<br/>Fulvic acid, a type of Dissolved Organic Carbon, could be key to examining the global carbon cycle and global warming. It’s of interest to determine photodegradation pathways for this molecule in aqueous solutions. First, we proposed models for the six potential initial decarboxylations of fulvic acid and calculated the ΔG° in each case to establish the most favorable scenario. We determined that one of the carboxylic groups on an aromatic ring was the most likely to break off first. We then calculated the ΔH for each model and compared these computational results to experimental results in the literature. With fulvic acid as a whole, we compared calculated thermodynamic parameters to thermal gravimetric experimental results. All calculations were performed with first principles electronic structure calculation software Gaussian-16 and visualized with GaussView. The free energy changes in each case were calculated as the difference between the sum of the G° of the products minus the G° of the reactant. The enthalpy changes were calculated as the difference between the sum of the EE + Thermal Enthalpy Correction of the products and the EE + Thermal Enthalpy Correction of the reactant.

Degradation of fulvic acid shown through computational modeling and calculations

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