Nitrogen dioxide in the air also reacts with water vapor to form nitric acid, one of the types of acid in acid rain. Nitric oxide concentration in unpolluted air is around 0. In smog, the concentration rises twenty-fold to about 0.
Although nitrogen oxides have gained dubious distinction as pollutants, they are also used beneficially in some industrial processes. Nitric oxide is manufactured on a large scale, and is subsequently used to make nitric acid HNO3. To create nitric oxide for industrial uses, chemists combine ammonia NH3 with oxygen O2 , releasing water H2O as a byproduct. Nitrogen compounds derived from nitric acid are used to create chemical fertilizers, explosives, and other useful substances.
Skip to main content. The Carbon Cycle The element carbon is a part of seawater, the atmosphere, rocks such as limestone and coal, soils, as well as all living things. Carbon moves from the atmosphere to plants. In the atmosphere, carbon is attached to oxygen in a gas called carbon dioxide CO2. Through the process of photosynthesis, carbon dioxide is pulled from the air to produce food made from carbon for plant growth.
Carbon moves from plants to animals. Through food chains, the carbon that is in plants moves to the animals that eat them.
Animals that eat other animals get the carbon from their food too. Carbon moves from plants and animals to soils. When plants and animals die, their bodies, wood and leaves decays bringing the carbon into the ground.
Some is buried and will become fossil fuels in millions and millions of years. Carbon moves from living things to the atmosphere. Each time you exhale, you are releasing carbon dioxide gas CO2 into the atmosphere. Animals and plants need to get rid of carbon dioxide gas through a process called respiration.
Carbon moves from fossil fuels to the atmosphere when fuels are burned. When humans burn fossil fuels to power factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as carbon dioxide gas. Each year, five and a half billion tons of carbon is released by burning fossil fuels. Because of our actions fossil fuels have become non-renewable recourses. Although the combustion of fossil fuels mainly adds carbon dioxide to air, some of it is also released during natural processes, such as volcanic eruptions.
In the aquatic ecosystem carbon dioxide can be stored in rocks and sediments. It will take a long time before this carbon dioxide will be released, through weathering of rocks or geologic processes that bring sediment to the surface of water. Carbon dioxide that is stored in water will be present as either carbonate or bicarbonate ions.
These ions are an important part of natural buffers that prevent the water from becoming too acidic or too basic. When the sun warms up the water carbonate and bicarbonate ions will be returned to the atmosphere as carbon dioxide. Schematic representations of the aquatic and terrestrial part of the carbon cycle are shown here:.
As many people know carbon dioxide is a greenhouse gas, which basically means that too much carbon dioxide in air causes the earth to warm up. Humans emit great amounts of carbon dioxide during combustion processes and because of this, the greenhouse effect consisted. The greenhouse effect means that the climate is affected by the concentrations of greenhouse gasses on earth.
In the past few decades a warmer climate has developed, because of the large amounts of carbon dioxide and other greenhouse gases that we emit. RomeroLankao, Appendix D. Carbon measurement approaches and accounting frameworks. Back to top. For the past three centuries, North America has been recognized as a net source of CO 2 emissions to the atmosphere Houghton , ; Houghton and Hackler ; Hurtt et al. Now there is greater interest in including in this picture emissions of CH 4 because it has 28 times the global warming potential of CO 2 over a year time horizon Myhre et al.
The major continental sources of CO 2 and CH 4 are 1 fossil fuel emissions, 2 wildfire and other disturbances, and 3 land-use change. Globally, continental carbon sources are partially offset by sinks from natural and managed ecosystems via plant photosynthesis that converts CO 2 into biomass. Highlighted in this chapter are persistent challenges in unravelling CH 4 dynamics across North America that arise from the need to fully quantify multiple sources and sinks, both natural Warner et al.
Adding to the challenge is disagreement on whether the reported magnitudes of CH 4 sources and sinks in the United States are underestimated Bruhwiler et al. Temporal patterns indicate that fossil carbon emissions have increased from 3. However, considerable uncertainty remains in the spatial patterns of emissions at finer scales over which carbon management decisions are made.
Most importantly, the sensitivity of terrestrial sources and sinks to variability and trends in the biophysical factors driving the carbon cycle is not understood well enough to provide good confidence in projections of the future performance of the North American carbon balance Friedlingstein et al.
Hayes , D. Vargas , S. Alin, R. Conant, L. Hutyra, A. Jacobson, W. Kurz, S. Liu, A. McGuire, B. Poulter, and C. Woodall, Chapter 2: The North American carbon budget.
Recorded webinars describing what is the carbon cycle, focusing on the Second State of the Carbon Cycle Report science findings and pertinent scientific and societally-relevant activities, are posted on our YouTube Channel.
The series desciption is here. Note: For the latest annual global carbon and methane budgets, please see the Global Carbon Project. The adjacent figure on the left represents recent global carbon budget estimates of annual carbon flows averaged from to , as provided in the Global Carbon Project's report.
Values in gigatons of carbon per year. The metric ton is also written as tonne in the British and French systems, as in this Global Carbon Budget figure. View a table presenting data and source for current greenhouse gas concentrations.
Read a discussion of the global carbon cycle. Find the latest carbon budget estimates. Source: Global Carbon Project. And, click here to see figures summarizing the global cycles of biologically active elements. Source: William S. View an illustration of the major world ecosystem complexes ranked by carbon in live vegetation.
Using 5. Anthropogenic CO 2 comes from fossil fuel combustion, changes in land use e. Houghton and Hackler have estimated land-use changes from , so it is convenient to use as our starting point for the following discussion.
Atmospheric CO 2 concentrations had not changed appreciably over the preceding years IPCC; The Scientific Basis so it may be safely assumed that they would not have changed appreciably in the years from to in the absence of human intervention. In the following calculations, we will express atmospheric concentrations of CO 2 in units of parts per million by volume ppmv. Each ppmv represents 2. According to Houghton and Hackler , land-use changes from resulted in a net transfer of PgC to the atmosphere.
During that same period, PgC were released by combustion of fossil fuels , and 5. Atmospheric CO 2 concentrations rose from ppmv in to The See the lastest State of the Carbon Cycle Report for details. How much carbon dioxide is produced from the combustion of cubic feet of natural gas?
If we start with cubic feet of natural gas and assuming it is pure methane or CH 4 at STP standard temperature and pressure, i. Since 1 mole of a gas occupies One mole of CO 2 has a mass of approx. A pound is about equivalent to g, so That is, the complete combustion of cubic feet at STP of natural gas results in the production of about lb of carbon dioxide.
Of course, the mass of the methane in cubic feet will vary if the temperature and pressure are NOT as assumed above, and this will affect the mass of CO 2 produced.
According to the Ideal Gas Law:. Solving again at this higher relative to STP temperature, we get:. That is, at the higher temperature, a given volume of gas will contain fewer moles, and less mass. Going again through the calculation for CO 2 emitted, but using the value of moles of CH 4 , results in an answer of approximately lb of carbon dioxide. When looking at CO 2 emissions estimates, it is important to look at the units in which they are expressed.
The numbers are sometimes expressed as mass of CO 2 but are listed in all of our estimates only in terms of the mass of the C carbon. Because C cycles through the atmosphere, oceans, plants, fuels, etc. Why is the sum of all national and regional CO 2 emission estimates less than the global totals?
There are four primary reasons for this. Why do some smaller nations have larger per capita emission estimates than industrialized nations like the US? Often it is difficult to attribute emissions to a source. Tignor and H. Miller eds. Doney, S. The dangers of ocean acidification. Scientific American, Emsley, J.
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