The bangs and fizzes of fireworks are rapidly replacing the chimes of Big Ben as the defining sound of New Year’s Eve celebrations in London, while around the world, city landmarks are becoming stages for increasingly spectacular pyrotechnic displays. Since the millennium, the popularity of fireworks has even extended into back gardens, where smaller fireworks or sparklers are lit up at the stroke of midnight.
Fireworks are great fun. We all enjoy guessing the colours of the rockets before they ignite in the sky, hearing the explosions echo off nearby buildings, or writing our names in light with hand sparklers.
But there is an environmental price to pay. Firework smoke is rich in tiny metal particles. These metals make firework colours, in much the same way as Victorian scientists identified chemicals by burning them in a Bunsen flame; blue from copper, red from strontium or lithium, and bright green or white from barium compounds.
There is more smoke from potassium and aluminium compounds, which are used to propel fireworks into the air. Perchlorates are also used as firework propellants; these are a family of very reactive chlorine and oxygen compounds, which were also used by NASA to boost space shuttles off the launch pad.