Effects of enzyme-induced carbonate precipitation on the heavy metals immobilization and hydraulic properties improvement of contaminated humus soil from municipal solid waste landfill

Abstract

The excavation of municipal solid waste landfill has generated numerous heavy metal (HM) contaminated humus soil. The humus soil can be used as the slope cover material to reduce rainwater infiltration after HM remediation and hydraulic properties improvement.This study is intended to explore the impacts of enzyme-induced carbonate precipitation (EICP) on both the immobilization of HMs and the enhancement of hydraulic properties in humus soil. The soil water retention curve (WRC), saturated permeability coefficient (k_s) and exchangeable HM concentration were measured, respectively. The results show that EICP can reduce the exchangeable HM concentrations to meet standard requirements through promoting HM carbonate precipitation. The carbonate precipitations mainly form in soil macro-pores, leading to a decrease of more than one order of magnitude in k_s and more obvious bimodal feature of WRC. The soil water retention ability can be improved through increasing the air-entry values for macro- and micro-pores, simultaneously reducing the desorption rate of macro-pores.

Graphical abstract

Keywords

humus soil / EICP / HM immobilization / pore structure / bimodal WRC / saturated permeability coefficient

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