The significance of dissolved organic matter photodegradation as a source of ammonium in natural waters

Samples of sea, river and pond water of different absorbance were exposed to artificial radiation resembling sunlight in the UV range. A statistically significant increase in ammonium concentration was detected in pond water of the highest absorbance after 5 h of irradiation. In sea and river water a corresponding increase (< 0.5 μM) was recorded after an exposure time of 25 hours. The bulk characteristics of the analysed samples were insufficient to explain the observed differences.