THE POLYNUCLEAR AROMATIC HYDROCARBON (PAH) CONTENT OF ARCHIVED SEWAGE SLUDGES

Twenty nine anaerobically digested, lagoon dried sewage sludges were analysed for polynuclear aromatic hydrocarbons (PAHs). These sludges had been applied to the plots of a long term agricultural experiment from 1942 to 1961. The exact dates of sludge production and treatment are unknown, although they are likely to be 1-5 years prior to sludge application dates. The sludges had a mean ΣPAH (defined as the sum of the compounds measured) concentration of 50 mg/kg, with a range of 18-125 mg/kg. The most abundant compound was benzo[ghi]perylene with a mean concentration of 10 mg/kg. A trend is apparent in the ΣPAH content through time, increasing until 1948 to over 125 mg/kg, then decreasing to 29 mg/kg by 1961. These changes are tentatively attributed to changes in air quality and smoke emissions. The PAH content of contemporary sludges is also reviewed. © 1990.