Aluminum beats iron at locking up arsenic in flooded soil
Lai YR, Basta NT
Soil Health
If you garden near a floodplain, old orchard, or industrial site with legacy arsenic contamination, the type of soil amendment used to lock it away actually matters once the ground gets soggy.
Arsenic in soil can leach into groundwater, and it gets more dangerous when soil becomes waterlogged and oxygen disappears. Researchers tested two common soil additives, iron sulfate and aluminum sulfate, to see which one keeps arsenic locked up under both dry and flooded conditions. Aluminum sulfate held onto the arsenic much better during flooding, while iron sulfate actually started releasing arsenic back out once the soil turned oxygen-starved.
Key Findings
In batch tests, iron and aluminum amendments cut water-soluble arsenic by 78.3% and 83.3% respectively.
In column leaching tests, aluminum sulfate reduced cumulative leachable arsenic by 89.7% versus 60.3% for iron sulfate.
Under flooded, strongly reducing conditions (Eh down to -259 mV), iron amendment showed Fe(II) buildup and arsenic remobilization, while aluminum stayed redox-stable but arsenic(III) still rose above 50% of total arsenic by days 20-30.
chevron_right Technical Summary
Scientists tested two soil treatments for cleaning up arsenic contamination and found that aluminum sulfate works better than iron sulfate when soils get waterlogged, like during floods, because flooding can make iron-based treatments release the arsenic back out.
Abstract Preview
Original paper
In-situ remediation for arsenic-contaminated soils using iron and aluminum amendments under varying redox conditions.
Arsenic (As) contamination can threaten groundwater quality and human health, particularly where redox conditions fluctuate. Although iron (Fe) and aluminum (Al) (hydr)oxides strongly adsorb arsena...
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