RESISTANCE OF MODEL HUMIC ACIDS TO ULTRAVIOLET-C RADIATION

A b s t r a c t . Increasing penetration of UV radiation in to the Biosphere raises the question about the photo resistance of humic substances. Is there any dependence between the photoresitance and chemical composition of their precursors? Humic aci ds synthesized from pyrocatechol, hydroquinone + tyrosine, purpurogalline and commercial Fluka of natural origin were irradiated with the UV-C radiation. Fluorescence emission spectra, chemiluminescence imaging and absorption spectra of alkali solutions of humic acids before and after various time of irradiation were measured. The most resistant to UV-C radiation was synthetic humi c acid from pyrocatechol, and the most labile was humic acid obtained from purpurogalline. Possible causes of the high/low photo resistance of humic acids are shortly considered. K e y w o r d s : humic acids, photo resistance, UV-C radiation, luminescence, chemiluminescence imaging