Hot Spring Water Research Articles

In situ gold adsorption experiment at an acidic hot spring using a blue-green algal sheet

Gold (Au), as one of the most precious metal resources that is used for both industrial products and private ornaments, is a global investment target, and mining companies are making huge investments to discover new Au deposits. Here, we report in situ Au adsorption in an acidic hot spring by a unique adsorption sheet made from blue-green algae with a high preferential adsorption ability for Au. The results of in situ Au adsorption experiments conducted for various reaction times ranging from 0.2 h to 7 months showed that a maximum Au concentration of 30 ppm was adsorbed onto the blue-green algal sheet after a reaction time of 7 months. The Au concentration in the hot spring water was below the detection limit (< 1 ppt); therefore, Au was enriched by preferential adsorption onto the blue-green algal sheet by a factor of more than ~ 3 × 107. Thus, our gold recovery method has a high potential to recover Au even from an Au-poor solution such as hot spring water or mine wastewater with a low impact on the environment.

Geochemical Characteristics of Trace Elements of Hot Springs in the Xianshuihe–Xiaojiang Fault Zone

Trace elements in hot-spring waters are indicators for tracing hydrochemical processes, such as the deep circulation of geothermal water, the degree of water–rock interaction, redox reactions, the contamination of shallow water by thermal water, etc. In this study, 74 hot springs in the Xianshuihe–Xiaojiang Fault Zone (XSHF-XJF) were chosen for an investigation of the geochemical characteristics of trace elements using classic geochemical tools and multivariate statistical analysis. The results indicated (1) the hot-spring waters were mainly derived from atmospheric precipitation as indicated by δD and δ18O values that generally increased with decreasing elevations; (2) the high concentrations of B, As, Fe, and Mn in the waters, as well as the values of the Water Quality Index (WQI), indicated that the water quality was spatially heterogeneous and the hot-spring waters are not entirely suitable for drinking; and (3) B/Cl ratios showed that hot springs have different reservoir sources in the XSHF and XJF, respectively. The leaching of surrounding rock during water circulation contributed predominantly to the trace elements of the study’s waters. Diversity of lithology was the main factor affecting their concentrations. In addition, deep circulation controlled by the fault could influence trace-element enrichment. Our results offer a guide for the exploration and use of geothermal resources.

Rediscovery of the waterlilyNymphaea thermarumEb. Fisch. in Rwanda

AbstractNymphaea thermarumEb. Fisch. (family Nymphaeaceae) is a small waterlily endemic to Rwanda that has been categorized as Extinct in the Wild since 2010. We report the rediscovery ofN. thermarumin July 2023, not far from its locus classicus, identify the current and potential threats to the wild population (mining and overharvesting by collectors, respectively) and recommend the urgent conservation measures and research required to save the species from extinction. The species occupies small muddy ditches fed by hot spring water used for avocado plantations and fish pools. The population comprises hundreds of individuals, including reproductive adult plants, and seedlings. In the short term, conservation actions should include land protection, negotiation to ensure that sufficient water is reaching the habitat ofN. thermarumand the reassessment of the species on the IUCN Red List, probably as Critically Endangered. In the medium term, the creation of a nature reserve, the restoration of the areas already affected by mining, and the reintroduction ofN. thermarumto its original site would support long-term in situ conservation of the species. Further research should clarify the total and effective population size, population structure, ecology and genetics of this species.

Exploring the Hot Springs of Golan: A Source of Thermophilic Bacteria and Enzymes with Industrial Promise.

In recent years, there has been a surge in research on extremophiles due to their remarkable ability to survive in harsh environments. Extremophile thermophilic bacteria provide thermostable enzymes for biotechnology and industry. Thermophilic bacteria live in extreme environments like hot springs at 45-80°C. This study screens and isolates thermophilic bacteria and thermozymes from the Golan hot springs in Karakocan, Elazig, Turkey. The study also characterizes thermophilic bacteria and their thermozymes to understand their features and applications better. Golan hot spring water samples at 50°C yielded 12 isolates. GKE 02, 07, 08, and 10 produce amylase, GKE 04, 08, and 11 cellulase, and GKE 06 xylanase. One isolate (GKE 08) displayed both amylolytic and cellulolytic activity on agar plates. GKE 02 had the highest plate assay amylolytic index (2.3) and amylase activity (67.87 U/ml). Plate assay indicates GKE 08 has 1.5 amylolytic index, 1.1 cellulolytic index, 38.57 U/ml amylase, and 6.81 U/ml cellulase. GKE 04 had the greatest cellulolytic index (1.7) and cellulase activity (27.46). GKE 06, the only xylanase producer, has 19.67 U/ml activity and 1.4 plate assay index. The investigation also included determining the optimal pH and temperature conditions for each enzyme. 16S rDNA gene sequencing revealed seven thermozyme-producing bacteria Bacillus, Geobacillus, and Thermomonas. Thermomonas hydrothermalis genome annotation showed glycosyl hydrolase genes for amylolytic and cellulolytic activity. The findings of this study on thermophilic bacteria and thermostable enzyme synthesis in the Golan hot springs are promising, particularly for T. hydrothermalis, which has limited research on its potential as a thermozyme producer.

Preparation of Lanthanum-Modified Tea Waste Biochar and Its Adsorption Performance on Fluoride in Water.

In this study, tea waste was used as a raw material, and TBC (tea waste biochar) was prepared by pyrolysis at 700 °C. La(NO3)3·6H2O was used as the modifier to optimize one-way modification; the orthogonal experiment was undertaken to determine the optimal preparation conditions; and La-TBC (lanthanum-modified biochar) was obtained. The key factors for the adsorption of fluoride by La-TBC were investigated by means of batch adsorption experiments, and kinetics and isothermal adsorption experiments were carried out on the adsorption of fluoride in geothermal hot spring water. The adsorption mechanism of fluoride by La-TBC was analyzed via characterization methods such as SEM-EDS (Scanning Electron Microscope and Energy Dispersive Spectrometer), BET (Brunauer-Emmett-Teller), FTIR (Fourier transform infrared), XRD (X-ray diffraction), and so on. The results show that La-TBC had the best adsorption effect on fluoride at pH 7. The process of adsorption of fluoride follows the pseudo-second-order kinetics and Langmuir isothermal model, and the maximum theoretical adsorption quantity was 47.47 mg/g at 80 °C, while the removal rate of fluoride from the actual geothermal hot spring water reached more than 95%. The adsorption process was dominated by the monolayer adsorption of chemicals, and the mechanisms mainly include pore filling, ion exchange, and electrostatic interaction.

The Hydrogeochemical Model of "YR" Geothermal Field, East Java

The YR Geothermal Field is located in East Java. This field is associated with an active volcano, implying a potential for a high enthalpy geothermal system. This field is still in the exploration phase, but no drilling has been conducted yet. Thus, insights into the geothermal system are obtained through geochemical analyses of geothermal manifestations. Geochemical analyses were performed on hot spring water samples to determine the characteristics, processes, origin, and fluid flow of the geothermal system. The research results indicate that the warm springs have temperatures ranging from 29.4 to 54.8°C, with a nearly neutral pH (6.14-6.44) and high contents of HCO3 (457-1150 mg/kg), Na (77.7-255 mg/kg), and Mg (37.4-110 mg/kg). Therefore, it can be concluded that all the warm springs fall into the bicarbonate type with immature conditions, indicating no direct association with the reservoir. The upflow zone is interpreted to be at the peak of Mount 7, while the outflow zones are in areas A, B, and C. The fluids flow from the upflow zone, then condense and advectively flow down the slope, experiencing dilution and reactions with rocks before emerging as outflows in the western and north-western areas.

Screening and characterization of thermostable enzyme-producing bacteria from selected hot springs of Ethiopia.

Thermostable microbial enzymes play an important role in industries due to their stability under harsh environmental conditions, including extreme temperatures. Despite their huge application in different industries, however, the thermostable enzymes of thermophilic microorganism origin have not yet been fully explored in Ethiopia. Here, we explored thermophilic bacteria and their enzymes from selected hot spring water and sediment samples. Accordingly, thermophilic bacteria were isolated and screened for the production of extracellular hydrolytic enzymes. Promising numbers of isolates were found as producers of the enzymes. The potent enzyme producers were further identified using matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry analysis and 16S rRNA gene sequencing. The findings revealed the presence of potential hydrolytic enzyme-producing thermophilic bacteria in hot springs of Ethiopia and necessitate further comprehensive study involving other extreme environments. Our findings also revealed the potential of Ethiopian hot springs in the production of thermostable enzymes of significant application in different industries, including food industries.

The distribution of hydrothermal alteration zone and acidic alteration by hot spring water in Unzen Jigoku, Nagasaki Prefecture, Japan

The distribution of hydrothermal alteration zone and acidic alteration by hot spring water in Unzen Jigoku, Nagasaki Prefecture, Japan

Isolation and screening of thermophiles producing Lipase enzyme

Samples were collected from Aravali, Unhale and Unhavare hot water springs and subjected to isolation of thermophiles. The thermophilic isolates obtained were screened out to check their ability to produce Lipase enzyme and named. Only one isolate was found worth studying further on the basis of yield of lipase. The isolate was identified as Bacillus sonorensis SGRP 3.

Physicochemical Parameters and Their Toxicity Level for Recreational Activity and Plaque Psoriasis Healing Effects of Hot Spring Water of Kharapani, Pokhara, Nepal

The current study involved the determination of water quality parameters, inclusively the dissolved mineral levels, to assess the therapeutic and toxicity states of the hot spring water of Kharapani, Pokhara, Nepal. People have widely used the hot spring for taking baths and soaking in to heal from allergic and fungal ailments, musculoskeletal disorders, arthritis, and different diseases. The high values of alkalinity (700 ppm), total suspended solids with the size of at least 2 μm (TSS) (50 ppm), total dissolved solids (TDS) (650 ppm), turbidity (13 NTU), soluble carbonate (150 ppm), soluble chloride (250 ppm), surface tension (72.98 Dynes cm-1) and total hardness (880 ppm) showed the spring water was unsuitable for drinking, swimming and soaking in. The mineral levels at nitrate (undetectable), iron (II) (&lt;0.3 ppm, undetectable), iron (II) (&lt;0.3 ppm, undetectable), aluminum (III) (&lt;0.3, undetectable) corresponded to safe utility levels, and the high sulphate content at 400 ppm showed that the spring was a sulphate rich hot spring with the properties of healing the fungal ailments and respiratory and musculoskeletal disorders. The hot spring water soakers reported healing and relief from itchy skin allergic rashes, and persisting skin disorders like acne, eczema, psoriasis, and joint pain, while the adverse effects such as skin blister, ooze and crust, dry and inflamed skin, dandruff, etc. were also found common among the prolonged soakers of the hot spring. The study showed an excellent healing effect of hot spring baths against psoriasis but associated with mild skin burn and dandruff. The study showed the necessity of technical moderation and maintenance of the minerals and water quality parameters at the acceptable range for swimming purposes.

Insights into Genomic Features and Potential Biotechnological Applications of Bacillus halotolerans Strain HGR5.

Algeria is one of the wealthiest countries in terms of hydrothermal sources, with more than two hundred hot springs. However, diverse and little-described microbial communities colonize these habitats, making them an intriguing research subject. This work reports the isolation of bacteria from two hot springs water samples in northeastern Algeria, evaluating their enzymatic activities and effect on plant pathogens. Out of the obtained 72 bacterial isolates and based on the 16S rRNA gene sequence analysis, the strain HGR5 belonging to Bacillus halotolerans had the most interesting activity profile. Interestingly, HGR5 was substantially active against Fusarium graminearum, Phytophthora infestans, and Alternaria alternata. Furthermore, this strain presented a high ability to degrade casein, Tween 80, starch, chitin, cellulose, and xylan. The genome sequence of HGR5 allowed taxonomic validation and screening of specific genetic traits, determining its antagonistic and enzymatic activities. Genome mining revealed that strain HGR5 encloses several secondary metabolite biosynthetic gene clusters (SM-BGCs) involved in metabolite production with antimicrobial properties. Thus, antimicrobial metabolites included bacillaene, fengycin, laterocidine, bacilysin, subtilosin, bacillibactin, surfactin, myxovirescin, dumulmycin, and elansolid A1. HGR5 strain genome was also mined for CAZymes associated with antifungal activity. Finally, the HGR5 strain exhibited the capacity to degrade polycaprolactone (PCL), a model substrate for polyester biodegradation. Overall, these results suggest that this strain may be a promising novel biocontrol agent with interesting plastic-degradation capability, opening the possibilities of its use in various biotechnological applications.

Effects of Hot-Spring Water Culture on the Nutritional Value of Muscle from Japanese Eel Anguilla japonica

ABSTRACT The chemical composition of muscles from Japanese eels cultured in hot-spring water was determined and compared with that of eels cultured in well water. The proximate composition did not differ significantly between the culture conditions, but the hepatosomatic indices of the hot-spring water eels were significantly higher than those of the well water eels. Amino acid levels were higher in the hot-spring water eels, and the carnosine content of the hot-spring eels was lower than that of the controls. Our results suggest that hot-spring water is a promising medium for eel culture, and its use may bring energy cost savings.

Chemical and thermal changes in hot spring waters and fumarolic gases related to volcanic unrest at Meakandake volcano, Japan: Results of long-term geochemical monitoring from 1986 to 2022

Phreatic eruptions at Nakamachineshiri and Ponmachineshiri reflect the vigorous fumarolic and hydrothermal activities of Meakandake volcano. Thus, phreatic eruptions are likely to reoccur in the future, and hydrothermal systems should be understood to mitigate the risks of potential future hazards. Here, we reveal the results of long-term geochemical monitoring of hot spring waters and fumarolic gases since 1986 and discuss the chemical and temperature changes in hot spring waters, discharging at the foot, related to volcanic unrest. In Nakamachineshiri, related to the increase in seismic and fumarolic activity since 2019, the HCl concentration of the fumarolic gas has increased, and δD and δ18O values have also increased to approach those of the andesitic water. Simultaneously, with the increase in fumarolic and hydrothermal activity, the temperature and Cl concentration of the Meakan Onsen (MO) hot spring water discharged at the western foot of Nakamachineshiri have increased. The chemical characteristics of the fumarolic gas and MO water indicate that they were derived from a hydrothermal system in the shallow subsurface of Nakamachineshiri. Thus, we can consider that the temperature and chemical increases in the MO water represent activation of the system, and monitoring the MO water provides important information for understanding the present state of Nakamachineshiri. At Ponmachineshiri, phreatic eruptions occurred in 1988, 1996, 1998, 2006, and 2008, and seismic and fumarolic activity has sometimes increased since 1986 when we began our monitoring program. At the western foot of Ponmachineshiri, hot spring water is discharged at Yunotaki (YNT_U and YNT_L) and Lake Onneto (ONT). The results of our monitoring suggest that the YNT_U water is formed by mixing thermal water with a high HCO3 molar ratio (HCO3-type) and thermal water containing Cl and SO4 (Cl-SO4-type), which causes temperature and chemical changes related to the mixing ratio of these thermal waters related to volcanic unrest, especially increases in seismic activity. The Cl and SO4 concentrations in the ONT water began to increase approximately two years before the phreatic eruptions and increase in fumarolic activity. Such chemical increases can be explained by the increase in the supply of Cl-SO4-type thermal water and are likely to indicate precursor changes in volcanic unrest. Therefore, we expect to utilize these hot spring waters to understand the present state of Ponmachineshiri and detect precursor changes to future volcanic unrest.

Formation processes of paper-thin raft and coated bubble: Calcium carbonate deposition at gas–water interface

Travertines are hot spring carbonate deposits that exhibit characteristic fabrics, including a paper-thin raft and a coated bubble formed by the calcification of water and bubble surfaces, respectively. A previous study interpreted that compared with the water surface, the bubble surface displays more active CO2 degassing and resultant active CaCO3 precipitation. However, considering the CO2 partial pressure and the volumes of atmosphere and bubbles, it is possible that more active CO2 degassing occurs on the water surface. In addition, the surfaces of water and bubbles at the travertine-depositing sites are negatively charged, but it is still unclear whether the CaCO3 nucleation on these surfaces occurs via amorphous precursors, like the CaCO3 nucleation on negatively charged organic matter. This study provides a solution to these uncertainties by examining the aragonitic travertines formed in the Nagayu area of Japan. Through field observations, two types of paper-thin rafts were recognized: one with a smooth surface and formed in approximately 1 h, and the other with a rough surface and formed in approximately 3 h. In addition, the bubbles generated on the microbial mat during the daytime were covered with white minerals within an hour, and with ivory-colored minerals over 8 h after sunset, forming firm coated bubbles. Microelectrode measurements revealed that the active CO2 degassing on the water surface significantly increased the CaCO3 saturation state to cause active CaCO3 precipitation. In contrast, less active CO2 degassing on the bubble surface did not increase the saturation state, and moderate CaCO3 precipitation occurred due to the moderately high saturation state of the hot spring water. Various microscopic observations revealed that the smooth-surfaced paper-thin raft comprises a micritic layer of approximately 10–20 μm, which represents tightly arranged submicron-sized granular aragonite. At the lower surface of this layer, hemispherical aragonite partially grew toward the hot spring water. In addition, the rough-surfaced paper-thin raft and coated bubble comprise bundled and acicular aragonites arranged along the surfaces of water and bubble, from which hemispherical aragonite grew toward the hot spring water. Neither the paper-thin raft nor the coated bubble contains primary amorphous CaCO3. These results suggest that the smooth-surfaced paper-thin raft is formed by active CaCO3 nucleation on the water surface and subsequent crystal growth, and that the water surface is unfavorable for preserving the amorphous precursors potentially involved in the nucleation. The rough-surfaced paper-thin raft and the coated bubble could have been formed by the attachment of externally formed acicular aragonite to the water/bubble surface and subsequent crystal growth. The revealed formation processes of the paper-thin raft and coated bubble provide valuable information for interpreting their formation mechanism in other travertine deposits, including those in the geological past.

Analysis of Trace Mineral Elements and Microorganisms in Two Hot Springs in Jazan Region of Saudi Arabia

Thermal springs have hydrothermal or volcanic activity, which causes the water to boil up and dissolve any metal that may be present there. It helps in recovery to reduce stress, promote sleep, boost blood circulation, relieve pain and heal skin problems. However, they consist of some heavy and trace metals and some non-metals, such as Mg, Mo, Na, As, Hg, Cd, Ni, Fe, Cu, Mn, Zn, Co, Ti, Cr and Pb are present. These hot springs are also known to exhibit natural microbiota, which is helpful in maintaining the public health and preventing consumer outbreaks with the advancement of research, microbiological monitoring of hot spring water can be done by utilizing high throughput sequencing. Taking these facts in concern, the present work, hot spring samples were collected from different locations of Al-Harth and Alarda hot springs, Jazan region, Saudi Arabia. The samples collected were analyzed for trace minerals and microbiological activity. These samples were found to exhibit the temperature range from 60 to 70 ºC and an average pH of 6.5 to 8.5. Almost all the samples had shown the presence of trace elements with electrical conductivity and total dissolved solids (TDS) ranged from 0.02 to 0.045 dms and 27 to 43 mg/L, respectively. Scattergun metagenomic analysis was performed to determine the microbiological content. The preliminary study reports the microbiome (bacteria, archea and viruses) of alarath hot spring water employing whole-genome high-throughput sequencing and bioinformatics. Bacterial species detected were members of the phyla 64% Proteobacteria, 20% Actinobacteria, 6.3% unclassified, 2.2% Deinococcus thermus, 1.4 Firmcutes and 1.6% others. Fecal indicator bacteria, i.e. Escherichia coli or enterococci, were not detected in any samples examined in this study. Both archaeal DNA (0.4%) and viral DNA (0.009%) were found.

A Study on IFN-γ and IL-10 Gene Expression Changes in Gallus gallus Embryo Infected with Pseudomonas aeruginosa and Its Possible Restoration by Bakreshwar Hot Spring Water

Bakreswar hot spring is a naturally occurring hot spring located at Birbhum district in West Bengal, India. The surface temperatures of the hot springs varies between 35°C to 66°C. The water of hot spring is alkaline with pH 9 and has curative properties. Pseudomonas aeruginosa is an important pathogen causing hospital acquired infections and in this study we used multi-drug resistance (MDR) isolate. The motive of the study is to compare the IL-10 and IFN-γ gene expression changes in Gallus gallus domesticus embryo infected with Pseudomonas aeruginosa by using the Bakreswar hot spring water.The curative properties of the hot spring water collected from Agnikund (65°C) was studied on 14thdays old chick eggs infected with Pseudomonas aeruginosa. After harvesting and allantoic fluid collection, RNA extraction was done and cDNA synthesis and RT-PCR were performed. After infection of the chick embryo with MDR Pseudomonas aeruginosa, both IL-10 and IFN-Ƴ gene expressions were increased, but in the curative sets those were challenged with Bakreswar hot spring water IL-10 and IFN- γ both gene expressions were decreased. From this study we may conclude that hot spring water of Bakreswar has antimicrobial activity against Pseudomonas aeruginosa due to which it decreses the cytokine gene expressions.

Utilization of Hot-Spring-Water-Bound CO2 for Horticulture Plants Using Incubation Method

This study focused on free carbon dioxide (H2CO3) contained in volcanic hot spring water. It was clarified whether free carbon dioxide can be emitted into the atmosphere and increase the CO2 concentration in greenhouses by using the incubation method. Factors influencing the increase in CO2 concentration were identified based on implementation time in a demonstration experiment, temperature and humidity in the incubator, the amount of hot spring water, and the contact area between the hot spring water and the air. An incubator with an inner volume of 2.17 × 107 mm3 was used in this study. The results showed that unrelated factors were the implementation time in the demonstration experiment, temperature, and humidity. There was a relationship with the amount of hot spring water. The increment of CO2 concentration in the air by free carbon dioxide increased proportionally by increasing the amount of water. Free carbon dioxide contained in hot spring water can be utilized by considering the volume of facility horticulture and plant factories. The ideal methods for utility are to replace the hot spring water every few minutes and to increase the contact area between the air and the hot spring water.

Unveiling the Elemental Composition and Categorization of Sikkim Hot-Spring Water with Laser-Induced Breakdown Spectroscopy and Advanced Analytical Techniques

The research investigates the elemental composition of hot-spring water in Sikkim, specifically in Yumthang, Tarum, and Reshi, using laser-induced breakdown spectroscopy. This technique involves exciting the sample with a high-energy laser pulse, causing it to emit light that can be analyzed to determine its elemental composition. The results of the study indicate that the hot-spring water in Sikkim is of meteoric origin, meaning it originated from precipitation. To understand the abundance of elements in the hot-spring water samples, the Sulphur/Nitrogen, Chlorine/Nitrogen, and Sulphur/Chlorine ratios were calculated using the ratiometric method. These ratios were then used to classify the samples using univariate and multivariate statistical tools. The box plot was used for the univariate analysis, while the bivariate normal distribution method was used for the multivariate analysis. We have also discussed the limitations of overlapping emission peaks on the classification of the samples. The study found that the abundance of nitrogen in the samples played a significant role in their classification. Principal component analysis was also employed to classify the samples. This technique involves identifying the most significant variables contributing to the variation in the data and using them to classify the samples. Overall, the study provides important insights into the elemental composition of hot-spring water in Sikkim and highlights the usefulness of laser-induced breakdown spectroscopy in analyzing such samples.

A Study on IFN-γ and IL-10 Gene Expression Changes in Gallus gallus domesticus Embryo Infected with E. coli and its Possible Alteration by Bakreshwar Hot Spring Water

In search of effective treatment against E. coli there are some conventional medicinal treatments available but it becomes difficult to fight against MDR strains as they are resistant to most of the antibiotics. It was found that Bakreshwar hot spring water has some therapeutic properties against various infections, mostly against skin infections. Bakreshwar hot spring having a pH range of 8.1-8.5 and temperature which varies from 35°-71°C, contains several chemical compounds. Our aim of this work was to study whether Bakreshwar hot spring water can cure infections caused by E. coli in Gallus gallus embryo in relation to their gross appearances and IFN- γ and IL-10 gene expression changes. The sample water was collected around March, 2023. To study the therapeutic activity of Bakreshwar hot spring water, different experimental sets were set up with 14days embryonated eggs. Freshly prepared 0.5Mcfarland E. coli culture was inoculated into the eggs and in curative set, 100µl hot spring water was injected to check any alterations. Allantoic fluid was collected and mRNA was extracted the very next day. cDNA was synthesized from the extracted mRNA. Along with master mixture (primers, nuclease free water, Syber green) the cDNA was run at RT-PCR and CT value was obtained. The mean gene expression shows that IL-10 and IFN- γ both gene expression was decreased in curative set after treatment with water as compared to control sets. These finding suggests that Bakreshwar hotspring water treatment can be a potential method to control E. coli caused infections.

Effects of salinity stress induced by hot spring water on tomato growth, yield and fruit quality under hydroponic cultivation in Japan

The objective of this research was to test hot spring water as a source of salt to improve tomato quality under the hydroponic system. This research was conducted at Yamagata University, in Japan from February to July 2017. Salt stress was induced using salts of hot spring wastewater collected from Yupoka Onsen (Tsuruoka, Japan). The treatments were EC 2, 4, 8 12, and 16 mS/cm which were arranged in a Randomized Complete Block Design (RCBD) with five replications. Tomato plants were grown at EC 2 until flowering and then subjected to different EC concentrations until harvesting. The data were collected on plant growth parameters and fruit quality. Fruits were harvested at the red stage until the 5th truss. The results showed that fruits' Soluble Solids Content, organic acid, Nitrate contents and Sugar: Acid ratio increased significantly at EC 16 mS/cm and in the upper trusses compared to EC 2 and in the lower trusses. In contrast, fruit weight significantly decreased at EC 16 mS/cm and in upper trusses. Leaf thickness, size and SPAD, and specific leaf weight significantly declined at EC 16 mS/cm and upper leaves compared to EC 2 and in lower leaves. Plant height started to decline significantly after three weeks of treatment at EC 16 compared to EC 2.