1-6: Nitrogen Cycle, Sulfur Cycle; Tropospheric Ozone

Pre-Class Preparation

• To examine the cycling of chemically active trace gases in the earth's atmosphere.
• To understand how reactivity of trace gases relates to their spatial and temporal distribution.

Procedure

1. Read the learning unit.

   Class images

2. Take the learning unit quiz. Quizzes are available from your portfolio. You may access your portfolio via the list of students participating in this year's course, as represented by the icon below.
   
   
3. Additional Required Reading. Although you are not ultimately responsible for content listed in this section, we encourage you to fully explore the links in order to provide a better scope on the upcoming class discussion.

   	Dead Zone in Gulf of Mexico
   	Global Nitrogen Overload
   	Nitrogen balance in the soil
   	Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p 25-30.

Class Discussion

• Problem to ponder...
  If nitrous oxide is the most inert of the atmospheric nitrogen compounds, why is it in some respects the most dangerous?

• Class Discussion Summary: by class members Reid Scholes and Aaron Pease

  Nitrous Oxide is a very stable gas which has a fairly constant concentration throughout the atmosphere. NO_X and Sulfur Dioxide have relatively short half-lives and pose problems in localized areas only. Biogeochemical processes are very complicated reactions and cycles between all components of the atmosphere. This makes it difficult to gage the severity and outcomes of global atmospheric problems. However, there´s yet an ethical question of industrialized nations´ emissions creating global problems that all nations must deal with.

Post-Class Activities

• Participate in the electronic dialog. Use this forum for:
  • continuing class discussion;
  • posing new questions to students or the instructor;
  • responding to issues/questions raised by students in class/electronic dialog.

  Visitor Access (Visitors are welcome to participate in the dialog. Just click on the icon below)	Student Access (Students must post all dialog from their portfolio. Click on the icon below to access the student list.)

• Recommended Reading Materials

  	Apel, William A. et al, 1995: Removal of nitrogen oxides from gas streams using biofilteration. Journal of Hazardous Materials. 41,315-326.
  	Bremner, J. M., et al., 1981: Effect of nitropyrin on emission of nitrous oxide from soil fertilized with anhydrous ammonia. Geophysical Research Letters, 8(4), 353-356.
  	Carlsson, Andre S., et al., 1994: Effects of moderately enhanced levels of ozone on the acyl lipid composition of leaves of garden pea. Physiologia Plantarum, 91, 754-762.
  	Charlson, R. J. et al., 1987: Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate. Nature, 326, 665-661.
  	Cofer, W. R., 1991: New estimates of nitrous oxide emissions from biomass burning. Nature, 349, 689-691.
  	Eckey-Kaltenbach, et al., 1994: Biochemical plant responses to ozone. Plant Physiology, 104, 67-74.
  	Houghton, J.T., G.J. Jenkins, J.J. Ephraums eds, 1990: 1990 Intergovernment Panel on Climate Change, Cambridge University Press.
  	Houghton, J. T., L. G. Meira Filho, B. A. Callander N. Harris, A. Kattenberg, and K. Maskell, 1996: Climate Change 1995. The Science of Climate Change. Cambridge University Press, 86-91.
  	Keller, M., et al., 1986: Emissions of N2O, CH4, and CO2 from tropical soils. Journal of Geophysical Research, 91(11), 791-802.
  	Naiman, Robert J., Gilles Pinay, Carol A. Johnson, and John Pastor, 1994: Beaver influences on the long-term biogeochemical characteristics of boreal forest drainage networks. Ecology, 75, 905-921.
  	Wigley, T.M.L., 1989: Possible climate change due to SO2 -derived cloud condensation nuclei. Nature, 339, 365-367.
  	Woodbury, P. B., et al., 1994: Chronic ozone exposure alters the growth of leaves, stems, and roots of hybrid Populus. Environmental Pollution, 85, 103-108.
  	Vaclav, Smil, 1997: Global population and the nitrogen cycle. Scientific American, July, 76-81.

• References

  	Malakoff, David, 1998: Death by suffocation in the Gulf of Mexico. Science 281, 190-192.
  	Falkowski, P. G., R. T. Barber, and V. Smetacek, 1998: Biogeochemical controls and feedbacks on ocean primary production. Science 281, 200-206.
  	Jickells, T. D., 1998: Nutrient biogeochemistry of the coastal zone. Science 281, 217-222.
  	Global Emissions Inventory Activity-- annual N2O emissions world map.
  	Sulfur Pollution from Natural Sources. --Full text paper from NOAA Pacific Marine Environmental Laboratories.