Repurposing enhanced rock weathering for brownfield cleanup: a practical carbonate–silicate remineralization method for stabilizing cationic metals in shallow soils

Quinn Zacharias 

Brownfield, mining-impacted, urban fill, and legacy agricultural sites often contain cationic metals concentrated in shallow soil horizons, where they sustain direct-contact, dust, and leaching risk and can complicate redevelopment. This paper reframes enhanced rock weathering (ERW), originally advanced for carbon dioxide removal, as a practical remineralization approach for immobilizing cationic metals in soil. The proposed method is not simply another mineral amendment. It uses controlled carbonate–silicate blends to accelerate soil-aging processes, acid neutralization, increased negative surface charge, Ca and Mg occupation of exchange sites, hydrolysis, sorption, and secondary Fe–Al mineral formation that shift metals from labile and leachable pools toward less mobile forms. The framework is grounded in a watershed-scale Vermont field deployment of low-Ni, Fe–Al-rich basalt and in prior liming, wollastonite, and ERW literature. Across these lines of evidence, silicate remineralization behaves as a slow-release liming system, hydrologically connected receiving zones can show strong buffering signatures, and metal lability can decline where alkalinity and base cations accumulate. Building from that evidence, this paper presents a field-executable remediation method covering site screening, feedstock selection, blend design, hotspot targeting, application, vegetative cover, verification, and boundary conditions. The method is best suited to shallow soils in which cationic metals such as Pb, Zn, Cu, Cd, and Ni are major risk drivers and where in situ stabilization is preferable to full excavation. Key practical recommendations are to use low-Ni, Fe–Al-rich mafic feedstocks, bench-test carbonate fractions to control pH trajectory, align placement with the contaminated depth interval, and verify performance using leachability tests together with mechanistic indicators such as soil pH, exchangeable acidity, exchangeable aluminum, and Ca:Al. Soil health improvement, local sourcing from quarry fines, reduced hauling, and incidental carbon sequestration may provide additional value, but remediation endpoints should govern design.