Calcium Concentration In Water Research Articles

Limited Migration From Physiological Refugia Constrains the Rescue of Native Gastropods Facing an Invasive Predator.

Biological invasions have caused the loss of freshwater biodiversity worldwide. The interplay between adaptive responses and demographic characteristics of populations impacted by invasions is expected to be important for their resilience, but the interaction between these factors is poorly understood. The freshwater gastropod Amnicola limosus is native to the Upper St. Lawrence River and distributed along a water calcium concentration gradient within which high-calcium habitats are impacted by an invasive predator fish (Neogobius melanostomus, round goby), whereas low-calcium habitats provide refuges for the gastropods from the invasive predator. Our objectives were to (1) test for adaptation of A. limosus to the invasive predator and the low-calcium habitats, and (2) investigate if migrant gastropods could move from refuge populations to declining invaded populations (i.e., demographic rescue), which could also help maintain genetic diversity through gene flow (i.e., genetic rescue). We conducted a laboratory reciprocal transplant of wild F0 A. limosus sourced from the two habitat types (high calcium/invaded and low calcium/refuge) to measure adult survival and fecundity in home and transplant treatments of water calcium concentration (low/high) and round goby cue (present/absent). We then applied pooled whole-genome sequencing of 12 gastropod populations from across the calcium/invasion gradient. We identified patterns of life-history traits and genetic differentiation across the habitats that are consistent with local adaptation to low-calcium concentrations in refuge populations and to round goby predation in invaded populations. We also detected restricted gene flow from the low-calcium refugia towards high-calcium invaded populations, implying that the potential for demographic and genetic rescue is limited by natural dispersal. Our study highlights the importance of considering the potentially conflicting effects of local adaptation and gene flow for the resilience of populations coping with invasive predators.

Feasibility of increasing calcium content of drinking tap water following quality regulations to improve calcium intake at population level.

Calcium intake is below recommendations in several parts of the world. Improving calcium intake has benefits not only for bone health but also helps to prevent pregnancy hypertension disorders. Calcium concentration of tap water is usually low The aim of the present study was to determine the maximum amount of calcium that can be added to tap water while complying with drinking water Argentine regulations. Tap water samples were collected from the Province of Buenos Aires (Argentina). Physicochemical properties and saturation index were measured. Different incremental concentrations of calcium chloride were added to the experimental aliquots. Baseline water had a mean calcium concentration of 22.00 ± 2.54 mg/L, water hardness of 89.9 ± 6.4 mg/L CaCO 3, and a saturation index of -1.50 ± 0.11. After the addition of 0.4554 ± 0.0071 g of salt, water hard-ness reached 355.0 ± 7.1 mg/L CaCO 3, a calcium concentration of 140.50 ± 2.12 mg/L, and a saturation index -0.53 ± 0.02. This study shows that at laboratory level it is feasible to increase calcium concentration of drinking water by adding calcium chloride while complying with national standards. Calcium concentration of drinking tap water could be evaluated and minimum calcium concentration of tap water regulated so as to improve calcium intake in populations with low calcium intake.

Impact and accumulation of calcium on soft-shell mud crab Scylla paramamosain in recirculating aquaculture system

Soft-shell crabs are highly valued for their commercial significance and culinary appeal. To enhance production of soft-shell crabs, careful attention should be paid to the water calcium concentration in their culture. This study investigated the influences of different levels of calcium concentrations on the molting and growth of mud crab (Scylla paramamosain) within a meticulously controlled recirculating aquaculture system (RAS). We established three distinct water calcium concentration gradients (200, 300, and 450 mg/L) to comprehensively assess feeding habits, molting patterns, growth, and tissue calcium levels of mud crab. Initially, we observed a gradual reduction in water calcium concentrations with increments of crab molting events in RAS. Throughout one molting cycle, the feeding incidence of the crabs remained consistently high from 4 days to 37 days post-molt, irrespective of different calcium concentrations. Nonetheless, high water calcium levels (300 and 450 mg/L) significantly shortened molt intervals and accelerated exoskeletal calcification. Specifically, the molt intervals were 52.30 ± 2.72 d, 41.65 ± 5.24 d, and 37.70 ± 3.02 d, while the carapace hardening durations were 21.51 ± 4.33 h, 17.23 ± 3.38 h, and 13.46 ± 2.76 h at water calcium concentrations of 200, 300, and 450 mg/L, respectively. Moreover, elevated calcium concentrations also significantly enhanced weight gain of the mud crab during molting. Noteworthy, regardless of fluctuations in water calcium concentration, the condition factor of the molting crabs was approximately 63%, which could be an indicator of crab selection in soft-shell crab cultivation. Furthermore, the dynamic changes in calcium concentrations were disparate among different tissues in the post-molt stage. Gill and exoskeleton tissues exhibited an upward trend in calcium concentrations, while hemolymph and hepatopancreas tissues displayed distinct patterns of decrease followed by increase. Gill and exoskeleton tissues were identified as primary sites for calcium absorption and utilization, evidenced by a positive correlation between high calcium concentrations and increased calcium content in these tissues at 6 h and 3 d post-molt. Overall, our findings provide practical evidence for optimizing aquaculture management strategies through adjustments in water calcium concentration, thus to enhance production efficiency and profitability in soft-shell mud crab aquaculture.

The Determination of Minerals in Soil, Water, Fodder, and Serum and their Effects on Reproductive Efficiency of Nili Ravi Buffaloes

Introduction: Minerals play an essential role in the reproductive performance of dairy animals, especially in buffaloes. The present study aimed to evaluate the mineral concentrations in different types of samples, including soil used for fodder cultivation, canal water used for fodder irrigation, drinking water for buffaloes, fodder used for buffalo feeding, and serum of buffaloes and their effects on the reproductive efficiency of buffaloes. Materials and methods: The current study was carried out for three months and samples were analyzed twice at the beginning and the end of the study. The concentrations of calcium, magnesium, and inorganic phosphorus in the soil were checked through the versinate method. The concentration of calcium, magnesium, and inorganic phosphorus in water was checked through the titration method and the concentration of calcium, magnesium, and inorganic phosphorus contents in fodder was checked through the wet digestion method. The minerals of blood serum (n = 80) were analyzed through commercial kits. Results: In canal water, calcium concentration was higher for irrigation compared to buffalo drinking water. Similarly, on the upper surface of the soil compared to its low surface, the level of calcium was high. Calcium values of serum were higher in cyclic buffaloes compared to buffalo heifers. In comparison to all groups, the levels of inorganic phosphorus were found to be lower in non-cyclic buffaloes. Similarly, the calcium-to-phosphorus ratio was found to be lower in non-cyclic buffaloes and heifers compared to repeat breeders and cyclic buffaloes. At the beginning of the study, cyclic buffaloes had higher magnesium levels than all other groups, except for non-cyclic buffaloes. By the end of the study, magnesium concentrations were higher in non-cyclic buffaloes and heifers compared to repeat breeders and cyclic buffaloes. Conclusion: The mineral deficiencies in water and soil can affect the fodder content in the feed of buffaloes.

Feasibility of increasing calcium content of drinking tap water following quality regulations to improve calcium intake at population level

Background Calcium intake is below recommendations in several parts of the world. Improving calcium intake has benefits not only for bone health but also helps to prevent pregnancy hypertension disorders. Calcium concentration of tap water is usually low The aim of the present study was to determine the maximum amount of calcium that can be added to tap water while complying with drinking water local regulations. Methods Tap water samples were collected from the Province of Buenos Aires (Argentina). Physicochemical properties and saturation index were measured. Different incremental concentrations of calcium chloride were added to the experimental aliquots. Results Baseline water had a mean calcium concentration of 22.00 ± 2.54 mg/L, water hardness of 89.9 ± 6.4 mg/L CaCO3, and a saturation index of -1.50 ± 0.11. After the addition of 0.4554 ± 0.0071 g of salt, water hard-ness reached 355.0 ± 7.1 mg/L CaCO3, a calcium concentration of 140.50 ± 2.12 mg/L, and a saturation index -0.53 ± 0.02. Conclusions This study shows that at laboratory level it is feasible to increase calcium concentration of drinking water by adding calcium chloride while complying with national standards. Calcium concentration of drinking tap water could be evaluated and minimum calcium concentration of tap water regulated so as to improve calcium intake in populations with low calcium intake.

Effects of climate and acidic deposition on interannual variations of stream water chemistry in forested watersheds in the Shimanto River Basin, southern Japan

AbstractAlthough the amount of acidic deposition has recently decreased in Japan, it has still deteriorated some forest ecosystems during the past several decades. Moreover, recent climate changes can affect stream water chemistry. We investigated the temporal trend and effects of climate conditions on stream water chemistry for more than 20 years in two areas (Yusuhara and Taisho) in the Shmanto River Basin, southern Japan, where the effects of acidic deposition are considered to be modest. Stream water samples were collected monthly from three forest watersheds selected at each site. The annual means of the stream chemistry were predicted by multiple regression analysis. The ammonium, nitrate, and sulfate concentrations in the bulk precipitation have decreased at Yusuhara, and the sodium, magnesium, calcium, chloride, nitrate, and sulfate concentrations in the stream water have decreased in both areas. The nitrate and sulfate concentrations apparently responded to the decreasing input of acidic deposition. The sunlight hours were positively related with the potassium, magnesium, calcium, nitrate, sulfate, and bicarbonate concentrations in stream water. The results suggest that long sunlight hours boost the photosynthetic activities, thus promoting soil respiration and decomposition of soil organic matter. Moreover, a higher carbonic acid concentration in the soil solution promotes cation weathering and carbonic acid dissociation to bicarbonate. Given the decreasing trends in magnesium and calcium concentration with no change in bicarbonate concentration, we inferred that previousinputs of acidic deposition enhanced the rate of rock weathering.

Community structure, environmental conditions and anthropogenic pressure on the habitat of the European endemic aquatic plant Luronium natans (L.) Raf.

Luronium natans (L.) Raf. is a European endemic species and is becoming increasingly rare and endangered in most countries. This study aimed to compare the community structure and environmental conditions of shallow and deep-water habitats of Luronium, and related anthropogenic influences. A total of 21 Luronium lake habitats were surveyed at Pomerania Lakeland (NW Poland). Luronium occurs mainly with other isoetids, as well as bryophytes, specifically Sphagnum denticulatum. It can also be found in oligotrophic lakes at a depth of 1.0 ± 0.6 m and in water with a large pH range (4.52 – 8.76), as well having a low conductivity (38.3 ± 20.9 µS cm−1; 19.0 – 106.1) and calcium concentration (3.9 ± 2.4 mg dm−3; 1.6 – 11,7).The largest Luronium cover occurs at a depth of 1.5 m (44.8 ± 35.3%), but occasionally as deep as 3.5 m. In the depth gradient, the structure of underwater vegetation and environmental conditions exhibit obvious changes, which presents a clear distinction between shallow and deep-water habitats of Luronium. The differences mainly pertain to the abundances of Isoëtes lacustris and Elodea canadensis in the community, as well as environmental factors, such as water calcium, nitrogen and phosphorus concentrations, PAR, conductivity, and water color.Compared to other isoetids, Luronium usually occurs in habitats with intermediate features, which are characterized by values between the typical, but deep-water, Isoëtes and shallow water Lobelia and Littorella. However, Luronium clearly prefers waters with higher temperatures (23.8 ± 2.7 °C), which are thus less oxygenated (96.6 ± 20.0%). In terms of pH, conductivity, and calcium concentration, Luronium occurs in waters having slightly lower values compared to other isoetids. Therefore, Luronium is a species that significantly expands the diversity of habitat number 3110 in the Natura 2000 network. Therefore, it can be considered as an indicator species of lobelia lakes.An increased anthropogenic pressure primarily results in an increased water conductivity and a decreased water transparency. Consequently, Luronium increasingly inhabits shallower waters that are more oxygenated. Moreover, Luronium abundance is decreasing, while the abundances of species comprising underwater communities are also decreasing, e.g., S. denticulatum and I. lacustris, with a concurrent increase in Myriophyllum alterniflorum and E. canadensis cover.

Yielding of aquaponics using probiotics to grow tomatoes with tilapia

Aquaponics is a cutting-edge technology where plants and fish are grown together in a close-loop re-circulating system. It is not feasible to use growth-promoting agents, such as pharmaceutical antibiotics, with this biological and ecologically friendly technology to prevent or treat fish diseases. Examination of different growth booster substances became necessary because of this, and probiotics are one potential solution. The purpose of this experiment was to figure out the effect of gut probiotics, water probiotics and biofloc inputs in aquaponics to grow tilapia and tomato. Tilapia was fed with 29.40% protein containing feed with the supplement of gut probiotics (AQ-GT), water additive probiotic (AQ-WT), combination of probiotics-molasses-yeast (AQ-BF) and without any probiotic supplement (AQ) as control in media-based aquaponics. The investigation was incorporated for 75 days with triplicates of each treatment. Water quality, tilapia and tomato plant were sampled at 15-days interval. Moreover, matured tomatoes were harvested regularly. The findings showed that the treatments differed significantly in terms of electric conductivity, dissolved solids, calcium, sodium, potassium, magnesium, phosphorus, boron, copper, ammonia, nitrite, and nitrate concentration in tank water. The highest tomato flower was recorded in control (P < 0.01). On the other hand, the highest tomato and tilapia production were in AQ-BF (P < 0.01). The research findings revealed that biofloc technology (AQ-BF) significantly lower the feed conversion ratio and enhance the specific growth rate of tilapia than the other treatments. Moisture, crude protein, crude lipid, crude fiber, ash, and nitrogen free extract percentage in tilapia varied significantly among the treatments. Contrarily, statistical similarity among the treatments exists in terms of moisture, lipid, and ash content of tomato. The results indicate that, combination of biofloc technology with aquaponics is more viable for higher fish and vegetable production with favorable water quality than the other ways of probiotic inclusion in aquaponics.

Water quality, WASH, and gender: differential impacts on health and well-being in Abeokuta City, Nigeria.

It is often assumed that humans experience the effect of poor water quality like multiple health and socioeconomic impacts in the same way. But these impacts are not gender neutral due to inequalities caused by physiological composition, age marginalization, and socioeconomic conditions, among others. A mixed method, comprising water quality assessment, a survey of 456 individuals, and medical record collection, was applied to examine the differential impacts of water quality and WASH practices in Abeokuta City, Nigeria. The assessment shows that without point-of-use water treatment, the water sources in the area are not safe for potable purposes, as the waters are hard in the sequence of borehole > surface water > hand-dug well > sachet water, with elevated levels of calcium (> 75 mg/L) and not free from microbial contamination. Among the area population segments, men and boys (relative to women and girls) may be more susceptible (55%) to the compounding health effects associated with the hardness and high calcium concentration in water. Girls are the most affected by the associated impacts of water collection. Men and boys are more vulnerable to the consequences of poor hygiene, while women are more susceptible to the health effects of toilet cleaning and the sharing of sanitation facilities, among others. We conclude that there are differential impacts of unsafe water, WASH services, and practices on human health. Gendered statistics through sex-disaggregated data is crucial to unmasking the differential impacts, which are neither gender neutral nor evenly distributed between women and men, and boys and girls.

Control of the Ionic Composition of Nanofiltration Membrane Permeate to Improve Product Water Quality in Drinking Water Supply Applications

Reverse osmosis is efficiently used for producing drinking water from groundwater sources containing dissolved impurities, including fluoride, ammonia, lithium, strontium, boron, arsenic, etc. The principal problems of utilizing reverse osmosis include scaling on membrane surfaces, concentrate discharges, and low permeate TDS that often require conditioning. The main goal of this work was to demonstrate the viability of a newly developed methodology that relies on low-rejection nanofiltration membranes to improve product water quality by increasing its TDS and calcium content, and its economic efficiency compared to conventionally used reverse osmosis. Disadvantages of employing reverse osmosis for the production of drinking water are attributed to the fact that several pollutants (including lithium, ammonia, and boron) are monovalent ions and, as such, are poorly rejected by membranes as compared to calcium, sodium, sulfate, and chloride ions. Thus, in cases in which lithium or ammonia are present in high concentrations, high rejection membranes are usually used that result in low TDS of the product water. This article presents the results of research aimed at developing a new approach to changing the ratio of monovalent and divalent ions in product water. The new method described in this paper relies on low rejection membranes in a two-stage application that enables us to reduce monovalent impurities and increase the concentration of calcium and TDS values in product water while leaving lithium concentration unchanged. This is achieved by applying a two-stage scheme with low-rejection membranes instead of the reverse osmosis stage. The two-stage treatment using nanofiltration membranes results in the same rejection of lithium and product water quality as reverse osmosis. However, the ratio value of calcium and lithium concentrations in the concentrate of nanofiltration membranes appears to be significantly higher compared with the ratio measured in the feed groundwater. This can be attributed to different rejections of these ions by membranes. Therefore, concentration (reduction of volume) of the feed water with nanofiltration membranes and further dilution of the concentrate with deionized water produce the same concentration of lithium and are associated with an increase of 2–4 times the concentration of calcium. Treatment of this water in the second nanofiltration membrane stage produces drinking-quality water with the required lithium content and increased calcium concentration. We focus on the real-world example of groundwater treatment in Yakutia, Russia, an area where lithium concentration exceeds drinking standards by 24 times. The paper presents a technique of ion separation and demonstrates experimental results that provide lithium removal while increasing the calcium concentration and TDS value. The resulting concentrations are 2–5 times lower than those obtained via conventional use of reverse osmosis membranes. A series of experiments were conducted to remove lithium from groundwater and demonstrate the efficiency of the newly developed method of ion separation. Experimental results of the concentration of obtained values of lithium, calcium, and TDS in permeate and concentrate flows at each membrane stage demonstrate that they provide separation of monovalent and divalent ions and increase product water TDS without increasing lithium. This experimental approach increases calcium and TDS values in product water by 2–4 times compared with the use of reverse osmosis membranes. Calculations of operational costs for different options (the use of reverse osmosis, two-stage nanofiltration, and ion separation in a two-stage approach) are presented. These results confirm the economic advantage of nanofiltration membrane applications to remove lithium as compared to the use of high-rejection reverse osmosis membranes. The increase in product water TDS facilitates the further reduction of concentrate flow rate and operational costs. The economic comparison involved the calculation of the required membrane area and number of membrane elements at each stage, calcium carbonate scaling rates, reagent consumption to prevent scaling, and amounts of concentrate discharged into the sewer. Experimentally obtained results confirmed the feasibility of increasing the calcium concentration and TDS values in product water by 2–5 times while leaving the lithium concentration at the same level. Design characteristics to calculate operational costs for conventional and new options are calculated and demonstrate a sufficient (30–40%) reduction of operational costs compared to conventional use of reverse osmosis. The reduction in reagent consumption is attributed to the utilization of low-rejection nanofiltration membranes that have lower scaling propensities compared with reverse osmosis membranes and a smaller payment for concentrate discharge. The developed approach to using two-stage nanofiltration instead of single-stage reverse osmosis provides multiple advantages that include improved product water quality, lower concentrate consumption, and lower reagent consumption that are attributable to the use of low-rejection membranes. Different case studies are planned to demonstrate the efficiency of the proposed techniques to reduce ammonia, fluoride, and boron in drinking water.

Calcium concentration of drinking water to improve calcium intake: A simulation study.

The risk of inadequate calcium intake is a worldwide problem. We performed a simulation exercise on the impact, effectiveness, and safety of increasing calcium levels in drinking water using the 2019 Health and Nutrition National Survey of Argentina, which provides water intake and water sources data at the individual level. We simulated the distribution of calcium intake assuming a calcium concentration of 100mg of calcium per liter of tap water and 400mg of calcium per liter of bottled water. After the simulation, all population groups had a slightly improved calcium intake. Higher impacts were observed in adults, as reported water intake was higher in adults 19-51 years old. In young adult women, the estimated calcium intake inadequacy decreased from 91.0% to 79.7% when calcium was increased in tap water and to 72.2% when calcium was increased in tap and bottled water. The impact was lower in adolescents and older adults who have higher calcium recommendations and reported lower water intake. Increased calcium concentration of water could improve calcium intake in Argentina, especially in adults as their reported water intake is higher. Combining more than one strategy to improve calcium intake might be required for countries like Argentina with low calcium intake.

Calculation of the contribution of water to calcium intake in low- and middle-income countries.

Dietary calcium intake is low in many countries, particularly in low- and middle-income countries (LMICs). Water is often overlooked as a source of dietary calcium despite it being universally consumed and providing good calcium bioavailability. Our objective was to assess water distribution systems in LMICs and to develop a formula to simulate the contribution of different water sources to calcium availability. We calculated the contribution of drinking water considering different calcium concentration levels to estimate total calcium availability. We consider a country's households' access to drinking water sources and the distribution of the country's population by age and gender. Calcium availability could be increased by an average of 49mg of calcium per person per day in the 62 countries assessed if calcium in drinking water was considered. In 22 (31%) of the countries studied, 80% of households are supplied by water sources that could increase calcium availability. Improving calcium concentration in water could be considered as a strategy in LMICs to slightly improve calcium availability.

Growth and shell hardness of the apple snail Pomacea flagellata Say, 1829, reared at three calcium concentrations.

The snail Pomacea flagellata inhabits aquatic systems with high calcium concentration and it is important to food webs; unfortunately, its natural populations are decreasing due to overfishing and habitat destruction. Here we tested the effect of three water calcium concentrations on the growth and hardness of snail shells in triplicate recirculation culture systems for 12 weeks. In each culture, 100 juvenile snails were seeded at constant density and fed with balanced tilapia feed. Thirty snails were randomly collected every 15 days and measured in length and total weight. The size, weight, and shell hardness of the snails for the 500 mg/L calcium treatment were significantly higher than the mean size of the snails in the other treatments (300 mg/L and 243.33 mg/L). The calcium supply in the culture promotes growth and allows the snails to produce healthier and stronger shells, in addition to improving their growth rate, which is important for the management of the species.

The Impact of the Watershed Use Changes on the Water Chemistry of the Shallow, Urban Lake—A Case Study of Lake Mielenko (Pomeranian Lakeland, Poland)

The research was carried out on the flow-through Lake Mielenko (7.8 ha; 1.9 m), which also acts as a stormwater receiver. In 2015, a disposal for road salts was created in the lake’s catchment area. As a result of the inflow of salt-contaminated stormwater, there was a significant increase in the concentration of calcium (57 mg Ca/L), chloride (220 mg Cl/L) and electrolytic conductivity (790 µS/cm). Increased calcium concentrations in lake waters changed their hardness from low to medium-hard. The ecological effect of the change in hydrochemical conditions in Lake Mielenko is the Potamogeton crispus that grows abundantly in this reservoir, which prefer calcium-rich water. The overall aesthetics of the lake have deteriorated significantly, and the availability of water for recreation has also been limited.

Acclimatization of fish to the higher calcium levels in the water environment

It is established that calcium concentration changes (variations) in the water environment significantly influence its intake and distribution in tissues and organs of hydrobionts. The decrease in calcium concentration in water from 100 to 60 mg.L-1 significantly reduces its content in fish liver. In the gills glandular apparatus of fish acclimated to the environment with lower calcium level (in comparison with control one), its concentration on the first day of the acclimation period slightly exceeded the initial level, thus testifying to its possible excretion of endogenous calcium by gills. The increase of calcium excretion through the renal and digestive systems in fish acclimates to the higher water level, and specific changes in phosphates excretion dynamics accompany oral intake. Long keeping fish in water with 100 mg.L-1 calcium is accompanied by the increase of total phosphorus in urine (by 2 – 2.5 times), and its day excretion increases by 1.9 – 2.4 times. During fish acclimation to higher calcium levels in the water environment, the excretion of total phosphorus with faecal matter increases. The increase of calcium in the water environment to 100 mg.L-1 leads to a temporary increase in total phosphorus excretion with faecal issues. The rise in cation concentration to 200 mg.L-1 increases significantly during long-time fish stay in such an environment.

Oyster shell amendment reduces cadmium and lead availability and uptake by rice in contaminated paddy soil.

Contamination with cadmium (Cd) and lead (Pb) in rice and paddy soil threatens food safety and human health. This study determined the effects of oyster shell amendment (0, 6, and 12gkg-1) on the mobility and uptake of Cd and Pb by two rice plants (ZY18, japonica and DL5, indica) in contaminated paddy soil. Oyster shell amendment significantly increased the pH of soil and pore water, and decreased the DTPA-extractable Cd concentration in soil, but not the Cd concentration in pore water. Furthermore, the DTPA-extractable Pb concentration in rhizosphere soil was not significantly influenced by oyster shell addition. Application of oyster shell reduced the Pb concentration in pore water and Pb uptake by both cultivars, but excessive application (12gkg-1) resulted in Cd accumulation in tissues for ZY18. Furthermore, oyster shell addition significantly increased the dissolved organic carbon, calcium, and magnesium concentrations in soil pore water, and decreased glutathione and phytochelatin levels in roots, all of which alleviated heavy metal toxicity and improved rice growth. These results demonstrate that amendment with the appropriate amount of oyster shell, combined with rice cultivar type, could simultaneously reduce Cd and Pb accumulation in rice grown in heavy metal-contaminated soil.

Testing for sensory threshold in drinking water with added calcium: a first step towards developing a calcium fortified water.

Background: Food fortification is an effective strategy that has been recommended for improving population calcium inadequate intakes. Increasing calcium concentration of water has been proposed as a possible strategy to improve calcium intake. The objective of this study was to determine the sensory threshold of different calcium salts added to drinking water using survival analysis. Methods: We performed the triangle test methodology for samples of water with added calcium using three different calcium salts: calcium chloride, calcium gluconate and calcium lactate. For each salt, a panel of 54 consumers tested seven batches of three water samples. Data were adjusted for chance and sensory threshold was estimated using the survival methodology and a discrimination of 50%. Results: The threshold value estimation for calcium gluconate was 587 ± 131 mg/L of water, corresponding to 25% discrimination, for calcium lactate was 676 ± 186 mg/L, corresponding to 50% discrimination, and for calcium chloride was 291 ± 73 mg/L, corresponding to 50% discrimination. Conclusions: These results show that water with calcium added in different salts and up to a concentration of 500 mg of calcium/L of water is feasible. The calcium salt allowing the highest calcium concentration with the lowest perceived changes in taste was calcium gluconate. Future studies need to explore stability and acceptability over longer periods of time.

МОЛЛЮСК СЕМЕЙСТВА BITHYNIIDAE (GASTROPODA, LITTORINIMORPHA) РАВНИННОЙ РЕКИ НИЖНЕГО ПОВОЛЖЬЯ

Background. Preservation of stable and sustainable natural conditions in aquatic ecosystems of various territories is the most urgent problem of nature management in many regions of the world. Occurring changes together with the anthropogenic factor intensify the processes of destabilization of watercourse biocenoses. The resulting transformations in the environment have already led to irreversible changes in the biosphere and a reduction in the number of species. The main causes of biodiversity reduction are habitat destruction, degradation and fragmentation. The most important component of aquatic ecosystems is the representatives of benthic fauna - benthos. One of the elements in the composition of macrozoobenthic are mollusks, as one of the most numerous and widespread groups of organisms, clearly responding to the changes in habitat conditions. Therefore, the purpose of our work is to study the distribution patterns and quantitative indicators of Bithynia tentaculata (Linnaeus, 1758) in the plains river sections with varying degrees of exposure to environmental factors. Materials and methods. In July 2017, hydrobiological samples were collected from the source to the mouth of the Samara River were examined 17 stations. Processing of the collected material was carried out in laboratory conditions. The number and biomass of individuals were counted and necessary morphometric measurements were made. The analysis of the obtained data by means of modern statistical programs was performed. Results. As a result of the study of the Samara River, individuals of the mollusk B. tentaculata were registered in 30% of the sample. The species was found in biotopes characterized by various abiotic and biotic conditions of the environment. In the river it prefers shallow (up to 3 m) unpolluted areas rich with vegetation. Quantitative values in the Samara River were low and significantly inferior to values in one of its tributaries by a factor of 4. The maximum values were noted at the station near the village Borskoe. The comparative analysis of morphological parameters of mollusk shells (height and width) at the river sites did not allow to reveal clear distinctions connected with ecological features on them. It was only noted that the presence of all size groups of the species in the middle reaches may indicate the most satisfactory conditions for B. tentaculata. A canonical analysis of the dependence of the species relative to the vectors of the gradient of environmental factors showed significant (p≤0,05) results for macrophyte overgrowth area, nitrate nitrogen content, dissolved oxygen and calcium concentrations in water. In order to understand the minimum number of factors affecting clam individuals, the rocky sediment criterion was applied, with results indicating 4 environmental variables explaining more than half (54%) of the variance. Conclusions. The obtained results allowed us to supplement the available information on the distribution of the Lower Volga region malacofauna. The species preferences in a complex of ecological conditions characteristic for biotopes of the Samara River have been revealed. All these new data will allow to carry out more effectively measures on preservation of biodiversity of aquatic ecosystems.

Reusing Flowback and Produced Water with Different Salinity to Prepare Guar Fracturing Fluid

Economical and environmental concerns have forced the oil and gas industry to consider reusing flowback and produced water for fracturing operations. The major challenge is that the high-salinity of flowback water usually prevents its compatibility with several fracturing fluid additives. In this paper, the authors explored an economic and effective method to prepare guar fracturing fluids with different salinity waters. The main research idea was to use chelating agents to mask metal ions, such as calcium and magnesium, that are harmful to crosslinking. Firstly, a complexometric titration test was conducted to measure the chelating ability of three chelating agents. Secondly, through viscosity, crosslinking, and hanging tests, it was verified that the complex masking method could cope with the problem of high-valence metal ions affecting crosslinking. Thirdly, the preferred chelating agent was mixed with several other additives, including thickeners, crosslinkers, and pH regulators, to prepare the novel guar fracturing fluid. The comprehensive performances of the novel fluid system were tested such as temperature and shear resistance, friction reduction, gel-breaking performance, and core damage rate. The results show that the organophosphate chelating agent (i.e., CA-5) had the greatest ability to chelate calcium and magnesium ions. There was a good linear relationship between the dosage of CA-5 and the total molar concentration of calcium and magnesium ions in brine water. The main mechanism was that the chelating agent formed a complex with calcium and magnesium ions at a chelation ratio of 1:5. The test results of the comprehensive performance evaluation indicate that the prepared guar fracturing fluid met the requirements for field application, and the lower the salinity of the flowback water, the more it is economical and effective.

Testing for sensory threshold in drinking water with added calcium: a first step towards developing a calcium fortified water

Background: Food fortification is an effective strategy that has been recommended for improving population calcium inadequate intakes. Increasing calcium concentration of water has been proposed as a possible strategy to improve calcium intake. The objective of this study was to determine the sensory threshold of different calcium salts added to drinking water using survival analysis. Methods: We performed the triangle test methodology for samples of water with added calcium using three different calcium salts: calcium chloride, calcium gluconate and calcium lactate. For each salt, a panel of 54 consumers tested seven batches of three water samples. Data were adjusted for chance and sensory threshold was estimated using the survival methodology and a discrimination of 50%. Results: The threshold value estimation for calcium gluconate was 587 ± 131 mg/L of water, corresponding to 25% discrimination, for calcium lactate was 676 ± 186 mg/L, corresponding to 50% discrimination, and for calcium chloride was 291 ± 73 mg/L, corresponding to 50% discrimination. Conclusions: These results show that water with calcium added in different salts and up to a concentration of 500 mg of calcium/L of water is feasible. The calcium salt allowing the highest calcium concentration with the lowest perceived changes in taste was calcium gluconate. Future studies need to explore stability and acceptability over longer periods of time.