Nitrogen Cycle

By: Britney Carreras Brianna Legra

What is the nitrogen cycle? Nitrogen Cycle- Cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment

Natural processes:

Four ways in which Nitrogen Cycles through the biosphere

• Nitrogen Fixation • Ammonification

(Decay) • Nitrification • Denitrification

Nitrogen Cycle Steps:

Nitrogen fixation • Specialized bacteria in soil

as well as blue-green algae (cyanobacteria) in aquatic environments combine gaseous N2 with nitrogen to make ammonia (NH3).

• Bacteria use some of the ammonia they produce as a nutrient and excrete the rest into the soil or water

• Ammonia not taken by plants may then undergo the nitrification, where specialized soil bacteria convert most of the NH3 and NH4

+ in soil to nitrate ions (NO3

-), which can easily be taken into the roots

• Lightning: lightning converts atmospheric nitrogen into ammonia and nitrate (NO 3-) that enter soil with rainfall.

Decay • Plants take up nitrogen compounds through their roots. • Animals obtain these compounds when they eat the plants. • When plants and animals die or when animals excrete

wastes, the nitrogen compounds in the organic matter re-enter the soil where they are broken down by microorganisms, known as decomposers (producing ammonia)

In ammonification: • Vast armies of specialized decomposer bacteria

convert this detritus into simpler nitrogen-containing inorganic compounds such as ammonia (NH3) and water-soluble salts containing ammonium ions (NH4

+)

In Denitrification • Specialized bacteria in waterlogged soil and in the

bottom sediments of lakes, oceans, swamps, and bogs convert NH3 and NH4

+ back into nitrate ions, and then into nitrogen gas (N2) and nitrous oxide gas (N20) .

• These gases are released to the atmosphere to begin the nitrogen cycle again

Natural Reservoir

• The major reservoir for nitrogen is the atmosphere- acts as vast storage reservoir for nitrogen because it is 78 percent nitrogen

• Aquatic systems, in soil, and in the roots of some plants, where specialized bacteria called nitrogen-fixing bacteria

• Organic reservoirs that contain nitrogen include: amino acids, peptides, nucleic acids and proteins- man-made fertilizers and ammonia.

Why is it so important?• Nitrogen is a crucial component of proteins,

many vitamins, and nucleic acids such as DNA• Cannot be absorbed and used directly as a

nutrient by multicellular plants or animals• Increased nitrogen inputs (into the soil) have

led to lots more food being produced to feed more people – known as ‘the green revolution’.

Global Nitrogen Cycle Global nitrogen fixation, natural and anthropogenic in both oxidized and reduced forms through combustion, biological fixation, lightning and fertilizer and industrial production. The arrows indicate a transfer from the atmospheric N2 reservoir to terrestrial and marine ecosystems, regardless of the subsequent fate of the Nr. Green arrows represent natural sources, purple arrows represent anthropogenic sources.

HOW WE INTERVENE IN THE NITROGEN CYCLE: FIRST WAY

• We add large amounts of nitric oxide (NO) into the atmosphere when N2 and O2 combine as we burn any fuel at high temperatures, such as car, truck, and jet engines

• In the atmosphere, this gas can be converted to nitrogen dioxide gas (NO2) and nitrate acid vapor (HNO3), which can return to the earth’s surface as damaging acid deposition, commonly called acid rain.

How We Intervene in the Nitrogen Cycle: Cont. Second way

• We add nitrous oxide (N2O) to the atmosphere through the action of anaerobic bacteria on commercial inorganic fertilizer or organic animal manure applied to the soil

• Greenhouse gas can warm the atmosphere and deplete stratosphere ozone, which keeps most of the sun’s harmful UV radiation from reaching the earth’s surface

Third Way • We release large quantities

of nitrogen stored in soil and plants as gaseous compounds into the atmosphere through destruction of forests, grasslands, and wetlands

How We Intervene in the Nitrogen Cycle: Cont.

Fourth Way • We upset the nitrogen cycle

in aquatic ecosystems by adding excess nitrates (NO3

-) to bodies of water through agricultural runoff of fertilizers and animal manure and through discharges from municipal sewage systems

• Can cause excess growth of algae

Fifth Way • We remove nitrogen from

topsoil when we harvest nitrogen –rich crops, irrigate crops (washing nitrates out of the soil), and burn or clear grasslands and forests before planting crops.

Human Impact: MDC• England, Nitrogen

Fertilizer: Nitrogen fertilizers are used in England for agricultural purposes resulting in nitrogen increasing in the form of ammonia from fertilizers and a increase in the rate of dentrification.

• Eutrophication:Excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land. This causes growth of plant life and death of animals from algae growth in the water and lack of oxygen.

Why? Will they Stop?• Want to help

their plants grow quicker.

• Doing nothing since they feel fertilizers are critical to helping feed the amount of people in their population.

Human Impact MDC • U.S.- Vehicle Emission: The Emission from vehicles increases

the amount of nitrous oxide in the atmosphere which results in smog and acid rain occurring. Vehicle exhausts from burning fossil fuels burn and allow nitric oxide to be admitted into the atmosphere, as well as the excessive amount of substances in the atmosphere resulting in a disturbance of the nutrient cycle. Nitric oxide- colorless toxic gas formed in many reactions in which nitric acid is reduced.

U.S.- Vehicle Emission Cont.Why? • Because people would

rather drive a car instead of riding a bicycle or using public transportation.

• Its more comforting to be in your own vehicle than in a bus with a bunch of other strangers you don’t know.

Will We Stop?• Engineers are finding out

different ways to power a vehicle that does not result in vehicle emissions.

• Examples of zero-emission vehicles include battery-electric, plug-in hybrid-electric, and hydrogen fuel-cell-electric vehicles.

Human Impact Cont. LDC• Brazil, livestock ranching:

Livestock contributes to 18% of the global warming effect. Since South America is huge in production of agriculture and use of land alters the nitrogen cycle. The livestock release large amounts of ammonia through their excretions.

• Just like any area, livestock is raised in order to provide beef, hides, skins, and horns.

• Brazil is not trying to fix the problem nor do they plan on stopping. They care more about providing food for their country more than the nitrogen cycle.

Why? Will They Stop?

Human impact LDC• Indonesia, Forest Burning:

Burning down forests results in an increase of nitrate levels. Charcoal deposited when trees are burned down have the potential to stimulate ammonia to nitrates, which is an important step in the nitrogen cycle.

Why? Will They Stop• Indonesia burns down trees

for palm oil, timber, and because it is a cheaper way to plant new trees.

• Indonesia, as far as we know, has not stopped the burning of trees.

Pathway affected by human activities:

• FERTILIZERS!

• Extra nitrogen fertilizer can runoff, where it contaminates surface water or infiltrates into ground water.

• In drinking water, excess nitrogen can lead to cancer in humans and respiratory distress in infants.

• In surface waters, extra nitrogen can lead to nutrient over-enrichment.

• This leads to – fish-kills, – harmful algal blooms, – and species shifts in

aquatic and land ecosystems.

WHAT ARE WE DOING TO FIX OUR MISTAKES?

• Projections: According to the 2005 Millennium Ecosystem Assessment, since 1950, human activities have more than doubled the annual release of nitrogen from the land into the rest of the environment: By 2050 it will have doubled again

Bibliography:

• http://www.esa.org/esa/documents/2013/03/issues-in-ecology-issue-1.pdf

• http://www.biology-pages.info/N/NitrogenCycle.html • https://blogs.ntu.edu.sg/hp331-2014-29/?page_id=1

10• http://www.ncbi.nlm.nih.gov/pubmed/23011299•

https://www.sciencedaily.com/releases/2010/08/100809093645.htm

• http://www.dec.ny.gov/chemical/8394.html