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Nationwide decadal source apportionment of PM2.5 with a focus on iron




Niño, Lance, author
Kreidenweis, Sonia, advisor
Barnes, Elizabeth, committee member
Bond, Tami, committee member

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Fine particulate matter pollution (PM2.5) has detrimental effects on human health, visibility, and the environment. One component of PM2.5, aerosol-phase iron, also has a multi-faceted effect on climate. In its largely insoluble iron oxide form, found in dust aerosol, it absorbs shortwave radiation. Emissions from anthropogenic processes, primarily industry and coal combustion, also contain iron, with most of that iron in soluble forms. Soluble iron is an important phytoplankton nutrient and thus its atmospheric abundance is intertwined with carbon sequestration. To ascertain the various sources of PM2.5 as well as aerosol-phase iron across the contiguous United States, we used the ME-2 version of PMF to obtain a 10-factor source apportionment solution using IMPROVE data from 2011-2019. The percentage of anthropogenic iron at various sites during that time span varied from nearly none in the inter-mountain West to over 50% over the eastern half of the US. The percentage of total iron detected that was classified as soluble iron reached over 20% along coastal sites but was only around 3% of the total iron emitted. Trends in PM2.5 component factors showed a pronounced decrease in PM2.5 from coal combustion and various industrial sources during the time period, but trends were mixed and not significant for other sources. Further research is needed applying source apportionment to nationwide speciated datasets like IMPROVE, and a more comprehensive global PM2.5 observation network would enable source apportionment on a global scale.


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source apportionment
anthropogenic iron
soluble iron


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