RESUMO
In order to determine the temporal variation in the levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in soils in the vicinity of an old municipal solid waste incinerator (Montcada, Barcelona, Spain), in 1997 we collected 24 soil samples at the same sampling points in which samples were taken 1 year before. Each sample was analyzed for PCDDs and PCDFs by GC/MS. While in the previous study PCDD/F concentrations ranged from 0.30 to 44.26 ng TEQ/kg (dry matter), (median and mean values: 3.52 and 6.91 ng TEQ/kg), in the present study PCDD/F levels ranged from 0.15 to 29.27 ng TEQ/kg (median and mean values: 2.56 and 4.47 ng TEQ/kg). PCDD/F concentrations decreased in 14 of the 24 soil samples, while the remaining 10 samples showed increases of different orders. No statistically significant differences in PCDD/F levels according to the main wind directions in the area were noted. In both surveys, the highest PCDD/F concentrations were found 750 m from the stack to the south. The current levels of PCDD/Fs in soils, as well as those found in the previous survey are similar or even lower than PCDD/F concentrations reported for soil samples taken near to municipal solid waste incinerators from different places.