TEMPORAL VARIATION OF PCDD F CONCENTRATIONS IN VEGETATION SAMPLES COLLECTED IN THE VICINITY OF A MUNICIPAL WASTE INCINERATOR (1996-1997)/

In 1996, the concentrations of polychlorinated dibenzo-p-dioxins (PCDD s) and dibenzofurans (PCDFs) were determined by HRGC/HRMS in 24 vegeta tion samples collected in the vicinity of a municipal solid waste inci nerator (Tarragona, Catalonia, Spain). In the present study 24 vegetat ion samples were again taken at the same sampling points and analyzed for the levels of PCDD/Fs. The results were compared with those obtain ed in the previous survey. While in the 1996 study, PCDD/F levels rang ed from 0.15 to 62.09 ng I-TEQ/kg (dry matter) (median value, 0.33 ng I-TEQ/kg; mean value, 4.11 ng I-TEQ/kg), the concentrations of PCDD/Fs in the 1997 survey ranged between 0.11 and 0.50 ng I-TEQ/kg (dry matt er) (median value, 0.20 ng I-TEQ/kg; mean value, 0.23 ng I-TEQ/kg). Th e individual comparison between PCDD/F levels in the samples collected in 1996 and 1997 showed a decrease in 15 of the 24 sampling points. W hen the comparison was carried out in relation to each of the four mai n wind directions in the area, the highest decrease in PCDD/F concentr ations (64%) corresponded to samples in the SE direction, while those in the NE direction showed also a notable reduction in total I-TEQ (44 %). In contrast, PCDD/F levels in vegetation samples from NW and SW di rections were increased (37% and 6%, respectively). When the data were evaluated according to the distance of the sampling points to the pla nt, the highest decrease in total I-TEQ was found at 500 m from the st ack. The results of this study seem to provide evidence for a decline in atmospheric emissions of PCDD/Fs in the area of Tarragona. (C) 1998 Elsevier Science B.V. All rights reserved.