Lead on to Antarctica!

Roman pipes, Queen Elizabeth I's white make-up, HEAVINESS...there are many things that might spring to mind when you think about lead. But would you associate this element with Antarctica? I certainly didn't. But apparently lead found its way to the southern-most continent even before we did (McConnell et al., 2014).

Lead had reached Antarctica before Captain Roald Amundsen and
Captain Robert Falcon Scott famously raced to the South Pole in 1911...
Source: www.thesundaytimes.co.uk; Universal History Archive/Getty

Just as mercury is transported to the Arctic from the northern mid-latitudes (see last week's post), lead is transported to Antarctica from lower latitudes in the southern hemisphere (McConnell et al., 2014). 

In a study published earlier this year, McConnell et al. examined 16 ice cores across Antarctica in order to construct a 410 year record of lead pollution in the region. By looking at "lead concentration, enrichment and deposition flux", the authors were able to conclude that lead pollution existed in Antarctica as early as 1889, and that it still persists today (McConnell et al., 2014). 

By 1900, lead concentrations had reached up to 5.4 pg/g (compared to ~0.6 pg/g and ~1.8 pg/g in 1650 and 1885, respectively); 21st Century concentrations are lower, but still somewhat greater than pre-industrial levels (McConnell et al., 2014). Hmm...perhaps a different type of statistic would be easier to conceptualise: the authors estimate that ~660 tonnes of lead have been deposited on the continent over the last 130 years - that's pretty striking (McConnell et al., 2014). Not only that, but they can actually work out exactly where it's come from. Ooh. Grab your deerstalker, it's time for some detective work...

I've somehow managed to work Sherlock Holmes
into the post - I for one didn't see that coming. But seriously,
using isotopic ratios to trace the source of pollutants is good
detective work. Source: www.sherlock-holmes.co.uk

Isotopic ratios can tell us a lot about the source of lead pollution. By measuring Pb-206/Pb-207 isotopic ratios over time in nine ice cores, McConnell et al. (2014) were able to attribute the early lead pollution to just one source: the Port Pirie smelter in Australia. This site, which processes the Australian Broken Hill lead and silver ores, could be traced owing to the characteristically low isotopic ratio signature of the ore (McConnell et al., 2014). Interesting. Furthermore, the removal of lead from petrol in many countries in the southern hemisphere by 1996 could also be identified by looking at the ratios (McConnell et al., 2014).

Of course, there's more to Antarctic pollution than lead, just as there's more to Arctic pollution than mercury. But I was interested to investigate whether industrial pollution could also reach the interior of this vast, remote continent from the mid-latitudes, and this recent research provides evidence that it can.