Geochemical processes controlling in situ contaminant solubility in landfills

Abstract

Sustainable management of landfills through actively
reducing contaminant emissions requires knowledge of underlying
geochemical processes, which is currently limited. To this end, pore
water was sampled across a vertical transect from a landfill subject
to leachate recirculation with an in situ collection system. The
samples were analyzed for pH and the concentration of inorganic
contaminants and dissolved organic matter fractions; all showed
similar distributions with depth. The underlying mechanisms of this
analogous behavior were identified using geochemical modeling,
which captured measured concentrations adequately for most
contaminants. While nonreactive contaminant concentrations were
best predicted considering limited interaction with the solid matrix
and reactive anions were best predicted by metal (hydr)oxide
binding, adequate predictions for reactive cations with a high organic matter binding affinity required a description of humic
substance fractions. Predictions of other reactive cations were steered by the formation of carbonate or sulfide minerals. The
importance of mineral precipitates deviates from previous lab experiments on sampled solid waste, highlighting the importance of
modeling in situ samples to explore processes in complex systems such as landfills. The obtained understanding can be used to test
landfill simulation reactor results, aid in understanding impacts of proactive waste management strategies, and ultimately facilitate
their implementation.

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Identifiers

ORCID for Tristan C. Rees-White: orcid.org/0000-0001-9009-8432

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