Arsenic is one of those substances that immediately brings to mind symbols of skulls and crossbones. But even though arsenic deserves its reputation as a powerful poison, it is not an artificial concoction brewed up in a lab.

Arsenic is an element, a natural part of the environment that is found in a wide range of minerals. Under normal circumstances, arsenic is released slowly from the rocks as they weather. But grind, crush and pulverize those same rocks, and you have a different story -- and potentially a nasty environmental problem.

Arsenic is often found along with gold in oxide deposits, and mining can release large quantities of arsenic into the environment. Surprisingly enough, even though gold has been mined for centuries, very little is known about arsenic in mine wastes. And one researcher who has been studying the issue is finding that it is a very complex problem.

Eric Soprovich, a pollution abatement scientist with Environment Canada in Whitehorse, has been analyzing the release of arsenic at the Ketza River Mine near Ross River since 1993. Canamax Resources mined gold at the site from 1988 to 1990.

When Canamax Resources first drew up an abandonment plan for the mine, the company assumed that the arsenic in the mine tailings was relatively stable, and that high levels of iron in the tailings would bind with any arsenic that was released.

The company had not actually tested the tailings when it proposed spending $400,000 to close down the mine. Soprovich's tests have shown that arsenic is anything but stable, and the estimated cost of closing down the mine is now more than eight million dollars.

But even after seven years of testing, Soprovich says he still has many unanswered questions about how arsenic is released into the environment. "This work has really shown that you open up a Pandora's box of questions, and one question begs another," he says.

When Soprovich started on this project, he could find little information on the best way to go about the testing. He says there are two main reasons why so little work has been done on arsenic chemistry so far.

For one, most of the research on mining pollution has focussed on acid mine drainage, which is produced when sulfide deposits are mined for base metals such as lead and zinc. Since base metal mines tend to be giant operations, with equally large environmental challenges, they attract most of the attention of both regulators and researchers. The oxide deposits that contain arsenic tend to be smaller and more widely dispersed.

Secondly, the chemical reactions that produce acid mine drainage tend to be straightforward compared to those involving arsenic. Soprovich says that arsenic chemistry is very complex, and releases of arsenic can occur at any pH level -- high, low or neutral.

"With acid rock drainage reactions, most everything happens when the rocks go acidic and produce sulfuric acid and liberate various metals like zinc and copper," says Soprovich.

Arsenic can be released from different types of minerals, and under all kinds of conditions. It can be released from tailings submerged under water, and tailings exposed to air. This makes it very difficult to predict and control arsenic when mines go out of production.

Soprovich has been running what are known as column tests to try and simulate what is happening to the arsenic in the tailings at the Ketza mine site. He sampled tailings taken from both the beach area bordering the tailings pond, and the pond itself.

These samples were put into Plexiglas columns and then periodically sprinkled with water to simulate the effects of rain percolating through the contaminated tailings. Other tailings samples were completely covered with water in the columns to simulate conditions in the tailings pond itself.

The column tests showed that the tailings were releasing more arsenic than is considered environmentally acceptable. The flow-through tests released the most arsenic, but significant amounts also leached out of the samples submerged in water.

Soprovich says he is not yet completely sure why more arsenic is released in some situations than in others. Exposure to atmosphere could be a trigger, or the milling process could be making the arsenic more unstable.

He plans to keep tracking this complicated problem, and looking for the best way to keep arsenic from polluting water around the mine. The results from this research could also help with arsenic problems at other mines around the Yukon and in other parts of the world.

We are getting closer to an answer," says Soprovich. "The long-term issue there is arsenic stability, and that is the very first question that we are trying to answer."

For more information on arsenic pollution, contact Eric Soprovich at 667-3410 or Environment Canada at 667-3400.