Disappearance Time of a Few Polycyclic Aromatic Hydrocarbons in Soil

The present study attempts to determine the order of reactions for degradation of four polycyclic aromatic hydrocarbons viz., anthracene, fluorene, naphthalene and phenanthrene in six selected soil samples by method of trials. The half-life period or the disappearance times in days for 50% (DT 50) of the hydrocarbons initially applied to the soil were determined after finding out the probable order of the reactions using the half-life equations. A few of the extracts are subjected to GC analysis. Nine of 21 samples studied in the experiment are degraded and zero-order while the remaining samples are of the first order. The increasing trend in electrical conductivity and decreasing trend of pH support the formation of polar substances from non-polar hydrocarbons. Average DT 50 values for a mixture of the cited PAHs are 6 and 16 days, respectively, in presence of Fenton's Reagent and without it in the samples having 200 ppm concentration. In a semi-closed system, where there is no horizontal spread of solids and liquids, the DT 50 depends on initial pollutant concentration. Fenton's Reagent has been found to enhance the rate of degradation by the rapid conversion of the hydrocarbons into derivatives or fragments.