Evaluation of photochemical properties of compost humic-like materials

Humic-like acids (HLA) were extracted from compost at the beginning and after 70, 130 and 730 days of maturation in order to be investigated for their ability to induce the transformation of 2,4,6-trimethylphenol under irradiation at 365 nm. The rate of 2,4,6-trimethylphenol phototransformation in the presence of HLA (25 mg l−1) varied within HLA0 << HLA70 ≈ HLA130 ≈ HLA730. The changes of photoinductive capacity paralleled the changes of HLAs absorptivity indicating that the formation of photoinductive constituents is related to that of the colored moieties. The polyacrylamide gel electrophoresis analysis showed that intensity of all humic electrophoretic fractions significantly increased during the first 70 days of maturation but did not undergo significant changes for longer composting times. These data confirm the changes of HLS during composting.