Development of a Manganese Speciation Method for Atmospheric Aerosols in Biologically and Environmentally Relevant Fluids
Titel:
Development of a Manganese Speciation Method for Atmospheric Aerosols in Biologically and Environmentally Relevant Fluids
Auteur:
Majestic, Brian J. Schauer, James J. Shafer, Martin M.
Verschenen in:
Aerosol science and technology
Paginering:
Jaargang 41 (2007) nr. 10 pagina's 925-933
Jaar:
2007-10
Inhoud:
Because the health effects of manganese are dependent its oxidation-state, we have improved upon oxidation-state resolved methods to quantify soluble manganese in atmospheric aerosols. Two spectrophotometric methods were adapted for measurements in atmospheric aerosols in order to measure total soluble manganese (Mnsol) and soluble oxidized manganese [Mn(III) and Mn(IV), Mnox]. Using the formaldoxime method, we noted a detection limit two orders of magnitude better than past studies using trace-metal clean techniques and a 1 meter path-length spectrophotometric cell. Extractions of co-located aerosol samples were performed in four environmentally or biologically relevant extract solutions and processed for soluble manganese analysis. The quantity of manganese extracted was a strong function of the fluid, and the greatest amount of manganese was extracted in the rain-water surrogate (acetate buffered solution). Mnsol in East St. Louis, IL, USA (6-20% of the total manganese) was less than the Mnsol in aerosols collected in Toronto, ON, Canada (40% of the total). Mnox was not detected in the PM10 samples collected in East St. Louis, however Mnox accounted for around 30% of the PM2.5 soluble manganese in Toronto. Mnox was not detected in the coarse fraction in Toronto, which may imply that soils are not a source of Mnox at this site. Oxidized manganese was not recoverable from extracts of samples from East St. Louis spiked with 1 μg Mnox L-1. This implies that a soluble component of the aerosol is responsible for reduction of oxidized manganese and that the chemical form of manganese in aerosols can quickly change when it comes into contact with a fluid.