Development of methods for the speciation of metals in atmospheric particulate matter.

摘要

This study focuses on advancing methods to measure and speciate trace-elements in atmospheric particulate matter (PM) to support human exposure and health studies. Methods were developed to measure Fe(II) and Fe(III) in PM samples using samplers collecting daily average particulate matter samples and personal exposure samples. Low-cost wet-chemical methods were also developed to measure the oxidation state of leachable iron, chromium and manganese present in low-volume PM samples. In addition, a study was conducted to determine if metals collected by different personal exposure samplers currently used in exposure and health studies were comparable. Results from the intercomparison study between co-located personal and fixed-site ambient samplers showed that different personal sampler designs display biases that are largest for metals predominating in the super-micron fraction.; Using one consistent personal exposure sampler, a pilot study was conducted to examine trace-metal concentrations in personal exposure samples from individuals residing in an assisted-living home. These results were compared to ambient outdoor and fixed-indoor concentrations, and generally, outdoor > indoor > personal exposure concentrations. The pilot study demonstrated that adequate tools exist to measure trace-element exposures under real-world conditions.; Using the methods developed in the study, labile Fe(II) and Fe(III) as well as total soluble manganese and soluble oxidized manganese from atmospheric PM were routinely detected in ambient and personal exposure samples. Samples extracted in a variety of environmentally and biologically relevant fluids showed that leachable iron and manganese strongly depends on the extractant. Atmospheric samples from a residential location in Toronto (which uses the fuel additive, MMT) showed that a significant fraction of oxidized labile manganese is present in the PM2.5 fraction, in contrast to US cities that do not use MMT.; Both the wet-chemical and XANES techniques developed here were applied to aged ambient aerosols to determine how iron speciation changes as aerosols are being atmospherically processed. Over the course of the 40 day aging period, we found that changes in total Fe(II) and Fe(III) depend on particle size. The labile Fe(II) fraction shows a strong dependence on aging time peaking around 1--3 days, a time-scale consistent with atmospheric life-times of urban aerosols.