Abstract

Mining in the Bolivian Altiplano is important and has historically provided much of the world's Ag, Sn, and Sb. This study aims to better understand the effects of important recent increases in Bolivian mining on the deposition of metals and metalloids in sediment near Oruro, Bolivia's fifth largest city, with special attention to natural and anthropogenic factors as well as early diagenesis, which could have broader implications in other high-elevation environments that have or will be affected by increased mining activities. To better assess the depositional trends of elements in sediments, five sedimentary cores collected in Lake Uru Uru and the Cala Cala Lagoon (nearby Oruro) were studied and analysis of the physicochemical variables coupled with radiometric dating indicate that (a) sediment deposited in Lake Uru Uru was likely sourced from local outcrops of Tertiary volcanics, Paleozoic shales, and ore and waste piles from mining activities material; (b) sedimentation rates in Lake Uru Uru were close to 3 mm center dot year(-1), 1 mm higher than the ancient Tauca paleolake (similar to 11,000-30,000 years ago); (c) early diagenetic effects have affected the distribution of Mn, As, and Cd in the sedimentary archive; and (d) the deposition of Ag, Sb, and Pb in the studied sediment has largely been related to historical trends in Bolivian Sn mining methods and production.