Group members preparing summary: Bobbier Johnson, Don Miller, and Jared AndersonThis unit concentrates on the buildup of nitrogen and sulfur concentrations in the atmosphere. One of the compounds in the nitrogen cycle that contributes to this is nitrous oxide N20. This oxide is quite stable and has been steadily increasing each year since the Industrial Revolution.
Some of the natural sources of nitrous oxide include oceans, tropical soils, wet forests, dry savannas and extra-tropical forests. Anthropogenic sources could be nitrogen fretilizers, biomass burning, combustion and acid production.
Other nitrogen compounds inclue NOx, which comes from soils, lightening, fossil fuels, biomass burning and contrails from aircraft in the troposphere. Nitrgoen commonly enters the atmosphere as NO, changes to NO2 or NO3 and then attaches itself to a raindrop. Once it rains out, the nitroen re-enters the soil.
One of the highlights from dialog is an explanation of the effect lightening has on the production of nitrogen in the atmosphere. It was concluded that while it wasn't a major source compared to anthropogenic sources, lighening is still a viable source.
Nitric oide (NO) entering the atmosphere can be converted by chemical oxidation reactions into NO2, which can combine with other materials and fall out as dry particles. NO can be further oxidized to NO3, which can dissolve in rainwater and come down as acid rain. NO can also attach to particles or raindrops and return to earth. Nitrous oxide (N2O) is much lesss reactive, being distributed throughout the troposhpere were it remains stable for long periods of time. It only reacts when it encounters UV radiation in the stratopshere. NO is the nitrogen compound that contributes to global warming.
Most sulfur emmissions come from the burning of coal, and most of the sulfur in the atmosphere is in the form of SO2. Current levels are over three times those of the 1850's. Volcanoes also contribute some SO2, and the ocean contributions of DMS are significant, but the majority of airborne sulfur compuonds are produced by anthropogenesis. SO2 reacts with rainwater to form the sulfuric acid, whic falls as acid rain. Concentrations tend to be greatest near high industrialized areas, and are greatly affected by local wind and weather paterns. SO2 can also produce a cooling effect by forming cloud droptlets that are very bright; hence, they reduce the amount of incoming solar radiation. The dimethylsulfide (DMS) released in ocean life processes assists in cloud formation, and is an example of a positive feedback loop whereby a direct link is established between life in the ocean surface and the precipitation patterns for that region.
Ozone is created in the troposphere by various chemical reactions. Comboniations of oxeides of nitrogen, volatile organic compounds (VOC). and diatomic oxyegen in the presence of sunlight produce higher concentrations of ozone. VOC are produced from the exhaust from automobiles.
Troposhperic ozone is an environmental problem mainly due to anthropogenic sources in major cities. Higher concentrations of ozone have advers effects on things that require oxidation. The human lung is prime example. People with respiratory problems are the most susceptible. Estimated yeild loss for crops is another consequence of incresed ozone.