Mercury In Fluorescent Bulbs Has A Unique Isotope Fingerprint

Compact fluorescent lightbulbs are a smart energy-saving swap for traditional incandescent bulbs. Environmental scientists are concerned, however, that as more fluorescent bulbs end up in landfills the mercury in the bulbs could leach into groundwater. Scientists often analyze the ratios of mercury isotopes in water and air to identify the metal’s source. A study suggests a way to monitor lightbulb mercury by looking for the characteristic isotopic signature generated when mercury atoms are excited to produce light in the bulbs. Chris Mead of Arizona State University and his colleagues let 14-W household lightbulbs burn continuously for up to about two years (Environ. Sci. Technol., DOI: 10.1021/es303940p). Afterward, they broke each bulb and isolated the mercury trapped in the glass. Using inductively coupled plasma mass spectrometry, the team measured the isotopic composition of the trapped mercury and compared it with a mercury standard. The difference between the isotope ratio of the bulb samples and that of the standard is larger than that of mercury from other sources, such as from burning coal, Mead says. The difference could be used to track bulb mercury in the environment.