Thermal Pools Research Articles

Extreme alteration in an acid-sulphate geothermal field: Sulphur Springs, Saint Lucia

Sulphur Springs is a vigorous geothermal field associated with the Soufrière Volcanic Centre in southern Saint Lucia. Intensely altered rocks occur over an area of at least 200 × 400 m, together with bubbling hot pools and fumaroles. The pools are sodium‑calcium-sulphate type, with pHs of 3–7 and temperatures of 41–97 °C. Fumaroles have temperatures up to, and at times above 100 °C. Gases collected from both fumaroles and bubbling pools have high contents of CO2 (601–993 mmol/mol) and commonly high H2S (3–190 mmol/mol).Least-altered host rocks surrounding Sulphur Springs comprise calc-alkaline, feldspar-quartz-porphyritic dacites of near-uniform chemical composition. These rocks, which form massive domes and volcaniclastic units, were emplaced 13–30 ka ago (Lindsay et al., 2013). Within the geothermal field, the dacites have been moderately to highly altered to acid-sulphate assemblages of kaolinite, illite, smectite, alunite, natroalunite, cristobalite, opaline silica, native sulphur, jarosite and amorphous compounds. Muddy sediments from grey to blackish thermal pools additionally contain iron sulphides.Despite intense alteration of the volcanic rocks (and derived volcaniclastic sediments), Zr and Ti have remained essentially immobile, which allows identification of the precursors (dacites) and calculation of mass changes. Many of the altered rocks and sediments show major depletions of Fe, Mg, Ca, Na. Extremely altered samples additionally show notable losses of Al, P, K, REE and Y, implying leaching by highly acidic waters. A few of the highly altered rocks, however, have gained Al, together with P, presumably due to neutralization or evaporation of acidic thermal waters. Also present within the geothermal field are metre-scale zones with very high contents of silica and native sulphur, and <1% Al2O3. Based on mass change results, the silica in the silica-sulphur zones, although recrystallized, was mainly inherited from the precursor dacites, rather than added as new hydrothermal precipitates.Surface thermal waters define a linear trend in a plot of δ18O vs. δD, and reach high levels of isotopic enrichment. The enrichment trend is ascribed to progressive evaporation in the thermal pools. The low slope of the isotopic trend (1.4) is interpreted as being due to surficial mixing between meteoric waters and steam condensates derived at about 230 °C from the deep brine that underlies the geothermal field. The whole-rock O-H-isotopic composition of four highly altered samples (kaolinite-smectite-opal-sulphates) can be accounted for if the alteration fluid was a 50:50 mixture of steam and meteoric water, and alteration occurred at 50–125 °C. Whole-rock δ34S values of samples containing variable amounts of sulphates, sulphides and native S are all notably negative (−5 to −16‰), consistent with derivation of sulphur from volcanic gases such as SO2 and H2S. Altered rocks and thermal pool sediments in the geothermal field are commonly enriched in Hg and Se (up to 50 mg/kg).At Sulphur Springs, primary dacitic rocks have been chemically and mineralogically transformed by reaction with acidic waters that formed when uprising volcanic gases condensed into neutral meteoric waters. In many cases, this has led to substantial mass losses or gains in Al, P and REEs. Regardless of the degree of alteration, however, the precursor rocks can still be identified using Ti-Zr relations.

Geochemistry of Thermal Waters of Ketoi Island, Kuril Island Arc

The data obtained during the fieldworks in July 2016 were used for the geochemical description of thermal manifestations of Ketoi and Pallas Peak volcanoes on Ketoi Island in the middle of the Kuril Island arc. It is shown that the older edifice of Ketoi Volcano hosts a high temperature hydrothermal system whose surface manifestations are concentrated in the eroded crater of the volcano. Two main types of thermal water are discharged there: the acid and low-acid waters of the Ca–SO4 composition in thermal pools that are diluted to varying degrees with meteoric water, and boron-rich neutral boiling water of the Na–Ca–SO4 composition. The isotopic composition of both water types is similar to that of the local meteoric waters. Calculation of mineral saturation indices for hydrothermal minerals, as well as the behavior of boron, suggest that the waters of the first type are formed nearer the surface, while the boiling sulfate waters are most likely derived from steam condensates formed at depth at a temperature of approximately 200°С. The thermal springs related to Pallas Peak Volcano discharge acid sulfate chloride water. The total measured hydrothermal output of Cl and SO4 from Ketoi and Pallas Peak volcanoes is 8.5 t/day and 30 t/day, respectively.

Wooden tools and fire technology in the early Neanderthal site of Poggetti Vecchi (Italy)

Excavations for the construction of thermal pools at Poggetti Vecchi (Grosseto, Tuscany, central Italy) exposed a series of wooden tools in an open-air stratified site referable to late Middle Pleistocene. The wooden artifacts were uncovered, together with stone tools and fossil bones, largely belonging to the straight-tusked elephant Paleoloxodon antiquus The site is radiometrically dated to around 171,000 y B.P., and hence correlated with the early marine isotope stage 6 [Benvenuti M, et al. (2017) Quat Res 88:327-344]. The sticks, all fragmentary, are made from boxwood (Buxus sempervirens) and were over 1 m long, rounded at one end and pointed at the other. They have been partially charred, possibly to lessen the labor of scraping boxwood, using a technique so far not documented at the time. The wooden artifacts have the size and features of multipurpose tools known as "digging sticks," which are quite commonly used by foragers. This discovery from Poggetti Vecchi provides evidence of the processing and use of wood by early Neanderthals, showing their ability to use fire in tool making from very tough wood.

Paleoenvironmental context of the early Neanderthals of Poggetti Vecchi for the late middle Pleistocene of Central Italy

AbstractWork on thermal pools at Poggetti Vecchi in Grosseto, Italy, exposed an up to 3-meter-thick succession of seven sedimentary units. Unit 2 in the lower portion of the succession contained vertebrate bones, mostly of the straight-tusked elephant,Palaeoloxodon antiquus, commingled with stone, bone, and wooden tools. Thermal carbonates overlying Unit 2 are radiometrically dated to the latter part of the middle Pleistocene. This time span indicates that early Neanderthals produced the human artifacts from Poggetti Vecchi. The elephant bones belong to seven individuals of different ages. Sedimentary facies analysis and paleoecological evidence suggest a narrow lacustrine-palustrine embayment affected by water-level fluctuations and, at times, by hydrothermal water. Cyclic lake-level variations were predominantly forced by the rapid climatic fluctuations that occurred at Marine Isotope Stage (MIS) 6–7 transition and throughout the MIS 6. Possibly an abrupt, intense, and protracted cold episode during the onset of MIS 6 led to the sudden death of the elephants, which formed an unexpected food resource for the humans of the area. The Poggetti Vecchi site adds new information on the behavioral plasticity and food procurement strategies that early Neanderthals were able to develop in Italy during the middle to the late Pleistocene transition.

Microbial diversity in acidic thermal pools in the Uzon Caldera, Kamchatka.

Microbial communities of four acidic thermal pools in the Uzon Caldera, Kamchatka, Russia, were studied using amplification and pyrosequencing of 16S rRNA gene fragments. The sites differed in temperature and pH: 1805 (60°C, pH 3.7), 1810 (90°C, pH 4.1), 1818 (80°C, pH 3.5), and 1807 (86°C, pH 5.6). Archaea of the order Sulfolobales were present among the dominant groups in all four pools. Acidilobales dominated in pool 1818 but were a minor fraction at the higher temperature in pool 1810. Uncultivated Archaea of the Hot Thaumarchaeota-related clade were present in significant quantities in pools 1805 and 1807, but they were not abundant in pools 1810 and 1818, where high temperatures were combined with low pH. Nanoarchaeota were present in all pools, but were more abundant in pools 1810 and 1818. A similar abundance pattern was observed for Halobacteriales. Thermophilic Bacteria were less diverse and were mostly represented by aerobic hydrogen- and sulfur-oxidizers of the phylum Aquificae and sulfur-oxidising Proteobacteria of the genus Acidithiobacillus. Thus we showed that extremely acidic hot pools contain diverse microbial communities comprising different metabolic groups of prokaryotes, including putative lithoautotrophs using energy sources of volcanic origin, and various facultative and obligate heterotrophs.

Preliminary results of radon survey in thermal spas in V4 countries

Abstract Radon concentration was measured in 11 thermal spas in Visegrad countries (Czech Republic, Hungary, Poland, and Slovakia). The results showed that in 84% of spas radon activity concentration is less than 400 Bq·m−3. However, areas with radon activity concentration exceeding 1000 Bq·m−3 were found in the Czech Republic and Slovakia as well. Preliminary analyses indicated that the highest radon activities in spas were found in places with thermal pools. Radon concentration in waters used in spas ranged from 0.5 Bq/l to 384 Bq/l. The influence of radon activity concentration in water on radon activity in the air inside the spa was observed. It was found to increase indoor radon with increasing radon in the waters. Correlation with indoor radon and radon in water was more significant for baths and less significant for pool waters. In the cases filling of the bath from water taps, significantly contribute to the increased radon was observed in the pool and bath areas of the spa.

Fungi as Architects of the Rimstone Dams in Huanglong, NSD, Sichuan, China.

The Huanglong park area of the Sichuan Province of China is a unique scenic area of the world. It is known for its thousands of aquamarine-colored pools that are formed behind naturally formed rimstone dams of travertine (calcite) along a cold water stream. The travertine, based on its crystalline structural analysis, is of biological origin. This makes sense since the temperature of the waters of Huanglong varies from 5 to 7°C and thus geochemical crystallization does not occur as it does in other locations around the world possessing thermal pools whose structures are primarily formed through cooling processes. Fungi and bacteria were discovered associated with both leaves associated with the calcite dams as well as in the older parts of well-established dams. Several species of Phytium, a phycomycete and an endophyte, accounted for over 45% of all of the fungi successfully isolated from the well-established dam samples and at least 85% in the floating leaf samples. Saprolegnia spp. (Phycomycetes) along with Phoma spp. (Ascomycetes) were noted along with Mortierella sp. as other dam-associated fungi. The fungal hyphae observed on dead leaf material as well as in the calcite dams directly served as nucleation points for the formation of crystalline CaCO3. Eventually, these crystals grow large enough to fuse to make calcite plates which form the main structural feature of all of the travertine dams in this area. Interestingly, each of the individual crystals associated with the dams has an associated hole in its core where a fungal hypha used to reside as observed by scanning electron microscopy. While diatoms were present in the analysis, they too seem to contribute to the structure of the dams but in a minor way. The only bacteria isolated from the older dam of this aquatic environment were Pseudomonas spp. and their role in dam formation is uncertain. Huanglong is a unique and beautiful place, and the water features present in this area can definitely be attributed to those fungal architects that encourage calcite crystal formation.

Quantifying peat carbon accumulation in Alaska using a process‐based biogeochemistry model

AbstractThis study uses an integrated modeling framework that couples the dynamics of hydrology, soil thermal regime, and ecosystem carbon and nitrogen to quantify the long‐term peat carbon accumulation in Alaska during the Holocene. Modeled hydrology, soil thermal regime, carbon pools and fluxes, and methane emissions are evaluated using observation data at several peatland sites in Minnesota, Alaska, and Canada. The model is then applied for a 10,000 year (15 ka to 5 ka; 1 ka = 1000 cal years before present) simulation at four peatland sites. We find that model simulations match the observed carbon accumulation rates at fen sites during the Holocene (R2 = 0.88, 0.87, 0.38, and −0.05 using comparisons in 500 year bins). The simulated (2.04 m) and observed peat depths (on average 1.98 m) were also compared well (R2 = 0.91). The early Holocene carbon accumulation rates, especially during the Holocene thermal maximum (HTM) (35.9 g C m− 2 yr− 1), are estimated up to 6 times higher than the rest of the Holocene (6.5 g C m− 2 yr− 1). Our analysis suggests that high summer temperature and the lengthened growing season resulted from the elevated insolation seasonality, along with wetter‐than‐before conditions might be major factors causing the rapid carbon accumulation in Alaska during the HTM. Our sensitivity tests indicate that, apart from climate, initial water table depth and vegetation canopy are major drivers to the estimated peat carbon accumulation. When the modeling framework is evaluated for various peatland types in the Arctic, it can quantify peatland carbon accumulation at regional scales.

Dissolved gases in hydrothermal (phreatic) and geyser eruptions at Yellowstone National Park, USA

Multiphase and multicomponent fluid flow in the shallow continental crust plays a significant role in a variety of processes over a broad range of temperatures and pressures. The presence of dissolved gases in aqueous fluids reduces the liquid stability field toward lower temperatures and enhances the explosivity potential with respect to pure water. Therefore, in areas where magma is actively degassing into a hydrothermal system, gas-rich aqueous fluids can exert a major control on geothermal energy production, can be propellants in hazardous hydrothermal (phreatic) eruptions, and can modulate the dynamics of geyser eruptions. We collected pressurized samples of thermal water that preserved dissolved gases in conjunction with precise temperature measurements with depth in research well Y-7 (maximum depth of 70.1 m; casing to 31 m) and five thermal pools (maximum depth of 11.3 m) in the Upper Geyser Basin of Yellowstone National Park, USA. Based on the dissolved gas concentrations, we demonstrate that CO 2 mainly derived from magma and N 2 from air-saturated meteoric water reduce the near-surface saturation temperature, consistent with some previous observations in geyser conduits. Thermodynamic calculations suggest that the dissolved CO 2 and N 2 modulate the dynamics of geyser eruptions and are likely triggers of hydrothermal eruptions when recharged into shallow reservoirs at high concentrations. Therefore, monitoring changes in gas emission rate and composition in areas with neutral and alkaline chlorine thermal features could provide important information on the natural resources (geysers) and hazards (eruptions) in these areas.

Distribution of Legionella pneumophila in Thermal Pools

The study was aimed at assessing whether there is a risk of Legionella pneumophila in thermal pools used in balneotherapy and recreation. Water samples were collected from five thermal baths, supplied by thermal waters. The total number of bacteria was determined in the direct microscopic count under a fluorescence microscope. The numbers of bacteria from investigated phylogenetic groups (Legionella sp. and L. pneumophila) were estimated with the use of a fluorescence in situ hybridization method. The highest average total number of bacteria in the entire research cycle was recorded in old pools labeled OB1 and OB2. Bacteria belonging to the Legionella genus along with L. pneumophila were identified in all water samples collected from each bath. Moreover, a biofilm containing cells of L. pneumophila was identified in the collected water samples. The number of bacteria in water was dependent on the bath's age, the operation and the maintenance of the facilities. In old pools, with water exchanged periodically, the risk of L. pneumophila was higher; in new pools with a continual flow of water, lower. The results of this research showed no correlation between the number of Legionella and water temperature. Legionella pneumophila can successfully develop not only in fresh water bodies but in thermal baths as well. Still, it is uncertain whether the commonly applied culture method, developed for freshwater bodies, is also suitable for thermal baths.

Identifying nitrogen sources to thermal tide pools in Kapoho, Hawai'i, U.S.A, using a multi-stable isotope approach

Nitrogen (N) enrichment often results in coastal eutrophication, even in remote areas like Hawai‘i. Therefore, determining N sources to coastal waters is important for their management. This study identified N sources to tide pools in Kapoho, Hawai'i, and determined their relative importance using three stable isotopes (δ15N, δ18O, δ11B). Surface waters and macroalgal tissues were collected along 100-m onshore-offshore transects in areas of high groundwater input for three months at low tide. Water samples from possible N sources were also collected. Mixing model output, along with macroalgal δ15N values, indicated that agriculture soil (34%) was the largest anthropogenic N source followed by sewage (27%). These findings suggest that more effective fertilizer application techniques and upgrading sewage treatment systems can minimize N leaching into groundwater. Overall, our multi-stable isotope approach for identifying N sources was successful and may be useful in other coastal waters.

Isolation and identification of Acanthamoeba spp. from thermal swimming pools and spas in Southern Brazil.

Free-living amoebae (FLA) are widely distributed in soil and water. A few number of them are implicated in human disease: Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia diploidea. Species of Acanthamoeba can cause keratitis and brain infections. In this study, 72 water samples were taken from both hot tubs and thermal swimming pools in the city of Porto Alegre, RS, Brazil, to determine the presence of Acanthamoeba in the water as well as perform the phenotypic and genotypic characterization of the isolates. The identification of the isolates was based on the cysts morphology and PCR amplification using genus-specific oligonucleotides. When the isolates were submitted to PCR reaction only 8 were confirmed as belonging to the genus Acanthamoeba. The sequences analysis when compared to the sequences in the GenBank, showed genotype distribution in group T3 (12,5%), T5 (12,5%), T4 (25%) and T15 (50%). The results of this study confirmed the presence of potentially pathogenic isolates of free living amoebae in hot swimming pool and spas which can present risks to human health.

Colors of thermal pools at Yellowstone National Park.

The brilliant visible colors of various hot springs and pools in Yellowstone National Park are explained with a combination of scattering from the water and from microbial mats that coat the bottoms of these thermal features. A simple 1D radiative transfer model was used to simulate the colors recorded in visible photographs and the spectrum of light making up these colors. The model includes attenuation in water by absorption and molecular scattering as well as reflection characteristics of the microbial mats and surface reflection of the water. Pool geometries are simulated as simple rough cones scaled to have depths and widths that match published data. Thermal images are also used to record the spatial distribution of water skin temperature. The measurements and simulations confirm that colors observed from shallow-water features arise primarily from the spectral properties of the microbial mat, which is related to the water temperature, while colors observed from deeper water arise primarily from the wavelength-dependent absorption and scattering in the water.

Optimizing Selective Withdrawal from Reservoirs to Manage Downstream Temperatures with Climate Warming

AbstractSelective withdrawal systems can take advantage of thermal stratification in reservoirs to manage downstream temperatures. Selective withdrawal might also help adapt operations to environmental changes, such as increased stream temperatures expected with climate change. This exploratory study develops a linear programming model to release water from different thermal pools in reservoirs to minimize deviations from target downstream temperatures. The model is applied with representative thermal dynamics to Lake Spaulding, a multipurpose reservoir on the South Fork Yuba River in California with climate warming represented by uniform increases in air temperature. Optimization results for thermal pool management with selective withdrawal are compared to a single, low-level outlet release model. Optimal selective withdrawal hedges the winter release of cold water to decrease summer stream temperatures. With climate warming, selective withdrawal can help lessen stream warming in the summer but at a cost...

Biological and Physicochemical Quality of Thermal Spring Pools, with Emphasis on Staphylococcus Aureus: Sarein Tourist Town, Ardabil

Background: This study aimed at evaluating the water quality of thermal spring of Sarein in the province of Ardabil, with emphasis on bacteria S. aureus as one of the organisms involved in skin and eye infections, in the first half of 2011. Methods: In this study, 85 composite samples were collected from all thermal spring pools of Sarein during May to September 2011; in the peak number of swimmers. The concentration of free residual chlorine, temperature, pH, turbidity, H2S, ORP, DO and EC were measured in-situ in the sampling sites by portable devices. Total and fecal Coliforms, Staphilococcus aurous, fecal Streptococci and HPC tests were done according to the Standard methods for examination of water and wastewater. Results: Data showed that the maximum contamination of total coliforms were occurred in August (MPN/100=309.82), fecal Coliforms in July (MPN/100=69.59), minimum contamination of samples were related to fecal streptococci in August and September, peak of HPC in September with 4774.12 cfu/mL, and Staphylococcus aureus with 1149.35 cfu/100mL in August were recorded. Results of averages comparing showed no significant difference between the months of sampling and contamination with bacteria S. aureus. Conclusion: Data showed that 3.53, 9.41, 84.71, and 81.18 of samples were contaminated to total Coliform, fecal Coliform, HPC and Staphylococcus aureus, respectively which were higher than standard limits that it was an alarm for the occurrence of skin diseases and infections to swimmers.

Impact of groundwater withdrawals on the interaction of multi-layered aquifers in the Viterbo geothermal area (central Italy)

The impact of groundwater withdrawals on the interaction between multi-layered aquifers with different water qualities in the Viterbo geothermal area (central Italy) was studied. In this area, deep thermal waters are used to supply thermal spas and public pools. A shallow overlying aquifer carries cold and fresh water, used for irrigation and the local drinking-water supply. Starting with a conceptual hydrogeological model, two simplified numerical models were implemented: a steady-state flow model of the entire groundwater system, and a steady-state flow and heat transport model of a representative area, which included complex interactions between the aquifers. The impact of increased withdrawals associated with potential future development of the thermal aquifer must be considered in terms of the water temperature of the existing thermal sources. However, withdrawals from the shallow aquifer might also influence the discharge of thermal sources and quality of the water withdrawn from the shallow wells. The exploitation of the two aquifers is dependent on the hydraulic conductivity and thickness of the intervening aquitard, which maintains the delicate hydrogeological equilibrium. Effective methods to control this equilibrium include monitoring the vertical gradient between the two aquifers and the residual discharge of natural thermal springs.

Microbiological Analysis in Three Diverse Natural Geothermal Bathing Pools in Iceland

Natural thermal bathing pools contain geothermal water that is very popular to bathe in but the water is not sterilized, irradiated or treated in any way. Increasing tourism in Iceland will lead to increasing numbers of bath guests, which can in turn affect the microbial flora in the pools and therefore user safety. Today, there is no legislation that applies to natural geothermal pools in Iceland, as the water is not used for consumption and the pools are not defined as public swimming pools. In this study, we conducted a microbiological analysis on three popular but different natural pools in Iceland, located at Lýsuhóll, Hveravellir and Landmannalaugar. Total bacterial counts were performed by flow cytometry, and with plate count at 22 °C, 37 °C and 50 °C. The presence of viable coliforms, Enterococcus spp. and pseudomonads were investigated by growth experiments on selective media. All samples were screened for noroviruses by real time PCR. The results indicate higher fecal contamination in the geothermal pools where the geothermal water flow was low and bathing guest count was high during the day. The number of cultivated Pseudomonas spp. was high (13,000–40,000 cfu/100 mL) in the natural pools, and several strains were isolated and classified as opportunistic pathogens. Norovirus was not detected in the three pools. DNA was extracted from one-liter samples in each pool and analyzed by partial 16S rRNA gene sequencing. Microbial diversity analysis revealed different microbial communities between the pools and they were primarily composed of alpha-, beta- and gammaproteobacteria.

Heat flow in vapor dominated areas of the Yellowstone Plateau Volcanic Field: Implications for the thermal budget of the Yellowstone Caldera

Characterizing the vigor of magmatic activity in Yellowstone requires knowledge of the mechanisms and rates of heat transport between magma and the ground surface. We present results from a heat flow study in two vapor dominated, acid‐sulfate thermal areas in the Yellowstone Caldera, the 0.11 km2 Obsidian Pool Thermal Area (OPTA) and the 0.25 km2 Solfatara Plateau Thermal Area (SPTA). Conductive heat flux through a low permeability layer capping large vapor reservoirs is calculated from soil temperature measurements at &gt;600 locations and from laboratory measurements of soil properties. The conductive heat output is 3.6 ± 0.4 MW and 7.5 ± 0.4 MW from the OPTA and the SPTA, respectively. The advective heat output from soils is 1.3 ± 0.3 MW and 1.2 ± 0.3 MW from the OPTA and the SPTA, respectively and the heat output from thermal pools in the OPTA is 6.8 ± 1.4 MW. These estimates result in a total heat output of 11.8 ± 1.4 MW and 8.8 ± 0.4 MW from OPTA and SPTA, respectively. Focused zones of high heat flux in both thermal areas are roughly aligned with regional faults suggesting that faults in both areas serve as conduits for the rising acid vapor. Extrapolation of the average heat flux from the OPTA (103 ± 2 W·m−2) and SPTA (35 ± 3 W·m−2) to the ∼35 km2 of vapor dominated areas in Yellowstone yields 3.6 and 1.2 GW, respectively, which is less than the total heat output transported by steam from the Yellowstone Caldera as estimated by the chloride inventory method (4.0 to 8.0 GW).

Arsenic speciation and trace element analysis of the volcanic río Agrio and the geothermal waters of Copahue, Argentina

Surface water originating from the Copahue volcano crater-lake was analysed for total arsenic and four arsenic species: arsenite (iAsIII), arsenate (iAsV), monomethylarsonic acid (MAV) and dimethylarsinic acid (DMAV) and other trace elements (Fe, Mn, V, Cr, Ni, Zn). A novel in-field technique for the preconcentration and separation of four arsenic species was, for the first time, used for the analysis of geothermal and volcanic waters. Total arsenic levels along the río Agrio ranged from <0.2–3783μg/l AsT. The highest arsenic levels were recorded in the el Vertedero spring (3783μg/l AsT) on the flank of the Copahue volcano, which feeds the acidic río Agrio. Arsenite (H3AsO3) predominated along the upper río Agrio (78.9–81.2% iAsIII) but the species distribution changed at lago Caviahue and arsenate (H2AsO4−) became the main species (51.4–61.4% iAsV) up until Salto del Agrio. The change in arsenic species is potentially a result of an increase in redox potential and the formation of iron-based precipitates. Arsenic speciation showed a statistically significant correlation with redox potential (r=0.9697, P=0.01). Both total arsenic and arsenic speciation displayed a statistically significant correlation with vanadium levels along the river (r=0.9961, P=0.01 and r=0.8488, P=0.05, respectively). This study highlights that chemical speciation analysis of volcanic waters is important in providing ideas on potential chemical toxicity. Furthermore there is a need for further work evaluating how arsenic (and other trace elements), released in volcanic and geothermal streams/vents, impacts on both biota and humans (via exposure in thermal pools or consuming commercial drinking water).

Ecology and evolution of hydrobionts in hot springs of the subarctic and arctic: Formation of similar assemblages, adaptation of species, and microevolutionary processes

In the Subarctic and Arctic, the fauna of hydrothermal systems is considered to be an allochthonous, migration-mediated system comprised of the representatives of different taxa, which are characterized by a set of preadaptations to life in hot springs. These adaptations evolved before species had colonized this thermal anomalous environment. Hot springs characterizing by a constant temperature and hydrochemical regime appear to be the favorable sites compared to the usual local environment. The short-term existence of thermal springs on the geological time scale and their evolutionary evanescence serve as preconditions for the low fauna endemism that make up the taxa on the intraspecific and species levels. The taxonomical status of many of these forms has not yet been defined with certainty, since populations of new species and intraspecific taxonomic categories of mollusks that inhabit thermal pools may evolve similar morphological, physiological, and biochemical features independently; i.e., they may exhibit convergent similarity.