<mediar rid='m1'><?xm-replace_text {mediar}?></mediar>A fire at an Iraqi sulphur plant caused the largest man-made release of polluting sulphur dioxide ever recorded. The event produced more of the gas than most volcanic eruptions, according to the scientists who used satellite monitoring to reveal the effects of the blaze.
Fire broke out at the Al-Mishraq state sulphur plant near Mosul on 24 June 2003, probably started by arsonists, and burned for almost a month. "This is the largest non-volcanic sulphur dioxide event we've detected since 1978," says vulcanologist Simon Carn from the University of Maryland in Baltimore, who led the analysis. That was the year that satellite monitoring of sulphur dioxide in the atmosphere began.
About 600,000 tonnes of sulphur dioxide was released in the fire. In comparison, the devastating Mount Saint Helens eruption in 1980 released about a million tonnes of sulphur dioxide.
On average, the fire generated some 21,000 tonnes of sulphur dioxide a day, about the same as the most polluting power plants release in a year, and equivalent to half of the daily sulphur dioxide emissions of the United States.
Local impact
The Al-Mishraq plant used to refine sulphur from the largest deposit in the world, estimated to be worth US$25 billion. Mining had continued even though exports were restricted by sanctions, so a huge amount of unprocessed sulphur had built up at the site.
“This is the largest non-volcanic sulphur dioxide event that we've detected.”
Simon Carn
Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore
Although unlikely to have a long-lasting global impact, the fire caused an estimated $40 million of damage to local crops, along with widespread respiratory problems in local residents and at least two deaths.
Observing the fire from space was the only way to find out how severe it actually was, says Carn, because there was no way to monitor the pollution from the ground, and news reports at the time were sketchy.
The team used data from two instruments - TOMS (Total Ozone Mapping Spectrometer) and MODIS (Moderate resolution Imaging Spectroradiometer) - on NASA's Earth monitoring satellites, Terra and Aqua, to calculate how much sulphur dioxide poured from the plant. They now report their conclusions online in Geophysical Research Letters1.
Pollution trail
The team hopes that a more sensitive orbiting device called OMI (Ozone Monitoring Instrument) could soon keep track of sulphur dioxide coming from coal-fired power plants. Sulphur dioxide emissions are currently estimated from the mass of coal burnt and its sulphur content, says Carn: "With actual measurements, we can find out if a power plant is putting out more sulphur dioxide than it says."
"This could be very useful for monitoring eastern European countries, where power stations are the major cause of sulphur dioxide pollution," agrees Ian Colbeck, an atmospheric physicist from Essex University, Colchester, UK.
OMI is a Dutch and Finnish contribution to NASA's Aura satellite, launched on 15 July this year. The team expects to start getting data from it in the next few months.
Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore
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