Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089;
Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964.
Proc Natl Acad Sci U S A. 2020 Nov 10;117(45):27862-27868. doi: 10.1073/pnas.2010315117. Epub 2020 Oct 22.
Fossil-fuel emissions may impact phytoplankton primary productivity and carbon cycling by supplying bioavailable Fe to remote areas of the ocean via atmospheric aerosols. However, this pathway has not been confirmed by field observations of anthropogenic Fe in seawater. Here we present high-resolution trace-metal concentrations across the North Pacific Ocean (158°W from 25°to 42°N). A dissolved Fe maximum was observed around 35°N, coincident with high dissolved Pb and Pb isotope ratios matching Asian industrial sources and confirming recent aerosol deposition. Iron-stable isotopes reveal in situ evidence of anthropogenic Fe in seawater, with low δFe (-0.23‰ > δFe > -0.65‰) observed in the region that is most influenced by aerosol deposition. An isotope mass balance suggests that anthropogenic Fe contributes 21-59% of dissolved Fe measured between 35° and 40°N. Thus, anthropogenic aerosol Fe is likely to be an important Fe source to the North Pacific Ocean.
化石燃料排放物通过大气气溶胶向海洋偏远地区提供生物可利用的铁，可能会影响浮游植物的初级生产力和碳循环。然而，通过对海水中人为铁的实地观测，这一途径尚未得到证实。在这里，我们呈现了整个北太平洋（158°W，25°至 42°N）的高分辨率痕量金属浓度。在北纬 35°左右观察到一个溶解铁最大值，与溶解铅的高浓度和与亚洲工业源相匹配的铅同位素比值一致，证实了最近的气溶胶沉积。铁稳定同位素提供了海水中人为铁的现场证据，在受气溶胶沉积影响最大的区域观察到低 δFe（-0.23‰>δFe>-0.65‰）。同位素质量平衡表明，人为铁在 35°至 40°N 之间测量的溶解铁中占 21-59%。因此，人为气溶胶铁可能是北太平洋的一个重要铁源。
