CARBON CYCLE

CONTENTS

• Introduction

• Carbon Cycle

• ProcedurePhotosynthesisRespirationWeathering of rocksAuto and factory emissons

• Imbalance of Carbon Cycle

• Effect of excess CO2 on plants

• Effect of excess CO2 on humans

• Effect of excess CO2 on global warming

CARBON CYCLEThe carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to making the Earth capable of sustaining life; it describes the movement of carbon as it is recycled and reused throughout the biosphere.

GLOBAL CARBON BUDGETThe global carbon budget is the balance of the exchanges (incomes and losses) of carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere ↔ biosphere) of the carbon cycle. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for carbon dioxide.

PROCEDUREPlants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.

Photosynthesis:Plants and photosynthetic algae and bacteria use energy from sunlight to combine carbon dioxide (C02) from the atmosphere with water (H2O) to form carbohydrates. These carbohydrates store energy. Oxygen (O2) is a byproduct that is released into the atmosphere. This process is known as photosynthesis.carbon dioxide + water + sunlight -> carbohydrate + oxygenCO2 + H2O + sunlight -> CH2O + O2

Respiration:Plants (and photosynthetic algae and bacteria) then use some of the stored carbohydrates as an energy source to carry out their life functions. Some of the carbohydrates remain as biomass (the bulk of the plant, etc.). Consumers such as animals, fungi, and bacteria get their energy from this excess biomass either while living or dead and decaying. Oxygen from the atmosphere is combined with carbohydrates to liberate the stored energy. Water and carbon dioxide are byproducts.

oxygen + carbohydrate -> energy + water + carbohydrateO2 + CH2O -> energy + H2O + CO2

Weathering:•Carbon dioxide and the other atmospheric gases dissolve in surface waters. Dissolved gases are in equilibrium with the gas in the atmosphere. •Carbon dioxide reacts with water in solution to form the weak acid, carbonic acid. Carbonic acid disassociates into hydrogen ions and bicarbonate ions. The hydrogen ions and water react with most common minerals (silicates and carbonates) altering the minerals. •The products of weathering are predominantly clays (a group of silicate minerals) and soluble ions such as calcium, iron, sodium, and potassium. Bicarbonate ions also remain in solution; a remnant of the carbonic acid that was used to weather the rocks.

Auto and factory emissions:•Aside from these natural processes, carbon dioxide is also emitted through the combustion or burning of fossil fuels such as coal, oil, and natural gas.•Combustion occurs when vehicles are driven as well as when power plants and industrial plants are utilized. Combustion, otherwise known as burning, is the greatest source of carbon dioxide emissions globally.• Typically, fossil fuels are burnt for electricity generation in homes and buildings, industrial uses, as well as transportation.•Petroleum is the largest share of domestic energy demands. Second is coal, followed by natural gas (EPA, 2006).• Electricity generation is the largest problem in relation to using petroleum as fuel, rivaled followed closely by industrial processes that use petroleum as fuel as well.

Image Credit: http://www.pbs.org/wgbh/pages/frontline/heat/art/graph3.jpg

IMBALANCE IN CARBON CYCLE•In addition to the carbon dioxide emissions that result from industrial processes, deforestation is a serious environmental threat in terms of carbon dioxide emissions.•Carbon is naturally removed from the atmosphere to be stored in oceans and the soil surrounding the roots of many plants. Areas where carbon is stored are otherwise known as carbon “sinks.”• Forested areas are large carbon sinks because enormous amounts of carbon dioxide are naturally stored in the soil, a result of photosynthesis. Because of this, logging is not encouraged as an eco-friendly practice, whether a small number of trees are cut down or a large number.

•When a large group of trees is removed at once, either deliberately by logging or accidently in a forest fire, it is titled as deforestation. When this occurs, carbon dioxide is released from the soil at rates that are damaging to the environment because there are no longer any trees to contain the carbon dioxide.•Technically defined as the “permanent removal of standing forests,” by the EPA, following the destruction of a forest, typically, a large number of trees are not planted.•This lack of growth throws off the equilibrium of the environment, causing massive CO2 emissions though no photosynthesis is occurring in order to utilize the carbon dioxide or trees to store it, thus making deforestation extremely problematic.•Normally, forested areas are not precarious because the decomposition that occurs naturally results in the slow release of carbon dioxide. However, in the case of a forest fire or mass logging, carbon dioxide is released at an alarmingly high rate, contributing significantly to the greenhouse effect with the increase. Overall, deforestation is a large contributor to carbon dioxide emissions globally.

This photo depicts a forest fire in Afghanistan, which has lost over 70% of its’ forests due to deforestation.

Effect of CO2 increase on plants •Elevated CO2 leads to changes in the chemical composition of plant tissues. •Due to increased photosynthetic activity, leaf nonstructural carbohydrates (sugars and starches) per unit leaf area increase on average by 30–40% under FACE elevated CO2 (Ainsworth 2008; Ainsworth & Long 2005). •Leaf nitrogen concentrations in plant tissues typically decrease in FACE under elevated CO2, with nitrogen per unit leaf mass decreasing on average by 13% (Ainsworth & Long 2005). •This decrease in tissue nitrogen is likely due to several factors: dilution of nitrogen from increased carbohydrate concentrations; decreased uptake of minerals from the soil, as stomatal conductance decreases and plants take up less water (Taub & Wang 2008); and decreases in the rate of assimilation of nitrate into organic compounds (Bloom et al. 2010).

Effect of CO2 increase on humans

•Carbon dioxide is a toxic gas which is odourless and colourless. Rising levels of carbon dioxide affect the human body.•Hypercapnia , is a condition where there is too much carbon dioxide (CO2) in the blood. Carbon dioxide is a gaseous product of the body's metabolism and is normally expelled through the lungs.•Hypercapnia normally triggers a reflex which increases breathing and access to oxygen, such as arousal and turning the head during sleep. A failure of this reflex can be fatal, as in sudden infant death syndrome.

Contribution of CO2 in Global Warming

•Carbon dioxide doesn't absorb the energy from the sun i.e.<4000 nm, but it does absorb some of the heat energy released from the earth i.e. >4000 nm.•So this leads to Green house effect , carbon dioxide lets the light energy in, but doesn't let all of the heat energy out, similar to a greenhouse.•Currently, the amount of carbon dioxide in the atmosphere is increasing at the rate of about one part per million per year.•If this continues, some meteorologists expect that the average temperature of the earth will increase by about 2.5 degrees Celsius. This doesn't sound like much, but it could be enough to cause glaciers to melt, which would cause coastal flooding.