Nitrogen+cycle


 * __//Nitrogen Cycle//__**

Nitrogen is an element. It is found in all living things like plants and animals. It is also an important part of non-living things like the air above and the dirt below.
 * What is nitrogen used for?**

Most of the nitrogen on Earth is in the atmosphere. Approximately 80% of the molecules in Earth's atmosphere are made of two nitrogen atoms bonded together (N2). The nitrogen in the atmosphere is not in a form that they can be used by plants and animals. The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, by certain types of bacteria, or by bacteria associated with bean plants.
 * Where do we find it?**

Nitrogen enters the food chain by means of nitrogen-fixing bacteria and algae in the soil. This nitrogen which has been 'fixed' is now available for plants to absorb. These types of bacteria form a symbiotic relationship with legumes--these types of plants are very useful because the nitrogen fixation enriches the soil and acts as a 'natural' fertilizer. The nitrogen-fixing bacteria form nitrates out of the atmospheric nitrogen which can be taken up and dissolved in soil water by the roots of plants. Then, the nitrates are incorporated by the plants to form proteins, which can then be spread through the food chain. When organisms excrete wastes, nitrogen is released into the environment. Also, whenever an organism dies, decomposes break down the corpse into nitrogen in the form of ammonia. This nitrogen can then be used again by nitrifying bacteria to fix nitrogen for the plants.
 * How does the cycle work?**

**__Nitrogen fixing__** --nitrogen needs to be broken apart so that its atoms can combine with others. This requires substantial amounts of energy. Three processes are responsible for most of the nitrogen fixation in the biosphere: __atmospheric fixation__ -- by lightning __biological fixation__ -- by certain microbes — alone (bacteria) or in a symbiotic relationship with some plants (alfalfa and soy beans) and animals (termites). __industrial fixation__ -- Under great pressure, at a temperature of 600°C, atmospheric nitrogen and hydrogen can be combined to form ammonia. __Decay__ -- each animal produces organic nitrogen compounds that return to the environment (waste). These microorganisms break down the molecules in other excretions and dead organisms into ammonia.

__Ammonification__ --- when a plant or animal dies or expels waste, the organic nitrogen is converted into ammonia. (ammonia nitrifies and can be reused)

__Assimilation__ ---the act of nitrogen being reincorporated back into the cycle. for example the absorption through plant roots.

When we cause nitrogen overload in an ecosystem, there are many drastic effects. 1. //Eutrophication// ---Dumping of raw sewage contains nitrogenous wastes, along with urban runoff, when these amounts of nitrogen collect in a water body. This large accumulation of excess nutrients causes a bloom in algae. The algae rapidly deplete all of the oxygen in the water, making it inhospitable for fish and other aquatic organisms. Eutrophication also brings about the deadly red tides. When the nitrogen-rich waters make their way downstream to the ocean, they cause even more problems. High nitrogen levels have caused a “dead zones” these areas are where the oxygen levels are too low for animals to survive. There are currently over 150 “dead zones” around the world.
 * How do humans interfere with this cycle?**

2. //Acidified soil// --- When plant communities are saturated with nitrogen, this causes the soil to become acidified. Acidified soil is inhospitable.

3. //Burning fossil fuels/wood// --- this contributes to a large amount of nitric oxide in the atmosphere. Nitric oxide can combine with oxygen gas to form nitrogen dioxide, which reacts with water vapor to form a strong acid (nitric acid). This can precipitate out of the atmosphere in the form of the deadly acid rain. Acid Rainà This acid can damage trees and kill fish.

4. U//sing fertilizers// ---Nitrogen from fertilizers sinks into soils, often creating conditions that favor the growth of weeds rather than native plants, it can also result in eutrophication.

5//. Air pollutants// --- products we put into the air, like chemical, power plant and factory fumes contain nitrogen. This decrease air quality and can create smog and Acid rain. If the Molecules break apart and attach to oxygen and form dangerous ground level ozone.

6. //Release of Nitrous Oxide// --- Nitrous oxide is a greenhouse gas Nitrous oxide forms during combustion and is also released into the atmosphere from farm animals, sewage, and fertilizers.

Natural releases--- Tiny microbes that alter nitrogen in the soils of tropical forests.