Formation of carbonyl compounds from UV‐induced photodegradation of humic substances in natural waters: Fate of riverine carbon in the sea

• DOI: 10.4319/lo.1990.35.7.1503
• Publication Date: 2010-04-10T02:32:50Z
• Authors: Robert J. Kieber; Xianliang Zhou; Kenneth Mopper
• Keywords: Absorbance; Photobleaching; Photodegradation

Low‐molecular‐weight (LMW) carbonyl compounds, e.g. formaldehyde, acetaldehyde, and the α ‐keto acid glyoxylate, were produced in a wide variety of natural waters upon irradiation with sunlight. Production rates linearly related ( r 2 > 0.98) to initial absorbance at 300 nm fluorescence (360/460 nm) all tested. Photochemical production was also loss (photobleaching) during irradiation, irrespective time prior photobleaching history sample. These results attributed absorption light by humic substances waters, as determined experiments where purified fulvic extracts added open‐ocean water. The wavelengths solar spectrum responsible for photoproduction LMW compounds bleaching dissolved organic matter are UV‐B region (280–320 nm). results, plus from time‐course irradiations, suggest that is closely absorbance. Based on our we estimate half‐life humic‐rich riverine C oceanic mixed layer 5–15 yr.