Environmental Records in Speleothems: Tracking Historical Heavy Metal Pollution from Mining and Metallurgy in the Peruvian Andes

Mining and metallurgy have a long history in the Peruvian Andes, dating back to pre-Incan times. Over centuries, these practices have resulted in significant environmental degradation, including the release of heavy metals that continue to affect ecosystems and human health today. Despite this legacy, little research has quantified the extent and environmental impact of early metallurgical activities. This study aims to trace historical metal pollution by analyzing heavy metal concentrations in speleothems and linking contamination spikes to metallurgical activities in the Peruvian Andes. A speleothem collected from Huagapo Cave, Peru (11°16'05.3"S 75°47'14.0"W), was analyzed using ICP-MS and laser ablation ICP-MS to determine metal concentrations of Pb, Cu, Mn, Zn, Ba, and Ni. Huagapo Cave is located near two prominent metallurgy centers: Cerro de Pasco and La Oroya. Peaks in metal concentrations above natural background levels within the speleothem would be a result of aerosol transport and deposition of metal emissions from local mines and smelters. Trace metal concentrations are compared with a combined age model, created using lamina counting and U-Th dating methods. Metal concentration peaks were cross-referenced with local lake sediment records, reinforcing the reliability of the findings and the validity of speleothems as proxies of anthropogenic metal contamination. The results of this study reveal significant increases and spikes in heavy metal concentrations within the speleothem that correlate with the timing of pre-Colonial to modern metallurgical activities in the Junín region of Peru. This study also demonstrates the potential of speleothems to be used as proxies for estimating the magnitude and extent of historic anthropogenic pollution, as the results provide precisely dated metal contamination that can be traced to local metallurgical activities. This research provides a deeper understanding of the environmental impact of pre-Colonial and modern metallurgical activities, using speleothem analysis to identify the enduring effects of historic pollution.