The Cycling of Materials

Chapter 5Section 2

Overview

• The carbon, nitrogen, and phosphorus cycles• How human activities affect these cycles?

The carbon cycle

The Carbon Cycle

• http://www.youtube.com/watch?v=0Vwa6qtEih8

How Humans Affect the Carbon cycle

Power plant

Carbon Sequesteration

• It involves capturing atmospheric Carbon dioxide and storing it in the terrestrial biosphere, underground, or in the oceans

• The U.S Department of Energy is currently focusing on ways to enhance carbon sequesteration in the terrestrial biosphere by increasing the storage of carbon in biomass and soils.

• They are focusing on enhancing the net oceanic uptake of carbon dioxide from the atmosphere by fertilizing phytoplankton as well as by injecting liquid carbon dioxide to ocean depths greater than 1000m.

• Scientists are also investigating methods of pumping carbon dioxide into abandoned mines and petroleum wells.

The Nitrogen Cycle

How Humans Affect the Nitrogen cycle?

• Humans have doubled the natural rate of nitrogen entering the land-based nitrogen cycle, through the use of chemical fertilizers and fossil fuels.

• The increase in nitrogen has increased water and atmospheric pollution, acidification of lakes, streams, and soils, and has contributed to greenhouse gases.

• Some plants adapted to soil low in nitrogen have been negatively affected or replaced by nitrogen-loving plants. This has affected the animals that consume those plants

• Read the article Human alteration of the Global Nitrogen cycle: Causes and Consequences. The article can be found online, or in the journal Ecological Applications (Volume 7, August 1997)

What impact fertilizers have on the environment?

• Energy is needed to produce nitrogen-rich fertilizers. This energy comes from fossil fuels, which add carbon to the atmosphere.

• When excess nitrogen compounds run off fields and into bodies of water, they can cause an overgrowth of algae and aquatic plants. When these aquatic plants die and decay, bacteria use oxygen to decompose the plant remains. When there is an abundance of plant remains, decomposers can deplete the water of oxygen which other aquatic organisms need to survive

Eutrophication

Acid Precipitation

Nitric Oxide is a harmful gas and it combines with oxygen and water vapor to form nitric acid. It can dissolve in rain and snow, which contributes to acid precipitation.