Why Venice’s Grand Canal Turned Bright Green

The Italian city of Venice has transformed from beautiful to bizarre over the past few days, with the waters of the famous Grand Canal turning green.

Sections of the canal, including near the Rialto Bridge, were found on Sunday to have changed color to a lurid green hue, leading local police to investigate after speculation it could be the result of a stunt by environmentalists.

The Regional Agency for Environmental Prevention and Protection of Veneto (ARPAV) concluded that the green glow was actually caused by the presence of fluorescein, a non-toxic substance used for testing wastewater networks, according to AFP. The origin of the dye was not revealed.

“No danger of pollution from the fluorescent green patch that appeared yesterday morning in the waters of Venice,” Veneto regional president, Luca Zaia, said in a translated tweet on Monday, also sharing a picture of the green water.

“ARPAV technicians took the colored water and carried out the first analyses in the late morning. The green liquid appears to be a coloring organic compound used for water inspections or in caving,” he said.

Fluorescein is a synthetic dye that appears dark orange-red in powdered form. When dissolved in liquid, its color depends on the pH, glowing a characteristic bright green in alkaline solutions.

This bright green hue led to its use in dying the Chicago River green for St. Patrick’s Day in 1962, according to the American Chemical Society, but was swapped for a vegetable-based dye in 1966. The dye is often used to trace flow in waterways of both surface and groundwaters, helping to locate water leaks, as well as detecting leaks in subsea oil and gas pipelines.

The fluorescent dye can also be used to detect abrasions and infections in the cornea of the eye.

Venice has seen its waterways dyed by this substance before: in 1968, the Grand Canal was dyed a similar green by Argentine artist Nicolas Garcia Uriburu, who released the fluorescein during the 34th Venice Biennale as an ecological awareness protest.

The similarity of the latest transformation of Venice’s waters to the 1968 stunt has spurred concern that it may also be an environmental protest, or even if it isn’t, it could spark similar acts in the future.

“The risk of emulation is worrying,” Zaia also tweeted. “Unfortunately Venice has become the stage for actions far beyond the lines: adequate and strong responses are needed.”

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