An environmental throwback in Bolivia.

Notes from different corners of the world.
Sept. 14 2006 11:51 AM

The Mountain That Eats Men

Welcome to Potosí, Bolivia, one of the most polluted places on Earth.

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Three members of the crew test the sewage-laden river

POTOSÍ, Bolivia—I don't envy the other members of the party down below me, taking samples of the malodorous brown liquid flowing through the strewn garbage. The three men are doing their best to maintain scientific detachment, but sewage smells bad no matter how objective your approach.

As a woman strolls atop the drainage pipe and nonchalantly tosses three bags of trash into the stream, I'm taken aback by her Earth-unfriendly behavior, until I remember how much the water in this part of Bolivia is already choked with lead, cadmium, and arsenic that have leaked out of the local mines—not to mention municipal waste. One more bag of trash probably isn't going to hurt things around here.

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Mining has defined Potosí for almost five centuries, but it has always come with a heavy price. In the 1500s, one of the local Indians leaked the secret of the vast veins of silver in Cerro Rico, the "rich mountain" that towers over Potosí, and the Spanish then started up a system of forced Indian labor to dig out the treasure. Between 1545 and 1824, about 8 million Indians and African slaves died in the process of producing between 22,000 and 45,000 tons of silver for the Spanish Empire. Cerro Rico has more than lived up to its monster-movie nickname "The Mountain That Eats Men."

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The mouth of one of the mines

These days, the Indians'minero descendants (and sometimes, their children) still travel deep into the mountain around the clock, bringing ore to the surface for processing in the nearby plants. When the mountain's silver yield and quality declined in the 1800s, Potosí took an economic hit and many mines closed, but then tin became a valuable commodity, followed by zinc, which is the primary product today. Most of the mines are owned by miners cooperatives, which sell the ore to private companies for processing. Dozens of gray piles of ore dot the mountainside and surrounding area, each pile representing the mouth of a mine.

My friend Bill Strosnider, a Ph.D. student at the University of Oklahoma, has been in Potosí for a month with the Universidad Autónoma "Tomás Frías," doing studies on the feasibility of passive-treatment projects to clean up the mine drainage that's taking a devastating toll on the local environment. Thanks to poor environmental-law enforcement and accumulated water in the area's numerous abandoned mines, Potosí's watershed is a worst-case demonstration of acid mine drainage in action.

The ores found in Cerro Rico—silver, iron, zinc, tin, lead, cadmium, and chromium, among others—are primarily in sulfide form: metal atoms bonded to sulfur atoms. When these metal sulfides (particularly iron pyrite, the traditional source of acid mine drainage) are exposed to air and water, they oxidize and produce hydrogen ions, sulfate ions, and metal ions. Any water that passes through these materials will then become acidic and will collect large quantities of the toxic heavy metals that remain in the ore and mine tailings—the piles of dust and gravel left over after the valuable materials have been removed from the metal ore. The oxidation of sulfides occurs naturally, but the huge amounts of rock exposed by large-scale mining drastically speeds up the process. It makes for a spicy stew of acid and toxic contaminants.

To grasp the scope of the damage, the crew of Freddy Llanos and Franz Mamani from the university's mining studies department, Yoichi Matsuda from JICA (the Japanese equivalent of USAid, here to study methods of cleaning the pollution), and Bill venture out each day in the school's aged red Nissan SUV to water-testing sites around the area. At each site, they test the water's pH level, conductivity, salinity, sulfate level, metals concentration, rate of flow, and temperature, all set against a picturesque mountainous backdrop that reminds me of northern Arizona. (This is allegedly the world's highest city.) Most of the samples test as expected: The water usually has an acidic pH level around 2 or 3, typical of acid mine drainage, and high levels of iron, lead, and deadly cadmium. One stream whose Quechua name means "spicy river" is aptly termed: At 20 milligrams of cadmium per liter of liquid, that's 4,000 times the EPA safety level of 0.005 milligrams per liter. When we later survey a single small stream that has plant life and a near-neutral pH value of 6.5, we're all astounded to have found such a thing.

Mine tours are popular among foreign visitors to Potosí, so I stopped in to see just how the mining is done. Despite myriad innovations in mining technology over the past 500 years, here the miners still do things the old-fashioned way: breaking the ore out of the walls and the floor with pickaxes and shovels, then carting it outside in wheelbarrows to be dumped into trucks and driven to the processing plants. Silica dust in the air causes silicosis, and few mineros live longer than 20 years after starting work in the mountain. There are charity hospitals in town, but health coverage is pretty much nonexistent.

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The Tío from the mine I visited; note his liquor-covered erection

It's customary for visitors to bring gifts to the miners—coca leaves, cigarettes, snacks, or drinks, including el puro, the 96-percent alcohol drink used for Bolivian benders. The miners leave some of the gifts for Tío, the devilish god represented by a statue in each of the mines. The Tío in the mine I visit also happens to have a porn-sized endowment. Emphasizing this fact, Helen, the guide for the tour, pours some booze down Tío's penis, explaining that it's a customary way to ensure that Tío fertilizes Pachamama (Mother Earth) so that the mines will produce more ore. It's nice to finally see something positive come from the combination of sex and alcohol.

The combination of extreme altitude and the mine's tiny crawlspaces is not easy on a tall gringo like me. At one point, Helen "volunteers" me to give one of the miners a break and push a wheelbarrow full of zinc ore down a hallway that's maybe 5 and a half feet high and about 4 feet narrow. As I'm panting heavily after only 50 yards, Helen shouts that it's time to go, and the miner takes over with embarrassing ease. On the way out of the depths, watching two dusty miners reel up a basket of rocks with a hand crank, I can't help but wish for the price of zinc ore to skyrocket.

Bill and I grew up in Pittsburgh's Monongahela Valley, where mine drainage is an occasional problem for neighborhoods like ours built on top of abandoned coal mines. But there, most of the pollution is cleaned up and out of sight, in compliance with strict environmental laws. Potosí looks like Pittsburgh in the early 1900s. We spent lots of time hiking around on top of enormous piles of yellowish-orange or gray tailings, where tiny bits of metal glint in the sun. Next to the piles are small creeks in colors I've never quite seen before: gray, yellow, and red, with frothy piles of white sulfates on top. Running water is not supposed to look like an ice-cream float.

Because the mineral ore in Potosí is extracted on the cheap at local processing plants that don't treat all the nasty stuff, piles of mine tailings come out of processing with high concentrations of zinc, lead, cadmium, arsenic, iron, and chromium intact, not to mention the cyanide used in the processing. The pollutants inevitably enter the watershed, causing health problems and the presence of heavy metals in crops downstream from the mines. The rocks in local streams are evidence of the high metal content—most are colored bright red (from oxidized iron), yellow (from the many sulfates in the water), or even a greasy jet black (from oxidized manganese). Bill tells me that when he arrived in town a few weeks before, a large new mine was planned near Cerro Rico, but after local campesino farmers, angry at further potential water pollution, used a popular Bolivian protest tactic and blockaded the major road into Potosí, the plan was abandoned.

In Potosí, effective mine-drainage treatment is still mostly theoretical. Passive-treatment programs—which use constructed wetlands, bacteria, and other natural methods to raise the pH levels and precipitate some of the heavy metals in mine-contaminated water—are used in parts of the United States and Europe around both abandoned and working mines, and they help to clean up the pollution. But down here, water and money are scarce commodities, and the scale of cleanup required is immense.

Franz says the Bolivian government has promised to treat some of the water that flows into the surrounding farms and causes the most damage to the region's agriculture. The government has also begun reforestation of the hillsides around Potosí, which will help to slow the flow of materials down the mountains. But one of the best ways to clean up Potosí may be good old capitalism: The heavy metals in the area are prized for industrial use, and the cadmium, lead, and zinc in all those piles of tailings could make a nice profit for a company with the resources to extract them.

In the right economic conditions, even a small cleanup effort in Potosí could mean both profit and an improved environment. For all that Potosí's metals have bought for the world, clean water for its miners seems like the least we can do.

Patrick Stack is a Web developer for Slate.

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