The Design and Characterization of a Chamber to Investigate the Impacts of Titanium Dioxide Under Ambient Conditions as an Air Quality Mitigation Strategy

Titanium dioxide (TiO₂) treated roadway surfaces are being investigated by the scientific and engineering communities as an air pollution mitigation strategy. These surfaces are photocatlitic in sunlight and remove nitrogen oxides (NO_x) and volatile organic compounds (VOCs) emitted from vehicles. The aim of this experiment is to modify and characterize a chamber that will be able to sample ambient air and allow TiO₂-coated surfaces to undergo photolysis from direct sunlight in order to simulate real-world conditions. Several tests were run to characterize chamber dynamics to ensure optimal mixing. This data was then compared to the expected values generated by a box-model equation. Additional experiments were conducted to determine the firsts-order loss coefficient, k (0.00377 1/s), and as well as the transport limited deposition velocity (V_t) (0.5068 cm/s). This was done by measuring ozone uptake to potassium iodide (KI) coated sample surfaces. The preliminary results of this experiment indicate that the chamber will be suitable for further experiments to test the reaction probabilities of NO_x and VOCs, the nature of TiO₂-coated asphalt, and the yield of hazardous byproducts such as nitrous acid (HONO) and aldehydes —which are a concern for public health as well as the environment. The implications of these studies will allow scientists and engineers to better understand the effectiveness of TiO₂ as an air pollution mitigation strategy in a variety of scenarios.