Nitrogen Cycle

Abundance of N in the atmosphere

78.1% N in the form of N2 (dinitrogen)

How is the N2 triple bond broken?

945 kJ per mole to break it.

What is a component of acid rain?

Decay: After nitrogen is incorporated into organic matter, it is often converted back into inorganic nitrogen by decay. When organisms die, bacteria and fungi consume the organic matter. During decomposition, a significant amount of the nitrogen contained within the dead organism is converted to ammonium.

How does nitrogen from fertilizer runoff affect coastal waters?

Eutrophication has been blamed for increased frequencies of harmful algae blooms, along with other negative effects such as dying fish and species shifts within ecosystems.

Atmospheric nitrogen (N2 gas) is easily taken up and used by plants and animals.

False, in order for plants and animals to be able to use nitrogen, N2 gas must first be converted to a different form, such as ammonium (NH4+), nitrate (NO3-), or organic nitrogen.

Synthetic fertilizers add _____________ to the soil.

Fixed nitrogen (ammonium); Using synthetic nitrogen fertilizers fixes nitrogen in the soil. Through the use of synthetic fertilizers, humans have more than doubled the amount of fixed nitrogen that is pumped into the biosphere every year.

Which process releases dinitrogen gas (N2) back into the atmosphere?

In the process of denitrification, bacteria convert nitrate to dinitrogen (N2), a gas which is rapidly lost to the atmosphere.

What forms of nitrogen do plants use?

Inorganic forms such as ammonium (NH4) and nitrate (NO3)

Ammonium (NH4) stays in soil, while nitrate (NO3) is easily leached out. Why do they behave so differently?

NH4 has a positive charge and sticks to soil particles; in nitrification, some positively charged ammonium ions are converted to negatively charged nitrate. The positive charge prevents ammonium nitrogen from being leached out of the soil by rainfall. In contrast, the negatively charged nitrate ion is not held by soil particles and so can be washed out of the soil and into surface and groundwater.

abiotic nitrogen fixation

Natural: lightening Anthropogenic: 1) Industrial (Haber Bosch process): N2 -> NH3 Uses natural gas, so is fossil fuel-based fertilizer 2) High temperature combustion (N2 -> NOx)

Once bacteria have fixed nitrogen, it can be taken up by plants and animals, where it is used in the production of

Proteins; In the process of nitrogen fixation, bacteria convert N2 from the atmosphere into ammonium, a form that plants and animals can use. The ammonia produced by nitrogen fixing bacteria is used to make protein.

Legumes host nitrogen fixing bacteria, and thus are good crops to plant to replenish the soil.

True; Burning fossil fuels, using synthetic nitrogen fertilizers, and cultivating legumes all fix nitrogen. Through these activities, humans have more than doubled the amount of fixed nitrogen that is pumped into the biosphere every year.

Processes fixing atmospheric nitrogen into usable forms

biological nitrogen fixation and abiotic nitrogen fixation

biological nitrogen fixation

biological organisms, such as bacteria or fungus, removing nitrogen from the atmosphere (N2) and adding it into the soil or plant body.

Emphasis is on cycling of nutrient nitrogen between:

gas phase (atmosphere), solid phase (life), soluble phase (DON, ions)

What is the most common way that nitrogen fixation occurs?

nitrogen fixing bacteria