WHAT THE EVIDENCE SAYS
Researchers incubated iron- and phosphorus-amended lake sediment under low and high sulfate conditions. As microbial sulfate reduction generated sulfide, vivianite progressively destabilized, iron shifted into sulfide minerals and total phosphorus-binding capacity declined; some released phosphorus was re-adsorbed near the oxic surface, but not enough to offset the net loss.
WHY IT MATTERS / OUR READ
For lake restoration, an iron amendment is not a one-time chemical lock. Sulfur cycling below the sediment surface can weaken phosphorus retention even when bottom water remains oxic, making porewater sulfide a potentially useful early-warning variable.
CAVEATS / UNCERTAINTY
The work used homogenized, constructed mesocosm cores from one lake and controlled sulfate treatments. It demonstrates mechanism, not the long-term field failure rate of iron amendments across lakes, doses or sediment types.
SOURCE
Biogeochemistry
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