| 11. |
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| 12. |
- Gosman-Hedström, Gunilla, 1947, et al.
(författare)
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Teknik i vardagen
- 2009
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Ingår i: Livslots för seniorer. Redaktör Dahlin-Ivanoff S. - : Vårdalinstitutet. ; , s. 93-119
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 13. |
- Mendoza, J. A., et al.
(författare)
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Hydrogeological and hydrochemical features of an area polluted by heavy metals in central Nicaragua
- 2006
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 14:5, s. 777-784
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Tidskriftsartikel (refereegranskat)abstract
- Geophysical and hydrochemical surveys were used to investigate the hydrogeological conditions in one of the Rio Sucio microbasins, in central Nicaragua. Zones of vertical structures (i.e. fractures and quartz veins) and weathering were mapped using Continuous Vertical Electrical Soundings (CVES), as such zones are of major importance for groundwater transport. Water from the springs was analysed to determine concentrations of major ions and heavy metals. Low ion concentrations and 180 analyses indicate that the springs occur close to their recharge areas and there is a relatively rapid groundwater circulation. Mercury (Hg) content in the springs was low, while comparatively high amounts of lead (Pb) were found. The results presented here demonstrate the important function of weathering and tectonics in the occurrence of groundwater systems in the basin. Hg and Pb found in the springs' water reveal the existence of an increase in pollution sources disseminating in the area. More than 100 years of using mercury in the gold-mining industry and releasing wastes into rivers has affected water quality and ecosystems. Further investigations are needed in this area to determine the groundwater vulnerability to this pollution as this resource may be needed in the future.
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| 14. |
- Mendoza, J. A., et al.
(författare)
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Resistivity imaging in steep and weathered terrains
- 2008
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Ingår i: Near Surface Geophysics. - 1873-0604. ; 6:2, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- In areas where tectonics and weathering have hydrogeological significance, electrical methods can assist in mapping the subsurface. In this work, resistivity imaging was used to map fractures, faults and quartz veins emplaced in strongly weathered volcanic rocks. The aim was to map geological units related to the formation of groundwater systems in the Rio Artiguas basin, Nicaragua. Eight 2D resistivity surveys selected from two sites with characteristic geological features are discussed in this article. The resistivity lines were carried out with a multi-electrode system together with different electrode geometries. The data inversion was done by applying the robust (L-i-norm) method and a finite element grid to accommodate the steep topography. The data interpretation included numerical modelling to assess the suitability of all used electrode arrays in relation to the expected geological settings. The results indicated a top high resistive layer consisting of colluviums with laterite (>50 Omega m), underlain by conductive clay weathered layers (10-50 Omega m). Below the conductive layer less weathered or fresh rock can be found with higher values (50-600 Omega m). The quartz veins and dykes stand out as the highest resistive bodies (100-4000 Omega m). The results indicated an overall weathering thickness of 10-30 m or more. In conclusion, the extensive resistivity imaging surveys allowed delineation of geological structures and weathering layers throughout the study area. Furthermore, the vertical extension of weathering was examined at all locations. A finite element grid in the inversion prevented distortions arising from topography regardless of the steep slope observed at the survey locations. The numerical modelling results revealed the strengths of different arrays for the particular cases of a fault and a quartz vein in irregular terrains.
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| 15. |
- Ulusoy, Inan, et al.
(författare)
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Multisource geophysical investigation of the Acıgöl caldera structure (central Turkey): preliminary results
- 2009
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Ingår i: ; , s. 7746-7746
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Konferensbidrag (refereegranskat)abstract
- Neogene and Quaternary volcanic activity formed the large volume ignimbritic units (about 10 different units, namely Cappadocian ignimbritic field) around Nevşehir, Derinkuyu and Acıgöl districts. These large volume ignimbrites are mostly caldera-related products but the calderas are partially or totally buried by later pyroclastic and sedimentary cover. Source estimations for the caldera-related pyroclastics in Nevşehir plateau indicate that the calderas concentrate around Derinkuyu and Acıgöl plains. Geophysical methods (resistivity imaging, self-potential, TDEM and magnetic surveys) were applied around Acıgöl plain and Mt. Erdaş to reveal out the near-surface structural elements related to the Acıgöl caldera system. Additionally, remote sensing coupled with morphology was used. Preliminary results show that the Acıgöl caldera complex may have an elongated shape. Possible structural models for the caldera system/complex are explained. Future geophysical studies and a detailed study of the geological relationship between the caldera-related products are necessary to better understand the Acıgöl caldera system.
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