| 1. |
- Mendoza, J. A., et al.
(författare)
-
Assessment of groundwater vulnerability in the Rio Artiguas basin, Nicaragua
- 2006
-
Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 50:4, s. 569-580
-
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.
|
|
| 2. |
- Corriols, Marvin, et al.
(författare)
-
Geophysical characterization of the Leon-Chinandega aquifer, Nicaragua
- 2008
-
Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 16:2, s. 349-362
-
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.
|
|
| 3. |
- Mendoza, J. A., et al.
(författare)
-
Hydrogeological and hydrochemical features of an area polluted by heavy metals in central Nicaragua
- 2006
-
Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 14:5, s. 777-784
-
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.
|
|
| 4. |
- Mendoza, Jose Alfredo, et al.
(författare)
-
Aquifer interactions with a polluted mountain river of Nicaragua
- 2008
-
Ingår i: Hydrological Processes. - : Wiley. - 1099-1085 .- 0885-6087. ; 22:13, s. 2264-2273
-
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.
|
|
| 5. |
- Mendoza, Alfredo
(författare)
-
Groundwater occurrence and risk of pollution in a mountain watershed of Nicaragua
- 2006
-
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.
|
|
| 6. |
- Athanasiadou, Maria, et al.
(författare)
-
Polybrominated diphenyl ethers (PBDEs) and bioaccumulative hydroxylated PBDE metabolites in young humans from Managua, Nicaragua.
- 2008
-
Ingår i: Environ Health Perspect. - : Environmental Health Perspectives. - 0091-6765 .- 1552-9924. ; 116:3, s. 400-8
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Our aim was to investigate exposure to polybrominated diphenyl ethers (PBDEs) in a young urban population in a developing country, with focus on potentially highly exposed children working informally as scrap scavengers at a large municipal waste disposal site. We also set out to investigate whether hydroxylated metabolites, which not hitherto have been found retained in humans, could be detected. METHODS: We assessed PBDEs in pooled serum samples obtained in 2002 from children 11-15 years of age, working and sometimes also living at the municipal waste disposal site in Managua, and in nonworking urban children. The influence of fish consumption was evaluated in the children and in groups of women 15-44 years of age who differed markedly in their fish consumption. Hydroxylated PBDEs were assessed as their methoxylated derivates. The chemical analyses were performed by gas chromatography/mass spectrometry, using authentic reference substances. RESULTS: The children living and working at the waste disposal site showed very high levels of medium brominated diphenyl ethers. The levels observed in the referent children were comparable to contemporary observations in the United States. The exposure pattern was consistent with dust being the dominating source. The children with the highest PBDE levels also had the highest levels of hydroxylated metabolites. CONCLUSIONS: Unexpectedly, very high levels of PBDEs were found in children from an urban area in a developing country. Also, for the first time, hydroxylated PBDE metabolites were found to bioaccumulate in human serum.
|
|
| 7. |
- Cuadra, Steven
(författare)
-
Child labour and health hazards: chemical exposure and occupational injuries in Nicaraguan children working in a waste disposal site
- 2005
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- About 600 children and teenagers work at Managua's landfill, the largest in Nicaragua. They collect and sort waste at the open dump, which covers an area of 7 km2 on the outskirts of the city on the shores of Lake Managua. Such work, which occurs in many large cities in developing countries, is considered to be one of the riskiest types of child labor that exists. Nevertheless, knowledge of such work and its risks is lacking.We investigated chemical exposure and risk of injury among 103 child laborers aged 6 to 15 years from Managua's landfill. Almost half of the children also lived in the dump area itself, while the rest lived in a nearby area, Acahualinca. For comparison, 102 children from Acahualinca and 34 children from central Managua, 10 km away, who did not work at the dump, were also studied. This provided the opportunity to also study the environmental exposure from the landfill. The children were interviewed about living conditions, working conditions, and all injuries that occurred at workplaces, at school, and at home during the last 12 months. They had to provide blood samples for examination of the levels of, among other things, heavy metals such as lead, mercury, and cadmium, and persistent organic environmental toxins such as pesticides and PCBs. We also investigated the levels of a relatively new organic environmental poison, the brominated flame retardant PBDE. At a later stage, soil samples were also collected from the landfill area and from Acahualinca for investigation of metal content.The children who worked at the landfill had higher levels of lead, mercury, and cadmium than the children in the comparison groups. One-third had blood lead levels higher than 100 μg/l, a level where measures to reduce exposure are clearly recommended. We also found that the children in the nearby residential area had higher lead levels than the children from central Managua. Although mercury levels were higher among the child workers, the levels were not such that they could be considered a present and clear health risk. Consumption of fish from Lake Managua only slightly affected mercury levels. The levels of several of the organic environmental toxins, especially PCBs, were also higher among the child workers than in the comparison groups. We know that PCBs, which have long been banned in the West, are still used in Central America, or stored in uncontrolled forms. The children in the comparison groups also had clearly higher levels of a breakdown product of the pesticide DDT and of PCBs than children in the USA and Western Europe. The levels of these substances are steadily decreasing in the Western world. There is extremely limited knowledge of how the development over time looks like in Central and Latin America because too few surveys have been carried out. Unexpectedly, we found extremely high levels of PBDEs among the children living and working at the dump, higher than previously reported. The children in the comparison groups also had unexpectedly high levels of these substances. This is the first investigation of human PBDE levels in Central and Latin America, and the findings clearly show that it is extremely important to study the spread of the new environmental toxins also in non-industrialized countries and among particularly vulnerable groups. Several of the different substances that we studied are toxic to reproduction, and they can negatively affect human reproduction and fetal development. It would therefore have been desirable to be able to make a balanced risk assessment, but this is not possible because there is a lack of knowledge about the synergistic effects of the substances, and especially about how other factors such as inadequate nutrition can further affect the risk picture. What is clear, however, is that the levels we found among the children are significant from a reproductive perspective, as many of the girls we surveyed will be mothers in a few years - a fifth of Managua's teenagers are pregnant or have given birth already.Injuries, which caused at least one day of absence from school or work, were seven times more common among the children working at the dump than among the children in the comparison groups. The vast majority of injuries occurred during work, corresponding to 2.2 injuries per 1000 working days. The children reported that approximately one in ten injuries had resulted in permanent disability or pain. We analyzed the injuries that occurred to clarify whether there were any clear injury patterns. Cuts and puncture wounds to the hands and feet in connection with material handling were most common and caused 70% of the injuries. This shows that simple protective measures – many children lack shoes and no one has gloves – could reduce the risk of injury. However, the most serious damage was caused by the vehicles at the dump.In our studies, we have wanted to measure exposure levels and quantify risks in order to clarify the situation of child workers, in the hope that increased knowledge and awareness can eventually contribute to change. We have also gained valuable knowledge about the levels of several common environmental toxins among ordinary poor city children in a developing country. This is something that has so far been too inadequately investigated.
|
|
| 8. |
|
|
| 9. |
- Corriols, Marvin, et al.
(författare)
-
Aquifer investigations in the Leon-Chinandega plains, Nicaragua, using electromagnetic and electrical methods
- 2009
-
Ingår i: Near Surface Geophysics. - 1873-0604. ; 7:5-6, s. 413-425
-
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.
|
|
| 10. |
|
|
