Geochemistry and metals concentrations in marine sediments exposed to solidified/stabilized municipal solid waste incinerator ash

Solidified and stabilized (S/S) municipal solid waste incinerator ash specimens were placed in tubes filled with organic-rich marine sediments and incubated in seawater for 48 months. Initially, the S/S ash and concrete control (CC) specimens increased the pH of the sediment/porewater system due to the leaching of hydroxide. After 10 months, their porewater pH values approached those in the sediment controls as magnesium and calcium precipitates accumulated on the surface of the specimens and limited diffusion of hydroxide. Sulfate was initially abiotically removed from the porewater of the concrete controls, most probably due to precipitation as CaSO4 at high pH. Depletion of sulfate in the S/S ash sediments was due at least in part to microbial activity based on measured sulfate reduction rates. Cadmium, copper and lead, metals enriched in the ash relative to the sediments, were not found in higher concentrations in the test sediments relative to the controls (confidence LEVEL = 90%), suggesting that metals dissolution from the S/S ash was minimal.