| Summary: | EPA Identifier: U914954 Title: Anomalous Ultraviolet Absorption by Chromophoric Dissolved Organic Matter in Coastal Seawater Fellow (Principal Investigator): Karen W. Patterson Institution: University of California - Santa Barbara EPA Grant Representative: Dale Manty Project Period: January 1, 1996 - January 1, 1999 Project Amount: $0 RFA: STAR Graduate Fellowships Research Category: Fellowship - Earth Sciences Description Objective: The objective of this research project is to discover the origin of anomalous peaks observed in spectrophotometric measurements of spectral ultraviolet radiation absorption by the chromophoric dissolved organic matter component of seawater. Approach: Seawater samples were collected in glass bottles, which had been acid washed and thoroughly flushed with organic-free water. Samples were filtered through 0.2-µm polycarbonate membrane filters. These filters were pre-washed with 50-100 mL organic -free water and about 30 mL of sample water. All samples were stored and refrigerated in the dark from the time of collection to the time of processing. Usually within 24-48 hours of collection, filtered seawater samples were scanned for spectral light absorption in the 250-750 nm range, using 10-cm pathlength cylindrical quartz cuvettes in a Perkin Elmer Lambda 2 spectrophotometer. All possible sources of laboratory contamination were either eliminated or randomized so that any sample contamination will appear in the dataset as a random distribution among stations. In addition, the exact method was used in two other regions of the world, the Florida Keys and the West Antarctic Peninsula. This feature did not appear in the Florida Keys dataset. A similar, if not the same type of feature, appeared in the West Antarctic Peninsula region in Marguerite Bay and in algae-laden sea ice. These two Antarctic environments were of markedly different character than the majority of the 400 x 200 km grid sampled. Data collected in these additional two regions support the hypothesis that the anomalous high absorption in the 310-340 nm range is a natural feature and is not caused by laboratory contamination. Currently, efforts are being made to discover the source of these anomalous absorption peaks through correlation analyses using a variety of other data variables collected at the same time. Supplemental Keywords: fellowship, chromophoric dissolved organic matter, CDOM, spectral ultraviolet radiation absorption, seawater, organic-free water, absorption peaks.
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