Metal pollutants show their true colours

A team of Brigham Young University researchers has created molecules that glow in the presence of certain metal pollutants, paving the way for an early warning system that can alert regulators to the contamination of drinking water and waste streams.

BYU researchers devised the molecules as an improved method of detecting and monitoring increased metal levels in the environment caused by mining, smelting, fossil fuel combustion and industrial use.

'Methods of tracking metal in water currently exist, but they're labour intensive and can be very slow,' said Paul B. Savage, associate professor of chemistry. 'This research will let us create a sensor that continually measures metal in a sample of water as it flows by, making it easier to respond to any problems more quickly.'

The US Environmental Protection Agency has set a limit of two parts of mercury per billion parts of drinking water.

Cadmium is a metal commonly found in industrial workplaces where ore is being processed or smelted. According to the EPA's Toxic Chemical Release Inventory, from 1987 to 1993 cadmium releases were primarily from zinc, lead and copper smelting and refining industries, with the largest releases occurring in Arizona and Utah.

Chronic cadmium exposure has been linked to biological effects including renal dysfunction, calcium metabolism disorders and an increased incidence of certain forms of cancer.

To detect metals such as zinc in water, BYU researchers first created compounds that seek out and bind to metal ions - those atoms with extra electrons.

Next, they created small molecules that attach to the metal-binding compounds.

The small molecules reveal the presence of bound metal ions by acting as fluorescent 'reporters' - when ultraviolet light is shined on them, the 'reporters' glow brightly.

If no metal ion is bound, the compounds remain dark. The colour of the glow depends on the type and concentration of the metal ions present.

Plans are under way to develop a device that will allow industrial plants and water treatment facilities to track the concentration of metal ions in water and waste streams over time, said Savage.