Microzonation, ecological risk and attributes of metals in highway road dust traversing through the Kaziranga National Park, Northeast India: implication for confining metal pollution in the national forest.

Despite the abundant literature on metal contamination through road dust (RD) in urban/suburban and residential/highway regions, the RD of highways traversing through the Kaziranga National Park, NE India, has not been studied and lacks baseline data. The objective of the present study was to ascertain the possibility of highway microzonation based on temporal and spatial variability of metal pollution level and ecological risk. It was found that the RD contains an average content of (1.7-33.5 mg/kg) for Cd, Co, Cu and Pb and (121-574 mg/kg) for Ni, Zn, Cr and Mn across the highway passing through the national forest attributed by various sources. The study revealed three possible microzones present in the studied highway NH-37 based on spatial trend of metal as well as human interference. An attempt was made to understand the possible source of metals by principal component analysis, and four sources were identified: Three were of vehicular origin, and another was related to road surface and subsurface condition. The use of noise barrier walls as an effective measure to control the translocation of RD from one place to other was recommended to reduce the hostile effects of metal accumulation in the sensitive ecosystem. Thus, the study suggested and necessitated micronizing the system based on human interference level, ecological risk factors, spatial variability of pollutants and traffic pattern for their efficient management and conservation.