Trace elements in daily collected aerosol: Level characterization and source identification in a four-year study

In this study, we measured atmospheric particulate concentrations at an industrial site in southern Italy over a four-year period, from September 2001 to December 2004. A total of 741 daily PM2.5 samples were collected using a low-volume gravimetric automatic sequential sampler. These samples were analyzed for heavy metals, including Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, while simultaneously recording temperature, relative humidity, wind speed, and wind direction. Data analysis incorporated both univariate and multivariate statistical methods, employing principal component analysis and cluster analysis to reveal correlations between heavy metals and particulate concentrations, as well as to characterize source profiles. The enrichment factor method was used to discern between natural and anthropogenic origins of the trace elements. Results indicated PM2.5 concentrations fluctuated widely, ranging from 0.04 to 117 μg/m³, with an average of 13 μg/m³. Heavy metal levels decreased over the study period, reaching their lowest in 2004, with most elements (excluding Mn) displaying anthropogenic characteristics based on enrichment factors. Furthermore, the multivariate analysis identified two distinct source profiles for heavy metals: one associated with natural soil dust and another linked to vehicular emissions.