Effect of Vehicle Classification and Activity on Field Evaluation of Photocatalytic Concrete Pavements’ Ability to Remove Nitrogen Oxides – A Case Study

Abstract

There has been an increasing interest in photocatalytic pavements, which can decompose pollutants to nonhazardous waste products with little energy requirements and selectivity. The objective of this study is to evaluate the effects of vehicle activity and classification on nitrogen oxide (NO_x) pollution emitted and correlating these factors to the NO_x reduction from photocatalytic pavements. To achieve this objective, a field study was conducted with 22.3 m^2 of photocatalytic spray coated area and 22.3 m^2 of uncoated control area. Evidence of photocatalytic reduction of NO_x was evaluated by directly measuring NO_x reductions from the ambient air. A traffic study was conducted for the photocatalytic control areas to characterize the variability in traffic classification and activity between the two areas and its effects on interpreting NO_x reduction. Results showed that the amount of NO_x emitted in the area predicted to be from traffic sources is no more than 5 grams per hour. Due to the low values of pollution emitted in the both the photocatalytic area and the control area, minor differences in traffic activity between these two areas resulted in significant differences in the amount of pollution emitted between the photocatalytic and the control areas. This may complicate the interpretation of the NO_x reduction results. Furthermore, there was no significant linear correlation of vehicle class and speed and NO_x reduction.