Assessment of contribution of metal pollution sources to attic and household dust in Pb-polluted area.

Attic and household dusts from Pb-polluted area were investigated using various analytical techniques for source apportionment and assessment of source contribution of metal-bearing phases. Mineralogically, attic dust consists of gypsum, anhydrite, and metal-bearing phases, while household dust comprises C-bearing particles and only minor metal-bearing phases. Sulfur isotope composition of sulfides and sulfates in attic dust shows that they result from past primary smelting of local sulfide ore, while those in household dust originate directly from local mine-waste material. Pb isotope ratios show that Pb-bearing phases in both dust types mostly originate from mining and primary smelting of local Pb-ore. Individual metal-bearing particles were apportioned by their composition, morphology, and mineralogy to phases from past Pb-smelting, present-day Pb-recycling, and past mining/mine-waste mechanical processing. Calculated source contribution of metal-bearing phases to indoor dust showed that primary Pb-smelting was important pollution source in the past, while active Pb-recycling has contributed only negligible amount of material so far. However, material from mining/mine-waste processing is an important currently active pollution source. Study demonstrated that simultaneous investigation of characteristics and isotopic composition of metal-bearing phases in different indoor dust types serves as tool for assessment of source contribution of past and recent airborne metal pollution.

Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility.

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu2S).

Assessment of metal pollution sources by SEM/EDS analysis of solid particles in snow: a case study of Zerjav, Slovenia.

Solid particles in snow deposits, sampled in mining and Pb-processing area of Zerjav, Slovenia, have been investigated using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Identified particles were classified as geogenic-anthropogenic, anthropogenic, and secondary weathering products. Geogenic-anthropogenic particles were represented by scarce Zn- and Pb-bearing ore minerals, originating from mine waste deposit. The most important anthropogenic metal-bearing particles in snow were Pb-, Sb- and Sn-bearing oxides and sulphides. The morphology of these particles showed that they formed at temperatures above their melting points. They were most abundant in snow sampled closest to the Pb-processing plant and least abundant in snow taken farthest from the plant, thus indicating that Pb processing was their predominant source between the last snowfall and the time of sampling. SEM/EDS analysis showed that Sb and Sn contents in these anthropogenic phases were higher and more variable than in natural Pb-bearing ore minerals. The most important secondary weathering products were Pb- and Zn-containing Fe-oxy-hydroxides whose elemental composition and morphology indicated that they mostly resulted from oxidation of metal-bearing sulphides emitted from the Pb-processing plant. This study demonstrated the importance of single particle analysis using SEM/EDS for differentiation between various sources of metals in the environment.