Persistence of two-, three- and four-ring of PAHs in sewage sludge deposited in different light conditions

The aim of the investigations was to determine the changes in the concentration of PAHs in sewage sludge stored under various light conditions. The sewage sludge samples were stored under aerobic conditions in dark, in laboratory conditions and exposed to UV rays. The changes in the concentration of PAHs were analysed in three series: in sludge samples taken from treatment plant, in sludge with the addition of a standard PAH mixture and in sewage sludge with the addition both a standard mixture and with added sodium azide (abiotic samples). Changes in 10 PAHs concentration in sewage sludge samples were studied at seven-day intervals for four weeks. The concentration of PAHs was determination using gas chromatograph–mass spectrometry. The losses of 10 hydrocarbons after four weeks of storing were in the range of 12–99%. The half-life of hydrocarbons was in the range of 5–953 d in sewage sludge taken from treatment plant. In sewage sludge amended with standard mixture, half-life of PAHs was not exceed 137 d.