Identification and Determination of Unstable Chemical Species Induced by the Solar Radiation in Natural Waters.

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It is considered that the active oxygen species generate in the surface of natural waters under irradiation of the sun. In coastal seawater which contains abundant organic substance, hydrogen peroxide, one of the major active oxygen, generates up to 300 nM by the solar irradiation. OH radical, superoxide negative ion, singlet oxygen are the active oxygen species other than hydrogen peroxide. However, these species have much shorter life time compared with hydrogen peroxide, and difficult to determine. We investigated the methods to determine OH radical and superoxide negative ion in river and seawater after irradiation of solar simulator. OH radical is detected by means of conversion rate of benzene to phenol and separated by HPLC. In the case of superoxide negative ion, lactate dehydrogenase-NADH reaction, nitroblue-tetrazolium method, and nitromethane method were investigated. However, deionized water produce more superoxide negative ion than river water after the irradiation of solar simulator. Flow injection type chemiluminescence detector was constructed and chemiluminescence was detected after alkaline luminol and superoxide negative ion. In this case, humic acid gave a strong chemiluminescence compared with deionized water after irradiation of solar simulator.