Fourth-grader Corey Brooks dipped the small white strip of test paper into the glass vial of cloudy water taken from the school parking lot.
"Look at all the sediment in the bottom," said one of his lab partners, Brady Meixsell.
A few minutes later, the fourth-grader and his peers at Sandymount Elementary School in Finksburg had determined the water's nitrogen and pH levels, and reasoned that its lack of clarity would mean a drop in the production of algae and zooplankton, minute animal life that floats in water.
"Smell it, man," said Chris Collins, 11, to Drew Fritz, 9, referring to the sample.
Drew declined. "I know - it smells like a dumpster," he said.
Their scientific investigation, which took place one afternoon in science teacher Collin Angell's class, was not an exercise in grossing themselves out. As they compared the results of the same tests on much clearer water from the Patapsco River, they learned about the impact that impervious surfaces, such as parking lots and roofs, can have on the environment - and that whatever is dumped on the ground eventually affects the water system.
For several weeks this spring, fourth-graders at Sandymount and Eldersburg elementary schools have ventured into murky waters, using their newfound knowledge to develop their own contribution to cleaning up the Chesapeake Bay. As part of a pilot project in the Carroll County schools, they are creating rain gardens, with native plants, to help retain water and remove nutrients that would otherwise go on to sully bay waters.
"It just opens their eyes to some problems that you do not see on a normal basis," Angell said. And it also shows the kids that "there are things we can do."
Rain gardens act similarly to natural wetlands, absorbing water and helping filter nutrients and sediment that otherwise cloud water, blocking sunlight and keeping submerged aquatic vegetation from growing, said Bryan Shumaker, Carroll's resource teacher for science, technology, engineering and mathematics.
Funded by a $150,000 grant the school system received to foster interest in the fields, the pilot project could become part of the school system's fourth-grade curriculum, with every school eventually having a rain garden, Shumaker said.
Teachers at Sandymount and Eldersburg say the project has brought something fresh to engage students as the school year winds down.
"Usually at this time of year, we're trying to find anything to keep them motivated. ... This seems to be a good way to do that," said Amy Mullinix, a fourth-grade reading teacher at Eldersburg. "The kids love it. They've really been into it."
Angell has seen a similar response from his students.
"I've never seen them actually get as excited about it, and have as much knowledge about a specific subject or topic that we do," he said. "For some reason, it hits home with them. ... It's a little more real to them."
Anything that allows the students to put what they learn into action "is one of the best educational experiences they could have," Angell said.
At Eldersburg, the fourth-grade team has expanded the project beyond science. Students have spent recent weeks reading - including some fiction - about gardens, the bay and the importance of recycling, Mullinix said. In math, they've measured the garden they are scheduled to begin planting next month on a plot of prepared soil at the school.
Fourth grade is a good time to teach environmental concepts, said Joanna Allen, who teaches science at the school.
"They are at the stage in their life where they are becoming aware of places and people other than themselves," Allen said. "It's a lifelong learning experience, and I think we're giving them a good start."
Lining the shelves of Allen's classrooms are books such as The Science of the Environment, The Future - Bleak or Bright? and Why Are the Ice Caps Melting?
On a recent afternoon, her science students pulled on green gloves and carried plastic shopping bags outside to search for trash on the lush grassy hill outside the school. They returned a short while later with their finds - ranging from McDonald's paper cups to cigarette butts to a fake bright green feather - and organized them into categories on a large plastic sheet on the floor.
"Can you believe how much trash we collected from our school grounds?" Allen said. "No one even lives here."
The students nodded and murmured in agreement.
She and the class tallied the number of things in each trash category: 113 paper items, and 62 plastic and various pieces of wood, aluminum and foam.
"Which type of trash do you think is going to last the longest?" Allen asked.
Several hands shot into the air.
"This is just a wild guess, but maybe aluminum?" Emily Halstead, 10, said.
"Actually, plastic," Allen said. That will remain for about 100 years, she added.
"The trash - what we see - is just the beginning," Allen said. Those things end up polluting the bay, and that's just the visible garbage, she would later explain to her students.
"It's very important for our students to become aware of their environment and how people use the resources," Allen said. "We're digging a hole. ... If anyone can do something about it, it's the kids we have right now. If we can do something right here, now, then it's going to make an impact."
Sun reporters write about education at baltimoresun.com/InsideEd