In this study, a previously unrecognized and purely abiotic humification process that takes place in frozen solutions containing phenolic compounds and nitrite was proposed and investigated. Polycondensation of phenolic compounds was initiated by nitrite ions. The concentration of humic-like acids (HLA) and fulvic-like acids (FLA) from the frozen phase were 37 and 16 times higher than under aqueous conditions. The enhanced reaction rate was attributed to the freeze-concentration effect, whereby nitrite ions in the ice grain boundary layer are transformed into nitrosonium ions (NO<sup>+</sup>) and phenols are oxidized to phenolic radicals to initiate the humification process. Inorganic nitrogen was transformed into organic nitrogen during the humification process. Mass spectrometry (MS) and elemental analyses, including pyrolysis-GC/MS and FT-Ion Cyclotron Resonance/MS, showed that humification products (HLA and FLA) have chemical structures and compositions similar to nature humic substances. This study identifies and proposes a new humic formation pathway that might work as a model abiotic “bottom-up” mechanism in frozen environmental conditions.

New abiotic pathway of humification in frozen solutions

2019 Fall National Meeting

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