On-site Evaluation of NOx Removal Efficiency on Photocatalytic Pavements and Analysis of Environmental Variables

The objective of this study was to identify the correlation between NOx concentration and environmental variables at photocatalytic concrete pavements containing TiO2 by direct monitoring in field. In order to confirm the NOx concentration according to various environmental variables of the photocatalytic concrete pavements, humidity, temperature, light intensity, and NOx concen-tration were measured continuously for 3 days at photocatalytic pavement, concrete pavement, and atmospheric conditions, respectively. We identified the NOx concentration at all measurement sites and calcu-lated the NOx removal efficiency of the photocatalytic pavements. As a result, the NOx concentration of the photocatalytic pavement was 0.086 ppm on the 1st day, 0.125 ppm on the 2nd day, and 0.106 ppm on the 3rd day, which was mostly lower than that of the concrete pavement and the atmospheric conditions. When the NOx removal efficiency of the photocatalytic pavement on days 1-3 was examined by time, the NOx removal efficiency was evidently higher in the order of 0-6 h > 18-24 h or 6-12 h > 12-18 h for all three measurement days. In addition, the relationship between NOx removal ef-ficiency and environmental variables was analyzed. As a result of corre-lation analysis between NOx removal efficiency and environmental variables of the site, relative hu-midity showed a positive (+) correlation, while temperature and light intensity showed a negative (-) correlation. Based on our results, we summarize some considerations for evaluating the NOx removal performance of photocatalytic pavements applied in the field.