Widespread pollution of the South American atmosphere predates the industrial revolution by 240 y

Chiara Uglietti; Paolo Gabrielli; Colin A. Cooke; Paul Vallelonga; Lonnie G. Thompson

doi:10.1073/pnas.1421119112

Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved January 13, 2015 (received for review November 14, 2014)

Significance

An exceptionally detailed ice core from the high-altitude location of Quelccaya (Peru) contains compelling evidence that the well-known metallurgic activities performed during the Inca Empire (A.D. 1438−1532) had a negligible impact on the South American atmosphere. In contrast, atmospheric emissions of a variety of toxic trace elements in South America started to have a widespread environmental impact around A.D. 1540, ∼240 y before the industrial revolution when colonial metallurgy began to pollute the Andean atmosphere. 20th century atmospheric pollution levels were the highest on record and remain unprecedented over the entirety of human history.

Abstract

In the Southern Hemisphere, evidence for preindustrial atmospheric pollution is restricted to a few geological archives of low temporal resolution that record trace element deposition originating from past mining and metallurgical operations in South America. Therefore, the timing and the spatial impact of these activities on the past atmosphere remain poorly constrained. Here we present an annually resolved ice core record (A.D. 793–1989) from the high-altitude drilling site of Quelccaya (Peru) that archives preindustrial and industrial variations in trace elements. During the precolonial period (i.e., pre-A.D. 1532), the deposition of trace elements was mainly dominated by the fallout of aeolian dust and of ash from occasional volcanic eruptions, indicating that metallurgic production during the Inca Empire (A.D. 1438−1532) had a negligible impact on the South American atmosphere. In contrast, a widespread anthropogenic signal is evident after around A.D. 1540, which corresponds with the beginning of colonial mining and metallurgy in Peru and Bolivia, ∼240 y before the Industrial Revolution. This shift was due to a major technological transition for silver extraction in South America (A.D. 1572), from lead-based smelting to mercury amalgamation, which precipitated a massive increase in mining activities. However, deposition of toxic trace metals during the Colonial era was still several factors lower than 20th century pollution that was unprecedented over the entirety of human history.

Footnotes

↵¹Present address: Laboratory of Radiochemistry and Environmental Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland.
↵²To whom correspondence should be addressed. Email: gabrielli.1{at}osu.edu.
↵³Present address: Alberta Environmental Monitoring, Evaluation and Reporting Agency, Edmonton, AB T6B 2X3, Canada.

Author contributions: P.G., C.A.C., and L.G.T. designed research; C.U. and P.G. performed research; C.U. and P.G. analyzed data; P.G., C.A.C., and P.V. wrote the paper; and L.G.T. planned the field operation and contributed to drill and date the Quelccaya North Dome ice core.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The data presented in this work will be archived at the National Oceanic and Atmospheric Administration World Data Center-A for Paleoclimatology: ncdc.noaa.gov/paleo/study/17418.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1421119112/-/DCSupplemental.