Popular Way to Assess Oil Spills Can Be Misused
Lippsett, Lonny, Oceanus
WHOI chemist issues warning before 'pompom' method becomes standard practice
Environmental assessment teams increasingly may be using a method to assess oil spill contamination in situations where it doesn't work well and are in danger of reaching false conclusions, a scientist at Woods Hole Oceanographic Institution has warned.
In a letter published online April 30 in the Marine Pollution Bulletin, marine chemist Christopher Reddy issued what he called "a cautionary tale" about using the "pompom" method as a universal practice for assessing oil contamination in ocean- or river-bottom sediments. The method uses long strands of absorbent polypropylene swabs, which look like cheerleaders' pompoms, dragged along bottom sediments. The method is in demand because it offers a rapid, low-cost way to locate large areas where oil has sunk to the sediments. But that doesn't mean it can effectively identify lesser amounts of oil that can have harmful impacts on ecosystems and public health, Reddy said.
Reddy pointed to the spill of 58,000 gallons of heavy fuel oil after the M/V Cosco Busan struck the San Francisco-Oakland Bay Bridge in November 2007. In late December, the pompom method was used to assess whether sediments dredged near the Port of Oakland could be safely used to help restore a tidal wetlands.
"The problem may stem from an unfortunate misinterpretation of research following a spill of the M/T Athos I in the Delaware River in 2004," Reddy wrote. In that case, responders used a boat to drag several beams with pompoms across sediments on the riverbed. Back on deck, personnel could see whether the pompoms came up white and clean or black and oilstained and could quickly determine the locations of large oil patches on the river floor. The information proved valuable for putting together the best emergency response and cleanup, Reddy said.
"But the method was never intended to assess contamination at much lower, but still significant levels," Reddy wrote. "A great tool for the circumstances of the Delaware River oil spill does not translate to the conditions in San Francisco Bay."
In the Port of Oakland, the U.S. Army Corps of Engineers used the pompom method to look for evidence of tar balls that may have sunk to the sediments after the M/V Cosco Busan spill. Finding none, the corps declared the dredged material safe and used it in the restoration project. …