Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes

Riverine suspended particulate matter (SPM) is essential for the delivery of micronutrients such as iron (Fe) to oceans. SPM known consist multiple phases with differing reactivity, but their role in elements oceans poorly constrained. Here we provide new constraints on source and composition reactive from Mackenzie River, largest sediment Arctic Ocean. Sequential leaching shows that river sediments contain labile Fe phases. We estimate flux substantial (0.21(+0.06,?0.05) Tg/yr) by quantifying concentrations weak leaches SPM. The phase hosts a considerable amount rare earth (REE), including neodymium (Nd). demonstrate dissolved load have radiogenic Nd isotope ratios are identical within uncertainty, up 8 epsilon units distinct silicate phase. interpret this evidence dynamic cycling between Fe-oxide water, demonstrating high reactivity elemental molar suggest significant Fe- Nd-bearing derived Fe-oxides sedimentary rock rather than mineral dissolution. Thus, erosion weathering provides an important Fe, manganese (Mn) extension potentially other trace metals. Our results imply both past future environmental change Arctic, permafrost thaw, may trigger changes supply These re-evaluation rivers required where uplifted rocks present.