Abstract
To characterize atmospheric dissolved iron over Newark, a large metropolitan city on US east coast, size-segregated (0.056–18 μm in aerodynamic diameter) aerosols were collected in downtown Newark, New Jersey during August to October 2012. Aerosols samples were analyzed for Fe(II) and total dissolved iron (Fe(TD)) by UV/Visible spectroscopy, and water soluble compounds were analyzed by ion chromatograph (IC). Results from this study showed that Fe(II) concentrations were 2.1 ng m−3 (range: 1.2–4.2 ng m−3), Fe(TD) concentrations were 2.4 ng m−3 (range: 1.3–4.9 ng m−3). Dissolved iron (Fe(II) and Fe(TD)) in general appeared as bi-modal size distribution, was mainly accumulated in the fine mode. The highest concentration of dissolved iron displayed in the fine mode, which was associated with high concentrations of sulfate, oxalate and nitrate, suggesting the potential for Fe–acids interactions. Dissolved iron presented positive correlations with sulfate in the coarse mode, and with nitrate in the fine mode, further suggesting the importance of acid processing in aerosol iron solubility. However, as the oxalate concentration was so low, a good correlation between dissolved iron and oxalate in both the fine and coarse mode was not found.
Highlights
Fe exists in the atmosphere in one of two oxidation states, Fe(II) or Fe(III)
The air mass back trajectories of Sample No.7 showed that high dissolved iron was associated with air masses passing over US southwest; especially at 2000 m height, the air mass came from American west, where the weather was dry and much dust suspended in the air (Figure 2)
Results from this study over the US east coast were generally comparable to those over marine environments, especially the investigation conducted over the North Atlantic
Summary
Fe(II) is readily soluble in seawater and presumably bioavailable to marine phytoplankton [1]. Fe is aeolian dust derived from major deserts in Asia, North Africa, South America, and Australia that is transported and deposited to the ocean [2,3,4,5]. Atmospheric Fe may come from anthropogenic sources, in particular from regions with heavy air pollution in the Northern Hemisphere. Major anthropogenic sources for Fe include agricultural practices [4], biomass burning [6,7] and combustion emissions [8,9,10]. Recent model results suggest that combustion-derived Fe can represent a large portion of soluble Fe fluxes, with the highest values (30%) close to the East Asian continent in the
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