Study on photodissociation and photoconversion characteristics of CS2 in O2/O3 environment using real-time conversion products obtained by UV-DOAS

Abstract

Carbon disulfide (CS2) is extremely susceptible to decomposition by ultraviolet radiation, and its decomposition products affect the concentration of trace gases in the atmosphere, which disrupts the balance of atmospheric chemistry. It is essential to elucidate the photochemical reaction characteristics of CS2 for more in-depth study of the complex chemical and physical changes in the atmosphere. Therefore, this paper firstly provides a clear visualization of the evolution process of CS2 and conversion products by UV differential optical absorption spectroscopy combined with multi-wavelength least squares method, and then the photodissociation and photoconversion characteristics of CS2 under trace-oxygen, additional-oxygen and additional-ozone conditions are explained. The results show that the generation of SO2 from CS2 is about 100 ppm when only trace-oxygen is present, and the main channels of the reaction are CS2+hv→CS+S and CS+4O→SO2+CO2. The SO2 concentration increased from 138 ppm to 150 ppm as the oxygen concentration increased with the main reaction channels CS2+6O→2SO2+CO2 and CS+4O→SO2+CO2. However, in the additional-ozone environment, the main reaction channels CS2+2O3→2SO2+CO2 and CS+4/3O3→SO2+CO2 gradually dominate as the ozone concentration increases, at which point the SO2 concentration decreases from 140 ppm to 125 ppm. The results indicate that in the photochemical reaction of CS2, the unstable products O atoms and CS directly affect the photochemical reaction rate and the concentration of SO2. This study not only enables real-time monitoring of the evolution process and conversion products of CS2, but also lays the foundation for future studies on the conversion properties of CS2 in photochemical reactions.