Hurricanes cleaned up lead-laden New Orleans

Celeste Biever in New Scientist: Could the devastation caused by hurricanes Katrina and Rita have had a silver lining? The sediment washed into New Orleans by the floods accompanying the storms may have blanketed over heavily polluted, lead-laden soil in the city, leading to a decrease in lead levels in the bloodstreams of children across the city.

So says Howard Mielke, who researches urban geochemistry at Tulane University in New Orleans, Louisiana. Mielke and his colleagues sampled soil in 46 neighbourhoods of New Orleans in 2000 and then again in 2006.

Before the hurricanes, which both occurred in autumn 2005, soil lead levels in 15 neighbourhoods exceeded the US Environmental Protection Agency's limit of 400 milligrams per kilogram, and that this dropped to just six neighbourhoods in 2006. Lead levels declined in 29 neighbourhoods between 2000 and 2006 by an average of 45 per cent.

As soil lead levels had remained fairly constant between 1990 and 2000, and as there were no efforts to remove lead from soil during this period that could have accounted for this reduction, the researchers conclude that this drop was due to the hurricanes, which likely brought unpolluted sediment in from Lake Pontchartrain and the coastal wetlands. "This material is generally much cleaner than what you see in the city," says Mielke.

…Mielke says the natural effects of the hurricanes could be mimicked by soil-remediation efforts – and that his results indicate that this is a good way to reduce the amount of lead absorbed by children. "It demonstrates the possibility of improving the environment for children and protecting them against lead poisoning."…

East New Orleans after Katrina, photo by Infrogmation, Wikimedia Commons, under the Creative Commons Attribution 2.5 Generic license