RESUMEN

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO4-Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ18 O and δ2H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99 °C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating.

Asunto(s)

RESUMEN

Porous sandstone geothermal water is an important geothermal resource, which is a low-carbon and clean resource, but lacks systematic research on a regional scale. The northern part of Jinan City is rich in geothermal resources, specifically porous sandstone thermal reservoirs. However, there is still incomplete research on the mechanism of geothermal genesis and the hydrochemical characteristics of geothermal water in porous sandstone. This study aims to address this gap by collecting 21 groundwater samples from northern Jinan and comparing their conventional ion and isotope characteristics to investigate the hydrochemical characteristics during the formation of geothermal water and uncover the genesis mechanism of porous sandstone geothermal water. The results indicate that the geothermal water is classified as Na-Cl type and Na-SO4-Cl type. The hydrochemical characteristics of geothermal water are primarily influenced by water-rock interaction and groundwater mixing. The water source primarily comes from the atmospheric precipitation in the Taiyi mountains, with an altitude of 910.75-1542.2 m.s.a.l.. The estimated temperature of the thermal reservoir ranges from 51 to 78 °C, and the depth of geothermal water circulation is estimated to be between 1316 and 2216 m. Based on the characteristics of the geothermal field, including the "cap rock, water source, heat source, reservoir, and channel," a conceptual model of the porous sandstone geothermal water flow system is proposed. This model offers novel insights into the genesis mechanism of geothermal water under similar geological conditions.

Asunto(s)

RESUMEN

In this research, the removal of boron and arsenic from geothermal water was examined by using novel N-methyl-d-glucamine functionalized gel-like resins (abbreviated as 1JW and 2JW) synthesized by the membrane emulsification method. The outcomes were compared with those of commercially available boron selective chelating ion exchange resin (Diaion CRB 05). According to the results obtained with the novel resins, it was possible to reduce both boron and arsenic concentrations in geothermal water by using these novel gel-like chelating resins below their permissible levels for agricultural irrigation (<1 mg B/L) and drinking water (<0.01 mg As/L) by using the batch method. The optimum resin concentration required for almost complete boron removal (more than 95%) with the two chelating resins was determined to be 2 g/L. The novel gel-like chelating resins 1JW and 2JW achieved 94% of arsenic removal by using the resin concentration of 8 g/L, while the required resin concentration was 32 g/L for 94% of arsenic removal using commercially available Diaion CRB05 resin. In addition, the column performance characteristics of the novel chelating resins for the separation of boron were studied, and the results were compared to those obtained with Diaion CRB05. According to the column data obtained, the total resin capacities of the Diaion CRB05, 1JW, and 2JW resins were calculated as 6.29, 5.08, and 4.64 mg B/mL-resin, respectively.

RESUMEN

Geothermal resources are green and environmentally friendly renewable energy. An accurate evaluation of geothermal resources will help subsequent efficient exploitation. However, to save costs and improve efficiency, core-free drilling and without mud logging are adopted in the actual exploration, which results in an inability to directly obtain the relevant evaluation parameters of a geothermal reservoir for exploration and evaluation. Well logging technology can effectively delineate the geothermal reservoir and determine the location of the major aquifer, while also allowing for the accurate measurement of key reservoir evaluation parameters, such as the shale content, porosity, and well temperature. Moreover, coupled with the calculated logging parameters, a volumetric method can be used to determine the regional geothermal reserves. This research takes the geothermal wells of the Guanghuasi Formation in the Qianjiang sag, Jianghan Basin as an example to conduct the application research. The findings can be of reference for similar geothermal wells in China and facilitate the development of "carbon neutrality."

RESUMEN

The efficient and renewable recovery of cesium and strontium by absorption from a new type of geothermal water liquid mineral resource is highly desirable but still challenging. In this work, a new Zr-doped layered potassium thiostannate adsorbent (KZrTS) was first synthesized and used for Cs+ and Sr2+ green and efficient adsorption. It was found that KZrTS had very fast adsorption kinetics toward both Cs+ and Sr2+ with an equilibrium reached within 1 min, and the theoretical maximum adsorption capacities for Cs+ and Sr2+ were 402.84 and 84.88 mg/g, respectively. Moreover, to solve the loss problem of the engineering application of the powdered adsorbent KZrTS, KZrTS was uniformly coated with polysulfone by wet spinning technology to form micrometer-level filament-like absorbents (Fiber-KZrTS), whose adsorption equilibrium rates and capacities toward Cs+ and Sr2+ are almost the same as that of powder. Furthermore, Fiber-KZrTS showed excellent reusability, and the adsorption performance remained virtually unchanged after 20 cycles. Therefore, Fiber-KZrTS has potential application for green and efficient cesium and strontium recovery from geothermal water.

RESUMEN

Fluoride (F-) is a common trace component in groundwater, and long-term exposure to high-F- groundwater is harmful to human health. Fluoride concentrations that exceed the World Health Organization guideline for drinking water (1.5 mg/L) have been detected in thermal and non-thermal groundwater from Southeast China, where the causes of the high fluoride occurrence are lack of study. To study the formation and migration mechanism of high fluoride groundwater from Southeast China, we carried out a systemic sampling of water samples in the surrounding area of Heyuan deep fault zone and Zijin-Boluo fault zone, then a comprehensive discussion including water hydrogeochemical, stable isotope composition, as well as hydrogeology analysis was conducted. Fluoride concentrations in geothermal and non-thermal water samples range from 1.11 to 22.76 mg/L and 0.04-8.3 mg/L, respectively. High temperature, alkaline conditions, and the depleted Ca2+ by reverse cation exchange and calcite precipitation would promote the release of fluoride from host rock to geothermal water. The availability of Ca-bearing and F-bearing minerals in host rock causes significant differences in fluoride concentrations between carbonate reservoir and granite reservoir. Hydrochemical diagrams reveal that the composition of groundwater is affected by mixing and that fractures act as the mixing channels in our study area. The addition of cold groundwater limits the fluoride concentrations by lowing temperature and increasing Ca2+ levels of geothermal water. Additionally, the relationship between F- and SiO2 indicates that geothermal water promotes the fluoride enrichment in cold groundwater, especially in confined aquifers which are more susceptible to geothermal water. The direct input of geothermal fluoride and secondary enrichment caused by alkaline condition contribute to the formation of high F- concentrations (7.2-8.3 mg/L) in confined groundwater. Our findings highlight that the natural evolution of geothermal systems in fault zone can result in the formation of geogenic contaminated groundwater.

Asunto(s)

RESUMEN

The state-of-the-art of sampling procedures is specified in appropriate guidelines, but there is a permanent need to minimise the risk to the water sample quality, in particular for waters with specific characteristics such as geothermal waters. Improper sampling leads to erroneous results and, consequently, e.g. increased uncertainty in models of geochemical processes (scaling, corrosion) in geothermal installations, aquifer geothermometry, or environmental assessments. The impact of the applied filters (nylon, PVDF, MCE), containers (HDPE, borosilicate glass) and preservation on concentration of 34 major, minor and trace elements was studied for the samples of two geothermal waters used in practice. The results of replicated chemical analyses in duplicated samples of geothermal waters and deionized water blanks were subjected to statistical analyses, including nonparametric tests (Kruskal-Wallis, Dunn's, Kolmogorov-Smirnov, Mann-Whitney U, Wald-Wolfowitz). The PVC housing of the used MCE syringe filters contaminates water samples with Sb. Borosilicate glass increases Al, Cu, Pb and Se concentrations in samples. Acidification protects against changes in concentrations of numerous elements (i.a. Al, B, Ba, Cu, Fe, Ni, Pb) in the solution. Results of analysis performed indicated that using nylon membrane filter and HDPE (properly precleaned to wash out extractables) containers for thermal water sampling is recommended.

Asunto(s)

RESUMEN

Arsenic (As) from deep crust is transported by geothermal waters to the earth surface and retained by sediment through adsorption, which depends significantly on the occurring As species. Adsorption of oxyarsenic species (i.e. arsenite [iAs(III)] and arsenate [iAs(V)]) on pure minerals was intensively investigated, yet studies with natural sediments and less known As species are scarce. To fill this gap, we investigated adsorption kinetics of nine different As species onto three typical geothermal sediments with different sedimentary organic matter (SOM) and iron (Fe) levels under anaerobic, sulfidic conditions (pH = 6). A multispecies pseudo-second-order (MPSO) model was applied to extract the adsorption rates of individual As species. Results showed that only the sediment with both high SOM and high Fe exhibited considerable As adsorption capacity. Air exposure or rise of either SOM or Fe levels in sediment favoured de-thiolation of aqueous thioarsenates, except for dimethylated thioarsenates. The overall adsorbed amount of the spiked As was affected by concurrent (de-)thiolation of the initial species, and the rates of their adsorption to the high SOM and high Fe sediment decreased in the order of tetrathioarsenate (TetraTA) > monothioarsenate (MTA) > iAs(V) > monomethyl arsenate (MMA) > dimethyl arsenate (DMA) > iAs(III) > monomethyl monothioarsenate (MMMTA) > dimethyl monothioarsenate (DMMTA) > dimethyl dithioarsenate (DMDTA). The fastest and slowest adsorption were suggested for inorganic thioarsenates and methylated thioarsenates, respectively. Therefore, under typical geothermal scenarios, thiolation of inorganic As would not necessarily increase its mobility, but the formation of methylated oxyarsenates and their further thiolation would endow geothermal As with strong migration ability.

Asunto(s)

RESUMEN

The article presents environmental aspects related to the use of geothermal waters of the Lower Jurassic in the area of the Szczecin Trough. The research area located in the north-western part of the country has been successfully using underground waters of the Lower Jurassic since the 1990s to generate thermal energy at two geothermal heating plants located in Pyrzyce and Stargard. In the case of the area in question, it was proposed a hypothetical geothermal doublet located in the vicinity of the city of Choszczno, for which numerical simulations were carried out for different variants of the locations of the wells and the intake capacity. On the basis of the obtained results, the environmental effect that could be achieved in the case of the analyzed investment was estimated. Reduction in pollutants emission might be expected on the global scale. Even taking into account the emission linked to the electricity consumed (more than 81% of electricity in 2020 in Poland was produced based on fossil fuels, the share of had coal is about half of them). Local reduction in emission is obvious, and it is strictly related to the amount of reduction of fuels consumption. Taking into account the health resorts and thermal pools that utilize groundwater operating in the Polish Lowlands, the chemical composition of the underground waters extracted in the region of Choszczno was also analyzed, and the possibilities of their use for therapeutic and balneotherapeutic purposes were indicated.

Asunto(s)

RESUMEN

BACKGROUND: The economic value of many fruit and vegetables is often linked to the ability to preserve such natural products. In the case of tomatoes, the manufacture of 1 kg of powder or concentrate requires the evaporation of about 16 kg water kg-1 dry matter. In the present work, the effectiveness and economic analysis of solar drying systems for drying of tomato paste with and without geothermal water heat exchanger (GWHE) were studied. RESULTS: The GWHE integration significantly increased the recorded drying temperature up to 53.41 °C, with an improvement of 11.5 °C compared to the conventional dryer. Moreover, the drying temperature inside the drying chamber exceeded ambient temperature after sunset and at night by 30.8 °C. GWHE ensured a continuous drying process, while drying time was 22 consecutive hours, compared to the basic dryer with 18 h in 3 days. Effective moisture diffusivity was found to be 1.617 × 10-9 and 1.202 × 10-9  m2  s-1 for hybrid and basic drying systems, respectively, using the slope. Three methods were used to perform economic analysis. The cumulative present worth of savings, at 23 382.6 USD, is much higher than the capital cost of the hybrid dryer, at 467 USD. The payback period is quite acceptable, at 2.21 years as compared to dryer lifetime of 15 years. Therefore, the hybrid dryer will dry tomato paste without additional charges for 12.79 years and is recommended for a large-scale tomato paste dryer. CONCLUSION: The hybrid system with GWHE ensures a continuous drying process during night-time, in addition to reduced drying time. The economic study revealed a high feasibility for the hybrid dryer, with a short payback period. © 2021 Society of Chemical Industry.

Asunto(s)

RESUMEN

This study presents the separation and recovery of boron from geothermal waters with a polymeric membrane system and suggests a transport mechanism. The optimum relative parameters of the transport were examined. The recovery value of boron was 60.46% by using polymeric membrane system from prepared aquatic solution to the acceptor phase. The membrane's capacity and selectivity of the transport process were examined. Kinetics values were calculated for each transport parameter. The optimum kinetic values were 1.4785 × 10-6 (s-1), 7.3273 × 10-8 (m/s), 13.5691 × 10-8 (mol/m2.s), 5.8174 × 10-12 (m2/s) for constant rate, permeability coefficient, flux, and diffusion coefficient, respectively. Boron was transported selectively and successfully from geothermal waters in the presence of other metal cations with 59.85% recovery value. This study indicates the application of real samples in polymeric membrane systems, which are very practical, economic, and easy to use for large-scale applications. The chemical and physical properties of polymer inclusion membranes (PIMs) offer the opportunity to be specially designed for specific applications.

RESUMEN

Unlike collectively treatable industrial wastewaters where only one or a few pollutants have concentrations much higher than the relevant standards, geothermal waters, in which multiple harmful constituents coexist, are usually discharged dispersedly, provoking a big challenge for their effective treatment. Here, a Mg/Fe layered double hydroxide with OH- intercalated (Mg-Fe-OH-LDH) was synthesized in a mechanochemical way and then applied in the treatment of various types of high-temperature geothermal waters in western Yunnan (China) containing a variety of harmful anions (As, Sb, W, and F) and inducing local environmental pollution. Due to the endothermic nature of removal of aqueous As, Sb, W, and F by Mg-Fe-OH-LDH, the original high temperatures of the geothermal waters could promote their sorption effectively. Batch sorption experiments demonstrated that over 94% and 80% of the As and W removal amounts could be reached within the first 10 and 20 min, respectively. On-site column experiments confirmed that the sorbent could remove the targeted harmful constituents from the investigated geothermal waters efficiently. In fact, the performance of the sorbent in the column studies was even better than that in the batch experiments, which can be ascribed to the continuous impetus for sorption caused by the concentration gradient in the flowing sorption system. Specifically, Mg-Fe-OH-LDH displayed the best sorption performance for As(V) among various harmful constituents, and the sorption of As along with W and F was little affected by the coexisting common anions in the geothermal waters, including Cl-, SO42-, and HCO3-/CO32-. In contrast, the removal of Sb(V) from geothermal waters may be impeded to a certain extent by SO42- and CO32-, which possessed stronger electronegativity or smaller ionic radii. This study is the first attempt to apply Mg-Fe-LDH in treatment of geothermal waters with multiple harmful constituents and sheds a light on providing a practical approach for field treatment of geothermal water-derived pollution.

Asunto(s)

RESUMEN

One of the factors that determine agricultural crops' yield is the quality of water used during irrigation. In this study, we assessed the usability of spent geothermal water for agricultural irrigation after membrane treatment. Preliminary membrane tests were conducted on a laboratory-scale set up followed by mini-pilot scale tests in a geothermal heating center. In part I, three commercially available membranes (XLE BWRO, NF90, and Osmonics CK- NF) were tested using a cross-flow flat-sheet membrane testing unit (Sepa CF II, GE-Osmonics) under constant applied pressure of 20 bar. In part II, different spiral wound membranes (TR-NE90-NF, TR-BE-BW, and BW30) other than the ones used in laboratory tests were employed for the mini-pilot scale studies in a continuous mode. Water recovery and applied pressure were maintained constant at 60% and 12 bar, respectively. Performances of the membranes were assessed in terms of the permeate flux, boron and arsenic removals. In laboratory tests, the permeate fluxes were measured as 94.3, 87.9, and 64.3 L m-2 h-1 for XLE BWRO, CK-NF and NF90 membranes, respectively. The arsenic removals were found as 99.0%, 87.5% and 83.6% while the boron removals were 56.8%, 54.2%, and 26.1% for XLE BWRO, NF90 and CK-NF membranes, respectively. In field tests, permeate fluxes were 49.9, 26.8 and 24.0 L m-2 h-1 for TR-NE90-NF, BW30-RO and TR-BE-BW membranes, respectively. Boron removals were calculated as 49.9%, 44.1% and 40.7% for TR-BE-BW, TR-NE90-NF and BW30-RO membranes, respectively. Removal efficiencies of arsenic in mini-pilot scale membrane tests were all over 90%. Quality of the permeate water produced was suitable for irrigation in terms of the electrical conductivity (EC) and the total dissolved solids (TDS) for all tested membranes with respect to guidelines set by the Turkish Ministry of Environment and Urbanisation (TMEU). However, XLE BWRO, CK-NF and NF90 membranes failed to meet the required limits for irrigation in terms of boron and arsenic concentrations in the product water. The permeate streams of TR-BE-BW, TR-NE90-NF and BW30-RO membranes complied with the irrigation water standards in terms of EC, TDS and arsenic concentration while boron concentration remained above the allowable limit.

RESUMEN

Abundant geothermal waters have been reported in the Yalabamei, Zhonggu, Erdaoqiao, and Yulingong geothermal areas of the Xianshuihe Fault Zone of western Sichuan, southwestern China. This study focused on the hydrogeochemical evolution, reservoir temperature, and recharge origin of geothermal waters using hydrochemical and deuterium-oxygen (D-O) isotopic studies. Shallow geothermal waters represented by geothermal springs and shallow drilled water wells are divided into two hydrochemical groups: (1) the Ca-Na-HCO3 type in the Erdaoqiao area, and (2) Na-HCO3 in other areas. Deep geothermal waters represented by deep drilled wells are characterized by the Na-Cl-HCO3 type. The major ionic compositions of geothermal water are primarily determined by the water-rock interaction with silicate and carbonate minerals. The reservoir temperatures estimated by multi-geothermometries have a range of 63-150 °C for shallow geothermal water and of 190-210 °C for deep geothermal water, respectively. The δ18O and δD compositions indicated geothermal waters are recharged by meteoric water from the elevation of 2923-5162 m. Based on the aforementioned analyses above, a conceptual model was constructed for the geothermal system in the Xianshuihe fault zone.

Asunto(s)

RESUMEN

Musculoskeletal pain is a health challenge with various treatment strategies. The study has been accomplished with the aim to reveal the effect of mineral water with different mineral content on musculoskeletal pain and related symptoms experienced. A randomized controlled single-blinded parallel-group study has been performed (145 participants with pain; 5 groups). The duration of treatment was 2 weeks, whereas follow-up has taken 3 months. Change in pain after a single procedure and the pain parameters with related symptoms during the study period have been measured. The effect size using Cohen's d has been estimated. Small effect (0.2-0.4) on pain has been distinguished after each mineral water procedure. Tap water procedures have been effective in 60% of cases. Twenty grams per liter water baths have had a small effect on pain intensity and tender points, body flexibility, and spinal mobility, and a medium one on sleep quality, and reduced CRP. Forty grams per liter water has had a small effect on pain intensity, frequency, and spinal mobility, and a medium one on flexibility, fatigue, and sleep quality, and reduced ESR. Sixty grams per liter water has had a small effect on pain parameters and fatigue, and a medium one on flexibility and sleep quality, and reduced ESR. The effect lasting up to 2 months has been identified mostly in the 60 g/L group. Tap water has had a short time effect on pain intensity and tender points. There have not been any changes of sufficient significance identified in the control group and any differences between mineral water groups. Sufficient difference between mineral and tap water groups has been determined in pain intensity, spinal mobility, and sleep quality, whereas in the case of the control group, significant difference in pain intensity and frequency, flexibility, and spinal mobility has been identified. The consumption of pain medication has significantly decreased in all mineral water groups. The total mineral content of the water has no significant influence on the reduction of musculoskeletal pain. Mineral water baths have small effect on pain and medium effect on other musculoskeletal disease-related symptoms and pain medication consumption lasting up to 3 months; it is more beneficial than tap water or no treatment for the improvement of symptoms associated with musculoskeletal diseases. Even single balneotherapy procedure results in small pain reduction.

Asunto(s)

RESUMEN

The widespread use of lithium-ion batteries has led to continuously increasing demands for lithium. In order to recover lithium from geothermal water, a novel composite lithium ion-sieve was synthesized and applied in this work. The stability of the material was successfully solved by granulating using acid-alkali resistant polyvinyl chloride as a binder, and its adsorption performances were also improved by using polyethylene glycol (PEG-6000) as a porogen to obtain a polyporous structure. When the developed material was applied for lithium separation from geothermal water, the adsorption capacity reached 12.84 mg/g at 328.15 K with an equilibrium time of about 12 h. The material can be well regenerated using 0.25 mol/L HCl to realize cycle use. The separation factors between Li+ and other co-existing ions were within the range of 273.58-521.28, and the attenuation of adsorption capacity after five cycles was no more than 2%. The high selectivity and reusability properties of the polyporous ion-sieve make the material a potential candidate for the selective separation and recovery of a low concentration of lithium from geothermal water.

RESUMEN

Fluoride (F) and arsenic (As) are two typical and harmful elements that are found in high concentrations in geothermal water in Tibet. In this work, yak dung, an abundant source of biomass energy in Tibet, was made into biochars (BC1, BC2 and BC3) by pyrolysis under different conditions, and the better biochar was modified by FeCl2 (Fe-BC3). The adsorption conditions were optimized to adsorb F and As in geothermal water. The results showed that BC3 can remove 90% F- and 20% As(V), which is the best effect of the three initial biochars. Fe-BC3 could remove 94% F- and 99.45% As(V) under the same conditions as BC3, which was an adsorbent dosage 10 g l-1, pH 5-6 and temperature of 25°C. It was also demonstrated that the removal rate did not decrease at 80°C. A quasi-second-order kinetic model best described the adsorption behaviour of ions on the surface of the biochar. The maximum adsorption capacity of F- and As(V) on Fe-BC3 was 3.928 mg g-1 and 2.926 mg g-1, respectively. The features of Fe-BC3 were characterized by X-ray diffraction, Fourier transform infrared, Brunauer-Emmett-Teller, energy-dispersive spectrometer and scanning electron microscopy to understand the adsorption process.

RESUMEN

The treatment of the geothermal water discharged through mining activity is a critical issue because the rate of discharge is 12,000 m3 per day and the discharge contains high concentrations of borate (>20 mg/L) and arsenate (ca. 0.4 mg/L) as well as silicate and carbonate. The simultaneous reduction of borate and arsenate concentrations to acceptable levels was successfully performed by co-precipitation with hydroxyapatite (HAp). Although the coexisting high concentrations of carbonate act as a disturbing element, the co-precipitation equilibrium of borate was shifted to lower values by adjusting the P/Ca molar ratio, and the removal rate of borate was accelerated by using Al3+ additives, resulting in the efficient reduction of borate within 1 h. The initially immobilized boron in HAp is in the tetragonal form, which probably occupies the hydroxyl sites in HAp, gradually transforming into the trigonal form in the solid state, as interpreted by 1H NMR and 11B-NMR. The coexisting silicate was also immobilized in an ellestadite form, as confirmed by 29Si-NMR measurements. Arsenate and silicate were immobilized before borate in geothermal water. A dissolution assay of borate in the solid residues after co-precipitation with HAp verified the acceptable stability of borate, which is independent of the amount of added Al3+.

Asunto(s)

RESUMEN

Disposal of used geothermal waters in Hungary often means temporary storage in reservoir lakes to reduce temperature and improve water quality. In this study, the physical and chemical properties and changes in the bacterial community structure of a reservoir lake system in southeast region of Hungary were monitored and compared through 2 years, respectively. The values of biological oxygen demand, concentrations of ammonium ion, total inorganic nitrogen, total phosphorous, and total phenol decreased, whereas oxygen saturation, total organic nitrogen, pH, and conductivity increased during the storage period. Bacterial community structure of water and sediment samples was compared by denaturing gradient gel electrophoresis (DGGE) following the amplification of the 16S rRNA gene. According to the DGGE patterns, greater seasonal than spatial differences of bacterial communities were revealed in both water and sediment of the lakes. Representatives of the genera Arthrospira and Anabaenopsis (cyanobacteria) were identified as permanent and dominant members of the bacterial communities.

Asunto(s)

RESUMEN

Naegleria spp. are free-living amoebae belonging to the family Vahlkampfiidae, in the class Heterolobosea. Among the recognized species, Naegleria fowleri causes primary amoebic meningoencephalitis (PAM), while two other species, Naegleria australiensis and Naegleria italica, have been reported as pathogenic in experimental animals. Due to the thermotolerance properties of some species, geothermal water sources including hot springs represent suitable habitats for their proliferation. The main aim of this study was a year-round sampling in two geothermal springs in Central Italy, to investigate the presence of Naegleria spp. using PCR/DNA sequencing based methods. The affinities between the sequences generated here and others reported in the literature were explored by using POY, which implements the concept of dynamic homology. Naegleria australiensis, Naegleria italica, and Naegleria lovaniensis, plus an unassigned Naegleria spp. were detected. Indels in the rDNA ITS1 and ITS2 turned out to be critical to distinguish the three species and confirmed their phylogenetic relationships. This is the first molecular report on the Naegleria spp. occurrence in geothermal waters in Central Italy, coupled with a fine genetic characterization.

Asunto(s)