Dye Experiment Helps Scientists Study Coastal Pollution - CBS News 8 - San Diego, CA News Station - KFMB Channel 8

Wednesday, January 28, 2009

Dye Experiment Helps Scientists Study Coastal Pollution

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If you've spotted some crazy colors in the water near La Jolla Shores lately, don't be alarmed. It's probably Scripps scientists hard at work figuring out a better way to keep our beaches clean. They're dumping dye into the water as part of an experiment to track ocean pollution.

Sewage, surf zones and dye - ever wonder where pollution goes or how quickly it disappears? Scripps institution of oceanography conducted an experiment that measured the amount of coastal mixing in the ocean.

What's exciting about this project is that it may help oceanographers and local agencies determine where pollution is headed during future spills in our ocean.

"In Southern California and the United States in general there's often chronic beach closure problems due to runoff pollution, and what happens is people measure bacteria concentration at beaches at certain time intervals when concentration exceeds in knee-high water, exceeds a certain rate, a certain count of bacteria, then you have to close the beaches," associate research oceanographer Falk Feddersen said.

Closing beaches often means losing precious tourist dollars. To protect both the local economy and health of beach goers, physical oceanographers have gone out into the surf. A team of scripps engineers had to ensure that the instruments for this project were robust enough to take a beating from the pounding waves.

"Three levels of instrumentation, and in each level we have what is called an acoustic Doppler velocimeter which measures the currents in the water," Feddersen said.

This project was led by Scripps professor Bob Guza and associate research oceanographer Falk Feddersen said.

Up until recently researchers say it's been difficult to measure vertical water movement in the surf zone.

"We're going to learn a lot about how turbulence is distributed in the vertical under breaking waves and then how the turbulence mixes up dye or tracers or sand or pollution," Feddersen said.

By watching this dye you can detect the direction of the current from the surface, which translates into detecting the direction of a possible pollution source, not to mention how fast it disappears.

"Pollution, you get a sewage spill that dumps a bunch of raw sewage on to the beach and then it cruises up and down the beach. One of the things we want to know is how rapidly does that dilute, and how well mixed is that in the vertical. Is it going to be strong at the surface and weak at the bottom or strong at the bottom and weak at the top," Feddersen said.

While oceanographers are still analyzing the data from this latest experiment, they hope many people will benefit from the study.

"Sanitation district managers, or public policy people who are interested in these results, there are people who have computer models that will tell you what the waves and currents do up and down the coast. The results we get will help the people who do more of the engineering work," Feddersen said.

In a place that draws concern from the coastal community as well as researchers, Imperial Beach is the next area of study for oceanographers.

"Next fall we're going to be doing a big experiment down in Imperial Beach, and there we're going to have a lot more stuff in the water, so there we're going to look at how the dye spreads vertically and horizontally," Feddersen said.

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