Changes of optical density and fluorescence intensity of river water samples during storage

Waters of river Okhta and its tributary polluted with domestic wastewater were studied during several weeks of water storage at 20°C and 8°C. At sampling day, concentrations of total organic carbon in waters were close (17-24 mgTOC/L), polluted waters had difference in electric conductivity, increased concentration of total nitrogen (TN) and NH4 +. During storage, concentrations of TOC, inorganic carbon, TN, NH4 + declined, and the decline was stronger in polluted waters and at room temperature of storage. Spectra of optical density (D) of waters showed no significant qualitative difference between polluted and not polluted waters. During storage, D254 of all samples decreased up to 40% in 12 days. Polluted water had higher fluorescence intensity (I) at emission wavelengths 320-370 nm (up to 200%) and 420 nm (up to 50%). During storage of polluted water I decreased at 320, 350, 370 nm and increased at 420 nm. For pollution detection in not diluted waters at the sampling day and after 2 weeks of water storage the following parameters can be recommended: I230,350, I230,370 or I270,350 together with ratio of protein-like to humic-like fluorescence I230, 350/420 or I270, 350/420. These parameters can be used with or without correction of I for D.