Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 10:15:00 AM

Location: San Miguel

Kaiser, E, , EAWAG-ETH, CH-8600 Duebendorf, Switzerland, edith.kaiser@eawag.ch

Sulzberger, B, , EAWAG-ETH, CH-8600 Duebendorf, Switzerland, sulzberger@eawag.ch

MOLECULAR CHARACTERISTICS AND PHOTOREACTIVITY OF RIVERINE DISSOLVED ORGANIC MATTER (DOM) AND HOW THEY IMPACT DOM BIOAVAILABILITY

The impact of photochemical transformations on the bioavailability of different DOM sampled along the river continuum was investigated on a seasonal base in the Tagliamento River, Italy. After exposing different size-fractions (ultrafiltration) as well as chemically different fractions (C18 solid phase extraction) of DOM to simulated or natural sunlight, the changes in the molecular composition and the utilization of DOM by natural riverine bacterioplankton were measured. DOM fractionation revealed that up to 80% of isolated riverine DOM consisted of hydrophilic low-molecular weight (LMW) organic acids and about 20% was made up by polyphenolic compounds. The bioavailability of LMW DOM was highest. In general a 4-hour exposure of all DOM fractions to the full solar spectrum resulted in a release of hydrophilic LMW organic acids and Fe(II), a concomitant consumption of hydrogen peroxide, and in a reduction (20-90%) in bioavailability. Iron-catalyzed phototransformations of DOM significantly decreased the microbial turnover of organic carbon compounds, and therefore appear to play a critical role in the cycling and transport of DOM in the Tagliamento River.

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Aquatic Sciences Meeting, Albuquerque 2001

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