Via Utica Daily News:
The river, which runs through the city of Langford, British Columbia, turned a fluorescent green on Dec. 30, when a passer-by captured stunning video of the verdant waterway.
At first it wasn’t clear what caused the river — and the water in a nearby fountain — to change color. But investigators now believe that the green hue was caused by the addition of fluorescein, a synthetic organic compound that is often used as a dye, or a “fluorescent tracer,” in the testing of water systems.
[Continues at Utica Daily News]