Geochemical investigations of potentially harmful elements (PHEs) in household dust of Idrija town

This study tackles geochemical investigation of potentially harmful elements (PHEs) in household dust from the town of Idrija (Slovenia), once the world famous Hg mining town that is now seriously polluted. After aqua regia... [ view full abstract ]

This study tackles geochemical investigation of potentially harmful elements (PHEs) in household dust from the town of Idrija (Slovenia), once the world famous Hg mining town that is now seriously polluted. After aqua regia digestion, the contents of mercury (Hg), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb) and zinc (Zn) were measured. PHE-bearing particles were recognised and observed by scanning electron microscopy and energy dispersive spectrometry before and after the exposure to simulated stomach acid (SSA). Mercury binding forms were identified by Hg thermo-desorption technique. With regard to rural and urban background values for Slovenia, only Hg (6−120 mg/kg) is severely enriched. Mercury pollution is a result of past mining and ore-processing activities. With regard to local topsoils, enrichments are observed for Cd, Cr, Cu, Mo, Ni and Zn, while As, Co and Hg show lower values and Pb shows similar values. SEM/EDS revealed the presence of Hg-, Cu-, Cd-, Pb-, Ni- and Zn-containing particles of geogenic and anthropogenic origin in dust samples. Hg sulphides in form of chemically stable cinnabar and potentially metacinnabar show no signs of dissolution in SSA, while for other recognised metal-bearing particles significant morphological and/or chemical alterations were observed. Four Hg binding forms were identified: Hg bound to the dust matrix, cinnabar (HgS), metallic Hg (Hg0) and minor amouts of mercury oxide (HgO). In average about 36 % of Hg is bound to potentially transformable secondary matrix bound Hg, of which specific compounds are not recognised.