Light-induced degradation of DDT in humic water

Humic water, spiked with DDT (13 nM), was subjected to ultraviolet radiation with a wavelength of 254 nm (UV254) and also to intense simulated sunlight. Sample extracts were analysed by gas chromatography/mass spectrometry (View the MathML source), the mass spectrometer working in the selective ion monitoring mode. DDT was degraded both by the UV254-radiation and the amplified artificial solar radiation. The degradation rate was substantially faster during UV-irradiations (minutes) than during the simulated sunlight-irradiations (hours). The presence of natural dissolved organic matter had a retarding effect on the photolytic degradation rate of DDT in the UV254-experiment, but an accelerating effect in the artificial sunlight-experiment, indicating that different reaction pathways are involved in the two experiments. The formation of associates between DDT and dissolved organic matter seems to promote the photolysis induced by the UV-radiation.