KOLONTAR, HUNGARY - Shortly after a red river from hell tore through this village on 4 October, destroying lives and homes, Hungary's junior minister for environmental affairs, Zoltan Illes, said aloud what many feared: Nobody really knew what was in the caustic sludge - a by-product of the aluminum industry whose pH can reach a dizzying 13 - that had broken through a nearby reservoir.
But scientists at the Institute of Materials and Environmental Chemistry in Budapest begged to differ. The institute, part of the Hungarian Academy of Sciences, has done research on the toxic residue - which chemists call "red mud" - for decades. "We know red mud better than we know our wives," says Easzlo Kotai, a chemical engineer at the institute.
Kotai is part of a nine-member scientific task force, called together by the Hungarian government, which has found itself battling not just mud but also a rising tide of rumors and misinformation. Illes, for instance, said that the sludge was radioactive and could cause cancer, and the environmental group Greenpeace announced that it contained dangerous levels of heavy metals. Those claims led to fears of a widespread ecological catastrophe - including a poisoning of the Danube, one of Eastern Europe's major rivers. But Illes has dropped his claim about radioactivity, and scientists say Greenpeace's report was alarmist and unscientific.
Two weeks after the disaster, Kotai and other scientists say its environmental impact may be less severe than widely broadcast images suggested at first. They don't want to diminish the human tragedy: Nine people have died and more than 100 have been injured; many suffered burn-like wounds from the sludge's alkalinity. But much of the sludge can be removed physically and taken back to one of the company's intact reservoirs; the remainder can be neutralized with mild acids, says Janos Szepvolgyi, an environmental chemist who heads the task force. Task force members predict only minimal effects on the ecology of the Danube and don't think drinking water is at risk. "It's not as dramatic as it seems," says Tamas Nemeth, the academy's general secretary and a soil scientist himself. "We can handle this."
About a million tonnes of red mud poured out when the dam on reservoir 10 of the Ajkai Timfoldgyar alumina factory near Kolontar broke just after noon on 4 October. The sludge is formed during the so-called Bayer process, when bauxite ore is pressure-cooked with sodium hydroxide in giant reactors to extract aluminium hydroxide. The residue was stored in giant reservoirs right next to the factory, as it is at similar facilities around the world.
What caused the break is still under investigation. Some environmental groups had suggested that Hungary's red mud reservoirs, a legacy of the communist era, were poorly monitored and prone to breaks. The Hungarian task force, which also includes biologists and ecologists, has set out to map the impact of the release and provide the government with advice on how to limit the harm. Aside from the sheer physical impact of the initial wave - some Kolontar residents likened it to a red tsunami - the sludge's main problem is its deadly alkalinity, says Szepvolgyi. The Torma, a small stream near the village that ultimately flows into the Danube, turned red and is now almost completely lifeless. But the environmental damage downstream was reduced, says Szepvolgyi, partly by dilution and possibly because government workers dropped large amounts of fertilizers and calcium sulfate into the rivers to bring down the pH. Elevated pH values of between 8 and 9 were measured locally in the Danube for a few days, but they have come down, says Szepvolgyi. No major fish die-offs in the Danube have been reported.
Nor do task force members believe heavy metals will be a major problem. During a press conference on 8 October, Greenpeace announced that red mud from Kolontar contained high levels of arsenic, chromium, and mercury, suggesting that illegal dumping had occurred in the sludge pond before it broke. For arsenic, the level was 25 times higher than the limit for drinking water, the group said.
But that's a nonsensical comparison because nobody is planning on drinking the sludge, says Szepvolgyi. A better reference is the arsenic level allowed in organic sludges that Hungarian farmers are permitted to spread on their lands; the level measured by Green-peace was just slightly above that. Szepvolgyi also criticizes the group for basing its findings on a single sample. The sludge wasn't homogenous, he says, and the task force's own measurements have found varying levels of heavy metals at different locations—but none dangerously high, Szepvolgyi asserts.
Greenpeace spokesperson Szabina Moses says the group stands by its findings and that the academy scientists are downplaying the risks. "We're talking about arsenic. I don't have to be a scientist to feel that that is dangerous," Moses says.
Initial news stories suggested that Kolontar and Devecser, a bigger town farther down¬stream, might have to be abandoned altogether. That was an exaggeration, task force members say. When Kotai gave Science a tour of the area last week - expertly talking his way past police roadblocks - cleanup activities in Kolontar were in full swing. Trucks were hauling away tonnes of red mud; a few homes were clean again, and a handful of residents, looking somber, were returning. Many yards and sidewalks were covered with calcium sulfate. The compound - which makes streets look as if they're covered with dirty snow—not only helps neutralize the mud but also prevents it from becoming an easily dispersible powder once it dries. Instead, the mix forms a cake that can be removed with shovels.
What will happen to the surrounding farm¬land? The layers of red mud there vary from 1 or 2 centimeters to more than 10 cm thick. Some will need to be removed, but small quantities can probably be mixed in with the soil, says Nemeth. The alkalinity can be neutralized with mild acids, such as acetic acid or humic acid, a complex organic mixture that occurs naturally in the soil. Studies will have to show whether crops can be grown safely in these areas, Nemeth adds, but it might be wise to stick with biofuel crops or trees for the foresee¬able future. "I don't think anybody will want carrots and potatoes from this area anyway."
As Science went to press, another breach from the same reservoir threatened. But a new dam would divert most of the sludge, even if that happened, says Nemeth. What's more, the reservoir contains far less fluid, so any escap¬ing mud would travel slowly and only a couple of hundred meters, models show.
Amid the media frenzy, scientists say they are trying to be the voice of reason. When Kotai encountered one roadblock in Devecser, two police agents wearing rubber boots and facemasks asked if they were at risk as they guarded a street full of deserted homes. Kotai tried to reassure them. "They are scared," he said after he got back into his mud-covered Volvo. "They have heard so many stories."
MARTIN ENSERINK
Science
22 October 2010
American Association for the Advancement of Science
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