ATMOSPHERIC METAL POLLUTION (CR, CU, FE, MN, NI, PB AND ZN) IN OPORTOCITY DERIVED FROM RESULTS FOR LOW-VOLUME AEROSOL SAMPLERS AND FOR THEMOSS SPHAGNUM-AURICULATUM BIOINDICATOR

A low-volume aerosol sampler with filters and bags of Sphagnum auricul atum were exposed, in parallel, to the atmosphere of Oporto city for a pprox. 2 months in 1994, during a dry weather period. The levels of Cr , Cu, Fe, Mn, Ni, Pb and Zn in the moss (weekly samples) and in the fi lters (daily samples) were determined by atomic absorption spectrophot ometry and the results were compared. For all the heavy metals, the ra te of metal uptake by moss was significantly correlated with the metal concentration in atmospheric aerosols. The results indicated that mos s bags of S. auriculatum can provide a quantitative estimation of the concentration of different heavy metals in urban atmospheres, when spe cific calibration by mechanic monitoring, at the same sampling point, is performed during a first stage of biomonitoring. The mean aerosol m etal concentrations found in the Oporto atmosphere were similar to tho se observed in other urban atmospheres in different countries. The rel ative order of the mean metal concentrations was Fe (1.8 mu g/m(3))> Z n > Pb > Cu > Cr > Mn > Ni (20 ng/m(3)). The aerosol Pb levels were mo nitored at different sampling points over various periods of time betw een 1991 and 1997. The mean Pb levels were less than or equal to 0.5 m u g/m(3) and approximately constant at each sample point up to January 1996. After that date it decreased by approx. 50%, in consequence of the reduction of the Pb concentration in leaded gasoline. (C) 1998 Els evier Science B.V.