CHEMICAL KINETIC MECHANISM FOR ATMOSPHERIC CHROMIUM

A chemical kinetic mechanism for the atmospheric chemistry of chromium has been developed. The chemistry of chromium is of particular intere st because its oxidation state is believed to affect its toxicity. Chr omium can be reduced from the hexavalent form to the trivalent form by several chemicals including trivalent arsenic, divalent iron, vanadiu m, and sulfur dioxide. Trivalent chromium can be oxidized to hexavalen t chromium by reactions with manganese. Computer simulations were cond ucted for several scenarios using typical atmospheric concentrations. The simulation results suggest that typical conditions favor the reduc tion of Cr(VI) to Cr(III). Under some extreme conditions, Cr(III) coul d be oxidized slowly to Cr(VI). Experimental data of chromium concentr ations in ambient air and precipitation are needed to evaluate these t heoretical results.