Toxic Minerals in Tibetan Glacier Meltwater

Posted by on Jan 18, 2017

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Tibetan landscape, with snow mountains (Source: reurinkjan/Creative Commons).

Higher concentrations of toxic minerals have recently been found in glacial meltwater in the Tibetan Plateau region and are raising health concerns. Meltwater has eroded rock which is newly exposed due to glacier retreat, releasing hazardous amounts of iron, lead and other minerals into streams and rivers. A recent paper in the Journal of Hydrology authored by Xiangying Li et al. presents evidence recorded in 2013 of tainted meltwater from Dongkemadi Glacier in central Tibet.

According to Voa News, climate research indicates that the Tibetan Plateau has been warming since the 1980s. The mass of ice in Tibet is the largest anywhere on Earth outside of the polar regions, and the plateau is increasing in temperature four times faster than the rest of the planet. Some of the meltwater, which has increased due to warming temperatures, deposits into the Yangtze, Mekong, Yellow and Indus rivers. Tibetan glaciers are estimated to hold 14.5% of the world’s glacier mass. It’s also estimated that 247 square kilometers of glaciers disappear annually, with a total of 18% of glaciers having disappeared since the 1950s. The Dongkemadi Glacier, which the researchers analyzed, is located in central Tibet and has an area of 15.89 km² and a maximum elevation of 5,275 meters.

Glacial meltwater (Source: The Virtous One/Creative Commons)

Glacial meltwater (Source: The Virtous One/Creative Commons)

To reach their findings, researchers took samples from the meltwater of the Dongkemadi Glacier and found bicarbonate and calcium were dominant ions, followed by magnesium, sodium and sulfate. Other minerals also included  iron, strontium, boron, aluminum, barium and lithium. Most of these elements are transported while they are in the dissolved phase, while carbonates may be absorbed by solids and remain highly mobile. Other chemicals were found to be at a level deemed insignificant, below the threshold of 1 μg/l (micrograms per liter). 

Katherine Alfredo, a research scientist at Columbia University’s Water Center, who spoke with GlacierHub about the research, said, “The results of the article, that glacial retreat can expose rock and lead to new weathering and contamination, are totally plausible. The methods of sampling and analysis are sound.”

Compared to meltwater from the Haut Glacier d’Arolla in Switzerland, which the researchers used as a benchmark for average glacial meltwater hydrochemistry, concentrations of sodium, calcium, magnesium, chlorine, bicarbonate, lithium, strontium and barium were higher in the Tibetan PlateauThis discrepancy may be due to a higher abundance of carbonates like calcite, which more heavily influences the meltwater’s chemistry in the Tibetan Plateau than compared to the Haut Glacier d’Arolla. This suggests that the Tibetan Plateau has higher chemical weathering than other glacial water networks, with a higher amount of chemicals potentially discharged into the water system in Tibet. 

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Calcite (Source: Macroscopic Solutions/Creative Commons).

The high concentrations of metals such as iron, lead, nickel, chromium, arsenic, copper and aluminum found in the meltwater can have significant negative impacts on human health and the environment. For example, lead exposure is known to cause impaired physical and mental developments, nickel exposure can cause kidney failure or birth defects, and aluminum exposure can increase chances of Alzheimer’s disease. The highest iron concentrations found by the researchers exceeded the Environmental Protection Agency’s guidelines, while concentrations of aluminium, zinc and lead are currently close to the guideline values. 

Monitoring of the Tibetan Plateau’s glacier meltwater for hazardous concentrations of minerals is important to public health and the environment. However, data is limited because long-term observance of hydrochemistry can be costly and isn’t typically included in glacial monitoring programs. As climate change continues to melt the glaciers and increase rock exposure, more chemicals will be deposited into the water system in Tibet, posing risks to health. Seeing how significant the effects have already been, it is important to continue monitoring glaciers, even if expensive.

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One Comment

  1. This study first clearly demonstrated the potential influence of glacier retreat on surface water quality.

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