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Airdate: Sep 01, 2008
Scientist: Adina Paytan

Science Diary: Water - Fingerprints

Science Diary: Water - Fingerprints
Bodies of water have unique identifying characteristics that enable scientists to trace pollutants to their source.

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AP: "If that's the seawater, what will happen if you pour this water into here gently?"
Student: "Yeah, I think it would stay on the top, because it's lighter."

Doctor Adina Paytan is an oceanographer at the University of California, Santa Cruz. When she's not doing field work, chances are Adina is inspiring future scientists. Welcome to Pulse of the Planet's Science Diaries, a glimpse of the world of science from the inside. Showing high school students how to distinguish salt water from fresh water is the first step in what Dr. Paytan calls 'water fingerprinting.'

"Different types of water have different characteristics, kind of fingerprints. For example, in an estuary you know you have freshwater that doesn't have salt in it, you have seawater or salty water, and they mix together. So, the salinity of the water is one way to identify it. Here, actually, in San Francisco Bay, a lot of the water is from sewage treatment plants. After the sewage is treated, it's released back into the Bay. This water has certain chemicals that are unique to sewage treatment facilities. It has more nutrients. It has more phosphorous. There are certain tracers or chemicals that are unique to different types of water."

Adina Paytan uses water fingerprinting to trace contaminants to their source. For example, if beach water tests positive for E. coli bacteria, and the water there reveals the fingerprint of a nearby river, that river is likely to be the culprit.

Students: "The salt in the water would make it more dense."
"It's heavier than tapwater."

AP: "Okay, good."

Dr. Paytan is one of the researchers participating in our latest project, which aims to get third to sixth graders excited about science; check out

Pulse of the Planet's Science Diaries are made possible by the National Science Foundation. I'm Jim Metzner.