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The forest headwater streams are important hubs for connecting terrestrial and aquatic ecosystems, with plant litter and sediments as the major carriers for material migrations; however, until now we knew little about the dynamics of trace elements such as iron (Fe) and aluminum (Al) in forest headwater streams. Here, we quantitatively identified the spatiotemporal dynamics of Fe and Al storages in plant litter and sediments and their influencing factors in a subtropical forest headwater stream, and assessed the potential pollution risk. The results showed that: (1) the mean concentrations of Fe and Al in plant litter (sediments) were 5.48 and 8.46 (7.39 and 47.47) g·kg−1, and the mean storages of Fe and Al in plant litter (sediments) were 0.26 and 0.43 (749.04 and 5030.90) g·m−2, respectively; (2) the storages of Fe and Al in plant litter and sediments significantly fluctuated from January to December, and showed a decreasing pattern from the source to mouth; and (3) storages of Fe and Al had no significant correlation with riparian forest type and the present of tributary and the Fe and Al storages in plant litter were mainly affected by water temperature and water alkalinity, and their storages in sediments were mainly affected by water temperature and frequency of rainfall; and (4) there were no anthropogenic pollution in Fe and Al in the forest headwater stream. Our study revealed the primary factors of concentrations and storages of Fe and Al in plant litter and sediments in a forest headwater stream, which will improve our understanding of the role of headwater streams in forest nutrient storage and cycling along with hydrological processes. [ABSTRACT FROM AUTHOR]

Key message: Compared with NaCl, NaHCO3 caused more serious oxidative damage and photosynthesis inhibition in safflower by down-regulating the expression of related genes. Salt-alkali stress is one of the important factors that limit plant growth. NaCl and sodium bicarbonate (NaHCO3) are neutral and alkaline salts, respectively. This study investigated the physiological characteristics and molecular responses of safflower (Carthamus tinctorius L.) leaves treated with 200 mmol L−1 of NaCl or NaHCO3. The plants treated with NaCl treatment were less effective at inhibiting the growth of safflower, but increased the content of malondialdehyde (MDA) in leaves. Meanwhile, safflower alleviated stress damage by increasing proline (Pro), soluble protein (SP), and soluble sugar (SS). Both fresh weight and dry weight of safflower was severely decreased when it was subjected to NaHCO3 stress, and there was a significant increase in the permeability of cell membranes and the contents of osmotic regulatory substances. An enrichment analysis of the differentially expressed genes (DEGs) using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes identified significant enrichment of photosynthesis and pathways related to oxidative stress. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the darkgreen module had the highest correlation with photosynthesis and oxidative stress traits. Large numbers of transcription factors, primarily from the MYB, GRAS, WRKY, and C2H2 families, were predicted from the genes within the darkgreen module. An analysis of physiological indicators and DEGs, it was found that under saline-alkali stress, genes related to chlorophyll synthesis enzymes were downregulated, while those related to degradation were upregulated, resulting in inhibited chlorophyll biosynthesis and decreased chlorophyll content. Additionally, NaCl and NaHCO3 stress downregulated the expression of genes related to the Calvin cycle, photosynthetic antenna proteins, and the activity of photosynthetic reaction centers to varying degrees, hindering the photosynthetic electron transfer process, suppressing photosynthesis, with NaHCO3 stress causing more pronounced adverse effects. In terms of oxidative stress, the level of reactive oxygen species (ROS) did not change significantly under the NaCl treatment, but the contents of hydrogen peroxide and the rate of production of superoxide anions increased significantly under NaHCO3 stress. In addition, treatment with NaCl upregulated the levels of expression of the key genes for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate-glutathione cycle, and the thioredoxin-peroxiredoxin pathway, and increased the activity of these enzymes, thus, reducing oxidative damage. Similarly, NaHCO3 stress increased the activities of SOD, CAT, and POD and the content of ascorbic acid and initiated the glutathione-S-transferase pathway to remove excess ROS but suppressed the regeneration of glutathione and the activity of peroxiredoxin. Overall, both neutral and alkaline salts inhibited the photosynthetic process of safflower, although alkaline salt caused a higher level of stress than neutral salt. Safflower alleviated the oxidative damage induced by stress by regulating its antioxidant system. [ABSTRACT FROM AUTHOR]

Key message: Compared with NaCl, NaHCO3 caused more serious oxidative damage and photosynthesis inhibition in safflower by down-regulating the expression of related genes. Salt-alkali stress is one of the important factors that limit plant growth. NaCl and sodium bicarbonate (NaHCO3) are neutral and alkaline salts, respectively. This study investigated the physiological characteristics and molecular responses of safflower (Carthamus tinctorius L.) leaves treated with 200 mmol L−1 of NaCl or NaHCO3. The plants treated with NaCl treatment were less effective at inhibiting the growth of safflower, but increased the content of malondialdehyde (MDA) in leaves. Meanwhile, safflower alleviated stress damage by increasing proline (Pro), soluble protein (SP), and soluble sugar (SS). Both fresh weight and dry weight of safflower was severely decreased when it was subjected to NaHCO3 stress, and there was a significant increase in the permeability of cell membranes and the contents of osmotic regulatory substances. An enrichment analysis of the differentially expressed genes (DEGs) using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes identified significant enrichment of photosynthesis and pathways related to oxidative stress. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the darkgreen module had the highest correlation with photosynthesis and oxidative stress traits. Large numbers of transcription factors, primarily from the MYB, GRAS, WRKY, and C2H2 families, were predicted from the genes within the darkgreen module. An analysis of physiological indicators and DEGs, it was found that under saline-alkali stress, genes related to chlorophyll synthesis enzymes were downregulated, while those related to degradation were upregulated, resulting in inhibited chlorophyll biosynthesis and decreased chlorophyll content. Additionally, NaCl and NaHCO3 stress downregulated the expression of genes related to the Calvin cycle, photosynthetic antenna proteins, and the activity of photosynthetic reaction centers to varying degrees, hindering the photosynthetic electron transfer process, suppressing photosynthesis, with NaHCO3 stress causing more pronounced adverse effects. In terms of oxidative stress, the level of reactive oxygen species (ROS) did not change significantly under the NaCl treatment, but the contents of hydrogen peroxide and the rate of production of superoxide anions increased significantly under NaHCO3 stress. In addition, treatment with NaCl upregulated the levels of expression of the key genes for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate-glutathione cycle, and the thioredoxin-peroxiredoxin pathway, and increased the activity of these enzymes, thus, reducing oxidative damage. Similarly, NaHCO3 stress increased the activities of SOD, CAT, and POD and the content of ascorbic acid and initiated the glutathione-S-transferase pathway to remove excess ROS but suppressed the regeneration of glutathione and the activity of peroxiredoxin. Overall, both neutral and alkaline salts inhibited the photosynthetic process of safflower, although alkaline salt caused a higher level of stress than neutral salt. Safflower alleviated the oxidative damage induced by stress by regulating its antioxidant system. [ABSTRACT FROM AUTHOR]

The Garua bacha, Clupisoma garua, holds considerable commercial and nutritional significance as a fish species. This study investigates the relationships between GSI (gonadosomatic index) and eco-climatic conditions, and provides comprehensive insights into several facets of reproduction, such as size at first sexual maturity (Lm), spawning season, peak spawning period, and proposes sustainable management strategies for C. garua in the Ganges River, northwestern, Bangladesh. Since January to December 2017, 570 female individuals have been gathered from the Ganges River using cast nets, gill nets, and square lift nets on a monthly basis. The total length (TL) of the specimens varied from 3.90 to 26.30 cm. Lm was estimated as 14.30 cm based on the results of the TL vs. GSI, MGSI (modified gonadosomatic index), DI (Dobriyal index), 14.00 cm through TL-FL regressions, and 15.18 cm depending on Lmax for this species. Furthermore, the spawning period was observed from May to August, peaking in June and July, based on greater GSI, MGSI, and DI values. Throughout the peak spawning season, there was not a significant differ from a value of 100 in the relative weight (WR) of the female species. During the spawning season, a substantial association between temperature and GSI (p = 0.0038); rainfall and GSI (p = 0.0043); DO and GSI (p = 0.0043); pH and GSI (p = 0.0002); and alkalinity and GSI (p = 0.0001) was detected. Analyzing a 55-year data series (1964–2018), it became clear that an increase in average air temperature of 0.0289 °C and a decrease in rainfall of 2.988 mm per year might possibly delay the spawning season of this species. As a consequence, the results of this study provide crucial information for developing management strategies to safeguard C. garua populations in the Ganges River and its adjacent ecosystems. [ABSTRACT FROM AUTHOR]

Although thermokarst alas lakes of Central Yakutia are of great climatic and economic importance, there is currently virtually no information on microbial communities and microbial processes in these lakes. This paper characterizes the hydrochemical features and presents a primary analysis of the diversity of planktonic microbial communities in three alas lakes of Central Yakutia—Tyungulyu, Taby, and Kharyyalakh. It was shown that in terms of the water physicochemical composition, the studied lakes were quite typical for this region; they had increased alkalinity and trophicity, but differed from each other in microbiological indicators. Chemoheterotrophic prokaryotes predominated in the studied planktonic communities, but a significant proportion of the 16S rRNA gene sequences were most similar to uncultured microorganisms whose functional potential is still unknown. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of different management strategies on the toxic nitrogen compounds and alkalinity patterns in nurseries and pre-grow-out of Penaeus vannamei culture with low salinity water (2.5 g L−1) and synbiotic system. A study case is presented using three individual experiments (E): two nurseries (EI and EII: 2000 shrimp m−3 or 600 shrimp m−2) and one pre-grow-out (EIII: 300 shrimp m−3 or 90 shrimp m−2). Key water quality management strategies included the adoption of artificial substrate and water reuse with a microbial-based synbiotic system. In EI experiment, mean TAN was less than 0.50 mg L−1 throughout the culture, NO2−-N reached a maximum concentration of 0.80 mg L−1, and NO3−-N showed a decrease over the time. In EII, mean TAN was 0.64 mg L−1 with a peak on day 10 of the experimental course, with the same pattern occurring for NO2−-N. On the other hand, NO3−-N constantly increased from 0.10 mg L−1 at the beginning to 2.32 mg L−1 at the end of the trial. In EIII, mean TAN was less than 0.50 mg L−1 reaching a maximum concentration of 0.93 mg L−1; NO2−-N reached a maximum mean concentration of 0.70 mg L−1 at the end of the experiment. NO3−-N had a mean of 1.50 mg L−1 at the beginning of the experiment and a reduction to 0.53 mg L−1 at the end of the trial. Alkalinity showed mean concentrations of 114.90 mg L−1, 88.04 mg L−1, and 88.27 mg L−1 for EI, EII, and EIII, respectively. The results demonstrated that the proposed management protocols adopted in EI, EII, and EIII were efficient for toxic nitrogen control in culture conditions using low salinity water and synbiotic system. [ABSTRACT FROM AUTHOR]

This article focuses on the issues related to the primary nature and metamorphism of gneisses from the Larba block of the Dzhugdzhur–Stanovoy fold area, which are based on the study of the mineralogical composition of supracrustal rocks. The PT-parameters for the highest temperature and pressure metamorphic transformations of rocks of the Larba block are estimated as P = 6.5–8.5 kbar and T > 800°C. Relatively low-temperature garnet–biotite and garnet–biotite–chlorite mineral parageneses were formed at the regressive stage of metamorphism at ~4–6 kbar and temperatures up to 500–600°C. Wide variations in paragneiss compositions indicate that the studied gneisses were derived from protoliths of different composition. Overall, Larba metasedimentary rocks had weakly and moderately weathered source areas. Most of the compositions of paragneisses are located in the field of chlorite–montmorillonite, montmorillonite–kaolinite–hydromica, and chlorite clays formed from the mafic protolith. The low alkalinity in combination with a high MgO content indicates the presence of rock erosion products with a significant admixture of basic volcanic material in the detrital material. Migmatization of the rocks is the most significant factor that distorts the reconstruction of the original rock composition. [ABSTRACT FROM AUTHOR]

Groundwater quality of Punjab, India, is a matter of huge concern due to the presence of various toxic contaminants (e.g., uranium, selenium, and arsenic) from either geogenic or anthropogenic origins. In this study, we have evaluated the potential of nanofiltration for uranium removal from contaminated groundwater under environmentally relevant conditions. The influence of membrane material properties for uranium retention capabilities in two different nanofiltration membranes, viz., NF2 and NF500, was explored. Aqueous speciation modeling of uranium (U) representing the geochemical conditions of groundwater at U-contaminated region of Punjab, India, was performed to identify the dominant uranyl species. Laboratory experiments for uranium removal by both nanofiltration membranes were conducted using synthetic groundwater. The pure water flux of NF2 and NF500 was 24 ± 0.62 L·m2·h−1·bar−1 and 5.4 ± 0.21 L·m2·h−1·bar−1, respectively, wherein the former was 5 times higher than the latter despite NF2 having lesser molecular weight cutoff (MWCO). The uranium removal was highly dependent on the aqueous speciation influenced primarily by solution pH. Uranium rejection was maximum at neutral pH in both the membranes, with 87% and 78% rejection for NF2 and NF500, respectively. Uranium uptake by the membranes was highest at pH 7.0 with 77.10% and 44.6% for NF2 and NF500, respectively. Membrane transport parameters, i.e., solute flux and solute permeability, indicated the prevalence of size exclusion and/or charge-based interactions operative over a range of pHs. The uptake of uranium onto the membrane was minimal at alkaline pH with the least flux decline (ca. 6.25% in NF2) that indicated low membrane fouling. Overall, our results indicate that both World Health Organization and Atomic Energy Regulatory Board (AERB) drinking water guideline values (i.e., 30 µgL−1 and 60 µgL−1) could be achieved via nanofiltration technology as U-affected regions of Punjab have the ambient groundwater pH in neutral-alkaline range. [ABSTRACT FROM AUTHOR]

The article discusses a new efficient technology for the preparation of additional water in heating networks. According to the technology, additional water is prepared through the process of cationization using polyfunctional sulfonated coal cationites regenerated with a stoichiometric amount of salt. The research was carried out according to a continuous flow scheme. To obtain accurate results, a laboratory setup was prepared by approximating the height of the cationite and the average diameter of its particles to the required values relative to the diameter of the filter (d : D < 1 : 20) by adjusting the operating regime of the filter closer to industrial conditions. The regeneration regime of the cationite is selected in such a way that the amount of salt in the filtrate during water treatment does not exceed 3–6% of the amount of salt absorbed by the cationite. The main goal of the newly developed technological regime is to reduce the specific consumption of salt during regeneration, increase the exchange capacity of the cationite, and improve both the economic and ecological indicators of the process. As a result of the research, it can be concluded that the exchange capacity of the cationite varies within the interval of 7–20% under the influence of selected factors, and when the specific consumption of salt is increased from 8 to 16 kg/m3, the exchange capacity of the cationite approximately doubles. It should be noted that when the carbonate index in the treated water increases due to the presence of carbonate and hydrogen ions, the degree of water softening increases. However, the rapid rise of the carbonation value in the filtrate increases the average value of the carbonate index and leads to fouling of the filter, which results in a lower exchange capacity of the cationite compared to the mentioned values. It should be emphasized that depending on the values of alkalinity and specific consumption of the regenerant during the process, the filtrate volume of the treated water exiting the filter becomes 2–12% of the total volume and is characterized by saltiness. The salinity in the filtrate is neutralized by the buffer filter. [ABSTRACT FROM AUTHOR]

The pH monitoring is significantly important in chemical industry, biological process, and pollution treatment. However, it remains a great challenge to measure pH in extreme alkalinity conditions. Herein, we employ an electrolyte-gated field-effect-transistor (FET) strategy using non-stoichiometric SrCoOx with rich oxygen-vacancy defects as channel materials for detecting extreme alkalinity. The corresponding channel can provide effective oxygen-ion-migration sites for reversible transformation of OH- ↔ O2- + H+ driven by electric field. The resultant electrolyte-gated FET sensor exhibits a sensitive linear response to high concentrations of alkaline solution, 1–20 M. Significantly, the sensor has the ability to directly indicate the pH values ranging from 14.0 to 17.0 in consideration of ion-activity coefficient data. This work offers a great possibility for directly detecting base concentration as well as pH values in extreme alkaline solutions. [ABSTRACT FROM AUTHOR]

Archived water quality data collected between 1901 and 2019 were used to reconstruct annual averages of various forms of C, N, P, and silicate concentrations and alkalinity in the lower Mississippi River. During this interval the average annual nitrate concentrations doubled pre-dominantly from fertilizer applications and tiling, silicate concentrations decreased by half as diatom sedimentation increased as dams were built, and alkalinity increased 16%. Variances in silicate concentrations were proportional to river discharge before 1980 and concentrations have been stable since then. Average annual temperatures, discharge and alkalinity increased simultaneously around 1980; this suggests that there was greater weathering thereafter and is supported by the positive relationships between variations in alkalinity and variations in nitrate, phosphate, and silicate concentrations. The conversion of forests and grasslands into farmlands and improved drainage resulted in less evapotranspiration, a higher percent of precipitation going into streams and altered soil water bio-geo-chemistries. Field trials demonstrating soil health improvements resulting from more live roots and soil cover and greater biodiversity demonstrate water quality improvements and no effect on farm profitability. Lowering nitrate loading to the coastal waters will reduce summertime hypoxic waters formation offshore, but alkalinity in the river will increase further with climate warming. [ABSTRACT FROM AUTHOR]

In coastal regions and marginal bodies of water, the increase in partial pressure of carbon dioxide (pCO2) in many instances is greater than that of the open ocean due to terrestrial (river, estuarine, and wetland) influences, decreasing buffering capacity and/or increasing water temperatures. Coastal oceans receive freshwater from rivers and groundwater as well as terrestrial-derived organic matter, both of which have a direct influence on coastal carbonate chemistry. The objective of this research is to determine if coastal marshes in Georgia, USA, may be "hot-spots" for acidification due to enhanced inorganic carbon sources and if there is terrestrial influence on offshore acidification in the South Atlantic Bight (SAB). The results of this study show that dissolved inorganic carbon (DIC) and total alkalinity (TA) are elevated in the marshes compared to predictions from conservative mixing of the freshwater and oceanic end-members, with accompanying pH around 7.2 to 7.6 within the marshes and aragonite saturation states (ΩAr) <1. In the marshes, there is a strong relationship between the terrestrial/estuarine-derived organic and inorganic carbon and acidification. Comparisons of pH, TA, and DIC to terrestrial organic material markers, however, show that there is little influence of terrestrial-derived organic matter on shelf acidification during this period in 2014. In addition, ΩAr increases rapidly offshore, especially in drier months (July). River stream flow during 2014 was anomalously low compared to climatological means; therefore, offshore influences from terrestrial carbon could also be decreased. The SAB shelf may not be strongly influenced by terrestrial inputs to acidification during drier than normal periods; conversely, shelf waters that are well-buffered against acidification may not play a significant role in mitigating acidification within the Georgia marshes. [ABSTRACT FROM AUTHOR]

In this study, the impact of salinity and alkalinity on the volumetric deformation of the Opalinus Clay from the lower sandy facies (LSF\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text{LSF}$$\end{document}) of Mont Terri site was investigated. Series of samples were exposed in parallel to alkaline solutions at four different pHs\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text{pHs}$$\end{document} (8.8,11.5,12.5\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$8.8, 11.5, 12.5$$\end{document} and 13.5\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$13.5$$\end{document}) or to saline solutions at three different osmotic suctions (π = 10,15\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$10, 15$$\end{document} and 34MPa\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$34\,\text{MPa}$$\end{document}). As a reference, samples were also exposed to synthetic water at pH7.5\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text{pH}\, 7.5$$\end{document} and π = 1MPa\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$1\, \text{MPa}$$\end{document}. It was found that the protocol followed above (“parallel testing”) was not suitable for the LSF\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\text{LSF}$$\end{document} Opalinus Clay due to the high mineralogy variability. Therefore, a new protocol (“gradual testing”) consisting of gradually exposing the same sample to different saline or alkaline solutions was adopted. It was found that the volumetric swelling strain increased with alkalinity and decreased with salinity. In the first case, the acid-base attack resulted in a dispersed structure with higher repulsive forces. Also, the precipitation of new compounds composed of the products of the dissolution of clay minerals and the species present in the alkaline solution contributed to the observed increase in swelling strain. For the saline solutions, the decrease of the thickness of diffuse double layer and the osmotically induced consolidation explained the observed decrease of swelling strain. [ABSTRACT FROM AUTHOR]