Water Pool Research Articles

Farm Sangkuriang Catfish (Clarias gariepinus) for 59 Days

This study aims to determine the cultivation of sangkuriang catfish (Clarias gariepines) for 59 days. The method used in this study is observation by collecting primary data directly from the field. During the study, the highest pool water temperature was found in the second week of 29.11 oC and the lowest temperature of pool water was found in the third week of 28.22 oC. The temperature of the pool water in the morning is lower than in the afternoon. This is influenced by sunlight that directly enters the pond which results in an increase in the metabolic process of the catfish body. The pH of Sangkuriang catfish farming pond ranges from 7.8-7.25. If the highest pH value indicates that the waters are alkaline, on the contrary, if the low pH value indicates acidic, the conclusion is that the salinity treatment of the medium does not have a significant enough effect (P<0.05) on the survival rate of catfish. Sangkuriang catfish is a type of fish that is able to survive and breed in conditions where water is less oxygen and low pH levels, in the first week the oxygen degree is 1.25 and the lowest at 0.65. Catfish tend to be more active in warm water temperatures, but they can also survive in winters with lower temperatures. However, they may become less active and require extra attention to ensure the water temperature remains within limits they can tolerate.

In vivo rat brain mapping of multiple gray matter water populations using nonparametric D(ω)-R1-R2 distributions MRI.

Massively multidimensional diffusion magnetic resonance imaging combines tensor-valued encoding, oscillating gradients, and diffusion-relaxation correlation to provide multicomponent subvoxel parameters depicting some tissue microstructural features. This method was successfully implemented ex vivo in microimaging systems and clinical conditions with tensor-valued gradient waveform of variable duration giving access to a narrow diffusion frequency (ω) range. We demonstrate here its preclinical in vivo implementation with a protocol of 389 contrast images probing a wide diffusion frequency range of 18 to 92 Hz at b-values up to 2.1ms/μm2 enabled by the use of modulated gradient waveforms and combined with multislice high-resolution and low-distortion echo planar imaging acquisition with segmented and full reversed phase-encode acquisition. This framework allows the identification of diffusion ω-dependence in the rat cerebellum and olfactory bulb gray matter (GM), and the parameter distributions are shown to resolve two water pools in the cerebellum GM with different diffusion coefficients, shapes, ω-dependence, relaxation rates, and spatial repartition whose attribution to specific microstructure could modify the current understanding of the origin of restriction in GM.

Neural Network-Based Electrochemical Sensors for Free Chlorine Detection

Free chlorine which refers to all chlorine present in water as Cl2, hypochlorous acid (HOCl), and hypochlorite ion (ClO-), is a widely used disinfectant in tap and swimming pool water, as well as for washing raw vegetables and other foods. The lack of disinfection of such water sources can lead to the outbreak of infectious diseases. Therefore, the World Health Organization (WHO) has developed guidelines for drinking water quality using Hazard Analysis and Critical Control Point (HACCP) principles for the food industry, and monitoring of free chlorine is becoming increasingly important.[1] Traditional methods for measuring free chlorine concentration, such as absorption spectrophotometry and the iodine method, face challenges in providing accurate continuous measurements. Similarly, electrochemical measurement methods face challenges in accuracy due to the variability in the electrochemical response of free chlorine. This variability is influenced by electrode surface conditions and pH variation, as the ratio of hypochlorous acid and hypochlorite ion present depends on pH. To overcome these challenges, we explored the potential of neural network-based machine learning techniques utilizing electrochemical responses to estimate free chlorine concentration. In this study, we developed a free chlorine sensor utilizing machine learning, employing a current-potential curve as input to estimate free chlorine concentration, regardless of pH variations.To collect data for training the neural network model, we built and employed an automated measurement system based on Raspberry Pi. This system facilitated the sequential preparation of various solutions using NaH2PO4, Na2HPO4, and sodium hypochlorite solutions, followed by electrochemical measurements using linear sweep voltammetry (LSV). A total of 480 LSV curves were generated, covering pH values ranging from 5.3 to 8.8, free chlorine concentrations from 0 ppm to 55 ppm, and scanning speeds of 100 mV/s with a range of 0.7 V to -1.5 V. Each measurement sequence consisted of 12 LSV curves representing various free chlorine concentrations. These concentrations were varied in constant increments at similar pH levels. In total, 40 sequences were performed through this process.Figures 1 and 2 show LSV curves obtained at pH 5.7 and pH 8.9, respectively. Under both pH conditions, the current increases with increasing free chlorine concentration. However, variations in curve shapes, particularly the reduction peak observed around -0.4 V, illustrate the influence of pH on the electrochemical response. This peak, attributed to the reduction of hypochlorous acid, becomes suppressed at higher pH levels due to the decreased proportion of hypochlorous acid relative to hypochlorite ion.Machine learning was conducted using 360 LSV curves for training and the remaining 120 LSV curves for validation, employing a neural network structure consisting of 5 affine layers with rectified linear unit (ReLU) as the intermediate layer and mean squared error (MSE) function as the output layer. Current value columns from LSV curves and corresponding free chlorine concentrations were utilized as inputs and outputs, respectively. The average error was low at 2.26 ppm, albeit with a maximum error of 15.4 ppm, attributed partly to variations in electrode surface conditions during measurements. To address this, we focused on the initial 0 ppm LSV curve in each sequence, which provides crucial information about changes in electrode surface conditions. Taking into account this insight, we performed a new approach. In this approach, we concatenated the current value columns from all LSV curves with the current value column from the corresponding 0 ppm LSV curve in the input data. This approach allowed us to effectively incorporate information about the electrode surface condition into machine learning, resulting in a significant improvement in accuracy. Figure 3 illustrates the predicted concentration plotted against actual concentration values, showing an average error of 1.04 ppm and a maximum error of 8.75 ppm, highlighting the efficacy of our machine learning approach.In conclusion, our developed sensor, which employs a neural network, demonstrates outstanding accuracy in estimating free chlorine concentration, even when the pH level is unknown.[1] World Health Organization, Guidelines for Drinking-Water Quality, 4th edn incorporating the first and second addenda, 2022. Figure 1

Picosecond Pulse Radiolysis Observation of the Formation and Spur Kinetics of Hydrated Electrons in Sodium Dodecyl Sulfate-Water-Cyclohexane-Hexanol Quaternary Microemulsions.

The observation of electron transfer and solvation processes in liquid-liquid multiphase systems is of great challenge, especially at the interface. In this study, the formation and spur kinetics of hydrated electrons (eaq-) were investigated in sodium dodecyl sulfate-water-cyclohexane-hexanol microemulsions with ω values (nwater/nsurfactant) from 18 to 48 using picosecond pulse radiolysis coupled with pulse-probe UV-vis spectroscopy. Interestingly, a relatively slow formation of eaq- was observed, corresponding to the electron transfer from the oil phase to water pools. The evolution curves of eaq- were simulated by using a simplified consecutive reaction model. It demonstrated that the electrons generated in the oil phase are solvated in the water pools of the microemulsions at a close rate. Surprisingly, the addition of NaNO3 could accelerate electron transfer into water pools. The decays of eaq- in the microemulsions were significantly slower than that in pure water and accelerated with increasing water content, indicating the absence of a nanoconfinement effect.

Orientation-independent quantification of macromolecular proton fraction in tissues with suppression of residual dipolar coupling.

Quantitative magnetization transfer (MT) imaging enables noninvasive characterization of the macromolecular environment of tissues. However, recent work has highlighted that the quantification of MT parameters using saturation radiofrequency (RF) pulses exhibits orientation dependence in ordered tissue structures, potentially confounding its clinical applications. Notably, in tissues with ordered structures, such as articular cartilage and myelin, the residual dipolar coupling (RDC) effect can arise owing to incomplete averaging of dipolar-dipolar interactions of water protons. In this study, we demonstrated the confounding effect of RDC on quantitative MT imaging in ordered tissues can be suppressed by using an emerging technique known as macromolecular proton fraction mapping based on spin-lock (MPF-SL). The off-resonance spin-lock RF pulse in MPF-SL could be designed to generate a strong effective spin-lock field to suppress RDC without violating the specific absorption rate and hardware limitations in clinical scans. Furthermore, suppressing the water pool contribution in MPF-SL enabled the application of a strong effective spin-lock field without confounding effects from direct water saturation. Our findings were experimentally validated using human knee specimens and healthy human cartilage. The results demonstrated that MPF-SL exhibits lower sensitivity to tissue orientation compared with , , and saturation-pulse-based MT imaging. Consequently, MPF-SL could serve as a valuable orientation-independent technique for the quantification of MPF.

Porous mesh manifold for enhanced boiling performance

High-performance electronics are continuously demanding cooling of higher heat fluxes. Phase-change cooling, including pool boiling, is a useful approach to address this challenge; however, competition between liquid and vapor flows generally limit the heat fluxes that can be dissipated. A range of strategies to control these flows have been investigated previously, including capillary guides. Here a manifold structure formed from a metallic mesh is investigated to control the disposition of liquid and vapor phases above a pool fed boiling surface enhanced with porous structures. Copper mesh forms defined liquid flow paths, using capillary action to guide and distribute liquid evenly over the heated surface, along with open channels to facilitate vapor escape. The mesh provides a novel structure for liquid guidance that imposes low resistance to liquid flow while occluding a minimal area of heated surface underneath. The manifold performance is characterized in boiling fed by a pool of water above a laser-textured aluminum nitride heat dissipation surface with pin–fin structures having heights of 110 µm and spacing of 30 µm with a heated area of 5mm x 5mm. A maximum heat flux of 490 W/cm2 is reached with the manifold in the pool fed configuration, representing an increase of more than 65% over the porous pin fin surface alone. The maximum stable superheat observed for the manifold of 36K is 14K higher than that for the porous surface without the manifold. The factors limiting performance of the manifold are analyzed. High superheat is attributed to partial flooding of the boiling surface as suggested by the reduction in superheat using external suction. Similar systems and structures for enhanced two-phase cooling are compared.

An ADCP Attitude Dynamic Errors Correction Method Based on Angular Velocity Tensor and Radius Vector Estimation

An acoustic Doppler current profiler (ADCP) installed on a platform produces rotational tangential velocity as a result of variations in the platform’s attitude, with both the tangential velocity and radial orientation varying between each pulse’s transmission and reception by the transducer. These factors introduce errors into the measurements of vessel velocity and flow velocity. In this study, we address the errors induced by dynamic factors related to variations in attitude and propose an ADCP attitude dynamic error correction method based on angular velocity tensor and radius vector estimation. This method utilizes a low-sampling-rate inclinometer and compass data and estimates the angular velocity tensor based on a physical model of vessel motion combined with nonlinear least-squares estimation. The angular velocity tensor is then used to estimate the transducers’ radius vectors. Finally, the radius vectors are employed to correct the instantaneous tangential velocity within the measured velocities of the vessel and flow. To verify the effectiveness of the proposed method, field tests were conducted in a water pool. The results demonstrate that the proposed method surpasses the attitude static correction approach. In comparison with the ASC method, the average relative error in vessel velocity during free-swaying movement decreased by 20.94%, while the relative standard deviation of the error was reduced by 17.38%.

Case study on thermal and flow analysis of a water mist on a pool fire in a ventilated engine compartment

Public transport buses and other large vehicles are facing increasing engine fire issues stemming from higher operating temperatures, phonic insulation and low maintenance time. The fire suppression systems currently employed or considered for vehicles could be used for the protection of buses. Water mist is one of these technologies. One of the challenges a water mist faces for the fire protection of small enclosures is the ventilation. Inside a full scale engine compartment of a truck, the interaction and heat transfer between a n-heptane pool fire and water mist droplets are studied using velocimetry techniques. Most notably, the influence of the nozzle operating pressure and a variable cross-flow ventilation on the extinguishing performance is explored. In this preliminary study without clutter, the results show the importance of the ventilation flow on the performance of the water mist. Moderate ventilation speeds up to 3.2ms-1 show an improvement of the extinguishing time over natural ventilation while a higher ventilation speed of 6.4ms-1 degrades the extinguishing performance of the mist. For low-pressure water mists, the momentum of the spray is the most important factor for water mist extinguishing performance.

Study on the impact of hydraulic characteristics of new stilling pool in the context of energy conservation, emission reduction, and green construction

In the context of peaking carbon dioxide emissions and carbon neutrality, the construction of hydropower projects has strict regulations on the demand for construction materials, which also puts forward new requirements for design organizations. Several power stations have successfully applied spillway and floodway double-discharge building shared stilling pools as the new requirements of the design program. By the stilling pool, we mean it is an energy dissipation facility that generates a bottom-flow water jump downstream of the discharge structure. However, this type of program will be due to the uneven distribution of the flow of the double building problems, leading to its flow pattern being too complex and stilling pool dissipation characteristics being unclear. For this reason, based on the hydraulic model test method, this paper studies and analyzes the hydraulic characteristics of the new type of stilling pool in the shared stilling pool scheme of the double-drainage structure when the flood relief hole is needed to dominate the flow in particular circumstances. For the problems exposed during the test, three auxiliary dissipation schemes were added to the stilling pool, and their influence on the hydraulic characteristics of the stilling pool was studied. The results show that the baffle block can effectively reduce the stilling pool's bottom flow velocity and improve the stilling pool's water flow pattern compared with other programs. The dissipation effect is better than other schemes. The related research can provide technical support for further engineering applications of the double-drainage structure shared stilling pool program.

The Impact of Chlorinated Water and Sun Exposure on the Durability and Performance of Swimwear Materials.

Understanding the factors that affect how materials age is essential for creating a durable product with long-lasting properties. It is also important to prioritize defining aging parameters that reflect the real-world conditions the materials will encounter. For this study, a range of swimwear materials were selected consisting of a blend of polymer (polyamide/polyester) and elastane in varying ratios. In order to simulate aging conditions, materials were immersed in chlorinated outdoor pool water during the summer season, either in shade or the sun, for 200 and 300 h. The materials were tested for mass per unit area, thickness, tensile properties, and moisture management. A slight mass per unit area increase was observed, rising from 1.0% after 200 h of chlorine and sunlight exposure to 3.7% after 300 h. Thickness increased by 1.7% after 200 h and 3.2% after 300 h of chlorine exposure, with no significant effect of sunlight. Breaking force dropped by 12.4% after 200 h in chlorine and 8.2% in chlorine and sunlight, becoming more pronounced after 300 h (65.7% in chlorine and 65.1% in chlorine and sunlight). The overall moisture management capability declined from 0.4888 to 0.3457 after 200 h in chlorine and 0.3393 with sunlight, dropping further after 300 h to 0.3838 and 0.3253, respectively.

Sanitary Surveillance Program for pools in Matosinhos, Portugal

Abstract The use of pools for sports, recreational, and therapeutic activities has increased over time. It is important to ensure and control the quality of the water and surrounding areas, as well as the hygienic-sanitary conditions of these spaces. The ‘2018 Pool Sanitary Surveillance Program’ of the Portuguese Northern Regional Health Administration proposes the surveillance of water quality, teaching accessories, and surfaces. The aim of this investigation is to conduct microbiological analysis of the teaching accessories and surfaces in public pools in the municipality of Matosinhos and assess if this program has improved the results for water quality, teaching accessories, and surfaces from 2018 to 2023. The environmental health team of our Public Health Unit performed swabs of the teaching accessories and surfaces of all seven public pools in Matosinhos for microbiological analysis. The swabs were performed in 2018 (21), 2019 (48) and 2023 (42). During each visit, three random points were selected for analysis. In 2019, 31 rugs (64,6%) were analysed, but in 2023 only 10 (23,8%) were rugs. It was found that rugs had the highest contamination by P. aeruginosa (94,4%), fungi (60,8%), and the only sample with coagulase-positive Staphylococci. There was a decrease in samples from twelve to six with P. aeruginosa and an increase from 22 (46.8%) to 29 (69.0%) with fungi from 2019 to 2023. Bacterial colonies grew in 20 samples (95.2%) in 2018, 44 (91,6%) in 2019, and 42 (100%) in 2023. All water samples collected for the evaluation of microbiological parameters outlined obtained compliant results. Fungal and P. aeruginosa detection indicate a potential risk to the health of pool users. A quality report with corrective measures was produce for each pool in each visit. Surveillance of pool water, teaching materials and surrounding surfaces, is crucial to ensure water quality and safety. By doing so, we may lower the risk of disease transmission and protect the population’s health. Key messages • To ensure the safety of pool users is a public health challenge. It would be relevant to have legislation that addresses this issue. • To survey pools and its surroundings and accessories must be a continuous task, allied with literacy to management and users.

Persistence of Helicobacter Pylori Coccoid Forms in Different Environments

Objective: The present study aims to determine the possibility of H. pylori coccoid forms to survive in our surrounding environments, thus exhibiting public health hazard. Method: Helicobacter pylori strain Makkah 7 accession number HQ622108, was inoculated in samples of soil, well, tap, swimming pool, and sewage water; in which, an average initial inoculum of 107 CFU/ml was inoculated. The experiment was conducted, outdoor where ambient temperature varied between 39-55°C in Jeddah city, Saudi Arabia. The survival rate of H. pylori strain was quantitatively and qualitatively studied for five months. Results: Viable counts were undetectable after 24 hours, while total count varied between 107 to 106, and declined to 103 bacterial cell/ml five months later. Interestingly, microscopic examination revealed few non-motile rods and motile coccoid forms. All samples were removed and placed at 4°C for one month. Following, total count, morphology, and motility were examined, showing motile coccoid forms. Electron microscopic and, molecular studies were carried out, confirming that the species is H. pylori, which was detected by using 16S rRNA primer for H. pylori with a product size of 163 bp. The ability of H. pylori strain to persist and survive, by being motile in the coccoid form, for five months under such hostile environment, strongly indicates that the coccoid form plays a vital role in the transmission, recrudescence, and therapeutic failure. It is indeed a hazardous and a crucial infectious phase of this bacterium. Conclusion: Detecting coccoid forms in water and soil, accompanied by their eradication, must be seriously considered and applied. Consequently, hindering and preventing different diseases caused by H. pylori.

Development of Multifunctional Tablet Formulation for Use In Swimming Pools

The pool waters pose certain risks to public health. Therefore, it is crucial for swimming pool water to meet the desired standards in terms of physical, chemical, and biological parameters, and to be regularly monitored to ensure the provision of healthy and safe swimming conditions. In our country, swimming pool water standards are determined in accordance with regulations set forth by the Ministry of Health. To maintain these standards, various pool chemicals are required, including pool water disinfectants, pH reducers, precipitators, brighteners, and algae inhibitors. The objective of our study is to develop a multifunctional tablet formulation, a technological innovation that combines the properties of these chemicals into a single product. To achieve this goal, we conducted physical and bactericidal tests on new formulations containing disinfectants such as calcium hypochlorite, trichloroisocyanuric acid, and sodium dichloroisocyanurate. The multifunctional tablet formulations developed provide an effective solution to meet and exceed the required standards for swimming pool water quality.

Data-driven effects of human activities and environmental factors on inland aquatic dissolved organic matter in China: Insights from machine learning

Aquatic DOM, a major carbon pool in inland waters, plays a key role in the global carbon cycle and is influenced by human activities and environmental factors. While watershed surveys have identified some drivers of aquatic DOM changes, national-scale knowledge remains limited. Spectral monitoring data from 721 aquatic DOMs in inland China were collected to predict and quantify the spectral properties of aquatic DOMs and the coupled effects of human activities and environmental factors by complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), random forest (RF) and structural equation modeling (SEM). Our results show that the dataset is relatively evenly distributed in terms of flow regimes, and the data are adequately representative of various types of water in China. Although the performance of CEEMDAN is affected by the skewed distribution of data sampling points (453 and 449 for eastern regions and eutrophic waters, respectively), CEEMDAN effectively processes the spatial sequences of aquatic DOM spectra, which significantly improves the reliability of the machine learning model (by 13%–68%) and reduces the error (by 63%–92%). CEEMDAN-RF and SEM results indicate that longitude and latitude are the most important environmental factors affecting the spectral properties of aquatic DOM through temperature, light and land cover differences, reducing the biogenic properties of aquatic DOM. Unlike observations in small watersheds and estuaries, environmental factors of season, precipitation and salinity have weak effects on aquatic DOM. Furthermore, the biogenic character of aquatic DOM is enhanced by urban human activities, represented by urbanization, population, and impervious land fraction, which have long-lasting and strong impacts on aquatic DOM by driving water eutrophication and enhancing phytoplankton and microbial activity. Our study informs the prediction and quantification of coupled environmental and anthropogenic impacts on aquatic DOM at large scales.

Prevalence of Intestinal Parasitosis Caused by Nematopsis sp (Protozoa: Apicomplexa) in Litopenaeus vannamei and its Relationship with Water Turbidity, in a Fattening Farm

Objective: This research aims to calculate the prevalence of intestinal parasitosis caused by Nematopsis sp (Protozoa: Apicomplexa) on white shrimp (Litopenaeus vannamei) and relate it to water turbidity, in a fattening farm. Methods: The work was carried out on the western coast of the state of Falcón (Venezuela), where the animals (for clinical and laboratory analysis) and the turbidity data of the pool water were obtained. For the turbidity analysis, the Secchi disk was used, which allowed the measurement to be recorded in centimeters of transparency. The shrimp were captured by random sampling in the lagoons and immediately transferred to the laboratory for clinical study, subsequently data on prevalence, correlation (R), and coefficient of determination (R2) were obtained. Results: Once the analyses were carried out, a correlation coefficient (R) of 0.319951628 was obtained, indicating the low dependence (weak positive connection) between the related variables (the prevalence of diseases and the levels of turbidity in the water). In the evaluation of the R2, the value of 0.102369044 was obtained, which indicated that in only 10.23% of the infected animals, there was an influence of turbidity on the prevalence of infected animals. Conclusion: The prevalence values obtained in this study are consistent with those reported in other research in Latin America. In turn, the related data demonstrated that water turbidity could be related (weakly) to the presence of the parasitic protozoan Nematopsis sp, however, their statistical relationship is very scarce.

An Experimental Study of an Autonomous Heat Removal System Based on an Organic Rankine Cycle for an Advanced Nuclear Power Plant

The present study focuses on the recovery of waste heat in an autonomous safety system designed for advanced nuclear reactors. The system primarily relies on passive safety condensers, which are increasingly integrated into the design of advanced Pressurized Water Reactors (PWRs). These condensers are typically immersed in large water tanks that serve as heat sinks and are placed at sufficient heights to ensure natural circulation. Such a heat removal system can operate for an extended period, depending on the size of the tank. This research is driven by the potential to recover part of the energy stored in the boiling water volume, using it as a heat source for an Organic Rankine Cycle (ORC) system via an immersed heat exchanger. The electricity generated by the ORC engine can be used to power the system components, thereby making it self-sufficient. In particular, a pump replenishes the water tank, ensuring core cooling for a duration no longer limited by the water volume in the tank. An experimental test setup, including a boiling water pool and an ORC engine with an electrical output of approximately several hundred watts, along with an immersed evaporator, was constructed at CEA (Grenoble, France). Several test campaigns were conducted on the experimental test bench, exploring different configurations: two distinct ORC working fluids, cold source temperature variation effects, and relative positioning of the submerged evaporator and heat source within the water tank impact. These tests demonstrated the reliability of the system. The results were also used to validate both the ORC condenser and evaporator models. This article presents this innovative system, which has recently been patented. Moreover, to the best of our knowledge, the investigated configuration of an ORC that includes an immersed evaporator is original.

Antibacterial bio pores as a river flow filter for the development of "Ndeso Park" water tourism

The realization of the full potential of natural resources in each village for the benefit of the local community has been observed as a significant challenge. The national village-owned enterprises program encourages villages to optimize the utilization of their existing natural and human resources with the objective of fostering their economic independence. The program entails the optimization of the national village-owned enterprises program in the tourism sector, specifically in the context of Taman Ndeso. The objective of this community service activity is to provide technological assistance and address the issue of river water filtration as a pool water source. The impetus for this activity is the declining tourism activities at Taman Ndeso due to the presence of turbid water in the pool, which was deemed unsuitable for use. The activity is realized through the construction of a water purification filtration system to produce clean and healthy water. The antibacterial biopores are applied as filtration technology. This technology is designed to capture bacteria from river water that flow into the pond. This research adopted the direct exploration method, which was divided into a number of stages, including planning and preparation, implementation, evaluation, and reporting. The research outcome manifests into the restoration of the Taman Ndeso water tourism pool, which will be capable of attracting tourists and reviving village income to the maximum extent possible, with the management of the village-owned business entity.

Elevated total mercury (THg) levels in water sources under the influence of artisanal and small-scale gold mining (ASGM) in Tanzania.

This study investigated the presence and distribution of mercury in water bodies under the influence of artisanal and small-scale mining (ASGM) activities in Tanzania, which continue to predominantly rely on mercury for gold extraction. Various water bodies available for domestic and animal use in mining communities were sampled from surface water sources in ASGM settlements during the rainy and dry seasons. Water samples were analysed using cold vapour atomic fluorescence spectrophotometer (CVAFS). The results indicate that most of water sources had THg levels above the WHO guideline of 1.0µg/L (1000ng/L) for safe drinking water. The levels were significantly higher during the wet season ranging from 3.4 to 96.3µg/L, whereas the range was from 0.84 to 2.12µg/L during the dry period. The higher THg values during the wet season are likely a result of increased lateral transport (e.g. via enhanced runoff) and physical properties of the waterways. Transportation and resuspension of matrix-bound mercury from surface soils and inflow of contaminated water from unprotected tailings were also observed to be potential means of lateral mercury transport. The lowest concentrations (0.846µg/L) were observed in water samples from the Mabubi River, upstream of a mining village. Downstream of the mining village in the same river, higher concentrations were observed in the Nungwe Bay region of Lake Victoria. In other surveyed mining settlements where there were no nearby rivers, pool water indicated high concentrations of THg, including levels above thresholds for safe human use. Immediate stringent measures are needed in order to ensure human and animal safety at ASGM mining settlements. Future investigation is suggested to focus on the distribution of mercury in different media, assessing the prevalence of different mercury species, and investigating the influence of weather and hydrological conditions on the impacts of mercury to organisms as part of the strategies to mitigate mercury pollution.

Tillage and cover cropping influence phosphorus dynamics in soil and water pools

AbstractWinter cover crops (CCs) have the potential to reduce phosphorus (P) loss by temporarily fixing P into CC biomass. A field experiment with no‐tillage (NT) and conventional tillage (CT) was used to study the ability of different CC species planted after corn (Zea mays L.) and soybean (Glycine max L.) harvests to reduce the P availability in soil solution. The effect of three crop rotations (corn–no CC–soybean–no CC [C–S], corn–cereal rye (Secale cereale)–soybean–hairy vetch (Vicia villosa) [C–R–S–HV], corn–cereal rye–soybean–oats (Avena sativa)+ radish (Raphanus sativus L.) [C–R–S–OR]) and two tillage (NT and CT) treatments was determined on soil available P and soil solution P content through pan (A horizon) and tension (100‐cm depth) cup lysimeters. The experiment was set up as a randomized complete block design with tillage as a split factor with three replicates. Over the study period, incorporating hairy vetch in C–R–S–HV rotation reduced the Mehlich‐3 P content in soil by 26%–29% compared to the C–S and C–R–S–OR rotation. Both CC rotations (C–R–S–HV and C–R–S–OR) were effective in reducing dissolved reactive P (DRP) concentration in pan and tension cup lysimeters compared to the C–S in both CT and NT systems. However, these results varied with CC species grown and seasonal variability in precipitation. A significantly lower DRP load with crop rotation and tillage treatments was observed mainly during the CC growing season. During the study period, crop rotations with reduced labile soil P content and DRP loss were ranked in an order of C–R–S–HV > C–R–S–OR > C–S. Overall, this study showed that CCs have the potential in both CT and NT systems to significantly reduce P in soil and soil solution, and these effects are resilient to a wide range of precipitation conditions.

Using water pool as cushion to mitigate ground vibration due to collapse of cooling tower with simulation of complete debris distribution

Large-scale cooling towers in inland nuclear power plants (NPPs) may collapse under extreme conditions. The collapse-induced ground vibrations threat the safety operations of the adjacent nuclear related facilities. Therefore, prediction and possible mitigation of the ground vibrations are significant in the NPP planning. This study proposed a novel method to arrange a water pool as a cushion underneath the cooling tower to mitigate the ground vibrations. The planar dimension of the water pool is determined by the debris distribution of the collapsed cooling tower. To achieve this, first, the mitigation effect was tested using a steel ball impacting on a concrete pedestal. Then, to obtain the complete debris distribution, a technique was developed to reproduce the disappearing elements in the finite element method-based simulation, and was validated against the tests of vase debris. Finally, the “cooling tower-water pool cushion-soil” models were established to demonstrate the vibration mitigation using the water pool cushion. For the concerned case with the water pool of 6 m depth, the vibration reduced by 56 % and 59 % for the maximum and average of the ground peak accelerations in the horizontal direction, as well as by 65 % and 60 % for those in the vertical direction, respectively.