Appearance of an enigmatic Pb source in South America around 2000 BP: Anthropogenic vs natural origin

• Main Authors: Kamenov, George D., Escobar, Jaime, Arnold, T. Elliott, Pardo-Trujillo, Andrés, Gangoiti, Gotzon, Hoyos, Natalia, Curtis, Jason H., Bird, Broxton W., Velez, Maria Isabel, Vallejo, Felipe, Trejos-Tamayo, Raul
• Other Authors: Earth and Environmental Sciences, School of Science
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: Lead isotopes; Northern Andes; Metal pollution; Lead; Tundra
• Online Access: https://hdl.handle.net/1805/32458

Neotropical wetlands in the paramo (a unique alpine-tundra ecosystem) region of South America have the potential to be natural archives for metal pollution by modern and past populations. An organic-rich sediment core from the El Triunfo mire, located in the paramo region, provides a record of natural and anthropogenic metal sources in the Northern Andes during the last four millennia. The Triunfo record is complex, as the mire is located in the Northern Volcanic Zone (NVZ) and receives direct input of volcanic material. Regardless of the volcanic input, calculated metal enrichment factors normalized to Sc show metal enrichment in the Northern Andes around 2000 years ago and again in recent industrial times. A number of samples show a shift to lower Pb isotope ratios indicating the appearance of a new, enigmatic Pb source around 2000 years ago. The topmost layer of the core shows the lowest Pb isotope ratios, reflecting input of modern anthropogenic Pb. In contrast to Pb, Nd isotopes do not show significant variations along the entire core, indicating mostly volcanic material input to the mire. The decoupling between Nd and Pb isotopes indicates that the enigmatic Pb source must be anthropogenic in origin. Based on the dominant atmospheric currents in the region, the El Triunfo mire can receive input from long-distance and local sources. Dispersion simulations validate the possibility of pollutant particle transport from Europe to the northern hemisphere Neotropics. As the first metal enrichment coincides with the Roman Empire times, the El Triunfo Pb isotopes are compared to contemporary peat records from Europe. All records show similar decrease in the Pb isotope ratios due to anthropogenic Pb input. Small Pb isotope differences between a record from Spain and El Triunfo indicate that the enigmatic Pb that appeared around 2000 years ago in the mire is unlikely to have originated from long-distance Roman Empire pollution. Instead, a group of deposits, namely San Lucas, San Martin de Loba, and El Bagre, located ...