(333g) Cr Speciation in Deliquesced Particulate Matter

This study investigates the mechanism of the Cr(VI) reduction to Cr(III) as well as the oxidation of Cr(III) to Cr(VI) in the atmospheric condition at the presence of the various chemical species. The reactants were assumed to be present in the atmosphere in the form of the droplets at pH=4 with water content of 7 μg/m³air. The observations were made based on results of the 23 equilibrium and knetics reactions using a computer simulation in Matlab. The effect of each individual reaction on reduction and oxidation were derived by obtaining the half- life time of them. Initial concentrations of chemical species were taken from the paper of Huang(Huang et al., 2014) and from the data of NJEPA^[11]. The computer simulation showed that Cr(VI) in the form of (NH₄)₂CrO_4(s), CaCrO_4(s), K₂CrO_4(s), and Na₂CrO_4(s) tend to dissociate into the deliquesced particle generating CrO4-- ions which will eventually sink in the form of Cr2O7--. On the other hand, Cr(III) ions in the solution tend to precipitate in the form of Cr₂(SO₄)₃. Overall, the solution chemistry of Cr is strongly driven by the equilibrium reactions compared to the interconversion kinetics reactions. In this study the Cr insoluble copunds where assumed to be present as non-limiting reactnats. However, this research continues to study the Cr speciations when insoluble Cr compounds are limiting reactants.