
CHENNAI: Look at the leaves of plants and trees growing in areas near an open cast mine and chances are you would find fine particles of dust sitting on them. Foliar dust is generated during the mining process.
While studies in the past have shown that the mining dust, which often contains a variety of metals like lead, aluminum and iron, negatively affects the health of the vegetation in areas surrounding the mine, a new research by the University of Southampton, UK and the National Institute of Technology in Rourkela, tries to quantify its impact.
“Pollution from open cast mines creates a layer of dust that settles on the leaves of trees, making them increasingly less productive and less healthy. We knew this was the case, but we have learned that it is unfortunately worse – and far more spread – than we thought,” said Jadu Dash, Professor of Remote Sensing at the University of Southampton, one of the authors of the study published in the Journal of Geophysical Research: Biogeosciences.
According to researchers, dust from mines that settles on leaves could impede a variety of functions crucial for the plants and trees to grow and remain healthy. These include photosynthesis, light interception, nutrient availability, gas-energy exchange, and plant-pathogen interactions.
“Dust particles obstruct the leaves’ stomata, the tiny openings through which plants exchange gases with the atmosphere,” the researchers wrote. They also affect a key function of the plants: carbon capture and release of oxygen.
The study found that vegetation-associated carbon uptake fell by 2 to 3 gC (grams of carbon) for every additional gram of foliar dust per square metre.
Quantifying the impact on transpiration, the researchers wrote: “The vegetation transpiration reduction per unit of FD ranged from approximately 0.0005 to 0.0006 mm/m2/day.” Transpiration is the process by which plants lose water in the form of vapour mainly through their leaves. This is a crucial mechanism through which plants maintain their internal temperature, much like how we humans sweat.
Another important finding is that the damage to vegetation is not restricted to the areas surrounding the mine. Researchers found coal mine dust on the leaves of trees up to 30 km from the mine. They found that the highest concentration of dust on the leaves of trees along transportation routes to and from the mines.
For this research, the team focused on the coal mining region of Jharsuguda in Odisha. As coal deposits are located closer to the surface, open cast mining, as opposed to underground mining, is the most commonly used method of coal extraction in Jharsuguda. As per the state Mining Department’s data, there are 16 mines under operation in Jharsuguda, which has a total reserve of 9361.26 million tonnes of power-grade coal.
The team examined more than 300 leaf samples taken from 30 different sites in Jharsuguda and found that they were coated with dust containing aluminum, silica, and iron.
Researchers also studied detailed satellite images to get a sense of how much area is affected. “We used data from multiple satellite sensors to develop a model to map dust levels on leaves. This enabled us to understand the regional impact,” Dash wrote.
When thinking about the negative impact of mining on plants and trees, what immediately comes to mind is deforestation, the effects of contaminated soil and water, etc. How foliar dust slowly chokes them to death is often overlooked.
“Our research should provide a solid foundation to inform future environmental management, as well as demonstrate the need for ongoing research to fully understand and mitigate the negative impact of mining on the delicate surrounding ecosystems,” Dash wrote.