Fig. 3: Iron source apportionment results (mean ± standard deviation) based on model calculations with iron isotope ratios of different size particles from urban and marine aerosols.

Source apportionment results in a Hiroshima, b North Atlantic and Northwest Pacific. Marine aerosols are classified according to the dominant impact of air masses^71,152. For the Northwest Pacific, bulk particles are referred to coarse (PM_>2.5) + fine (PM_2.5) fractions. Original data of Hiroshima, Northwest Pacific and North Atlantic is from Kurisu et al.^148,152. and Conway et al.⁷¹, respectively. See Supplementary Tables 4–6 for model calculation uncertainties of the results.