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Hydrogeochemistry and spatial variability of arsenic and other trace elements in the Lower Katari Basin around Lake Titicaca, Bolivian Altiplano.

Impact on drinking water quality and groundwater management.

Time: Thu 2020-06-11 13.00

Location: Via Zoom --, Du som saknar dator/datorvana kan kontaka eller / Use the e-mail address if you need technical assistance, Stockholm (English)

Subject area: Land and Water Resources Engineering

Doctoral student: Israel Quino Lima , Vatten- och miljöteknik, Universidad Mayor de San Andres, KTH-International Groundwater Arsenic Research Group

Opponent: Professor Jerker Jarsjö, Department of Physical Geography, Stockholm University

Supervisor: Professor Prosun Bhattacharya, Vatten- och miljöteknik

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Arsenic (As) contamination in drinking water is a world-wide problem. Thenatural origin of As, its mobility and transport are of great interest in BolivianAltiplano (Lower Katari Basin: LKB and Sothern Poopó Basin: SPB) due topresence of mineral ore deposits, brines, hot springs and volcanic rocks.Hydrogeochemical spatio-temporal and spatial variability investigations wereapplied to groundwater, surface water and sediments with a statistical approachto better understand the spatial distribution of As, major ions and trace elements,and evaluate the sources of dissolved species and elucidate the processes thatgovern the evolution of natural water in the LKB. The result reveal high levelsof As, boron (B), antimony (Sb), manganese (Mn) and salinity in shallow wells,which exceeds the guideline values of the Bolivian regulation (NB-512) andWorld Health Organization (WHO). The seasonal variation and its impact onthe water quantity, on top of the solids and liquid residual (origin Pallina River)poses significant negative health risk for the community at the banks of theKatari River. The first evaluation of the hydrogeological study indicates that thegroundwater flow was observed in the direction southeast - northwest (SE -NW), and there is an interaction between groundwater and surface water. Thespatial distribution of As varies considerably due to geological characteristics ofthe area as well as due to the heterogeneously distributed evaporites in thesediments (in LKB and SPB). However, the highest concentrations of As arefound in the alluvial sediments of the northern region. Sequential extraction ofsediment along with geochemical modeling (mineral saturation indices) indicatesthat the iron (Fe) and aluminum (Al) oxides as well as their hydroxides are mostimportant adsorbent minerals of As in central and southern region of LKB. Thechemistry of water bodies in LKB and SPB is strongly influenced by theinteraction with the sediment constituents and by the spatial-temporal variations.The results of spatial analysis indicate that despite of the outliers there is a goodautocorrelation for As, B and Sb, since Moran's I values are positive. The globalspatial dependence analysis indicated a positive and statistically significant spatialautocorrelation (SA) for all cases and TEs are not randomly distributed at 99%confidence level.