Numerical modeling vs experiment of formic acid and formate ion behavior under gamma radiation at several pH values: Implications on prebiotic chemistry.

Abstract

Formic acid is consistently produced and detected in prebiotic chemistry experiments, constituting a precursor of many carboxylic acids and amino acids. Its behavior with exposure to gamma radiation varies with the pH and solution concentration. This work aimed to model different environmental conditions for formic acid under ionizing radiation using a system of coupled differential equations based on chemical kinetics. An ensemble of radiolysis reaction mechanisms was generated for formic acid at pH 1.5 and formate ion at pH 9, both with radiation doses from 0 to 2 kGy. This was also done for systems with both species in equilibrium, using high molar concentrations, long irradiation times, and large irradiation doses (from 0 to 70 kGy). The results show that these systems can be modeled with a high statistical relationship between the computed solutions and the experimental data; furthermore, the synthesis and degradation of the radiolysis products can be followed. Another dimension of the issue of prebiotic environments was explored using ionizing radiation and analyzing the reactions at various pH values (acidic to basic media). These models allow one to gain insights into the behavior of molecules that are difficult to detect or analyze in the laboratory. Additionally, they offer the possibility of studying potential prebiotic environments.