Most of the buses and heavy trucks that traverse the Manali-Leh Highway burn diesel fuel, contributing to pollution on one of the most remote mountain roads in the world, say researchers from the University of Cincinnati.
The researchers examined soil pollution along the highway, a tortuous 300-mile route – much of it gravel or dirt — that winds its way over one of the highest navigable mountain passes in the world at 17,480 feet.
"We measured incredibly high amounts of sulfur close to the highway. Some of those values are the highest ever reported in the literature and were likely connected to truck traffic," said Brooke Crowley, Assistant professor of Geology and Anthropology.
For the study, University of Cincinnati graduate student Rajarshi Dasgupta took soil samples at four places along the highway and at six prescribed distances, starting with samples literally on the dirt road and extending out 150 meters.
Soil samples were collected at three, nine and 15 centimeters in depth.
The results, published in the journal Archives of Environmental Contamination and Toxicology, showed high concentrations of sulfur, a major pollutant in the exhaust of diesel-powered engines.
The study found low levels of heavy metals and no relationship between their concentrations and the distance from the highway.
"This area provided us with a rare opportunity to examine the effects of multiple contaminants in a remote, diesel-dominated, mountainous environment," Dasgupta said.
Comparative studies have found that India's diesel contains an especially high sulfur content, the researchers said.
Sulfur dioxide in the atmosphere contributes to acid rain.
"At first glance, it's easy to consider the region to be a pretty pristine place. But there are environmental impacts from humans," Crowley said.
Completed in the 1970s, the road between Manali and Leh sees about 50,000 vehicles per year, mostly during the summer when the mountain passes are free of snow, according to government traffic counts.