Iron filings application to reduce lake sediment phosphorus release

Natarajan P, Gulliver JS, Arnold WA. 2021. Iron filings application to reduce lake sediment phosphorus release. Lake Reserv Manage. 27:143–159. Surface water impairments due to excess phosphorus loading from the watershed and internal recycling from sediments have been reported worldwide. This study investigated the application of iron metal filings to lake sediments as a method to control sediment phosphorus release. Using batch studies, a zero-valent iron filings material was selected for laboratory dosing experiments with lake sediment cores. Iron filings doses of 0 (control), 0.01, 0.1, and 1 g/cm² were added to sediment cores collected from a eutrophic lake in Minnesota, United States, to determine the impacts of iron addition on the oxic and anoxic phosphate (PO₄-P) flux at 20 C and 10 C in the laboratory. Under oxic conditions, PO₄-P release did not occur from the sediments, and low water column PO₄-P concentrations were maintained in the iron-dosed and control cores. After switching to anoxic conditions, the 0.1 and 1 g/cm² iron doses continued to reduce or fully prevent sediment PO₄-P flux. The enhanced supply of iron in the sediments was found to reduce the porewater PO₄-P, resulting in no apparent PO₄-P diffusion across the sediment–water interface and low PO₄-P in the overlying water under oxic and anoxic conditions. Further evaluation using in situ experiments is needed to assess the effectiveness of iron filings addition in sequestering sediment phosphorus under natural conditions.