Photolysis of 2,4,6-Trinitrotoluene in Seawater: Effect of Salinity and Nitrate Concentration

The photolysis rate of 2,4,6-trinitrotoluene (TNT) was examined in a variety of natural waters from pure water to a seawater end member. Photolysis experiments were performed using a Suntest CPS+(R) solar simulator equipped with an optical cell holder with eight positions for long-pass cutoff filters ranging from 295 to 495 nm. The rate of disappearance of TNT followed first order kinetics in all water types examined, and occurred at wavelengths less than 320 nm, but not significantly at wavelengths above 395 nm. The rate of photolysis decreased in the order seawater > estuarine water > fresh water > pure water, with the photolysis half-life for each water type at wavelengths less than 320 nm of 70, 120, 200 and 700 minutes, respectively. Changes in ionic strength from fresh to seawater do not account for the observed differences. Photolysis rates of TNT were not affected by the concentration of nitrate over the range expected in natural waters.