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Experiments were conducted at the bench scale to determine the effects of pH, totalorganic carbon (TOC), alkalinity, temperature, and Hsub2/subOsub2/sub dose on the removal rate of atrazine(ATZ) using ultraviolet light (UV) emitted from a medium-pressure mercury lamp. Simulatednatural water was used to control these parameters independently. Initial experiments showedvery little effect of alkalinity alone, and the effect of TOC was ascribable solely to lightscreening since TOC had no effect on the UV dose-based rate constants (which account for lightscreening by the water matrix). On the other hand, increasing temperature and Hsub2/subOsub2/sub dosepositively affected the removal rates while increasing the pH had a small but negative effect bothwith and without Hsub2/subOsub2/sub that was most discernable at higher temperatures. These three parameters(Hsub2/subOsub2/sub, T, and pH) were therefore selected for further study to design a dose-response model ofATZ removal.Other experiments examined whether nitrate (NOsub3/subsup-/sup) has a photosensitizing effect on ATZdegradation (via sup./supOH production during NOsub3/subsup-/sup photolysis). Nitrate concentrations up to 7 mg-N/Lenhanced the ATZ removal rates (ssup-1/sup) in deionized water but decreased the rates slightly insynthetic natural water. This latter effect is due to a combination of light screening and sup./supOHscavenging by natural organic matter. Nonetheless, the rates remain higher than expected on thebasis of light screening alone indicating that a large fraction of ATZ reacts with sup./supOH even in thepresence of sup./supOH scavengers. Includes 19 references, tables, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 13File Size: 1 file , 220 KB