Geochemical properties of airborne particulate matter (PM 10) collected by automatic device and biomonitors in a Mediterranean urban environment

Abstract

The mineralogy and geochemistry (major and trace elements) of particulate matter collected from 14 April to 29 May 2003 by automatic device (PM 10) and entrapped by moss and lichen exposed in bags in a monitoring site of Naples urban area were studied with the aim to obtain useful information for risk assessment and control measures feasibility. PM 10 concentrations were generally above the threshold values fixed by the 1999/30/EC directive. Constant and low intensity winds enhanced re-suspension of fine particles and dispersion of gaseous pollutants. PM 10 samples contained trace elements in relatively lower amounts compared to literature reports from other Mediterranean monitoring sites. Significant correlations between Al, Ca, Cu, Fe, K, Mg and Mn indicated that soil dust largely contributed to the accumulation of fine particles on filters and exposed mosses and lichens. Highly significant correlations were also found between Ni and V, indicative of oil combustion processes, Fe, Cu and Cr, indicative of vehicle emissions and mechanical components abrasion, and Na and Mg, indicative of marine aerosols. Lead and Hg did not correlate significantly with any other element. Comparison of element EFs, calculated with respect to the composition of Naples surface soils, indicated higher contribution of soil dust to PM and moss chemical composition compared with lichens, which in turn, according with their better preserved vitality, intercepted/absorbed more efficiently anthropogenic particles and elements of metabolic interest. Crystalline and amorphous detrital components (quartz, calcite, feldspars, volcanic glass, mica, kaolinite and smectite) and sea-bearing salts phases (halite, gypsum, Mg–K sulphates, Mg–Ca carbonates) were the main minerals in PM 10, along with silica fibers and tuff particles.