Program

The flux of dissolved iron (Fe) from sediments to the water column was determined using a novel ²²⁴Ra/²²⁸Th disequilibrium approach along the China coast. High benthic fluxes of Fe were commonly observed in the coastal zones within the 50 m isobath. The Fe flux estimates were ~1-2 orders of magnitude higher than previous measurements conducted over the outer continent shelf with water depth >50 m, and were on average 20 times larger than flux values derived from the pore water concentration gradient method. Our results suggest that compared to the outer continental shelf, coastal zones play a disproportionally important role in the source function of Fe. When taking into account the Fe source term in the coastal sediments, the Fe input from continental marginal sediments into the open ocean will be much larger than previously recognized.