Análisis del contenido de arsénico en los depósitos terciarios y cuaternarios de la llanura pampeana: factores litogénicos que determinan su concentración en las aguas subterráneas

Content Provider	Semantic Scholar
Author	Sosa, Numa N.
Copyright Year	2018
Abstract	Sosa, 2018 Tesis Doctoral (U.N.L.P.) In the Claromecó fluvial basin, facies and architectural analyses of the sedimentary successions were conducted based on the two main geomorphological units identified. The hills and plain unit, which constitute the bedrock of the fluvial basin, is composed of loess and fluvial sediments (sheet flows and channels) that are capped by a calcic paleosol. These deposits were assigned to the late Miocene-middle/late Pliocene subcycle. The valley unit consists of sediments assigned to the late Pleistocene-Holocene subcycle, and is composed of fluvial sediments (channels and floodplain) with hydromorphic paleosols superimposed, marshy sediments, and loess mantles which represent the parental material of the present day soils. The sediments are mainly composed of coarse silts and subordinated fine silts and clays. Very fine and fine sand are associated to channel deposits. Mineralogy is relatively homogeneous with some variations through the sedimentary successions. It comprises quartz, volcanic glass shards, plagioclase, feldspar, amphiboles, pyroxenes, with minor amounts of magnetite, Fe (Mn, Al) oxi-hydroxides (e.g. hematite, goethite, ferrihydrite), biotite, garnet and fluorite. Clay minerals include interstratified illite/smectite, smectite, illite, and very low proportions of zeolite (clinoptilolite-heulandite), kaolinite and chlorite. Enrichment in volcanic glass shards and in the alterations products (zeolite and low crystallinity smectite) is present in the late Pleistocene-Holocene deposits, particularly in the hydromorphic paleosol with increased amounts of Fe amorphous and crystalline oxides. The morphological and compositional analyses of volcanic glass shards point out the presence of particles adhered to the glass surface. The chemical composition of these particles reflects a zeolite composition (clinoptilolite-heulandite group). Arsenic concentrations vary according to the sedimentary environments and the age of deposits. In this sense, low As concentrations are found in Mio-Pliocene sediments with As mean concentrations above 10 mg kg. The late Pleistocene-Holocene sediments presents higher As concentrations, exceeding 10 mg kg. The highest values are located in the hydromorphic paleosols (22.6 mg kg) and in the B horizons of the present day soils (26.0 mg kg). There, As is mostly associated to Fe crystalline oxides (e.g. magnetite, titanomagnetite), Fe amorphous oxi-hydroxides (e.g. hematite, goethite, maghemita) and residual phases (e.g. volcanic glass shards, silicates, organic matter). The distribution of As concentrations in the Claromecó fluvial basin increase uniformly from the upper basin to the lower basin with localized heterogeneities in the middle basin.
File Format	PDF HTM / HTML
DOI	10.35537/10915/67281
Alternate Webpage(s)	http://sedici.unlp.edu.ar/bitstream/handle/10915/67281/Documento_completo.%20SOSA_2018.pdf-PDFA.pdf?isAllowed=y&sequence=1
Alternate Webpage(s)	https://doi.org/10.35537/10915%2F67281
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article