Alkaline Freshwater Research Articles

Quench-Induced Surface Engineering Boosts Alkaline Freshwater and Seawater Oxygen Evolution Reaction of Porous NiCo2 O4 Nanowires.

The electrochemical oxygen evolution reaction (OER) by efficient catalysts is a crucial step for the conversion of renewable energy into hydrogen fuel, in which surface/near-surface engineering has been recognized as an effective strategy for enhancing the intrinsic activities of the OER electrocatalysts. Herein, a facile quenching approach is demonstrated that can simultaneously enable the required surface metal doping and vacancy generation in reconfiguring the desired surface of the NiCo2 O4 catalyst, giving rise to greatly enhanced OER activities in both alkaline freshwater and seawater electrolytes. As a result, the quenched-engineered NiCo2 O4 nanowire electrode achieves a current density of 10 mA cm-2 at a low overpotential of 258mV in 1 m KOH electrolyte, showing the remarkable catalytic performance towards OER. More impressively, the same electrode also displays extraordinary activity in an alkaline seawater environment and only needs 293mV to reach 10 mA cm-2 . Density functional theory (DFT) calculations reveal the strong electronic synergies among the metal cations in the quench-derived catalyst, where the metal doping regulates the electronic structure, thereby yielding near-optimal adsorption energies for OER intermediates and giving rise to superior activity. This study provides a new quenching method to obtain high-performance transition metal oxide catalysts for freshwater/seawater electrocatalysis.

Rise of Subgen. Rhoicosphenula Lange-Bert. to the Genus Level, and Description of a New Gomphosphenia s.s. Species from Puerto Rico

The subgenus Rhoicosphenula Lange-Bert. has a unique character combination that differentiates it from Gomphosphenia subgen. Gomphosphenia Lange-Bert. In particular, Rhoicosphenula has striae/areola features that are similar to Gomphosphenia, but is differentiated from that genus by also having pseudosepta present on both poles of the valves, copulae with septa at one of the poles, and frustules almost rectangular in girdle view. Together, this character combination strongly supports it as an independent genus following modern diatom-taxonomy criteria. Moreover, the only species of Rhoicosphenula known so far was collected from a peculiar acidic and dystrophic habitat, whilst most Gomphosphenia s.s. species colonize medium-conductivity, alkaline inland waters. On the basis of LM and SEM studies, we also propose a species of Gomphosphenia (G. patrickiana Cantonati, Lange-Bert., Kociolek & A.A.Saber, sp. nov.) as new to science. The new species is mainly defined by its valve outline and dimensions, length to breadth ratio, striation density, and geographical distribution. It was found in several samples of two streams in Puerto Rico, sometimes with high relative abundance. Gomphosphenia patrickiana Cantonati, Lange-Bert., Kociolek & A.A.Saber, sp. nov. was much more abundant in the stream with lower nutrient (in particular P) concentrations, and higher ecological integrity. The new species seems to prefer moderately alkaline freshwater habitats with medium-high conductivity and oligo- to mesotrophic conditions, with moderate tolerance to N enrichment. Also noteworthy is the occurrence of the new species in streams with above-average magnesium concentrations (due to the local geology). This Neotropical, warm-water species might be a potential indicator of global warming effects.

High-Performance Ammonium Cobalt Phosphate Nanosheet Electrocatalyst for Alkaline Saline Water Oxidation.

The development of highly efficient electrocatalysts toward the oxygen evolution reaction is imperative for advancing water splitting technology to generate clean hydrogen energy. Herein, a two dimensional (2D) nanosheet ammonium cobalt phosphate hydrate (NH4CoPO4·H2O) catalyst based on the earth‐abundant non‐noble metal is reported. When used for the challenging alkaline saline water electrolysis, the NH4CoPO4·H2O catalyst with the optimal thickness of 30 nm achieves current densities of 10 and 100 mA cm−2 at the record low overpotentials of 252 and 268 mV, respectively, while maintaining remarkable stability during the alkaline saline water oxidation at room temperature. X‐ray absorption fine spectra reveal that the activation of Co (II) ions (in NH4CoPO4·H2O) to Co (III) species constructs the electrocatalytic active sites. The 2D nanosheet morphology of NH4CoPO4·H2O provides a larger active surface area and more surface‐exposed active sites, which enable the nanosheet catalyst to facilitate the alkaline freshwater and simulated seawater oxidation with excellent activity. The facile and environmentally‐benign H2O‐mediated synthesis route under mild condition makes NH4CoPO4·H2O catalyst highly feasible for practical manufacturing. In comparison with noble metals, this novel electrocatalyst offers a cost‐effective alternative for economic saline water oxidation to advance water electrolysis technology.

Major Ionic Characteristics and Factors of Karst Groundwater at Huixian Karst Wetland, China

To investigate the major ionic chemical characteristics and seasonal variations, 27 groundwater samples were collected from the wet season, flat season, and dry season during 2018-2019 in the Huixian Karst wetland, which is the largest low-altitude karst wetland in China. The single pollution standard index was applied to evaluate the groundwater pollution during different periods, and the major ionic factors of the karst groundwater were analyzed using the statistical analysis method, Gibbs diagram, and ion ratio. The results revealed that the groundwater samples were a weakly alkaline fresh water that were rich in Ca2+ and HCO3-. The average concentrations of the primary ions followed the order of flat season > wet season > dry season; meanwhile, the water quality in the dry season was better than that in the wet and flat seasons. The K+ and NO3- in the karst groundwater were mostly affected by the spatial distributions of the aquifers, and the Mg2+, SO42-, NO2-, NH4+, and TDS were related to the space-season scale. Na+, Ca2+, HCO3-, and Cl- were relatively stable ions in the karst groundwater. The hydrochemical characteristics were primarily determined by carbonate rock dissolution and were found to be the HCO3-Ca type, which accounted for 77.78%, 77.78%, and 88.89% in the wet season, flat season, and dry season, respectively. The karst groundwater was predominantly polluted by SO42-, NO3-, and NO2-; particularly, NO3- exhibited serious pollution points, and SO42- had heavy pollution points in the wet and flat seasons. The chemical composition of the karst groundwater was controlled mostly by water-rock interactions. Ca2+ and HCO3- primarily came from calcite dissolution, and the high concentrations of Mg2+ and SO42- in a few number of points were controlled by dolomite, dolomitic limestone, and pyrite. K+, Na+, SO42-, NO3-, and Cl- partly came from atmospheric precipitation, and Na+ and Cl- partly came from human activities; K+ was related to potash fertilizer, and the main source of NO3- was chemical fertilizer.

Efficient Hydrogen Evolution of Oxidized Ni-N3 Defective Sites for Alkaline Freshwater and Seawater Electrolysis.

For mass production of high-purity hydrogen fuel by electrochemical water splitting, seawater electrolysis is an attractive alternative to the traditional freshwater electrolysis due to the abundance and low cost of seawater in nature. However, the undesirable chlorine ion oxidation reactions occurring simultaneously with seawater electrolysis greatly hinder the overall performance of seawater electrolysis. To tackle this problem, electrocatalysts of high activity and selectivity with purposely modulated coordination and an alkaline environment are urgently required. Herein, it is demonstrated that atomically dispersed Ni with triple nitrogen coordination (Ni-N3 ) can achieve efficient hydrogen evolution reaction (HER) performance in alkaline media. The atomically dispersed Ni electrocatalysts exhibit overpotentials as low as 102 and 139mV at 10mAcm-2 in alkaline freshwater and seawater electrolytes, respectively, which compare favorably with those previously reported. They also deliver large current densities beyond 200mAcm-2 at lower overpotentials than Pt/C, as well as show negligible current attenuation over 14 h. The X-ray absorption fine structure (XAFS) experimental analysis and density functional theory (DFT) calculations verify that the Ni-N3 coordination, which exhibits a lower coordination number than Ni-N4 , facilitates water dissociation and hydrogen adsorption, and hence enhances the HER activity.

Hydrochemical and isotopic characteristics of groundwater in the Jiuquan East Basin, China

To investigate the hydrochemical characteristics and evolution of groundwater in the Jiuquan East Basin, 133 groundwater samples were collected and tested. Statistical analysis, Piper diagram, Gibbs plot, ion ratio and isotope techniques were used to analyse the samples. Our results suggest that both shallow and deep groundwater generally consist of weakly alkaline freshwater, with SO42− and HCO3− as the main anions, and Mg2+ and Na+ as the cations. The shallow groundwater has gradually evolved from the HCO3·SO4–Mg·Ca type in the southern part of the basin (the groundwater recharge runoff area) to the SO4·Cl–Na·Mg type in the northern part of the basin (the groundwater discharge area). Similarly, deep groundwater has progressively evolved from the HCO3·SO4–Mg·Ca type to the SO4·HCO3–Na·Mg type. In the groundwater recharge-runoff area, the chemical components in the shallow and the deep groundwater are mainly originated from the silicate rock weathering, the evaporite rock dissolution and the carbonate weathering. From the groundwater recharge-runoff area to the discharge area, the evaporation concentration, the cation exchange and the adsorption gradually become the main controlling factors of the shallow groundwater hydrochemical composition. The deep groundwater mainly undergoes the leaching, the cation exchange and the adsorption, during the runoff. Furthermore, based on isotope analysis, ice-snow melt water and atmospheric precipitation are identified as the main recharge sources of the shallow and deep groundwater in the area. This paper is great significance for the further protection of water resources and ecological environment, in the area.

Hydrogeochemical processes and suitability assessment of groundwater in the Jiaodong Peninsula, China.

Groundwater is the primary source of water for domestic use and agricultural irrigation in Jiaodong Peninsula. This study collected 80 groundwater samples from Jiaodong Peninsula to characterize groundwater hydrogeochemical processes and the suitability of groundwater for domestic use and agricultural irrigation. The groundwater of Jiaodong Peninsula was categorized as slightly alkaline freshwater, with a Piper diagram classifying most samples as SO4·Cl-Ca·Mg and HCO3-Ca·Mg types. Major ions were Ca2+, Na+, SO42-, and HCO3-. The major processes driving the hydrochemistry of groundwater were identified as water-rock interactions as well as evaporation. The dissolution of silicate and cation exchange were the predominant hydrogeochemical processes responsible for groundwater chemistry. Four water samples showed seawater intrusion and some indicated pollution from anthropogenic activities such as industry, agriculture, and domestic sewage discharge. Overall, it was found that groundwater in most areas of Jiaodong Peninsula is suitable for domestic use and agricultural irrigation.

Three New Species of Ulnaria (Kützing) Compère (Bacillariophyta) from China, with Reference to the Fine Structure of Their Valvocopula

Three new species of Ulnaria (Kutzing) Compere are described based on light and scanning electric microscopy observations. Ulnaria oxybiseriata D.M. Williams & Bing Liu, sp. nov., has linear-lanceolate to lanceolate valves with apiculate and produced ends, biseriate striae, and a central area mostly forming an incomplete fascia surrounded by shortened striae on one side. Ulnaria jinbianensis S. Blanco & Bing Liu, sp. nov., bears linear-lanceolate valves with rostrate to subrostrate ends in larger valves and cuneate ends in smaller valves, uniseriate stria, and a central area forming a rectangular to trapezoid fascia. Ulnaria dongtingensis Bing Liu, sp. nov., possesses a narrow-lanceolate valve outline with produced rostrate to capitate ends, uniseriate stria, and a central area forming almost square fascia. The valvocopula of all three new species bears the same ultrastructure: 1) a complete valvocopula is a closed ring with the same shape as the valve outline, closely attached to the mantle interior surrounding the valve margin; 2) each valvocopula present a row of poroids which bisects the pars interior and exterior; 3) valvocopula with sawtooth-shaped projections attached to the valve over virgae internally; and 4) the valvocopula closed and hyaline at both apices. All three species were found in alkaline freshwater (around pH 8) with moderate conductivity (c. 102-221 µS/cm).

Major Ionic Characteristics and Controlling Factors of Karst Groundwater at Xiangshui, Chongzuo

To investigate the major ionic characteristics, seasonal variation, and controlling factors of karst groundwater at Xiangshui, Chongzuo, 210 groundwater samples were collected and measured in wet season, dry season, and flat season in 2016. The controlling factors of karst groundwater were analyzed by using multivariate statistical analysis method. The results showed that the groundwater samples were weakly alkaline fresh water and rich in Ca2+ and HCO3-, which accounted for more than 75% and 70% of total ion concentration. The average concentrations of K+, Na+, Cl-, and NO3- decreased in the order of wet season > flat season > dry season. None of the concentrations of Ca2+, Mg2+, HCO3-, SO42-, pH, TDS, TZ+, and TZ- showed significant seasonal variation. The hydrochemical characteristics were found to be of HCO3-Ca type and mainly determined by carbonate rock dissolution. Only a small proportion of them were of HCO3·Cl-Ca and HCO3·SO4-Ca type in wet season and flat season, Cl·NO3-Ca type appeared in flat season, and HCO3-Ca·Mg type appeared in dry season, reflecting the influence of dolomite and ferric mudstone dissolution in the stratum, and of NO3- and Cl- input from anthropogenic activities. Groundwater Ca2+ and HCO3- mainly came from limestone dissolution; Na+, Cl-, K+, and NO3- came from atmospheric precipitation and human activities; while Mg2+ and SO42- came from dolomite and ferric mudstone dissolution. The chemical composition of groundwater was controlled by water-rock interaction, the groundwater in the carbonate aquifer was controlled by carbonate rocks dissolution, and the groundwater in villages and densely populated areas was affected by atmospheric precipitation and human activity.

Three species of Ulnaria (Bacillariophyceae) from China, with reference to the valve central area and apices

Three needle-shaped Ulnaria species are studied using light and scanning electron microscopy. One is identified as Ulnaria acus (Kützing) Aboal and two are proposed as new: Ulnaria rhombus sp. nov. and Ulnaria wulingensis sp. nov. These three species have many common characters: needle-shaped valve outline, ghost striae, a central area circumscribed by shortened striae composed of one or a few areolae, a closing plate composed of a solid plate with some struts connecting the areola wall, and characteristic virgae-vimines structure. Ulnaria acus and U. wulingensis have almost parallel central area margins whereas U. rhombus never has parallel central area margins. Ulnaria wulingensis and U. rhombus (excluding few very small specimens) possess distinctive parallel distal regions of variable length, between 3 and 40 µm, but U. acus only has parallel distal regions in a few, very long specimens. Comparison with similar Ulnaria taxa was carried out and the distinguishing characteristics are summarized. All three species were found in alkaline freshwater (pH 8.3–8.5) with low-moderate conductivity (109.2–286.4 µS/cm).

Hydrogeochemical Characterization and Quality Assessment of Groundwater in a Long-Term Reclaimed Water Irrigation Area, North China Plain

Water scarcity has led to wide use of reclaimed water for irrigation worldwide, which may threaten groundwater quality. To understand the status of groundwater in the reclaimed water irrigation area in Beijing, 87 samples from both shallow and deep aquifers were collected to determine the factors affecting groundwater chemistry and to assess groundwater quality for drinking and irrigation purposes. The results show that groundwater in both shallow and deep aquifers in the study area is weakly alkaline freshwater with hydrogeochemical faces dominated by HCO3-Na·Mg·Ca, HCO3-Mg·Ca·Na, HCO3-Ca·Na, and HCO3-Na. The chemical composition of groundwater in both shallow and deep aquifers is dominantly controlled by the dissolution of halite, gypsum, anhydrite, and silicates weathering, as well as ion exchange. Geogenic processes (rock weathering and ion exchange) are the only mechanisms controlling groundwater chemistry in deep aquifers. Besides geogenic processes, evaporation and anthropogenic activities also affect the chemistry of shallow groundwater. Quality assessment reveals that both shallow and deep groundwater are generally suitable for drinking and irrigation purposes. The quality of deep groundwater is more excellent for drinking than shallow groundwater. However, long-term use of deep groundwater for irrigation exhibits higher potential risks to deteriorate soil property due to the relative higher permeability indexes (PI). Therefore, it is recommended that deep groundwater is preferentially used for drinking and domestic purpose, and shallow groundwater for agricultural irrigation.

Investigation of Geochemical Characteristics and Controlling Processes of Groundwater in a Typical Long-Term Reclaimed Water Use Area

The usage of reclaimed water can efficiently mitigate water crises, but it may cause groundwater pollution. To clearly understand the potential influences of long-term reclaimed water usage, a total of 91 samples of shallow and deep groundwater were collected from a typical reclaimed water use area during the dry and rainy seasons. The results suggest both shallow and deep groundwater are mainly naturally alkaline freshwater, which are composed mainly of Ca-HCO3, followed by mixed types such as Ca-Na-HCO3 and Ca-Mg-HCO3. A seasonal desalination trend was observed in both shallow and deep aquifers due to dilution effects in the rainy season. Groundwater chemical compositions in both shallow and deep aquifers are still dominantly controlled by natural processes such as silicate weathering, minerals dissolution and cation exchange. Human activities are also the factors influencing groundwater chemistry. Urbanization has been found responsible for the deterioration of groundwater quality, especially in shallow aquifers, because of the relative thin aquitard. Reclaimed water usage for agricultural irrigation and landscape purposes has nearly no influences on groundwater quality in rural areas due to thick aquitards. Therefore, reclaimed water usage should be encouraged in arid and semiarid areas with proper hydrogeological condition.

Diatoms, Spatial Distribution and Physicochemical Characteristics of the Wular Lake Sediments, Kashmir Valley, Jammu and Kashmir

ABSTRACT Lakes and wetlands are dynamic geomorphic units of a landscape that hold geochemical signatures of sediment provenance and paleo-environmental shifts and are major sinks for organic matter accumulation. The source of organic matter is diverse in lake sediments and varies widely with the type and size of the lake and hence it is important to understand the source of organic carbon (terrestrial or in situ) in lake systems in order to monitor the health of the lake. Wular lake, located in north Kashmir, is one of the largest fresh water lake in India, situated at an average elevation of 1580m ASL. The lake is fed by a number of watersheds that bring a diverse type of sediments and organic matter and thus deposit them into the Wular lake basin. In order to understand sediment distribution pattern, content and source of organic matter, sediment provenance and the persisting environment in the Wular lake, 32 lake floor sediment samples covering the entire lake were collected and analyzed for organic element analysis, CaCO3, organic matter, sediment texture and diatom analysis. The results indicated that sediments in the lake are dominated by silt and silty clay. The organic carbon in the lake ranged from 0.83%-4.52% and nitrogen varied from 0.06%-0.5%. The Carbon to Nitrogen (C/N) ratios (9.04 to 22.03) indicate a mixed source of organic carbon but dominated by in situ lake sources from the vascular and lake biota accumulation. The diatom analysis revealed the occurrence of a diverse type of species along the sampling sites present within the lake. The wide distribution of the diatom species such as Cymbella, Cyclotella and Tabularia etc. in the lake indicate high organic pollution and alkaline fresh water environment prevailing in the lake.

The effects of elevated atmospheric CO2 on freshwater periphyton in a temperate stream

This study examines the effects of elevated CO2 on the benthic biology of a temperate freshwater stream. We tested the hypotheses that elevated CO2 would increase periphyton biomass, alter elemental composition, and change community composition by increasing the frequency of algal taxa most limited by CO2 availability. Carbon dioxide was bubbled into reservoirs of stream water, increasing the ambient pCO2 by approximately 1100 ppm. The CO2-enriched water then flowed into artificial stream channels. Ceramic tiles were placed into the channels to allow for periphyton colonization. Dissolved inorganic carbon increased and pH decreased with added CO2. Measurements of biological parameters including periphyton biomass, algal C:N:P ratios, and community composition suggest that the periphyton were unaffected by the changes in stream water chemistry. We infer that rising atmospheric CO2 will impact stream water chemistry but that periphyton may not be the first to respond to these changes. Impacts to alkaline freshwater streams from elevated CO2 initially may be due to changes to terrestrial inputs that affect microbial decomposition and grazer activity, rather than through increases in periphyton carbon fixation. However, environmental characteristics of freshwater systems vary considerably, and additional studies are needed for accurate predictive modeling and monitoring of the effects of increasing atmospheric CO2 on freshwater streams.

Hydrochemical appraisal of groundwater quality for drinking and irrigation purposes and the major influencing factors: a case study in and around Hua County, China

Groundwater is the major source of water for drinking and irrigation purposes in and around Hua County, China. However, long-term industrial effluents in the upstream of the area have produced contamination to groundwater. To provide a clear and better understanding of the status and extent of groundwater pollution to local decision makers, groundwater quality was assessed for drinking and irrigation purposes in this study using sodium adsorption ratio (SAR), residual sodium carbonate (RSC), soluble sodium percentage (%Na), permeability index (PI), an entropy weighted water quality index (EWQI), and some graphical approaches such as Wilcox and US Salinity Laboratory (USSL) diagrams. Factors that have significant influences on the hydrochemistry and quality of groundwater were also discussed in detail. Finally, some measures for the protection and management of groundwater in the study area were provided to local decision makers. The results show that shallow groundwater in and around the Hua County is mainly slightly alkaline freshwater with the majority of the samples falling in the category of HCO3–Ca and mixed HCO3·SO4–Ca·Mg. Medium quality water is prevalent in the study area for drinking purpose, and the main contaminants in groundwater are total dissolved solid (TDS), total hardness (TH), SO4 2−, Cl−, NO3 −, NO2 −, and oil. Groundwater in the study area is suitable for agricultural irrigation with regard to sodium hazard, but mixing of low and high salinity water is recommended before irrigation to reduce the salinity hazard in local areas. Natural processes such as weathering of parent rocks, cation exchange, and groundwater evaporation are the dominant factors influencing groundwater chemistry in the study area. However, river water leakage and human interference are becoming increasingly important in altering natural groundwater chemistry. The recommendations suggest in this study may help to prevent further groundwater pollution in the study area, and the results and recommendations reported here will also be useful for many other regions facing similar problems.

A histological study of the kidney structure of Van fish (Alburnus tarichi) acclimated to highly alkaline water and freshwater

Kidneys are important organs that play a role in ion and water regulation in different aquatic environments. The Van fish (Alburnus tarichi, Güldenstädt, 1814) has acclimated to the alkaline waters of the largest saline soda lake in the world. In this study, changes in kidney tissue were examined histologically in alkaline and freshwater as the fish entered freshwater for reproduction. In addition, immunological changes were examined for Na+, K+, ATPase (NKA), an important transmembrane protein in kidneys. A histological comparison of the kidneys of fish taken from both environments was made. The glomerular volume was larger in fish acclimated to freshwater, and the collecting tubules were larger in diameter and had thicker walls. The fish acclimated to alkaline lake water had reduced numbers of glomeruli of smaller size. NKA enzyme was present in tubules within kidneys in both environments. It was, however, observed more frequently in fish acclimated to freshwater. Although plasma osmolality and Cl− values decreased in the fish acclimated to freshwater, hematocrit values increased (p < 0.05). No changes were observed in the muscle water content between alkaline water- and freshwater-acclimated fish. We clearly demonstrate that histologic and immunochemical changes take place in the kidney of the Van fish acclimated to the different physicochemical characteristics of alkaline and freshwater environments.

Evaluation of DGT as a long-term water quality monitoring tool in natural waters; uranium as a case study

The performance of the diffusive gradient in thin film technique (DGT) was evaluated as a tool for the long-term monitoring of water quality, using uranium as a case study. DGTs with a Metsorb™ (TiO2) sorbent were deployed consecutively at two alkaline freshwater sites, the River Enborne and the River Lambourn, UK for seven-day intervals over a five-month deployment period to obtain time weighted average concentrations. Weekly spot samples were taken to determine physical and chemical properties of the river water. Uranium was measured in these spot samples and after extraction from the DGT devices. The accuracy of the DGT device time weighted average concentrations to averaged spot water samples in both rivers was 86% (27 to 205%). The DGT diffusive boundary layer (DBL) (0.037-0.141 cm - River Enborne and 0.062-0.086 cm - River Lambourn) was affected by both water flow and biofouling of the diffusion surface. DBL thicknesses found at both sites were correlated with flow conditions with an R(2) value of 0.614. Correlations were also observed between the DBL thickness and dissolved organic carbon (R(2) = 0.637) in the River Lambourn, indicating the potential presence of a complex zone of chemical interactions at the surface of the DGT. The range of DBL thicknesses found at the River Lambourn site were also attributed to of the development of macro-flora on the active sampling surface, indicating that the DBL thickness cannot be assumed to be water flow dependant only. Up to a 57% under-estimate of uranium DGT concentration was observed compared to spot sample concentrations if the DBL was neglected. This study has shown that the use of DGT can provide valuable information in environmental monitoring schemes as part of a 'tool-box' approach when used alongside conventional spot sampling methods.

Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH-, Cl-, CO3 2-, SO4 2-, and PO4 3- systems (IUPAC Technical Report)

Abstract The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl&amp;ndash;, OH&amp;ndash;, CO3 2&amp;ndash;, SO4 2&amp;ndash;, and PO4 3&amp;ndash; requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 &amp;beta; p,q,r &amp;deg; valid at I m = 0 mol&amp;middot;kg&amp;ndash;1 and 25 &amp;deg;C (298.15 K), and reports the empirical reaction ion interaction coefficients, ∆&amp;epsilon;, required to calculate log10 &amp;beta; p,q,r values at higher ionic strengths using the Br&amp;oslash;nsted&amp;ndash;Guggenheim&amp;ndash;Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆r H, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO3 2&amp;ndash; system and for the Zn2+ + OH&amp;ndash; and Zn2+ + SO4 2&amp;ndash; systems at I &amp;gt; 0. In acidic and weakly alkaline fresh water systems (pH &amp;lt; 8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato- and hydroxido- complex formation become important at pH &amp;gt; 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH &amp;gt; 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 &amp;deg;C (log10 {[H+]/c&amp;deg;} &amp;asymp; 8.2) the MCO3(aq) complex dominates over the MCl n (2&amp;ndash;n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3 % of [MII]T, respectively.

&lt;p class="HeadingRunIn"&gt;&lt;strong&gt;&lt;em&gt;Staurophora brantii&lt;/em&gt;, a new diatom (Bacillariophyta, Anomoeoneidaceae) from the northwestern Great Plains, USA&lt;/strong&gt;&lt;/p&gt;

Staurophora brantii is described from streams of the northwestern Great Plains in the western United States. The new species is placed in Staurophora by virtue of its plastid type, valve structure, and ecology. It is distinguished from similar species by its size, valve shape, end shape, striae count, and habitat. Staurophora brantii sp. nov. lives in alkaline freshwater streams with soft, muddy bottoms and elevated concentrations of electrolytes, particularly sodium and sulfate. Stauroneis tackei, an associate of Staurophora brantii on the Great Plains, is transferred to Staurophora.

The Fate of the Submarine Ikaite Tufa Columns in Southwest Greenland Under Changing Climate Conditions

Abstract Ikaite is considered a metastable mineral forming and stable only at low temperatures and therefore an indicator of low-temperature carbonate precipitation often associated with cold marine seeps. It is found world-wide but most spectacularly in Ikka Fjord in southwest Greenland as submarine carbonate tufa columns. Here, ikaite is formed as a result of submarine spring water mixing with cold seawater. As ikaite disintegrates at temperatures above 6–7°C, it has been speculated that global warming could endanger this unique habitat as well as other sites. In Ikka Fjord in situ water chemistry in and around an ikaite column measured continuously over two years showed that the column water is alkaline (pH > 9–10) throughout the year with temperatures of −1.3–6.0 °C and conductivities of 5.7–7.9 mS cm−1, favoring year-round growth of columns at 4–5 cm per month. Short-term in situ measurements with needle micro sensors from both older dehydrated and calcified parts and more recently formed solid parts of an ikaite tufa column showed similar pH and temperature values, including a temperature variation over the tidal cycle. In the uppermost, recently deposited ikaite matrix, spring water escaping at the top causes passive drag of seawater into the porous ikaite matrix, leading to a mixing layer several centimeters thick that has pH values intermediate to the spring water in the column and the surrounding seawater. We conclude that the main part of the columns, consisting of fossilized ikaite (inverted to calcite) partly sealed by calcifying coralline algae and with year-round flow of alkaline freshwater through distinct channels, are resistant to warming. In the more diffuse top part of the columns, the formation of ikaite, and thus column growth, will be limited in the future due to increased fjord water temperature during the