A scoping study of component-specific toxicity of mercury in urban road dusts from three international locations.

This scoping study presents an investigation of the total and bioaccessible mercury concentrations in road dust (RD) from three international urban sites, where a one-off sampling campaign was conducted at each. This was done to address the hypothesis that the matrix in which mercury is found influences its ability to become accessible to the body once inhaled. For that purpose, the samples were analysed for total and pulmonary bioaccessible mercury and the data compared to the chemical structure of individual particles by SEM. The results obtained from this study suggest that a high mercury content does not necessarily equate to high bioaccessibility, a phenomenon which could be ascribed to the chemical character of the individual particles. It was found that the Manchester samples contained more pulmonary soluble mercury species (as determined by elemental associations of Hg and Cl) in comparison to the other two samples, Curitiba, Brazil, and Johannesburg, South Africa. This finding ultimately underlines the necessity to conduct a site-specific in-depth analysis of RD, to determine the concentration, chemical structure and molecular speciation of the materials within the complex matrix of RD. Therefore, rather than simply assuming that higher bulk concentrations equate to more significant potential human health concerns, the leaching potential of the metal/element in its specific form (for example as a mineral) should be ascertained. The importance of individual particle behaviour in the determination of human health risk is therefore highlighted.

Adsorption of sugarcane vinasse effluent on bagasse fly ash: A parametric and kinetic study.

Sugarcane and bioethanol production produces large amounts of bagasse fly ash and vinasse, which are solid and viscous liquid wastes, respectively. However, these wastes are often disposed into the environment without treatment, thus posing an environmental and public health risk. This study investigated the treatment of vinasse effluent in terms of reduction of chemical oxygen demand (COD) and acidity removal using sugarcane bagasse fly ash. A maximum COD removal efficiency of 72% was obtained using an effluent volume of 100 mL, contact time of 180 min, and shaking speed of 240 rpm. The adsorbent dose and particle sizes were 4.5 g and 90-125 µm, respectively. Furthermore, the potential application of bagasse fly ash as an adsorbent in a sand filtration bed was assessed using a column test. A maximum recovery of 68% was obtained at the 25-min interval. The adsorption data was found to fit the Freundlich model best (Kf = 2.16 mg g-1; R2 = 0.96), and the kinetics fit the pseudo-second order model (R2 = 0.98).