Impact Assessment of metal-rich airborne particulate on air quality and Oxidative Potential: a case study in Trentino region

The chemical composition and toxicological impact of metal rich PM10 samples was assessed in an industrial (Ala) and background (TN) sites in Trentino region. Source apportionment study using Positive Matrix Factorization assessed that the main emission sources of airborne metals at Ala are a zinc coating facility located in the area, traffic on the A-22 Brenner motorway and pesticide/fungicide spraying in the surrounding vineyard district. PM10 toxicological impact was quantified by measuring the oxidative potential OP using two a-cellular assays, i.e., dithiothreitol (DTT) and ascorbic acid (AA) assays. The responses of the DTT assay (volume-normalized OPVDTT) are similar at both sites (mean values ~ 0.60±0.23 nmol min-1 m-3) while OPVAA values show significantly higher values at Ala (1.4±1.1 nmol AA min-1 m-3) than at TN (0.7±0.4 nmol AA min-1 m-3). This is consistent with the different sensitivity of the two assays towards the same redox-active species present in ambient PM, as elucidated by linear correlation analysis of OPV with the concentration of tracer pollutants and highlighted by Heat Maps representation. At the industry site OPVDTT is correlated only with potassium and rubidium (R ~ 0.8), while OPVAA almost exclusively with Cu (R= 0.88). Otherwise, at TN both OPVDTT and OPVAA are both correlated with several species (R ≥ 0.7), such as WSTC, SO42-, NH4+, K, Mn, Cu and Zn. In addition, at Ala pronounced day-of-week evolution was observed for OPAAV values confirming the contribution of heavy metals from the anthropogenic sources. In conclusion, our study clearly show that PM10 oxidative potential is strongly enhanced by few selected metals, mainly Zn and Cu, emitted by the anthropogenic activities carried out in the investigated area, even if they only weakly impacted PM10 chemical composition. Concerning the still open question of different sensitivity of the DTT and AA assays, our results may be considered an experimental proof of the highest sensitivity of AA assay towards transition metals.