Dark recovery of photodegraded chromophoric dissolved organic matter

Aged samples of natural waters filtered with Whatman GFF filters had been irradiated with UVA radiation then stored in darkness and checked for changes in absorbance of chromophoric dissolved organic matter (CDOM). The recovery of absorbance (integrated within 250-600 nm wavelength range) of irradiated river water, lake water and seawater during 72 h dark storage at room temperature was 17, 34 and 25% respectively. The highest relative increase in absorbance was in the long wavelength part of the optical spectrum. The recovery was smaller in the samples kept at lower temperature.