Hydrochemical assessment with respect to arsenic and other trace elementsin the Lower Katari Basin, Bolivian Altiplano

• Hydrochemical investigations of groundwater and surface water were carried out to better understand the spatial distribution of As, major ions and trace elements.The study was carried out to evaluate the sources of dissolved species and elucidate the processes that govern the evolution of natural water in the Lower Katari Basin.The study area is close to the Titicaca Lake (Cohana Bay) formed by sediments of the Quaternary system, deposited in the fluvio-glacial to fluvio-lacustrineenvironment and geologic formations of the Devonian and Neogene system of volcanic origin. The study area has several environmental problems mainly caused bycontaminants such as heavy metals, nutrients, and bacteria. These problems are linked to the urban and industrial wastes, natural geologic conditions, and miningactivities carried out upstream of the Katari Basin, where rivers discharge into the Cohana Bay.A total of 37 water samples were collected during wet season, 31 groundwater samples including drinking water wells and six surface water samples. Thehierarchical cluster analysis and principal component analysis were applied to hydrochemical data. Results show high salinity in groundwater related to theevaporation causing serious problems for the groundwater quality and rendering it unsuitable for drinking. Dissolved As concentration ranges from 0.7 to 89.7 μg/L;the principal source of As could be the alteration of volcanic rocks, more than 48% of the shallow groundwater samples exceeded the WHO guideline value for As andmore than 22% for NO3-. Groundwater has neutral to slightly alkaline pH, and moderately oxidizing character. The groundwater chemistry reveals considerablevariability, ranging from Na-SO4,Cl type through mixed Na-HCO3 type and Ca,Na-HCO3,Cl type. The distribution of trace elements shows a large range of concentrations.Speciation of As indicates that the predominant oxidation state is As (V). The geochemical modelling indicates that As could be associated with ironoxides and hydroxides which are probably the most important mineral phases for the As adsorption. The spatial distribution and the variation of dissolved Asconcentration in groundwater is governed by the variability in geological characteristics of the region that raises a significant concern about drinking water quality.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

Nyckelord

Hydrochemistry; arsenic; trace elements; multivariate analysis; Lower Katari Basin

Bolivian Altiplano

Land and Water Resources Engineering

Mark- och vattenteknik

Publikations- och innehållstyp

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