Photokinetics of azaarenes and toxicity of phototransformation products tothe marine diatom Phaeodactylum tricornutum

UV radiation is absorbed by PAHs, structurally altering these compounds int o a variety of oxygenated products. Until recently, only hazards of parenta l PAHs in the environment were investigated. This study aims to determine t he fate and effects of azaarenes (N-heterocyclic PAHs) together with their photoproducts in marine environments. Photoreaction kinetics of eight azaar enes, ranging from two-ringed to five-ringed structures, were examined usin g two different light sources: one with an emission peak at 300 nm (UV-B) a nd the other with an emission peak at 350 nm (UV-A). Azaarenes degraded rap idly in the presence of short-waved light, UV-B being more effective than U V-A. Especially preexposure of azaarenes to UV-A radiation led to products toxic to the marine diatom Phaeodactylum tricornutum. Since UV-A constitute s a larger fraction of sunlight at the earth surface and in the water colum n, photolysis by UV-A may increase the toxic risk of aromatic compounds in the marine environment.