Decline in PCDD and PCDF levels in sewage sludges from Catalonia (Spain)

Nineteen sewage sludges from rural and urban wastewater treatment plants (W WTPs) in Catalonia (Spain) were analyzed for PCDDs and PCDFs using:HRGC-HRM S to determine the present levels of contamination. Total I-TEQ values for these samples ranged from 7 to 160 pg/g, with a mean value of 55 pg/g and a median value of 42 pg/ g. Moreover, archived sewage sludge samples collect ed and stored between 1979 and 1987 from 15 WWTPs were analyzed to gain som e;insight into temporal trends and possible variations in source inputs. To tal I-TEQ values for archived samples ranged from 29 to 8300 pg/g, with a m ean value of 620 pg/g and a median value of 110 pg/g. Our findings show tha t contemporary sewage sludge PCDD/F concentrations have declined since the 1980s. In addition to the variations in PCDD and PCDF concentrations, there were also some changes in the isomeric patterns. These variations in level s and isomeric patterns could reflect changes in PCDD and PCDF sources to t he environment over time.