Assessment of Elevated Road Traffic Pollution on Roadside Trees and Vegetation in Urban Environments

Dr. Avnish Chauhan¹Gaurav Pandey²Man Vir Singh^3*Muneesh Sethi¹Prateek Gururani⁴Dr. Amit Awasthi^5*Shshank Chaube⁶Abhishek Lodh^7*

• ¹Department of Environmental Science, Graphic Era Hill University, Dehradun, Uttarakhand, India
• ²Forest Research Institute, Dehradun (Uttarakhand), India
• ³Uttaranchal University School of Applied and Life Sciences, Dehradun, India
• ⁴Graphic Era Deemed to be University, Dehradun, India
• ⁵Applied Science Cluster, School of Advance Engineering, UPES, Dehradun, Uttarakhand, India
• ⁶Symbiosis Institute of Technology, Hyderabad Campus, Symbiosis International (Deemed University), Pune, India
• ⁷Swedish Meteorological and Hydrological Institute, Norrköping, Sweden

In the present research work, efforts have been made to study the impact of motorway flyovers and at-grade roads on air pollution (PM10, SOx, NOx, AQI) and roadside vegetation in Dehradun by considering the important biochemical parameters such as chlorophyll, ascorbic acid, leaf pH, and the Air Pollution Tolerance Index (APTI). Five species of plants were selected along the busiest highway in Dehradun, including Mangifera indica (Mango) and four varieties of Bougainvillea in Red, Pink, Gold, and white colors. The monthly monitoring of PM₁₀, SOₓ, and NOₓ concentration during the study period showed significant seasonal variations at all three selected sites. Maximum PM10 (58µg/m³) and NOₓ (33µg/m³) were observed at Site 2 (On Flyover) during December 2024, while the highest Air Quality Index (AQI) value at this site reaching 270. Regression analysis showed that the AQI trends from winter to spring were declining, and Site 2 experienced the greatest monthly reduction (-13.25 units month-1; R² =0.88). PM₁₀ and NOₓ were the most influential factors about AQI (r = 1.00 and r = 0.90), indicating that degradation of these pollutants is a major component of urban pollution. Biochemical parameters were used as markers to assess the plants' responses to pollution in Mango and Bougainvillea (red, white, pink, and gold varieties). Mango showed a higher tolerance (APTI 8.09) when compared to Bougainvillea varieties, where the maximum stress was caused (APTI up to 4.65), and also exhibited a marked reduction in the levels of chlorophyll and ascorbic acid. Results show meteorological-emission effects on urban air quality, supporting plant-based biomonitoring programs.