Processes in confined pores are of critical importance as they influence transport and retention of metal(loid)s in soils.This study shows that abiotic and biotic processes in confined pore spaces of mineral surface coatings are often in disequilibria with their environment although changes in their major chemical constituents reflect variances in the soil chemistry. In order to assess the relationship between chemical and mineralogical processes in confined pore spaces and those in the bulk soil, mineral surface-coatings are characterized on the nanometer scale from soils of the Greater Sudbury area, Ontario, Canada. The soils received contamination from smelters from 1900 to 1972, when roughly 3.5 million tons of SO2 and 1000 tons of Cu and Ni were emitted annually just from the one smelter closest to and upwind from our study area. Subsequent recovery and remediation of the soils in the 1970’s and 80’s resulted in an increase in soil pH and decrease and increase in sulfate and phosphate concentrations, respectively. The (bio)mineralogy, and chemical composition of confined pore spaces in coatings formed prior to the peak of contamination are characterized by nano-crystals of Fe-hydroxides, bacteria cocci and small abundances of Cu, Ni, Pb and As. Aggregates of jarosite in pore spaces reflect a decrease in soil pH and high input of (SO4)2- and metal(loid)s during the peak of contamination, whereas higher concentrations of P in nano-size crystals indicate time periods of recovery and remediation. Contrary to this, abiotic and biotic reductive dissolution of jarosite and nucleation of Ni-spinels in confined pore spaces are processes that one would not expect to occur in a low-T oxidizing environment. Furthermore, the presence of nanometer size jarosite aggregates in recovered soils with pH values around 4.5 indicate that metal(loid)-bearing components in confined pore spaces can be preserved and thus not equilibrated with their environment over several decades.

Confined pore spaces in mineral coatings of contaminated soils: Disequilibria between abiotic and biotic processes and their environment

249th National Meeting (2015)

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