T233 Arsenic in Geologic Systems I

Wednesday, 3 November 2010
8:00 AM - 12:00 PM
Room 612

EVALUATION OF SEDIMENT -WATER INTERACTIONS FOR THE MOBILITY OF NATURAL ARSENIC IN SOUTHERN POOPó BASIN, BOLIVIAN ALTIPLANO

Paper number: T233-8
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Abstract

Contamination of As and other heavy metals in Lake Poopó as a consequence of the adjacent mining industry, was first investigated in 1985 but more comprehensive studies were carried out 1993 to 1996 in the Proyecto Piloto Oruro (PPO). The PPO work was followed by a research project in 2000 to 2006, initiated by Universidad Major de San Andres (UMSA) in La Paz and the Lund University of Sweden, focusing on heavy metals in Lake Poopó and contributing rivers and the impact of the mining industry. Studies more focused on As occurrence and behavior were started in 2007 in a cooperation between UMSA and the Royal Institute of Technology (KTH), Sweden, through the SIDA research program SAREC. The project detected natural elevated levels of As in groundwater to the south of Lake Poopó, emphasizing the need for further studies of the geogenic arsenic in the area. The aims of the study are to find the possible sources of geogenic arsenic and to determine the factors controlling the high arsenic content in groundwater.

Groundwater used as drinking water in most of the localities show high levels of dissolved arsenic ranging from less than 10 μg/L to 207μg/L. (n=19). Almost all samples show high salinity the pH were circum neutral and the predominant water type is Na-Ca-Cl-HCO3. Two holes have been drilled using an auger instrument in two different localities and the sediments collected for laboratory analysis. Sequential extractions on the sediments were carried out showing the variations in sediment properties between the two drilling locations. Sediments in Condo K contain five times more As than the concentrations of Quillacas. Both locations have iron oxide present which correlates well with the As-concentrations. The amount of Fe is, however, about the same and the differences in As in the sediments need another explanation. Condo K is more distant to any surface water than Quillacas and the As in the sediments of Quillacas might therefore been flushed by the higher groundwater flow.