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What's on today's high school student's mind? Well, if you're one of the smartest students in America it could be climate change or clean drinking water.

For the past week, 40 top high school science students have been showing off their research at the National Academy of Sciences in a competition for $530,000 in scholarships.

The Intel Science Talent Search, run by the Society for Science & the Public, will culminate tonight with the announcement of the top winner who will receive $100,000. Nine other winners will take home between $20,000 and $75,000. All of the 40 finalists will each get $5,000 and a laptop.

In this story, we've picked three research projects that focus on the environment. See what the students have to say about their work and be inspired.

Name: Smitha Ramakrishna
Age: 17
School: Corona del Sol High School in Tempe, Ariz.
Subject: Clean Drinking Water

Ramakrishna's interest in clean water began when she visited an Indian orphanage in New Delhi when she was 12. She saw the hardship endured by the children there, and their lack of potable water left a lasting impression.

"I live in Arizona, which has been in a drought for over 10 years. But you can turn on the tap, and the water would gush out," said Ramakrishna, who has since joined organizations to raise money for the orphanage, as well as to promote water conservation in her local community.

She has also been doing water and sanitation research at the Arizona State University. Her research looks at whether sucralose, the artificial sweetener sold as Splenda, can break down easily during the wastewater treatment process. Ramakrishna noted that other studies have shown that chemical compounds consumed by people, such as medicines, can end up harming the wildlife or in our drinking water supplies because they aren't filtered out or detected during wastewater treatment.

What Ramakrishna has found is that sucralose doesn't break down using standard, bacterial treatment methods. She tested different treatment methods and found that using a combination of ultraviolet light and titanium oxide can break down the compound into biodegradable molecules. The process requires a lot of time and a high concentration of the two key ingredients, which would add costs to the treatment process.

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Name: Patrick Jeffrey Abejar
Age: 17
School: Smithtown High School West in Smithtown, N.Y.
Subject: Climate Change

Do you believe in climate change? That was the question Abejar heard quite a lot of in the summer of 2008, when he was doing research at Stony Brook University in New York. So he decided to figure out a way to quantify whether our Earth’s climate has changed over time.

"When I get confronted with a question like that, I don’t want to just read articles without getting some hands-on feel for the subject matter," Abejar said.

He formed his researche based on prior studies showing that carbon dioxide levels in the atmosphere can affect the Ph in seawater, which in turn affects the ratio of boron 10 and 11. In fact, these changes can be found in fossil records. So Abejar decided to see how the boron isotope ratio in the shells of brachiopod, Neospirifer, had changed over time. He specifically wanted to test brachiopod samples from the late Pennsylvanian and early Permian periods (306 to 298 million years ago), because other research has shown those times to be marked by rapid decrease and then increase in global temperatures.

Using shells from the Peabody Museum at Yale University, Abejar first performed two tests to select those that were in good physical shape and hadn’t been contaminated by chemical elements that shouldn’t exist in those samples, such as manganese. The he used a drill commonly found in a dentist’s office to retrieve powdery samples from the shells.

He then added hydrochloric acid to the samples and ran them in a mass spectrometer to determine the boron isotope ratio. What Abejar confirmed was that the boron ratio in the shells increased when the global temperatures declined, and vice versa.

"What I did was to establish that boron is an ideal tracer for climate change," Abejar said. "In a modern day context, we don’t have to use the brachiopod. We can collect seawater directly and observe the boron ratio for additional proof that we do have global warming."

Name: Aniruddha Sandeep Deshmukh
Age: 17
School: Bellarmine College Preparatory in San Jose, Calif.
Subject: Ecosystem Preservation

Wildfires are common occurrences in California. They sometimes create room for invasive grasses to take hold when native species aren’t able to grow back quickly. After reading a research report that shows a connection between a build-up of cyanide, which occurs after a fire, and the difficulty of native plants to re-grow, Deshmukh set out to analyze cyanide content in post-fire soils and figure out how to lower cyanide’s concentration.

He picked the sagebrush Artemisia californica as well as five other plant species that are part of the coastal sage scrub ecosystem. The ecosystem has shrunk by 70 percent over the past 20 years, Deshmukh noted.

Dicobalt edentate has been shown to be effective in treating cyanide poisoning. And Deshmukh found the compound to work well in binding cyanide in the soil and preventing it from accumulating.