Handmade boats bring citizen science to the Mystic River

A time-lapse image shows the paths of low-cost water monitoring devices in the Mystic.
A time-lapse image shows the paths of low-cost water monitoring devices in the Mystic.

The dock in Medford’s Mystic Reservation was too sunny to see the glow, so spectators peered into a paper grocery bag while Catherine D’Ignazio held a ultraviolet flashlight inside it. In the dark, tampons that had been dipped in polluted water lit up purple.

“A humble tampon!” she had told the group earlier.

D’Ignazio, an organizer for the Public Laboratory for Open Technology and Science, a Cambridge nonprofit, was demonstrating low-cost, open-source tools anyone can use to study their own environments.

The Public Lab met up with a group of 18 artists and other interested people, who were on a daylong journey down the Mystic Saturday in homemade boats, to show off simple tools for water monitoring.

One tool, the Thermal Fishing Bob, links a temperature sensor to lights inside a waterproof container. Northeastern University student Erik Hanley demonstrated how it works. The lights turn from blue to green to red as the temperature goes from cool to warm. Dunked in a river, the bob’s changing colors can indicate a warm area where a power plant dumps wastewater, for example. The Public Lab has taken time-lapse photos of the bobs moving through water at night, creating rainbow-colored ribbons that show how this wastewater dissipates. “It’s very cool to be able to paint the environmental data,” Hanley said.

Scientists in the United Kingdom recently showed that tampons dipped in water can detect pollution. Human wastewater contains chemicals called optical brighteners, which are added to detergents to make clothes look cleaner, for example. Since tampons are so absorbent, they soak up a concentrated sampling of whatever is in the water. Under a UV flashlight, tampons that have absorbed optical brighteners will glow purple — a signal that the water’s been polluted.

Public Lab organizer Don Blair showed visitors a tool called the Coquí, named for a noisy Puerto Rican frog. The device broadcasts a squealing sound when dipped in water. A higher pitch indicates water that’s more conductive, meaning it has more substances dissolved in it. Another device, the Babbling Brook, is a red plastic flower with a tall base that stands in water. It monitors water temperature, depth and conductivity, then combines that information with local weather data to make cheesy jokes it tells out loud. It’s meant as a science literacy tool for kids, who can write the jokes themselves.

Visitors arrived at Saturday’s demonstration in a flotilla of seven handmade boats. Most had been built during early September in public workshops. Mare Liberum, a boatbuilding and art collective based in Brooklyn, led the workshops during a residency at Harvard’s Carpenter Center for the Visual Arts. The group’s goal is to make the water more accessible to the public, says Mare Liberum artist Sunita Prasad. While the Public Lab connects citizens to their environment using new technologies, Mare Liberum uses the older craft of boatbuilding.

In earlier projects, the artists have built boats based on historic designs and boats made of paper. The crafts they designed for the Mystic were punts, flat-bottomed work boats that resemble canoes with squared-off ends.

The Carpenter Center residency culminated with the journey down the river on Saturday. The group invited the public to join them in paddling most of the river’s seven-mile length. In addition to the Public Lab, they heard from local groups including the Mystic River Watershed Association and Clean Water Action at stops along the way.

Cambridge resident and artist Nancy Hart joined in the boat-building workshops as well as Saturday’s journey. “It was really empowering,” Hart said, to use power tools to help build the crafts that would carry them down the Mystic.

Mare Liberum’s exhibition at the Carpenter center, called or, The Other Island, will include photographs and documentation from the river journey and be on display through Sept. 27.