Artificial weathering reveals reduced elemental leachability from hardened biomass ash.

Biomass ashes are potential soil amendments that reduce soil acidity and provide plant nutrients, but trace elements in ash may be leached from the solid phase, thereby posing environmental concerns. We determined the leachability of major and trace elements as influenced by ash pre-treatments, the presence of soil, and the pH of the receiving environment. Weathering was simulated by serial batch extraction where pH was uncontrolled, and by single extraction under controlled pH conditions. We found that hardening reduced the solubility of ash, and reduced the leachability of Al, Ba, Ca, Cu, Mo, Sr, and V, as determined by ICP-MS. In a separate experiment, extractions of ash samples showed that when pH was lowered the leachability of most elements increased while a few decreased. The results of the weathering experiments support the use of ash as a soil amendment. --Leaf ii.