When the rain begins to fall in Southern California, the freeways get slippery because the water lifts the oil and grease that has collected on the pavement. The initial cloudburst also breaks loose tons of pollutants, sending them down the storm drains and into the ocean, according to Michael K. Stenstrom, professor of civil and environmental engineering at UCLA's Henry Samueli School of Engineering and Applied Science.
Stenstrom and his team are currently trying to ascertain how much higher the concentration of pollutants is in the first part of the storm-water runoff. If the data support his theory that the first burst of storm water contains the most potent concentration of toxins, Stenstrom said, "we have the opportunity for some natural treatment systems."
His goal is to find a way of reducing the amount of pollutants reaching the ocean. He hopes to use the data he is collecting "to save money because there is such a high volume of storm water that you can't possibly treat it all."
This is the fourth year of a $1.2 million research project, funded by Caltrans.
Mixed with the crankcase drippings and partially burned fuels that become polynuclear aeromatic hydrocarbons (PAHs), some of which are carcinogenic, the toxic stew that makes up storm-water runoff also contains heavy metals such as zinc, copper, nickel and chrome, Stenstrom said. Some of these are the products of automobile corrosion; some comes from brake pads.
"When a car hasn't been washed in a while, you can see a layer of black powder around the wheels. That powder is from the brake pads and can be loaded with heavy metals," Stenstrom said.
Stenstrom noted that some PAHs can be found in soot-like, micron-size particles. He cited diesel engines as one
Contact: David Brown
University of California - Los Angeles