Heavy metals in South America aerosol during 20$\mathsf{^{th}}$ century from Illimani ice-core, Eastern Bolivian Andes

A 137 m ice-core drilled from Eastern Bolivian Andes at Nevado Illimani ($16^\circ37'$ S, $67^\circ46'$ W, 6350 m asl) allows studying historical concentrations of heavy metals in South America aerosol along the 20$^{\rm th}$ century. About 50 m of this ice-core were dated by multi-proxy analysis, providing a record of environmental variations of about 80 years from 1919 to 1999. Elemental concentrations for 45 chemical species (Li to U) in 744 samples along the upper 50 m ice-core section were determined by Inductively Coupled Plasma-Mass Spectrometry. This work focuses on heavy metal concentrations along the ice-core profile. Further discussion on other trace elements is given elsewhere [1]. Most elements like Al, Fe, La, Th and U show a pattern for concentration averages and standard deviations with little variation along 20$^{\rm th}$ century, evidencing their natural origin. Other heavy metals like: Pb, Mo, Zn, Cd, Ni, Co and Cu show increases in average concentrations and standard deviations from the beginning of 20$^{\rm th}$ century to recent years. For example, Cu average concentration values change from $0.604\pm0.440$ ng g$^{-1}$ to $3.46\pm3.02$ ng g$^{-1}$ along 20$^{\rm th}$ century. Time evolution of these elements concentrations' may be related to local economic growth and human activities in South America.