Date of Award

6-2012

Document Type

Open Access

Degree Name

Bachelor of Arts

Department

Geology

First Advisor

Donald Rodbell

Second Advisor

Daniel Mosquera

Language

English

Keywords

sediment, contamination, metal concentrations, geology, rivers, lakes

Abstract

Lake Junín covers 530-km2 and is located at 4,430-m in an intermontane basin between the eastern and western cordillera of the central Peruvian Andes. The lake sits between the large sulfide mining districts of La Oroya and Cerro de Pasco. Designated a National Reserve in 1974, Lake Junín drains northward to the Río San Juan, which joins the Río Mantaro within several kilometers of the lake. Dam construction by the Cerro de Pasco Copper Corporation on the Río Mantaro in 1932 caused the Río San Juan, the principal river draining Cerro de Pasco, to back up into the lake. Using an ICP-MS, this report documents the contamination of Lake Junín with Co, Cu, Zn, Pb, Fe, and Mn; constrains the timing of the heavy metal pollution by correlating the δ18O record of a Lake Junín Core with a core from nearby Lake Pumacocha; and quantifies the contribution of heavy metals delivered via surficial runoff by comparing metal concentrations in Lake Junín sediments with those of Lake Pumacocha, which receives heavy metals only through atmospheric deposition and airfall. We analyzed six sediment cores, and the results reveal dramatic peaks in most metal concentrations at depths ranging from 10-55 cm below the sediment surface. Comparison of the sediment record from Lake Junín with Lake Pumacocha indicates that metal laden sediment transported into Lake Junín from the Río San Juan has formed a deposit with concentrations at least one order of magnitude greater than lakes that received only atmospherically transported metals.

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