Inorganic substrates in frozen solutions: Transformation mechanisms and interactions with organic compounds - A review

In cold environments, such as polar regions and high latitudes, the freezing of aqueous solutions plays a crucial role in releasing and transforming nutrients, organic compounds, and trace gases. Freezing processes typically affect biogeochemical cycles and environmental processes by reducing the rate of chemical reactions. However, substantial studies have found that some chemical reactions may accelerate unexpectedly under freezing conditions. These reactions include oxidation of nitrite, dissolution of metals/metal oxides, transformation of halogen species, etc. Although freezing process significantly affects the interaction between the inorganic substrate and coexisting organic compounds, there are few review articles on the behavior of the inorganic compound. Therefore, this review examines the transformation behavior of inorganic substrates and their interactions with organic compounds during freezing. The transformation behavior of inorganic substrates during freezing was comprehensively discussed, their underlying mechanisms were elucidated, and the interactions between inorganic substrates and coexisting organic compounds were highlighted. Meanwhile, key factors influencing the freeze-induced chemical processes were articulated. Furthermore, the potential application of freezing reactions in engineering processes is explored. This article aims to improve understanding of the important role of freezing processes in the recycling of substrates in the natural environment and supplement knowledge in the field of ice chemistry.