Change search
ReferencesLink to record
Permanent link

Direct link
Distribution and Mobility of Arsenic in the Shallow Aquifers of Northeastern of La Pampa Province, Argentine.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

More than two million people in the Chaco-Pampean plain in central Argentina are affected by high As levels in groundwater. The concentrations of As are far exceeding the WHO standard limit for safe drinking water of 0.1 μg/L and the provisional Argentinean limit of 0.5 μg/L. The NE of La Pampa province is one of the areas affected with geogenic As in shallow aquifers within the Chaco-Pampean plain. These aquifers are in closed basins and they are only available water resource of the region for drinking and agriculture purposes. The Pampean aquifer is composed of a multi-layered system of Quaternary loess deposits covered by aeolian sands and also containing layers of rhyolitic volcanic ash, which is considered the primary source of As. Volcanic ash layers can be visible in the shallow sediments or intermixed in the loess. During the weathering of volcanic ash sediments As is dissolved to the aqueous phase and can be quickly adsorbed or co-precipitated on secondary Fe, Al and Mn oxy-hydroxides under favourable conditions. Also, previous more arid climatic conditions have led to the formation of carbonate "calcrete" layers in the top sequences of the loess and this has affected the geochemistry of the aquifer. Two sites were investigated in the NE of La Pampa province in order to assess (i) the quality of groundwater for drinking water use, (ii) the distribution of As and other trace elements in shallow aquifers and (iii) to understand better the factors controlling its mobility in groundwater. The results showed that groundwater was circum-neutral to alkaline and under moderate oxidizing conditions. The predominant groundwater composition was of Na-HCO3 for fresh water and Na-Cl-SO42- for brackish water types. High salinity levels are evidenced by the high Electrical Conductivity and might be explained by to the high evaporation rates. Groundwater sampled in both areas was enriched with As, F and other trace elements at different ranges of concentration. From the total As concentrations, arsenate As(V) predominated over arsenite As(III) species. Shallow groundwater is also enriched with fluoride exceeding the WHO standard limit of 1.5 mg/L and placed in the same As hotspots. One possible factor controlling the mobility of As is the high pH of groundwater, which is controlled by the carbonates equilibrium. Under this high pH conditions As is less strongly bind to Fe, Al and Mn oxy-hydroxides and can be easily mobilized to groundwater when other competing ions are getting adsorbed on the surface sites of binding minerals.

Place, publisher, year, edition, pages
, TRITA-LWR Degree Project, ISSN 1651-064X ; 2913:34
Keyword [en]
Arsenic, fluoride, shallow aquifer, La Pampa, loess sediments and volcanic ash
National Category
Civil Engineering
URN: urn:nbn:se:kth:diva-171820OAI: diva2:844643
Available from: 2015-09-21 Created: 2015-08-07 Last updated: 2015-09-21Bibliographically approved

Open Access in DiVA

fulltext(5223 kB)23 downloads
File information
File name FULLTEXT01.pdfFile size 5223 kBChecksum SHA-512
Type fulltextMimetype application/pdf

By organisation
Land and Water Resources Engineering (moved 20130630)
Civil Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 23 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 62 hits
ReferencesLink to record
Permanent link

Direct link