| 1. |
- Mendoza, J. A., et al.
(författare)
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Assessment of groundwater vulnerability in the Rio Artiguas basin, Nicaragua
- 2006
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Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 50:4, s. 569-580
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Tidskriftsartikel (refereegranskat)abstract
- The Rio Artiguas basin in central Nicaragua shows a distinctive case of environmental deterioration due to anthropogenic activities. Heavy metals used in gold mining and other wastes are continuously released into the rivers, representing a threat to the water quality. This article aims to evaluate the groundwater intrinsic vulnerability in the Rio Artiguas basin and to provide information for sustainable use of water resources. The DRASTIC and GOD methods were used to analyse the relative pollution potential within the basin. DRASTIC was modified to include the degree of influence that geological structures have on the vulnerability. Moderate vulnerability areas cover most of the basin along stream valleys and lowlands, increasing downstream in the basin. The resulting vulnerability maps show that the limited groundwater resources are susceptible to surface water pollution as high vulnerability areas converge along the river valleys.
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| 2. |
- Corriols, Marvin, et al.
(författare)
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Geophysical characterization of the Leon-Chinandega aquifer, Nicaragua
- 2008
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 16:2, s. 349-362
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Tidskriftsartikel (refereegranskat)abstract
- Electrical geophysical surveys in the mode of vertical electrical soundings (VES) and continuous vertical electrical soundings (CVES) were conducted in the Leon-Chinandega plains, northwestern Nicaragua, in order to obtain detailed information about the geometry of the different hydrogeological layers in the aquifer and depth to the basement. A total of 51 VES were carried out within the plains. The results show a complex structure towards the north east of the area, and the southwestern part of the plains presents a smoother stratification. The geoelectrical measurements and borehole information indicate that the basement topography is characterized by hills and deep valleys with highly variable basement depths. Fifty CVES where done in a smaller area in the center of the plain. The resistivity data yielded considerable information revealing the existence of two main geo-electrical units. The combined interpretation of geological and geophysical data shows an environment typical of sedimentary volcanic coastal plains. The information collected during this investigation provides valuable data for estimating the fresh-water resources of the Leon-Chinandega aquifer system and for development of a groundwater management plan.
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| 3. |
- 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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| 4. |
- Mendoza, Jose Alfredo, et al.
(författare)
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Aquifer interactions with a polluted mountain river of Nicaragua
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 1099-1085 .- 0885-6087. ; 22:13, s. 2264-2273
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between a stream and nearby shallow aquifers were investigated in a mountain basin being polluted by mercury released during mining in central Nicaragua. Hourly data series of water levels and temperatures were analysed using cross-correlation. Resistivity imaging was used to map the subsurface and to complement the hydrological data interpretation. The results show the complex hydrogeological conditions that characterize the region, with weathering and fractured rock as main contributors to groundwater transport. The resistivity images suggest the presence of two vertical dykes perpendicular to the stream, and zones rich in clay. The data series indicate a rapid response from the aquifers to recharge events, followed by immediate discharge on a yearly basis. Furthermore, alternating periods of stream infiltration and aquifer discharge were identified. This work demonstrates that surface water pollution is a threat to groundwater quality in the area.
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| 5. |
- Mendoza, Alfredo
(författare)
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Groundwater occurrence and risk of pollution in a mountain watershed of Nicaragua
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogeological and geophysical methods were applied in the Río Artiguas watershed, a mountain basin located in central Nicaragua. This area is under environmental stress from anthropogenic activities like gold mining using mercury and waste disposal into the streams. The aim of this work was to characterise the hydrogeological conditions in the basin with emphasis on understanding the possible connections between streams and groundwater. It was also important to evaluate the vulnerability and risk of groundwater pollution. Hydrogeological mapping, resistivity imaging, hydrological measurements and hydrochemical surveys were combined to meet the aims of the work. The hydrogeological characterisation permitted identification of a) recharge areas, b) geological units that contribute to the formation of the groundwater system and c) a mechanism of discharge through springs and streams. The geophysical surveys allowed mapping the extension of weathering and tectonic features with hydrogeological significance, e.g. faults, dykes and fractures. A total of 99 perennial springs were documented and classified according to their mechanism of formation. Isotopic data indicate that the recharge occurs very close to the sites where the springs are formed. This is also supported by the relatively low ion concentrations found in the water of the springs. The weathering layers together with fractures and dykes form shallow aquifers that commonly discharge in a spring or along the streams. The high precipitation regime is an immediate source of water to the system, and in conjunction with the geology and steep topography it generates a constant and rapid circulation of water from recharge areas to discharge zones. The natural implication of this hydrogeological framework is that the formation of large or regional flows is not evident at the current state of knowledge. The same factors that influence groundwater occurrence are to some extent responsible for the degree of groundwater vulnerability to pollution. The vulnerable areas are situated along the steep valleys of the basin, where the interactions between subsurface and surface water can facilitate the spreading of pollutants. Since the pollution sources are located near the streams the risk of groundwater pollution is concentrated there. The pollutants disposed into the streams are rapidly removed by the river flow, which has a high contribution from precipitation. The pollutants are then transported far away from the sources. The urgent need to end the pollution of Río Artiguas is obvious. The tools to prevent further deterioration are not only to be found in the hydro geosciences and mining technology sphere, but they are also located in the socio?political arena. In this respect, the research presented in this thesis will gain importance as it reaches and informs local decision makers about the vulnerability and risks of pollution that the current anthropogenic activities represent for the groundwater resources.
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| 6. |
- Korsak, Larisa, et al.
(författare)
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Alternatives of Sludge Use in Nicaragua
- 2005
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Ingår i: Proceedings of the 27th Annual HWEA Conference "New Technical Knowledge for Clean Water".
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Korsak, Larisa, et al.
(författare)
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Evaluation of anaerobic sludge activity in wastewater treatment plants in Nicaragua
- 2006
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Ingår i: Water Pollution VIII. - 184564042X ; , s. 571-579
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Konferensbidrag (refereegranskat)abstract
- Sludge of three municipal anaerobic wastewater treatment plants was evaluated. This study was initiated due to the low activity observed in the anaerobic wastewater treatment plants in Nicaragua. An additional goal to select one of them, if possible, as an inoculum for the brewery treatment plant was proposed. Two of these plants work with an Imhoff tank and one with a Septic tank followed by an anaerobic upflow filter. The study consisted in the characterization of biomass in terms of Specific Methanogenic Activity (SMA), Volatile Suspended Solids (VSS), density, pH, and redox potential (RP). The treated waters were also analysed for nutrients, heavy metals and the organic load. The substrate used in the experiments for determining the methanogenic activity was acetic acid. NaHCO3 was added to maintain pH in the normal range of operation. The tests were carried out at a sludge load of 1.5 g VSS/l. The results indicate that treated wastewater does not have any impediment to proper development of microorganisms; no presence of toxic substances and enough essential nutrients were detected. The specific methanogenic activity of sludge (SMA) in the Imhoff tanks is relatively close and oscillates between 0.16-0.28 g CH4-COD/g VSS/day, and in the septic tank is 0.09 g CH4-COD/g VSS/day. These values agree with the methanogenic activity found in the literature for septic tanks (0.02-0.1 g CH4-COD/gVSS/day). The highest methanogenic activity measured during the test was 0.28g CH4-COD/g VSS/day in the sludge of the Imhoff tank in The Viejo city, so this sludge could be proposed as a seed for the brewery treatment plant.
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| 8. |
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| 9. |
- Lacayo, Martha, et al.
(författare)
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A toxaphene-degrading bacterium related to Enterobacter cloacae, strain D1 isolated from aged contaminated soil in Nicaragua
- 2005
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Ingår i: Systematic and Applied Microbiology. - : Elsevier BV. - 0723-2020 .- 1618-0984. ; 28:7, s. 632-639
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Tidskriftsartikel (refereegranskat)abstract
- Enterobacter sp. strain D1 is a facultative anaerobic, Gram-negative heterotrophic bacterium isolated from toxaphene-contaminated soil. This organism was identified and characterized through phylogenetic and taxonomic studies. Based on 16S rDNA analysis, the strain D1 was clustered closely with the species Enterobacter cloacae subsp. dissolvens (LMG 2683) and E. cloacae (ATCC 13047T). Strain D1 resembled these E. cloacae strains with respect to various biochemical and nutritional characteristics, but also exhibited differences. Moreover, strain D1 is able to grow and survive with toxaphene supplied in the medium in the range 3-96 mg/L. Amongst the chemical components of toxaphene, octachlorocamphenes, nonachlorobornanes and decachlorobornanes were seen to be rapidly metabolized, although levels of hexachlorocamphenes and heptachlorobornanes were found to be slowly degraded, and subsequently accumulated during the last stage of the cultivation.
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| 10. |
- Corriols, Marvin, et al.
(författare)
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Aquifer investigations in the Leon-Chinandega plains, Nicaragua, using electromagnetic and electrical methods
- 2009
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Ingår i: Near Surface Geophysics. - 1873-0604. ; 7:5-6, s. 413-425
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Tidskriftsartikel (refereegranskat)abstract
- The Leon-Chinandega plains are located in the north-western part of Nicaragua and represent the most important groundwater reservoir of the country. The aquifer is comprised of three hydrogeological units. The top unit is an unconfined alluvial and below a more consolidated volcanic aquifer is found. These aquifers rest on an ignimbrite unit that acts as the basement of the aquifer. The plains are mainly used for agricultural purposes and most of the irrigation comes from upper aquifer wells (not deeper than 70 m) allocated within the shallow unconfined aquifer. Transient electromagnetic soundings (TEM) and continuous vertical electrical soundings (CVES) were carried out in order to obtain information regarding the geology of the study area. Two TEM profiles extending from the Pacific coast towards the volcanic chain were carried out with an approximate separation between soundings of 250 metres. A grid of TEM soundings was also performed in an area located between the towns of Posoltega and Quezalguaque. CVES were carried out in different areas of the plains in order to obtain detailed information on the geology and distribution of the shallow aquifer. This information was later correlated with information available from wells in the area. One of the objectives of this investigation was to test and evaluate the applicability of the TEMfast48 equipment in the study area. In the plains area the TEM method shows very good results where a general geophysical model of mostly a three-layered earth can be obtained. In the coastal areas the models are more irregular and complex. The results from the CVES generally agree with the TEM models but present more details, especially in areas of complex geology. The penetration depth for the TEM soundings reached almost 100 m at most, depending on the depth to a low resistivity layer. In some areas the depth to the basement was estimated with long-layout CVES. In general, it was possible to obtain consistent geoelectrical models of the area and the methods complement each other well. The geoelectrical models are an excellent addition to other investigation methods as they provide an overview of the aquifer system and can serve as a basis for refining the conceptual and numerical models of the aquifer system. This information is expected to become very valuable for the exploration, management and protection of the groundwater resources in the Leon-Chinandega plains to ensure sustainability of the resource.
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