The Nitrogen Cycle http://www.nitrousoxide.org/images/fig2.gif

Learning Targets Explain the importance of nitrogen to living things Trace the movement of nitrogen through the nitrogen cycle including: Sources of nitrogen Processes and organisms that convert nitrogen Spheres involved Form used by plants Explain how humans impact the nitrogen cycle and the how excess nitrogen affects human health and the environment

Importance of Nitrogen (N) N is an essential plant nutrient (N, P, K) All living things need nitrogen for amino acids, proteins and nucleic acids (DNA and RNA) Concentrations of N are important indicators of water quality. Excess N also affects air quality and human health

http://extension.missouri.edu/p/WQ252

Forms of Nitrogen Nitrogen exists in all four spheres: The atmosphere is 78% N2 gas Nitrogen exists in several forms, organic and inorganic Organic means it is part of living organisms or the biosphere Examples - amino acids, proteins, DNA and RNA all contain Nitrogen Inorganic forms in soil (geosphere) and water (hydrosphere) include Nitrate (NO3), nitrite (NO2), and ammonium (NH4+)

Plants can’t use N2 Plants cannot absorb the Nitrogen gas from the atmosphere It must be fixed in the soil or water for them Meaning changed to a useable form Plants use ammonium or nitrate nitrogen

Nitrogen Fixation Lightning makes nitrate and rain carries it into the soil Bacteria – living in root nodules of legumes (soybeans, clover) convert N2 to ammonia Humans manufacture fertilizers and burn fossil fuels Cyanobacteria (blue-green algae) fix nitrogen in water

Decomposers produce ammonia Ammonium ion is in waste products from animals (sewage) and produced from bacterial decomposition of dead plants and animals

Denitrification by anaerobic bacteria (without oxygen) Converts ammonia to nitrite and nitrate and N Gases are released into the air

Human impact Over last 100 years we’ve more than doubled the amount of N entering the cycle 60% of N entering the cycle comes from commercial inorganic fertilizers Burning fossil fuels adds nitrates to the air which forms nitric acid in our atmosphere and contributes to acid deposition and global warming Nitrous oxide, N20 from anaerobic bacteria working on livestock waste and fertilizer contributes to global warming and ozone loss. Discharge of municipal sewage also add N to lakes Excess nitrates enters ground water and can harm young children and pregnant mothers (blue-baby syndrome)

Cultural Eutrophication: Excess nutrients (nitrogen and/or phosphorus) stimulate plant growth (algal bloom) When these plants die, decomposers use up the available oxygen during decomposition

http://zolushka4earth.wordpress.com/tag/oligotrophic/

This can lead to Dead Zones

Learning Target Check Explain the importance of nitrogen to living things Trace the movement of nitrogen through the nitrogen cycle including: What are the sources of nitrogen? What are processes and organisms that fix nitrogen in soil/water? What are the processes and organisms that release nitrogen to the atmosphere? What spheres contain nitrogen, and in what form? What form of nitrogen is used by plants? How do humans impact the nitrogen cycle and the how excess nitrogen affects human health, water quality/aquatic ecosystems, and air quality?