varying rates. The slowest part of the cycle involves carbon that resides in sedimentary rocks, where most of the Earth’s carbon is stored. When in contact with water that is acidic (pH is low), carbon will dissolve from bed rock, under neutral conditions, and carbon will precipitate out as sediment such as calcium carbonate (limestone). This cycling between solution and precipitation is the background against which more rapid parts of the cycle occur.

Figure 10: Atmosphere Carbon Store

Adopted: http://www.carbonequity.org/types-of-global-co2-emissions-caused-by-human-activity/

Carbon is constantly cycling from the air into plants and soil, and back into the air. Life is built on the conversion of carbon dioxide into the carbon-based organic compounds of living organisms.

CARBON CYCLE – SOURCES AND SINKS

The carbon cycle illustrates the central importance of carbon as it is stored on our planet in the major sinks namely the biosphere, ocean and lithosphere based on their importance:

  • Organic molecules in living and dead organisms found in the biosphere;
  • As the gas carbon dioxide in the atmosphere;
  • As organic matter in soils;
  • In the lithosphere as fossil fuels and sedimentary deposits such as limestone, dolomite and chalk; and
  • In the oceans as dissolved atmospheric carbon dioxide and as calcium carbonate shells in marine organisms.

BIOSPHERE

Carbon dioxide is stored in the biosphere within living or recently dead plants, animals and microorganisms in the ocean and on land. The forests contain 86% of the planet earth’s carbon, with the Amazon rainforest in Brazil being one of the major sink for carbon dioxide the Amazon Rainforest (illustrated below showing a picturesque image of the largest rainforest in the world) is the only existing rainforest in the world today in terms of size and diversity.

It is worth noting that trees have hidden attributes and plays a key role in reducing pollutant levels in the atmosphere. Now trees are critically important in reducing the massive amounts of carbon dioxide pumped into the air by human activities this includes but not limited to the burning of fossil fuels, coals, oil and natural gas (a major driver for global climate change) and under natural environmental conditions, trees and plants from CO2 from the atmosphere and absorb it for photosynthesis.

Arial view of the Amazon Rainforest

Adopted: http://wwf.panda.org/what_we_do/where_we_work/amazon/about_the_amazon/why_amazon_important/

This is referred to the energy-creating process that allows oxygen to be released back into the air and carbon used by plants and trees to grow.

Importantly, without tropical rainforest and all forest as a matter of fact the greenhouse effect would likely be much more prominent and climate change could to a great extent worsen in the future if the trend of deforestation continues ultimately leading to less CO2 being transformed through photosynthesis the process responsible for life on earth.

This normal mechanism by which CO2 is removed from the atmosphere as it stands cannot cope with the quantities now being emitted into the environment leading to an enhanced greenhouse effect.

This system is intricately connected to animals since they receive carbon by eating plants followed by the release carbon dioxide into the atmosphere upon exhalation. Now, when animals and plants die, their carbon turns to fossil fuels after millions of years in the form of coal, oil and natural gas. The burning of these hydrocarbons in power plants and automobiles releases more carbon into the air and contributes to global warming.

LITHOSPHERE

Carbon is stored in the lithosphere in both inorganic and organic forms. Inorganic deposits of carbon in the lithosphere include fossil fuels like coal, oil and natural gas, oil shale and carbonate based sedimentary deposit like limestone. Organic forms of carbon in the lithosphere include litter, organic matter and humic substances found in soils. Some carbon dioxide is released from the interior of the lithosphere by volcanoes. Carbon dioxide released by volcanoes enters the lower lithosphere when carbon-rich sediments and sedimentary rocks are subducted and partially melted beneath tectonic boundary zones.

The carbon cycle also includes carbon dioxide dissolved in water, carbonate in sedimentary rocks like limestone and methane in the atmosphere. The element recycles through the atmosphere, down to plants, then into rocks and water before going back into the air. Carbon is not one of the most abundant elements on earth, but it is necessary for all life to exist.

OCEAN

In the open ocean environments the uptake of atmospheric carbon is primarily controlled by biological activities, seasonal and long-term changes in the heat content along with the overall chemistry of the surface and deep waters. In understanding atmospheric concentration of CO2 we must note that it is the impacted and uptake ecosystems play through the fixation of organic and mineral carbon by plankton productivity as well as the resulting sedimentation of particulate carbon through oceanic waters. It is extremely important to understand the role in which human activities play whether directly or indirectly as it pertains to the ocean carbon process, the ocean protects the climate and maintains its balance by absorbing and storing carbon dioxide by microscopic plants and animals.

Scientists believes that the ocean absorbs around 30-50% of the CO2 produced by the burning of fossil fuel and that is the ocean stopped absorbing these amounts the atmospheric CO2 levels would jump from a current level of 355 parts per million to 500-600 parts per million. The ocean has the greatest reservoirs of carbon, rapidly converting between an organic and inorganic state due to the short life cycle of phytoplankton.

Now ask me again why study the carbon cycle?

While convenient and easy to blame industrialization but what are we doing right not to curb the damages already done and to avoid future occurrences. We are all to be blamed for the almost all the increases in harmful / toxic gases being emitted daily in the atmosphere and even without the changes in CO2 to the atmospheric temperatures, excessive CO2 can alter the growth of plants around the world making too difficult for human and animals to source food which should alarm us.

ut never the less as we attempt to cut back on actions that increase the carbon dioxide (CO2) release into the environment more and more we realize that nothing is possible without complete agreement and that without awareness climate change is inevitable.

BY NAZINA BELLE

REFERENCE –

Pidwirny, M. (2006). “The Carbon Cycle”. Fundamentals of Physical Geography, 2nd Edition. [Date Viewed 27th January, 2015]. http://www.fibershed.com/education/carbon-cycle-curriculum/.

PMLE Carbon Program; 2015. Ocean Carbon Uptake [Website] Available at< http://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake> [accessed on 5 February, 2015].

Shrink that Footprint; 2015. Electricity Emissions around the World [Website] Available at< http://shrinkthatfootprint.com/electricity-emissions-around-the-world

> [accessed on 5 February, 2015].

Skeptical Science; 2015. Explaining how the Water Vapour Greenhouse Effect Works [Website] Available at< http://www.skepticalscience.com/water-vapor-greenhouse-gas.htm&gt; [accessed on 29 January, 2015].

Tutor Vista; 2015. Greenhouse Effect [Website] Available at< http://www.tutorvista.com/content/biology/biology-iv/environmental-changes/green-house-effect.php&gt; [accessed on 29 January, 2015].

UNEP; 1993. Oceans and the Carbon Cycle [Website] http://www.gdrc.org/oceans/fsheet-02.html&gt; [accessed on 5 February, 2015].

United States Environmental Protection Agency; 2014. Overview of Greenhouse Gases [Website] Available at< http://www.epa.gov/climatechange/ghgemissions/gases/co2.html> [accessed on 27 January, 2015].

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GREENHOUSE EFFECT

While all the other planets in the earth’s solar system is either scorching hot or bitterly cold,  planet Earth’s surface on the other hand is relatively mild and stable in temperature, this is because carbon dioxide (CO2) helps to maintain the Earth’s temperature by the way of the “Greenhouse Effect”.

Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities causing global warming and ultimately changing the climate which adversely affects the health and wellbeing of all living thing on the planet Earth, now although it is naturally present in the atmosphere as part of the Earth’s carbon cycle during the natural circulation of carbon among the atmosphere, oceans, soil, plants and animals.

Human activities have adversely altered the carbon cycle both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks such as the forest to remove CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

Global warming is essentially a problem of too much carbon dioxide (CO2) in the atmosphere, caused by carbon overload when fossil fuels such as coal, oil and gas and even deforestation. It is worth continuously noting that there are many other heat trapping gases such as methane and water vapours but CO2 poses the greatest risk of irreversible changes if it continues to accumulate unabatedly in the atmosphere for two (2) main reasons:

Carbon dioxide (CO2) more than any other climate driver, has contributed the most to climate change since the 1750’s.
CO2 remains in the atmosphere through the radiative forcing longer than any other major heat trapping gas emitted as a result of human activities.

ANTHROPOGENIC GENERATION AND SINKS OF CARBON DIOXIDE

Industrialization has brought about a greater demand for energy hence the rapid increase in the burning of fossil fuel, resulting in greater amount of carbon dioxide emitted to the atmosphere.

Now, although carbon dioxide is essentially important for the survival of all life on earth, it is also the primary greenhouse gas emitted through human activities. Human activities are altering the carbon cycle both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere.

While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

image

anthropogenic sources of greenhouse effect

The main human activity that emits CO2 as the combustion of fossil fuel (coal, natural gas and oil) for energy and transportation, although certain industrial processes and land-use changes also emit significant amounts of CO2.

To understand and gain an appreciation for the greenhouse effect and its link to global warming it is extremely critical I explain the lingering role of greenhouse gases and undertake an in-depth appreciation of the primary greenhouse gas sources caused by human activities CARBON DIOXIDE.

The main reason CO2 is considered the most important primary greenhouse gas as opposed to all the others is simply because methane (CH4) emissions converts into CO2 to exit the atmosphere, nitrous oxide (N2O) takes about a century to exit while CO2 emissions 80% will be gone within a century but 20% will linger around in the atmosphere for approximately 800 years, consequently CO2 stays in our atmosphere for a long period and any addition has a much more long-term effect.

This literally means that this heat trapping emission will set the climate for our children and grandchildren.

Now methane and water vapour can be considered as an important heat trapping gas, when considering human induced climate change, but not having the same effect as CO2.

The Greenhouse effect  warms the earth temperature; and without this process the ocean would freeze and life on earth as we know would be impossible.

image

greenhouse effect

Greenhouse effect involves radiation emitted from the sun and absorption by the earth, through this the planet Earth undergoes a delicate daily balancing act involving the radiation the planet receives from outer space and the radiation that is reflected back out,  the Earth is continuously bombarded with an enormous amount of radiation, mainly from the sun, this solar radiation strikes the Earth’s atmosphere in the form of visible light along with ultraviolet (UV), infrared (IR) and other types of radiation that are not visible by the human eye.

Few thing to note is that UV radiation has a shorter wavelength and a higher energy level than visible light, while IR radiation has a longer wavelength and a weaker energy level, radiation from the Sun is absorbed by the surface, with the amount absorbed depending highly on the type of surface, with approximately 30% of the radiation striking the Earth’s atmosphere reflected back into space immediately by clouds, ice, snow, sand and other reflective surfaces.

The remaining 70% of this incoming solar radiation is absorbed by the ocean, the land and the atmosphere, heating up and releasing heat in the form of IR thermal radiation, which passes out of the atmosphere and into space, noting that much of it is absorbed by greenhouse gases which makes the atmosphere warmer, that re-emits the radiation in all direction and warms the atmosphere further. This essentially traps the heat in the Earth’s atmosphere, and as more greenhouse gas is added, the temperature will increased.

image

direct vs indirect radiative forcing

Now we must understand that at the mention of global warming and greenhouse effect, the true underlying scientific concept surrounding this process is radiative forcing. This concept of radiative forcing is fairly simple and straightforward.  Energy is constantly flowing into the atmosphere in the form of sunlight that always shines on half of the Earth’s surface.

This means that everything on the Earth is at equilibrium and nothing will change except for some small unsystematic variant, a number of factors must be considered in the effect on the Earth’s balancing act; with each having it own level uncertainty and difficulties in being precisely measured, because many of the factors overlap for instance different greenhouse gases absorb and emit at the same infrared wavelengths of radiation so their combined warming effect is less than the sum of their individual effects.

BY NAZINA BELLE

REFERENCE: Pidwirny, M. (2006). “The Carbon Cycle”. Fundamentals of Physical Geography, 2nd Edition

ACID RAIN

From the beginning of civilization, human beings have used various natural resources for their benefits, creating conveniences that make the most of many of the Earth’s energy resources in order of making life easier.

While these developments have made our lives easier we can all agree that industrialization has resulted in pollution by the release of harmful substances into the environment. The major contributors, called precursors to acid rain are emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx) – nitric oxide (NO) and nitrogen dioxide (NO2) and to a smaller extent of carbon dioxide (CO2).

  • nitrogen oxides – Nitrogen oxides (NOx) consist of nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O) and are formed when nitrogen (N2) combines with oxygen (O2). The lifespan of nitric oxide and nitrogen dioxide in the atmosphere range from one to seven days as oppose to up to 170 years for nitrous oxide.  Nitric oxide has no colour, odour, or taste and is non-toxic. In the air it is rapidly oxidized to nitrogen dioxide.Nitrogen dioxide is a reddish-brown gas with a pungent, irritating odour. It absorbs light and leads to the yellow-brown haze sometimes seen hanging over cities. It is one of the main components of smog.Nitrous oxides is naturally present in the atmosphere as part of the Earth’s nitrogen cycle, and has a variety of natural sources and results from bacterial processes, biological growth and decay, lighting and forest and grassland fires.However, human activities such as agricultural, fossil fuel combustion, waste water management and industrial processes are increasing the amounts of N2O in the atmosphere. Note, that agriculture plays a role in nitrogen oxide emissions with the use of fertilizer contributing nitrous oxide to the atmosphere.
  • sulfur dioxide (SO2) – SO2 is a dense, colourless gas formed when many sulphur compounds are burnt in air. It is also very toxic, and has a suffocating odour. SO2 occurs naturally as one of the decay products of plant and animal matter, and is also one of the gases which are emitted from volcanoes.  Man-made sources include sour gas processing, oil sands production, coal combustion, ore refining, chemical manufacturing and other fossil fuel processing burning.

These substances are released into the environment from burning of oil and coal by plants and factories, homes and cars which are considered the main source of chemicals that cause acid rain, although some air pollution comes from natural sources, most is as a result of human activities.

Now acid rain in its simplest term is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions.

DEPOSITION OF ACID RAIN

Understand that acid rain is made when pollutants arise from the use of coal in the production of electricity, from base metal smelting and from fuel combustion in vehicles.   When these gases are discharged into the atmosphere they react with the water, oxygen and other gases already present to form sulphuric acid, ammonium nitrate and nitric acid.

Once the sulphur and nitrogen oxides from these man-made causes are released into the air they are caught by wind currents and wind pattern and are blown hundreds of miles away falling back to the ground as acid rain or other forms of precipitation. Since the gas pollutants drift along in clouds they mix with moisture in the atmosphere caused by rain eventually converting sulphuric dioxide into sulphuric acid, and the nitrogen oxide into nitric acid.

It is worth noting, that acid precipitation and water droplets in the air and in clouds are highly affected by the form of precipitation and amount of water vapour in the air. Generally, water would be less acidic, the more drops there is, since the acid particles are dissolved and diluted.  Also, the more precipitation and the faster it falls, the less acidic the rain water, because of the dilution factor.

forest damaged by acid rain one of the main effect of acid rain 

During rapid rainfall such as a thunder storm the air “cleans”, causing most of the pollutants to wash out and temporarily cleaning the air. This system works strategically to protect the environment constantly fighting the force of human factors.

Acid precipitation is affected by how much sulphur and nitrogen bearing pollution and soil in the air. Soil generally helps to neutralize the acidic pollution in rain, where soil is alkaline and where it is windy (so that soil becomes airborne), generally have less acidic precipitation as a result.

Acid rain, acid fog and acid mist all fall in the category of acid deposition.  This primarily concerned with the long-range as opposed to local effects simply because the pollutants are mixed into the atmosphere and therefore can be difficult to link to local attributes or sources

These pollutants are normally more disseminated and of lower concentration than local ground level pollutants. Acid deposition is used to refer to acid rain because this term includes other forms of acidic precipitation such as snow. It is two (2) types of deposition:

dry deposition = dust foil & wet deposition = rainfall 

     Wet Deposition

This refers to acidic rain, fog and snow, occurring when the acid chemical in the air are blown into areas where the weather is wet. The acid then falls to the ground as rain, snow, fog or mist. This acidic water flows over and through the ground severely affecting all living things.

The strength of this effect depends highly on acidity of water, the chemistry and buffering capacity of the soils involved along with the types of fish, trees and other living things that rely and live in and on the water.

Dry Deposition

Dry deposition is the second method of acid deposition. Whilst wet deposition involves the precipitation of acids, dry deposition occurs when the acids are first transformed chemically into gases and salts before falling under the influences of gravity back to Earth. Dry Deposition is highly dependent on the re-activity of gases and the size distribution if the particles along with the surface on which the dry deposition occurs with hilly areas increasing deposition.

Sulphur dioxide for example is deposited as a gas and as salt. SO2 is absorbed by soil, leaves and stones and then is oxidized to acid sulphate, with the rate of adsorption proportionally dependant on the amount of SO2 in the air, types of materials, along with the surface area of the material and weather since wet surfaces removing more sulphur from the atmosphere than dry.

The major environmental pollutants deriving from the advance movement of industrialization is the fact that these pollutants cause acid rain, travel distances meaning that it is a transboundary problem, meaning that acid pollutants are not necessarily deposited in the same country where they were produced, acidic emissions produced by one country can be deposited in another, for example Sweden and Norway, both receive more than 90 percent of their sulphur pollution from abroad and is the main reason this issue is of great concern worldwide.

It is worth continuously noting that rain is one of the most essential ingredients for human and animal life on Earth.  While, most of the Earth’s surface is covered by water most of it we cannot drink, 97% is salty sea water, which is useless to most plants and animals on land, leaving us with only 3% consumable.

rain is everything to all live on Earth 

Hence, the importance of rain to life on Earth, the water provided by rain allows all life on Earth to survive; precipitation provides life on land with salt free water while supporting hydrologic cycle, aquatic life and ground water.

BY NAZINA BELLE

REFERENCE:

Carter, L, 2013.Acid Rain. [Book Abstract]

National Environmental Forum, 1997. Nitrogen Dioxide. [Report]