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- Ramos Ramos, Oswaldo Eduardo, 1966-
(författare)
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Geochemistry of Trace Elements in the Bolivian Altiplano : Effects of natural processes and anthropogenic activities
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The occurrence of As in groundwater in Argentina was known since 1917; however, the occurrence, distribution and mobilization of As and other trace elements (TEs) in groundwater in the Bolivian Altiplano are still quite unknown. An investigation applying a geochemical approach was conducted in the Poopó Basin and Lake Titicaca to understand processes of TEs in different systems such as water, soils, crops and sediments in mining areas.In Poopó Basin,As, Cd and Mn concentrations exceed World Health Organization (WHO) guidelines and Bolivian regulations for drinking water in different places around the basin, but Cu, Ni, Pb and Zn do not.In soils, the sequential extraction methods extracted up to 12% (fractions 1 and 2), which represent < 3.1 mg/kg of the total As content, as potentially mobilized fractions, that could be transferred to crops and/or dissolved in hydrologic system. The large pool of As can be attached due to amorphous and crystalline Fe oxide surfaces (fractions 3, 4, and 5) present in the soils.Furthermore, the concentrations of As, Cd and Pb in the edible part of the crops revealed that the concentrations of As and Cd do not exceed the international regulation (FAO, WHO, EC, Chilean) (0.50 mg/kgfw for As and 0.10 mg/kgfw for Cd), while Pb exceeds the international regulations for beans and potatoes (for beans 0.20 mg/kgfw and for potato 0.10 mg/kgfw).In the Lake Titicaca, principal component analysis (PCA) of TEs in sediments suggests that the Co-Ni-Cd association can be attributed to natural sources such as rock mineralization, while Cu-Fe-Mn come from effluents and mining activities, whereas Pb-Zn are mainly related to mining activities. The Risk Assessment Code (RAC) indicate “moderately to high risk” for mobilization of Cd, Co, Mn, Ni, Pb and Zn, while Cu and Fe indicate “low to moderate risk” for remobilization in the water column.
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| 2. |
- Sullivan, Alexis R., 1988-
(författare)
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A forest dark : an evolutionary history of Norway spruce
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded within the relationships among species is a dense forest of gene trees, each with a potentially unique and discordant history. Such widespread genealogical heterogeneity is expected, but embracing this hierarchy of discordance while reconstructing the histories of populations and species remains a major challenge.In this thesis, I studied the history of the genes and genomes contained within Norway spruce (Picea abies: Pinaceae), a forest tree distributed throughout boreal and montane Europe. I sequenced plastid genomes from all the commonly-recognized Picea species and developed a novel strategy to assemble the bacterial-sized mitochondrial genome of Norway spruce. Using multispecies coalescent network models, I reconstructed the relationships among populations of Norway spruce and the parapatric Siberian spruce (P. obovata) and distinguished between drift and hybridization as sources of phylogenetic discord.Norway spruce holds heterogenous histories at multiple levels of organization. Although organelle genomes are expected to be clonal and uniparentally inherited, the chloroplast genome held by Norway spruce originated after sexual recombination between two divergent lineages. In the mitochondrial genome, recombination creates a diverse population of genome arrangements subjected to drift and selection within individuals and populations. Genetic diversity among populations is shaped in nearly equal measure by divergence and hybridization. Norway spruce is discordance distilled.
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