Antarctic Snow Shows Record Of Airborne Arsenic And Other Pollutants

Tiny particles of metal and metalloid elements spray into the air from natural sources, such as volcanoes, or from human-made sources, such as ore processing. Wind currents send them to the far reaches of the globe. Researchers have tracked some of these particles to the Arctic but have little data from Antarctica. Now scientists have measured levels of several of these elements deposited in snow in the Antarctic (Environ. Sci. Technol., DOI: 10.1021/es303086c). They report a decline in arsenic concentrations, possibly due to controls on copper smelting emissions in South America.

Sungmin Hong of Inha University, in South Korea, and his colleagues carefully collected layers of snow deposited over the past 50 years or so, near Dome Fuji, the site of a Japanese research station in Antarctica.

Back in the lab, they melted the snow samples and used inductively coupled plasma sector field mass spectrometry to measure several ion species, including sulfate, and five metal and metalloid elements: arsenic, molybdenum, antimony, thallium, and barium. The team dated layers according to depth and by matching spikes in sulfate concentrations with records of volcanic eruptions. Using the eruptions record, they estimated how much of each element the volcanoes contributed.

Hong’s group found levels of arsenic, molybdenum, antimony, and thallium that they think are high enough to suggest human activity enriched them. Over the decades, the researchers found, arsenic’s concentration peaked from 1990 to 1994 at 24 pg per gram of snow. The team thinks that the main arsenic source is Chile’s copper smelting industry. Arsenic occurs naturally in the ores processed by the copper facilities and is emitted during the smelting process. The drop in arsenic levels corresponds with regulations in the mid-1990s to control emissions from the smelting industry.