VACUUM UV PHOTOLYSIS OF AQUEOUS-SOLUTIONS OF NITRATE - EFFECT OF ORGANIC-MATTER .2. METHANOL

Vacuum UV irradiation of aqueous solutions containing NO3- and methano l results in the simultaneous mineralization of methanol and depletion of NO3-, yielding NO2- and NH4+. Moreover, the depletion rates of NO3 - are two to three orders of magnitude faster in the presence of metha nol than in corresponding experiments with pure nitrate solutions. A p ossible mechanism is discussed in which the reactions of NO2. and NO. with the radicals formed during methanol oxidation are proposed to be mainly responsible for the overall behaviour observed. The reactions b etween these intermediates and NO. seem to follow reduction pathways l eading to NH4+ formation, whereas a one-electron reduction yielding N2 O is observed in the absence of organic material. The formation of CNO - as an intermediate product is a clear indication that reactions betw een nitrogen-containing ions, carbon-centred radicals and/or methanol and its oxidation products occur. The present results are in complete agreement with previously reported data concerning the enhanced reduct ion of NO3- in the presence of phenol, thus suggesting that the behavi our observed may probably be generalized to most organic substrates.