Lead pollution resulting from Roman gold extraction in northwestern Spain

Abstract

Roman mining and metallurgy left a detectable signal of lead pollution throughout Europe, northern Africa, and the Middle East. Las Médulas, in Northwestern Iberia, was the largest Roman gold mine and fundamentally altered the local landscape. To document the environmental consequences of this activity, we present a 4000-year record of lake sediment geochemistry from Laguna Roya, 35 km south of Las Médulas. Using the concentrations of trace metals weakly bound to sediment including lead, antimony, bismuth, and arsenic, we find increased levels of these metals from 300 BC to AD 120, during the Roman Republic/Empire. We attribute these increases to the atmospheric deposition of heavy metals arising from the regional extraction, processing, and/or smelting of gold ores. Lead pollution at the peak of this activity (15 BC) is twice as high as modern-day concentrations, suggesting that the amount of pollution generated by pre-Industrial civilizations and the associated environmental impacts are much larger than previously estimated. We find additional increases in antimony and bismuth from AD 1500 to 1700, possibly associated with post-medieval mining activity. Concentrations of lead begin to increase again ~AD 1860 during the start of the Industrial Revolution and reach a peak in AD 1990. Declining modern-day levels of lead can be attributed to the phase out of leaded gasoline. This is one of only a handful of studies to document pre-industrial pollution levels substantially higher than present-day, adding to a growing body of evidence that anthropogenic environmental degradation has been taking place for several thousands of years.

First human impacts and responses of aquatic systems: A review of palaeolimnological records from around the world

“…Hamilton et al, 2015). One notable exception is the Pb concentration in Laguna Roya (NW Iberia, close to Las Médulas, the largest Roman gold mine), where the concentration during Iberian-Roman times (c. 2300 b2k to 120 ce) was of similar magnitude or even higher than during industrial times (Hillman et al, 2017). Another example of very high levels of metals archived in lake sediments was observed in Diss Mere, UK.…”

“…Almost simultaneously, an 'ancient period of atmospheric lead (Pb) pollution' was detected in multiple Swedish lakes (Renberg et al, 2000). Early mining impacts associated with Roman activities (2100-1800 b2k) were found throughout Europe as both an increase in heavy metal atmospheric deposition and run-off (Guyard et al, 2007;Renberg et al, 2001), although the impact on the aquatic systems remains unclear (Camarero et al, 1998(Camarero et al, , 2017Hillman et al, 2017). The processing of fibres, especially hemp retting, on the other hand, had clear impacts on some aquatic systems, even though only nutrients (i.e.…”

Appraising the cohesion of palaeoenvironmental reconstructions in north-west Spain since the mid-Holocene from a high temporal resolution multi-proxy peat record

“…3200–2000 cal. BP (Hillman et al, 2017; Martínez-Cortizas et al, 2005; Silva-Sánchez et al, 2014). In Pena de Cadela, the start of this deforestation induced erosion appears at 2800 and lasts until 2270 cal.…”

“…The phase coincides with the Roman occupation of Galicia starting at 19 BC and the later invasion by Germanic tribes. In Galicia and elsewhere, lead pollution associated with mining activities peak during this period (Hillman et al, 2017; López-Merino et al, 2014; Martínez-Cortizas et al, 2002, 2013; Pontevedra-Pombal et al, 2013). Even so, the sediments show less mineral input than during the last phase.…”

Paleolimnological characterization of metal(loid) sources and transport processes in Canadian subarctic lakes

“…Most metal(loid)s are essential micronutrients for life in trace amounts but toxic at higher doses. The anthropogenic release of metals from mines, smelters, refineries, fossil fuel burning and other industrial activities has disturbed the natural cycling of metal(loid)s at the earth's surface during the last few centuries (Brännvall et al, 1999;2001;Cooke et al, 2009;Hillman et al, 2017;Uglietti et al, 2015;Weiss et al, 1997). Thirteen metal(loid) elements commonly released by modern anthropogenic sources are listed by the USEPA (2014) as priority pollutants to survey, including antimony (Sb), arsenic (As), berylium (Be), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), selenium (Se), silver (Ag), tellurium (Tl), and zinc (Zn).…”