Implications of the evolution of organic acid moieties for basalt weathering over geological time

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Abstract
Concentrations of organic acids in prebiotic soils were presumably low, given limitations in abiotic synthesis and the limited lifetimes of organic molecules before the ultraviolet shield developed on early Earth. Prokaryotes, the first land-colonizing organisms, commonly secrete aliphatic carboxylic acids, and, less extensively, secrete aromatic compounds as siderophores and antibiotics. In contrast, secretion of aromatic acids is considerable for fungi, lichens, and vascular plants. Aromatic acids are also produced by degradation of high-molecular-weight compounds from lignin and tannin, both abundant in vascular plants. The proportion of aromatic carboxylic acids in soil solutions therefore probably increased with the evolution of higher order organisms. As biomass of organisms increased over geological time, concentrations of organic acids in soil solutions and, in turn, the extent of ligand-promoted dissolution of minerals probably increased.