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Interactions of Changing Solar Ultraviolet Radiation and Climate with Light Induced Chemical Reactions in Aquatic Environments
Citation:
ZEPP, R. G. Interactions of Changing Solar Ultraviolet Radiation and Climate with Light Induced Chemical Reactions in Aquatic Environments. Presented at Michigan State University, Department of Chemistry, East Lansing, MI, October 10, 2008.
Impact/Purpose:
see description
Description:
Changes in the ozone layer over the past two decades have resulted in increases in solar ultraviolet radiation that reach the surface of North American aquatic environments. Concurrent changes in atmospheric CO2 are resulting in changes in stratification and precipitation that are affecting the chemical composition and light-induced processes of freshwaters and coastal marine environments. Recent research has provided evidence that interactions of solar UV radiation and the chromophoric component of dissolved organic matter, often referred to as CDOM, may play an important role in the functioning of aquatic ecosystems. CDOM strongly absorbs UV radiation and thus controls the penetration of biologically-harmful solar ultraviolet radiation into many freshwater and marine ecosystems. On irradiation, CDOM and its complexes with metals such as iron produce excited state and reactive oxygen species that mediate photosensitized reactions in aquatic environments. Photodegradation of CDOM results in loss of its UV and visible absorbance and fluorescence, a process referred to as photobleaching, changes in the biological availability of its carbon- and nitrogen-containing constituents, and production of carbon dioxide, carbon monoxide, volatile hydrocarbons, and sulfur-containing gases. This presentation will discuss kinetic and mechanistic approaches that are used to study these intriguing photoreactions in the laboratory and field.