Ice core samples confirm higher metal content in the Himalayas

Ice core samples from Mount Everest that represent 800 years of atmospheric history contain much higher levels of certain metals in the last three decades than in the previous seven centuries. The metals are linked to the rising use of fossil fuels in Asia during that same time period.

Economic growth and more burning of fossil fuels by industries and cars in central Asia since the 1970s has resulted in higher levels of metals deposited in recent layers of ice collected from Mount Everest.

Data from a recent study that examined the cores from the Himalayan Mountains are the first to show that levels of arsenic, molybdenum, tin and antimony in the ice samples have sharply increased during the last 30 years when compared to the previous 700 years. During those centuries, the metal levels varied but were fairly stable.

Researchers use core samples of lake sediments, glaciers and ice caps to show that even remote locations – like the Arctic – contain evidence of human activities, such as the use of pesticides, metals and industrial chemicals. Slices of the cores are like pages in a history book; they record when and how much pollution a region has received during past decades, centuries or even milleniums.

It is known that chemicals originating in warmer regions of the world can be carried by air currents and deposited in soil and ice at the colder, higher latitudes and altitudes. Fossil fuels burned in cars or coal-fired generating stations release metals into the atmosphere that also can be moved long distances and deposited in remote ecosystems. Several prior studies from North America, Europe and Greenland confirm the higher levels of metals found in recent layers of sediment, glacier and ice cap cores are related to heavier reliance on fossil fuels during the last century.

More recently, the number of coal-burning generating stations and industries and vehicles that rely on fossil fuels has increased along with economic growth in central Asia. As a result, Asia now releases more metals into the atmosphere than any other region of the world. Despite these rapid increases, it was not known if the metals were being deposited at higher levels now than before Asia's recent industrial growth.

This recent study was done to find out. Researchers collected ice cores high up on the northern slope of Mount Everest. The cores represented what has been deposited in this region for more than 800 years, spanning from 1205 to 2002 AD. In the cores the researchers measured the levels of several metals – arsenic, molybdenum, tin and antimony – that are primarily released during fossil fuel combustion.

The results clearly show the effects of the booming economy in central Asia. In layers of the core representing the 1970s and more recent times, levels of these metals are up to 3 times higher than what was measured in older layers.

The findings show that the increased industrialization of central Asia has led to higher metals levels in remote areas of the Himalayas and that environmental contamination in this region is mirroring what has been seen in North America.
Synopsis by Karen Kidd

Hong, S, K Lee, S Hou, SD Hur, J Ren, L Burn, KJR Rosman, C Barbante and CF Boutron. 2009. An 800-year record of atmospheric As, Mo, Sn, and Sb in Central Asia in high-altitude ice cores from Mt. Qomolangma (Everest), Himalayas. Environmental Science and Technology.