| 1. |
- Lebbad, Marianne, et al.
(författare)
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Dominance of Giardia assemblage B in León, Nicaragua.
- 2008
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Ingår i: Acta Tropica. - : Elsevier BV. - 0001-706X .- 1873-6254. ; 106:1, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- Giardiasis is a major problem in León, Nicaragua, yet despite this no data are available regarding the prevalence of different Giardia genotypes in this area. To address this question, a molecular analysis of Giardia isolates from humans and dogs living in the same area in León, Nicaragua was performed. Giardia isolates from 119 Nicaraguan patients and 8 dogs were successfully genotyped using single and/or nested beta-giardin PCR with subsequent restriction length fragment polymorphism (RFLP) analysis. The analyses of human samples yielded 94 (79%) assemblage B isolates and 25 (21%) assemblage A isolates. Only the non-human-associated assemblages C and D were found in the dog samples. Sixteen isolates with assemblage A pattern, 26 isolates with assemblage B pattern and all dog isolates were further characterized by sequencing the nested beta-giardin PCR product and by molecular analyses of the glutamate dehydrogenase (gdh) gene. Within the study area the assemblage A isolates were highly genetically homogenous, showing only sub-genotypes A2 (n=3) or A3 (n=13) at the beta-giardin locus and AII only at the gdh locus while assemblage B showed a high genetic polymorphism at both loci. Seven different sub-genotypes were identified within 13 of the sequenced assemblage B beta-giardin isolates. The remaining 13 sequenced assemblage B-isolates appeared to contain several different variants of the beta-giardin gene since the chromatograms displayed one to seven double peaks. The gdh sequences showed an even higher polymorphism since only 2 of 26 assemblage B isolates were without double peaks. Two mixed infections between assemblage A and B were found when the gdh gene was analyzed. Polymorphisms were also observed in the dog-associated assemblages C and D, but to a lesser extent than in assemblage B.
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| 2. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
- García, Indiana, et al.
(författare)
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Presence of trihalomethanes in drinking water plants in Nicaragua
- 2006
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Ingår i: Journal of Water Supply. - 0003-7214 .- 1365-2087. ; 55:3, s. 221-231
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Tidskriftsartikel (refereegranskat)abstract
- The impact of enhanced coagulation on the formation of trihalomethanes (THMS) from drinking water was studied in four treatment plants in Nicaragua. Enhanced and conventional coagulation techniques were compared with regard to the removal of natural organic matter (NOM), which was measured by surrogate paramametres. The enhanced coagulation process showed a better removal of NOM, and as a consequence the THM formation was up to 50% lower than with conventional coagulation. The influences of chlorine dosage, temperature, PH and contact time on the THM formation in water treated by enhanced and conventional coagulation were also studied.
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| 6. |
- Kern, Christoph, et al.
(författare)
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Halogen oxide measurements at Masaya Volcano, Nicaragua using active long path differential optical absorption spectroscopy
- 2009
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Ingår i: Bulletin of Volcanology. - 0258-8900 .- 1432-0819. ; 71, s. 659-670
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Tidskriftsartikel (refereegranskat)abstract
- Active Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) measurements of halogen oxides were conducted at Masaya Volcano, in Nicaragua from April 14 to 26, 2007. The active LP-DOAS system allowed night-time halogen measurements and reduced the ClO detection limit by an order of magnitude when compared to previous passive DOAS measurements, as wavelengths below 300 nm could be used for the DOAS retrievals. BrO was detected with an average BrO/SO2 molecular ratio of approximately 3 × 10−5 during the day. However, BrO values were below the detection limit of the instrument for all night-time measurements, a strong indication that BrO is not directly emitted, but rather the result of photochemical formation in the plume itself according to the autocatalytic “bromine explosion” mechanism. Despite the increased sensitivity, both ClO and OClO could not be detected. The achieved upper limits for the X/SO2 ratios were 5 × 10−3 and 7 × 10−6, respectively. A rough calculation suggests that ClO and OClO should be present at similar abundances in volcanic plumes. Since the DOAS technique is orders of magnitude more sensitive for OClO than for ClO, this indicates that OClO should always be detectable in plumes in which ClO is found. However, further LP-DOAS studies are needed to conclusively clarify the role of chlorine oxides in volcanic plumes.
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| 7. |
- García, Indiana, 1966-
(författare)
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Removal of natural organic matter by enhanced coagulation in Nicaragua
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The existence of trihalomethanes (THMs) in a drinking water plant of Nicaragua has been investigated in order to see whether the concentration exceeded the maximum contaminant level recommended by the environmental protection agency of the United States (USEPA) and the Nicaragua guidelines. The influence of pH, temperature, chlorine dose and contact time on the formation of THMs were studied. The contents of organic matter measured by surrogate parameters such as total organic carbon, dissolved organic carbon, ultraviolet absorbance and specific ultraviolet absorbance were also determined in order to show which type of organic matter is most reactive with chlorine to form THMs. Models developed by other researchers to predict the formation of trihalomethanes were tested to see whether they can be used to estimate the trihalomethane concentration. In addition, empirical models were development to predict the THM concentration of the drinking water plant analysed. The raw water was treated by conventional and enhanced coagulation and these processes were compared with regard to the removal of natural organic matter (NOM). The significance of the results was assessed using statistic procedures. The average concentration of THMs found at the facility is below the USEPA and Nicaragua guideline values. Nevertheless the maximum contaminant level set by USEPA is sometimes exceeded in the rainy season when the raw water is rich in humic substances. Comparison between the water treated by conventional and enhanced coagulation shows that enhanced coagulation considerably diminished the trihalomethane formation and the value after enhanced coagulation never exceeded the guidelines. This is because enhanced coagulation considerably decreases the organic matter due to the high coagulant dose applied. The study of the trihalomethane formation when varying pH, time, temperature and chlorine dose using water treated by conventional and enhanced coagulation showed that higher doses of chlorine, higher pH, higher temperature and a longer time increases the formation of THMs. However, combinations of two and three factors are the opposite. The predicted THM formation equations cannot be used for the water at this facility, since the results shown that the measured THM differs significantly from the THM concentration predicted. Two empirical models were developed from the data for enhanced coagulation, using linear and non-linear regression. These models were tested using the database obtained with conventional coagulation. The non-linear model was shown to be able to predict the formation of THMs in the Boaco drinking water plant.
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| 8. |
- Gonzalez-Rivas, B, et al.
(författare)
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Species composition, diversity and local uses of tropical dry deciduous and gallery forests in Nicaragua
- 2006
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Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 15:4, s. 1509-1527
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Tidskriftsartikel (refereegranskat)abstract
- The floristic composition and diversity of tropical dry deciduous and gallery forests were studied in Chacocente Wildlife Refuge, located on the Pacific coast in Nicaragua during 1994 and 2000. Density, dominance and frequency as well as species and family important values were computed to characterize the floristic composition. A variety of diversity measures were also calculated to examine heterogeneity in each forest community. A total of 29 families, 49 genera and 59 species were represented in 2 ha dry deciduous forest. In the gallery forest, the number of families, genera and species recorded in 2000 inventory was 33, 48 and 58, respectively and slightly higher than the 1994 inventory. The number of stems >= 10 cm dbh varied from 451 to 489 per hectare in the deciduous forest, and from 283 to 298 per hectare in the gallery forest. The basal area was much larger for species in the gallery than dry deciduous forest. Fabaceae, sub family Papilionoideae, was the most specious family in the deciduous forest while Meliaceae was the dominant family in the gallery forest. Similarity in species composition and abundance between deciduous and gallery forests was low. In terms of species diversity, the gallery forest was found more diverse than the deciduous forest using Fisher's diversity index. Both forest communities were characterized by a typical inverse J shape. Therefore, emphasis should be given to the protection of rare species, i.e. as the forests are still under continued human pressure, an immediate action should be taken to conserve the remaining flora.
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| 9. |
- Garca, I., et al.
(författare)
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Removal of natural organic matter by conventional and enhanced coagulation in Nicaragua
- 2007
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Ingår i: Water Resources Management IV. - : WIT Press. - 9781845640743 ; , s. 399-409
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Konferensbidrag (refereegranskat)abstract
- Enhanced coagulation was applied to raw water from a drinking water plant in Nicaragua through bench scale jar test in order to reduce the presence of natural organic matter (NOM) and decrease the trihalomethanes (THMs) formation which has been linked to carcinogenic diseases. Due to the lack of information about the presence of chlorination by-products (CBPs) like trihalomethanes, a study of their formation by varying pH, contact time, temperature and chlorine dose was also performed; following conventional or enhanced coagulation treatment. The results show that enhanced coagulation decreases considerably the formation of THMs because it reduces strongly the presence of organic matter due to the fact that higher alum doses were used in comparison with conventional coagulation utilized at the facility. The removal of dissolved organic carbon (DOC) was improved from 44 at the facility to 67 with enhanced coagulation. Trihalomethanes concentration increases drastically when extreme conditions of the four parameters evaluated were applied exceeding the maximum contaminant levels of USEPA (80 g/L) but not the Nicaraguan target value (460 g/L) for both coagulation types.
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| 10. |
- Lacayo-Romero, Martha, et al.
(författare)
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Degradation of toxaphene in aged and freshly contaminated soil
- 2006
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 63:4, s. 609-615
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Tidskriftsartikel (refereegranskat)abstract
- Degradation of toxaphene in soil from both newly contaminated (from Sweden) and aged spills (from Nicaragua) were studied. The newly contaminated soil contained approximately 11 mg kg(-1) toxaphene while the aged Nicaraguan soil contained approximately 100 mg kg(-1). Degradation was studied in anaerobic bioreactors, some of which were supplied with lactic acid and others with Triton X-114. In this study we found that the lower isomers Parlar 11, 12 were degraded while the concentration of isomer Parlar 15 increased. This supported an earlier evaluation which indicated that less chlorinated isomers are formed from more heavily isomers. Lactic acid when added to the soil, interfere with the degradation of toxaphene. Lactic acid was added; several isomers appeared to degrade rather slowly in newly contaminated Swedish soil. The Swedish soil, without any external carbon source, showed the slowest degradation rate of all the compounds studied. When Triton X-114 at 0.4 mM was added, the degradation rate of the compounds increased. This study illustrates that biodegradation of toxaphene is a complex process and several parameters have to be taken into consideration. Degradation of persistent pollutants in the environment using biotechnology is dependent on bioavailability, carbon sources and formation of metabolites.
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