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Anomalous Ultraviolet Absorption by Chromophoric Dissolved Organic Matter in Coastal Seawater

EPA Grant Number: U914954
Title: Anomalous Ultraviolet Absorption by Chromophoric Dissolved Organic Matter in Coastal Seawater
Investigators: Patterson, Karen W.
Institution: University of California - Santa Barbara
EPA Project Officer: Manty, Dale
Project Period: January 1, 1996 through January 1, 1999
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996)
Research Category: Academic Fellowships , Fellowship - Earth Sciences , Ecological Indicators/Assessment/Restoration

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. , Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, RFA, Monitoring/Modeling, Ecology and Ecosystems, Environmental Monitoring, coastal watershed, seawater, dissolved organic matter, coastal zone, spectrophotometric measurements

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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