Distribution, pollution status and ecological risk assessment of heavy metals in dust from different areas of the Southwest of Andalusia (Spain)

Dust is a complex environmental matrix, which can be enriched in heavy metals from both anthropogenic and natural sources. Various studies in the scientific literature have reported that dust formation can have various sources in urban and industrial areas such as vehicle traffic, contributing exhausted and non–exhausted emissions (NEE), asphalt and road paint wear, emissions from industries involved in the production and coating of metal alloys. This research aims to determine the distribution (concentration of metals and sources), pollution status (comparison with natural background), and ecological risk assessment (relationship between metal concentration and relative toxicity) of the dust in southwestern Andalusia. Samples for this study were collected from Cádiz Bay and Algeciras Bay. A particle size study of the samples was made, determining what its distribution was in different particle size classes. Then they were treated with acid digestion based in reverse aqua regia (HNO3 and HCl, 3:1) and analyzed by inductively Coupled Plasma – Optical Emission Spectrometer (ICP – OES) to determine and quantify the concentrations of Cd, Cr, Pb, V, Al, Fe, Cu, As, Ag, Ni, and Zn. Finally, indices were calculated regarding pollution status (Igeo, CF, Cdeg, PLI) and potential ecological risk assessment (Ei, RI). Analysis of data obtained, together with thorough literature research, identified possible sources for the different heavy metals that enrich the dust. The calculation of the indices succeeded in characterizing the areas from contamination and potential ecological risk point of view, finding in Algeciras a critical situation due to the high presence of metals probably due to the presence of the stainless steel plant and its geographical location subject to strong winds that could have transported pollutants also from other industries present in the bay.