Speciation In Waters Research Articles

FactSage Modelling of Pb and Ni Speciation in Surface Water from Woji Creek, Rivers State, Nigeria

The present study is designed to use FactSage version 7.3 to simulate and predict the ionic speciation of lead (Pb) and nickel (Ni) in surface water sampled from Woji creek in Rivers State, Nigeria. Along the 3 km stretch (stations 1 to 5) of Woji creek, in-situ records were taken for temperature, pH and electrode potential (Eh); surface water samples to be assessed for Pb and Ni were collected in sterile bottles. Along the creek, surface water Eh is in the order: station 2 > station 4 > station 5 > station 3 = station 1, with mean value of Eh as 140 ± 20 mV. Surface water pH was close to neutral, and in line with: station 4 > station 2 > station 5 > station 1 > station 3; with 6.81 ± 0.13 as the mean value of pH. The trend of temperature values was recorded as: station 1 > station 2 = station 3 = station 4 > station 5; with the mean value deduced to be 25.6 ± 0.4. Mean concentration of Pb and Ni across the creek were 0.92 ± 0.27 mg/l and 0.46 ± 0.23 mg/l respectively. Pb species exists predominantly in the forms: Pb6(OH)84+(aq) (45%), Pb4(OH)44+(aq) (45%). Other forms of Pb present in the surface water are PbO(s) (5%), PbO2(s) (4%) and Pb2+(aq) (1%). NiO(s) had the highest proportion of Ni in the surface water (67%), followed by Ni(OH)2(s) (30%) and Ni2+(aq) (3%). The predicted metallic species could possibly be sorbet to particulates; thereby increase their chances of bioavailability and subsequent ingestion by fishes and other aquatic organisms. This will in turn influence their bioaccumulation via food chain and increase the tendency of risk impact on man and aquatic ecosystem.

ОСОБЕННОСТИ ПОВЕДЕНИЯ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ В СИСТЕМЕ ВОДА–ПОРОДА РАЙОНА РАЗРАБАТЫВАЕМОГО КАРЬЕРА БУТОВОГО КАМНЯ В ПИТКЯРАНТСКОМ РУДНОМ РАЙОНЕ (КАРЕЛИЯ)

Актуальность. Изучение особенностей перераспределения химических элементов в системе вода–порода в районах, где ведется активная разработка месторождений полезных ископаемых, актуально ввиду потенциального влияния этих процессов на экологическую обстановку и изменение геохимических условий природной среды. В частности, это важно для выбранного района, который входит в площадь водосбора крупнейшего природного резервуара пресной воды в Европе – Ладожского озера. Целью представленного исследования является изучение выноса химических элементов водой из гранитоидных пород, вскрытых карьером, и их дальнейшего поведения в природных водах и донных отложениях района. Объектом исследования являются природные воды и донные отложения района разрабатываемого карьера бутового камня (Питкярантский рудный район, республика Карелия). Авторы проследили изменения химического состава природных вод и связанных с ними донных отложений по мере движения воды от ее сброса из карьера до впадения в речную сеть. Методы. Анализ химического состава природных вод и донных отложений проведен стандартными методами: потенциометрия, титриметрия, ICP-AES, ICP-MS. Исследования минералов в составе пород карьера бутового камня проведено при помощи LA-ICP-MS, химический состав горных пород изучен методами XRF, ICP-MS и ICP-AES. Физико-химическое моделирование форм нахождения в природных водах и осаждения минералов проведено в программном комплексе HydroGeo. Верификация модели проведена на основе анализа химического состава донных отложений. Результаты. В изученных водных объектах в отдельных точках отмечены превышения ПДК Fe, Mn, Cu, Zn, Mo, V. При удалении от карьера бутового камня снижается величина общей минерализации природных вод и содержание макрокомпонетов, а также Sr, U, V, Mo, Zn, Cd. Концентрация железа, наоборот, увеличивается ввиду роста содержания органического вещества в воде. В донных отложениях пик концентрации многих элементов (Fe, Mn, Co, Cu, Zn, Cs, Ce, La, Y) наблюдается в точке сброса воды из карьера. Максимальное содержание U отмечается чуть ниже по потоку изучаемых вод, что согласуется с данными по составу донных отложений и моделирования, которые указывают на возможность выпадения уранинита из водного раствора в водоеме, сформировавшемся при сбросе воды из карьера бутового камня и истоке ручья, берущего начало в этом водоеме. Роль органического вещества в изученных водах высока для процесса накопления железа в воде за счет образования устойчивого гидроксо-фульватного комплекса железа, а также для редкоземельных элементов за счет образования комплекса с гуминовой кислотой. Анализ распространенности, форм нахождения и осаждения химических элементов позволили заключить, что эксплуатация карьера бутового камня вносит существенный вклад в перераспределение химических элементов в изучаемом районе.

Cadmium Water Pollution Associated with Motor Vehicle Brake Parts

With increasing industrial growth, there is a greater need to understand factory production processes, the resulting products, and the pollution caused by the fabrication processes leading to these products. Cadmium (Cd) is used in the electro-less Nickel-Cadmium bath phase of the brake manufacturing process, which provides the brake coating that produces corrosion-resistant brake parts. During the operation, the friction created during braking corrodes the Cd layer and releases Cd particles into the environment. Cd particles can enter water bodies and drinking water supplies through stormwater runoff. This research will first examine Cd pollution associated with motor vehicle brake discs from cradle to grave. Following this comprehensive look into the role of Cd in the brake manufacturing process as well as Cd speciation in natural waters, three interventions are proposed to prevent Cd pollution associated with brake parts: (i) Carbon-reinforced silicon carbide as an alternative for metal based brake parts; (ii) bacteria “coating” instead of Cd coating; (iii) permeable roads that can effectively remove Cd from runoff with nearly 98% reduction. A discussion into the advantages and disadvantages of each proposition are provided with this presentation.

Metal Speciation in Water of the Flooded Mine “Arsenic” (Karelia, Russia): Equilibrium-Kinetic Modeling with a Focus on the Influence of Humic Substances

Equilibrium-kinetic modeling allows investigating metal behavior in the water–rock-organic matter system with time to evaluate anthropogenic effects on the environment. In the article, the interactions of stagnant mine drainage water of the flooded mine “Arsenic” with ore and gangue minerals were simulated using different organic matter incorporation approaches. If the model is closed to humic substances (no additional organic matter input), most fulvic acids are bound in the Fe fulvate complex. While under the removal of Fe fulvate from the model, the Cu fulvate becomes prevalent, the contribution of the fulvate complexes with Zn, Mg, and Ca also increases. This scenario simulates the organo-mineral complexes behavior well and allows identifying the sequence of metal binding to organic ligands as follows Fe > Cu > Zn > Mg > Ca. The second scenario imitates the constant input of organic matter to the model (open system regarding humic substances). The dissolved metal concentrations in the model solution are extremely high in comparison to the mine drainage water. This scenario demonstrates that excessive input of organic matter leads to the accumulation of the metals in a dissolved form and blocks the secondary mineral formation despite the faster dissolution of the primary minerals under a more acidic pH than in the first scenario. However, despite the differences between the model solution and the mine drainage water, this scenario is useful to address specific issues associated with changes in natural and anthropogenic conditions. Both scenarios show the importance of organic matter incorporation to the equilibrium-kinetic models.

Detection of Thioarsenates in Rice Grains and Rice Products.

Inorganic and methylated thioarsenates have recently been reported to contribute substantially to arsenic (As) speciation in paddy-soil pore waters. Here, we show that thioarsenates can also accumulate in rice grains and rice products. For their detection, a method was developed using a pepsin-pancreatin enzymatic extraction followed by chromatographic separation at pH 13. From 54 analyzed commercial samples, including white, parboiled and husked rice, puffed rice cakes, and rice flakes, 50 contained dimethylmonothioarsenate (DMMTA) (maximum 25.6 μg kg-1), 18 monothioarsenate (MTA) (maximum 5.6 μg kg-1), 14 dimethyldithioarsenate (DMDTA) (maximum 2.8 μg kg-1), and 5 dithioarsenate (DTA) (maximum 2.3 μg kg-1). Additionally, we show that the commonly used nitric acid extraction transforms MTA to arsenite and DMMTA and DMDTA to dimethylarsenate (DMA). Current food guidelines do not require an analysis of thioarsenates in rice and only limit the contents of inorganic oxyarsenic species (including acid-extraction-transformed MTA), but not DMA (including acid-extraction-transformed DMMTA and DMDTA).

Centrifugal ultrafiltration preconcentration for studying the colloidal phase of a uranium-containing soil suspension

The objective of this work was to explore centrifugal ultrafiltration (UF) to separate and / or preconcentrate natural colloidal particles for their characterization. A soil suspension obtained by batch leaching was used as a laboratory reference sample. It was preconcentrated with concentration factors (CF) varying from 10 to 450. The dimensional analysis of the colloidal phase was carried out by Asymmetric Flow Field-Flow Fractionation (AF4)-multidetection. The colloidal masses were estimated by mass balance of the initial suspension, its concentrates and filtrates. The size-dependent distribution (expressed in gyration radius) and total colloidal mass (especially recovery), as well as chemical composition and concentration (including species partitioning between dissolved and colloidal phases) were determined to assess the effects of UF preconcentration on colloidal particles. The gyration radius of the colloidal particles recovered in these concentrated suspensions ranged from about 20 nm to over 150 nm. Neither de-agglomeration nor agglomeration was observed. However, only (64 ± 4) % (CF = 10) of the colloidal particles initially in the soil suspension were found in the recovered concentrated suspensions, and this percentage decreased as CF increased. The filter membrane trapped all other particles, mainly the larger ones. Whatever the CF, the centrifugal UF did not appear to change the dissolved-colloidal partitioning of certain species (Al, organic carbon); whereas it led to an enrichment of the colloidal phase for others (Fe, U). The enrichment rate was specific to each species (15% for Fe; 100% for U). By fitting the observed trends (i.e. conservation, depletion or enrichment of the colloidal phase in the concentrate) as a function of CF, the colloidal concentrations (total and species) were assessed without bias. This methodology offers a new perspective for determining physicochemical speciation in natural waters, with a methodology applicable for environmental survey or site remediation studies.

Magnetism-assisted in-tube solid phase microextraction for the on-line chromium speciation in environmental water and soil samples

In the present study, a new method for chromium speciation was proposed by on-line coupling of magnetism-assisted in-tube solid phase microextraction (MA/IT-SPME) with high-performance liquid chromatography-diode array detector (HPLC-DAD). Firstly, Cr(III) and Cr(VI) were coordinated with ammonium pyrrolidinedithiocarbamate (APD) to form Cr(III)/APD and Cr(VI)/APD complexes, separately. After that, a microextraction column based on porous monolith doped with magnetic nanoparticles was in situ fabricated in a capillary. The microextraction column was twined with a magnetic coil which was employed to engender changeable magnetic fields during extraction period. Various main factors influencing the extraction performance were inspected in detail. Results well indicated that the implementation of the magnetic field could assist the enhancement of extraction efficiency for Cr(III)/APD (80.4%) and Cr(VI)/APD (86.2%) complexes. Under the optimized parameters, the limits of detection for Cr(III) and Cr(VI) in water sample were 0.0059 μg/L and 0.0020 μg/L, respectively, and the corresponding values in soil sample were 0.47 μg/kg and 0.057 μg/kg, separately. The enrichment factors were 59 and 72 for Cr(III) and Cr(VI), respectively. The successful quantification of Cr(III) and Cr(VI) at trace levels in environmental water and soil samples well demonstrated the reliability and practicality of the proposed on-line approach for chromium speciation.

Trace Element’s Speciation in the Water and Bottom Sediments of the Pirogovo Reservoir

The composition and speciation of trace elements were studied in surface and interstitial waters along with solid phase of bottom sediments to characterize the abiotic segment of the Pirogovo Reservoir. It was found that the concentrations of metals in surface waters did not exceed the MACs for fishery basins, excluding Zn and Cu (2–9 and up to 2 MACs, respectively). According to thermodynamic calculations, the predominant metal speciation in water is free ions (Sr, Ba, Zn, Ni, Co, and Cd), as well as fulvate and carbonate complexes of Cu and Pb, respectively. Interstitial waters showed a regular increase of the fraction of the sulfate complexes of trace elements in loamy sediments. The solid phase of the latter as well was characterized by low anomalous concentrations of Zn, Cd, Co, and Ni. According to the data of extraction, the metals were either fixed in bottom sediments within crystal structure of silicates or bound to oxides and hydroxides of iron and manganese, excluding Cd and Mn, which are characterized by a considerable role of their exchangeable and bound to carbonates fraction in the particulate matter.

Role of the (pseudo)halido ligand in ruthenium(II) p-cymene α-amino acid complexes in speciation, protein reactivity and cytotoxicity.

The reactions of the dimeric complexes [RuX2(η6-p-cymene)]2 (X = Br, I, SCN) with L-proline (ProH) and trans-4-hydroxy-L-proline (HypH), in methanol in the presence of NaOH, afforded [RuX(κ2N,O-Pro)(η6-p-cymene)] (X = Br, 1b; I, 1c; SCN, 1d) and [RuX(κ2N,O-Hyp)(η6-p-cymene)] (X = Br, 2b; I, 2c; SCN, 2d), respectively. Alternatively, the one-pot, sequential addition of the appropriate α-amino carboxylate and X- salt to [RuCl2(η6-p-cymene)]2 led to [RuX(κ2N,O-Pro)(η6-p-cymene)] (X = N3, 1e; NO2, 1f; CN 1g) and [Ru(N3)(κ2N,O-Hyp)(η6-p-cymene)] (2e). Complexes [Ru(κ3N,O,O'-O2CCH(NH2)(R)O)(η6-p-cymene)] (R = CH2, 3h; R = CHMe, 4h; R = CH2CH2, 5h) were prepared from the reaction of [RuCl2(η6-p-cymene)]2 with the appropriate α-amino acid and NaOH in refluxing isopropanol. Treatment of the L-serine (SerH2) derivative [RuCl(κ2N,O-SerH)(η6-p-cymene)] (3a) with 1,3,5-triaza-7-phosphaadamantane (PTA) in water at reflux produced [Ru(κ2N,O-Ser)(κP-PTA)(η6-p-cymene)]Cl ([3i]Cl). The products were isolated in good to excellent yields, and were characterized by elemental analysis, IR and multinuclear NMR spectroscopy. The structures of 1f and 2b-e were ascertained by X-ray diffraction studies. The behaviour of the complexes in water and cell culture medium was investigated by multinuclear NMR and UV-Vis spectroscopy, revealing a considerable influence of the monodentate ligand on the aqueous chemistry. Complexes 1d-e, 2d-e, 3h, 4h and [3i]Cl, showing substantial inertness in aqueous media, were assessed for their cytotoxicity towards A2780 and A2780cisR cancer cell lines and the noncancerous HEK 293T cell line. A selection of compounds was also investigated for Ru uptake in A2780 cells and interactions with cytochrome c as a model protein. Combined, these studies provide insights into the previously debated role of the 'leaving' ligand on the biological activity of Ru(II) arene α-amino acid complexes.

Trace element speciation in water and bottom sediments of the Pirogov water reservoir

The composition and speciation of trace elements (Cu, Pb, Zn, Cd, Ni, Co, Mn, Fe, Ba, and Sr) in surface water and bottom sediments of the Pirogov water reservoir have been studied. It was found that the metal content in surface water does not exceed the maximum permissible concentration (MPC) for fishery water reservoir excluded Zn (2–9 MPC) and Cu (up to 2 MPC). According to results of thermodynamic calculations, the predominant metal speciation in water is the free ion (Sr, Ba, Zn, Ni, Co, Cd), fulvate (Cu) and carbonate (Pb) complex. The interstitial water is characterized by an increase in the content of sulfate complex of trace elements in loams, the solid phase of which is also characterized by slightly anomalous contents of Zn, Cd, Co, and Ni. According to data of sequential selective procedure, metals are predominantly immobilized in solid phase of bottom sediments in the crystal structure of silicates or bounded to iron and manganese oxides. Only for Cd and Mn exchangeable and bound to carbonates fractions are characterized by considerable relative contents.

Geochemical Features of Element Speciation in Natural Waters of the Valdai Rise (March–November, 2019)

This paper considers the element distribution between species in the lysimetric waters and lakes of the Valdai National Park in different seasons. Seasonal studies of natural waters and element speciation in them in 2019 using membrane filtration and ion-exchange separation showed the differences in the seasonal distribution of species depending on geochemical factors. The seasonal temperature factor causes a change of metal speciation from suspended (after meltwaters) through soluble mainly organic (summer) to inorganic/organic low-molecular (autumn) forms. The humus content in the water objects affects the transformation of colloid systems.

Investigation on trace metal speciation and distribution in the Scheldt estuary

The biogeochemical behavior of Cd, Co, Cr, Cu, Ni and Pb along the historically polluted Scheldt estuary (Belgium - The Netherlands) was investigated in this study. As never studied before in this area, labile trace metals were measured using the passive sampling technique of Diffusive Gradients in Thin-films (DGT), while total dissolved and particulate trace metal concentrations were assessed using classic active sampling techniques. This dual approach allowed us to highlight the variations of trace metal speciation and distribution in the estuarine surface waters, considering environmental and physicochemical gradients along the transect. The large data set obtained was then compared with literature data of historical measurements along the Scheldt (from 1980 until now), but also from other estuaries. As emphasized by our results, trace metal mobility and partitioning along the Scheldt estuary was mainly driven by biogeochemical reactions which were strongly influenced by gradients of specific estuarine physico-chemical parameters, such as salinity, turbidity, temperature and so on. Hence, all species of trace metals displayed a non-conservative behavior. More precisely, dissolved labile fractions of trace metals showed higher levels in the middle estuary, where many solubilization and remobilization processes occurred due to turbulent mixing mechanisms and an increasing salinity. Our study confirmed the decreasing trend historically observed for particulate metals along the Scheldt, as well as the rising concentrations recorded for dissolved trace metals which might also lead to an increase of their labile fraction measured by the DGT. Finally, these preliminary results suggested that a more regular monitoring of labile metal along the Scheldt estuary is essential to have an in-depth understanding of trace metal speciation and to review bioavailability of trace metals within estuarine ecosystems.

Influence of agricultural amendments on arsenic biogeochemistry and phytotoxicity in a soil polluted by the destruction of arsenic-containing shells

Agricultural soils can contain high arsenic (As) concentrations due to specific geological contexts or pollution. Fertilizer amendments could influence As speciation and mobility thus increasing its transfer to crops and its toxicity. In the present study, field-relevant amounts of fertilizers were applied to soils from a cultivated field that was a former ammunition-burning site. Potassium phosphate (KP), ammonium sulfate and organic matter (OM) were applied to these soils in laboratory experiments to assess their impact on As leaching, bioavailability to Lactuca sativa and microbial parameters. None of the fertilizers markedly influenced As speciation and mobility, although trends showed an increase of mobility with KP and a decrease of mobility with ammonium sulfate. Moreover, KP induced a small increase of As in Lactuca sativa, and the polluted soil amended with ammonium sulfate was significantly less phytotoxic than the un-amended soil. Most probable numbers of AsIII-oxidizing microbes and AsIII-oxidizing activity were strongly linked to As levels in water and soils. Ammonium sulfate negatively affected AsIII-oxidizing activity in the un-polluted soil. Whereas no significant effect on As speciation in water could be detected, amendments may have an impact in the long term.

Migration Forms of Heavy Metals and Chemical Composition of Surface Waters in the “Arsenic” Shaft Area (Pitkäranta Ore District, South Karelia)

Ore-bearing rocks and natural waters of the Pitkaranta ore district (near the “Arsenic” shaft, the Hopunvaara mine field) were sampled and analyzed. The permanganate value as well as iron and manganese contents in surface water are higher than MPC values, while water samples from the “Arsenic” shaft have the elevated contents of zinc, copper, and arsenic. The Fe, Mn, Cu, Zn, Cr, As, and Ni speciation in waters have been determined by thermodynamic calculations, taking into account the possibility of the formation of metal complexes with humic and fulvic acids. The fulvic acid is almost completely consumed for the formation of the complex Fe(OH)2Fu-. Ni, Cd, Co occur mainly in the ionic form, and the fraction of Mn and Zn in the ionic form is also significant.

Metal bioavailability in northern low-salinity water: Case study of lakes in the Kola region, Russia

This paper presents metal speciation calculations that are based on mathematical modelling of chemical reactions in natural waters. Metal concentrations (Hg, Cd, Pb, Ni, Cu, Al, Sr) were determined, and their speciation in water were calculated for 22 water areas in the Kola region. Meanwhile, the accumulation of metals in fish organs and tissues was studied (e.g. whitefish). The biogeochemical activity of metals determines the proportions of labile and non-labile speciation in water. In the distribution zones of non-ferrous industry effluents, metal aqua-ions prevail; during the distribution, the proportions change in accordance with the metal activity. The bioavailability of metal speciation is estimated depending on aqueous geochemical conditions and, accordingly, the speciation of metals (in situ), based on the original studies of the lakes of the Kola region in northern Russia. The connection among the metal contents in fish and water has been identified using multidimensional scaling and redundancy analysis techniques. Using the example of natural conditions in northern low-salinity freshwaters, it is demonstrated that labile Cd, Pb, Ni, Cu, Al, and Sr are the species most bioavailable and able to penetrate fish; meanwhile, the organic complexes of Hg, Pb, and Al have a greater affinity to accumulation in the gills. This study demonstrates the need to correct the approved water quality standards in Russia, taking into account the high bioavailability of metals in northern low-salinity waters.

Antimony uptake by mangroves and its environmental fate in the Sundarbans, India

Antimony (Sb), a naturally occurring trace element, tends to be enriched in the top-soil and contributes to soil contamination due to continued human activities. However, little is known about plant uptake of Sb, its storage in plant biomass and recycling in large littoral zones of tropical regions, subjected to strong anthropogenic impact. Biogeochemistry of Sb has been studied in the world's largest Sundarbans mangroves by measuring Sb concentration in sediment, plant organs, river water, sea water and pore water, and by determining Sb fluxes within the ecosystem reservoirs. Mangrove estuarine water and sediment appeared to be non-polluted in Sb as confirmed by their ecotoxicological indices. Sediment represented major pool of Sb (2170 g ha−1) compared to plant biomass (2.2 g ha−1). Antimony concentration (μg kg−1) in mangrove roots was highest (17 ± 6) followed by leaf and wood (10.5 ± 6, 9 ± 4, respectively, n = 24). Species-specific variability in Sb concentration was observed with Aegiceras corniculatum, showing highest concentration (48.8 μg kg−1) and Avicenna marina lowest (16.6 μg kg−1). Riverine input of Sb (9.3–12 Mg yr−1) was 3-order of magnitude higher than the mangrove sediment-derived input (0.02–0.05 Mg yr−1), suggesting the latter as negligible contributor of Sb to the Sundarbans coastal water. The mass balance calculations demonstrate that 63–88% of the annual riverine discharge of Sb export to the Bay of Bengal. Further biogeochemical studies should address Sb transport and speciation in surface waters and pore waters of this region.

Inorganic Chromium Speciation in Geothermal Water of the Podhale Trough (Southern Poland) Used for Recreational Purposes

The results of total chromium determination (by ICP-OES method) in samples collected from nine working wells named GW1–GW9, exploiting geothermal water from the Podhale Trough (southern part of Poland, near the Tatra Mountains), which is used for recreational purposes, were implemented for hydrogeochemical modeling to indicate dominating chromium speciation. The reliability of the results was determined by the application of a quality assurance/quality control program, both in the laboratory and during field work. Based on chromium speciation, the risk associated with the utilization of geothermal water was calculated. The outcome showed that the concentration of Cr(III) is almost equal to the total chromium concentration (1–2 µg·L−1). Crtot concentrations were also used in a health risk assessment in the case of epidermal absorption (EDIderm) during bathing in thermal pools and four assumed scenarios in relation to the handling of geothermal water. The effect of the very low Crtot concentration in the analyzed water on health risk calculation was estimated as low (hazard quotient value <10−7). In the case of risk matrix analysis, the environmental risks were estimated as moderate, major and very severe, dependent on the assumed scenario.

Quantification and Speciation of Trace Metals under Pollution Impact: Case Study of a Subarctic Lake

Monitoring the quantity and quality of metals in lake water is a major part of assessing water toxicity. A fundamental aspect of geochemical monitoring studies is the evaluation of the equilibrium distribution of metal speciation in water and the influence of environmental conditions on this process. It is important to understand the difference between the behavior of nanoparticles, dissolved particles, colloid particles, and suspended particles. This study involved environmental aquatic chemistry research and the assessment of the geochemical processes of metal speciation in an arctic lake in the metallurgical waste zone and other areas where natural processes prevail. Consecutive and parallel membrane filtration methods were used to compare the results of water analysis in Imandra Lake. The membrane pore sizes were 8, 1.2, 0.45, and 0.2 µm. The following filtrate characteristics were used: microfiltration-based mechanical suspension and oxidized contaminants (>8, 1.2, 0.45, 0.2, 0.1 μm), and ultrafiltration-based colloids, bacteria, viruses, etc. (less than 0.1 μm). Industrial effluents led to the formation of higher concentrations of elements (Ni, Cu, and Pb) in their labile forms. In the wastewater-mixing zone, the concentrations of most elements were evenly distributed in depth. In more distant areas, we found a significant increase in the concentration of elements in the near-bottom horizon in comparison with the surface water (Fe by more than three times). The obtained results showed that numerous elements had diverse distributions by speciation in the points located closer to the source of wastewater. This indicated the significant influence of the adsorption process on the system balance of elements such as Fe, Cu, and rare earth elements. The impact of the regional geochemical and anthropogenic speciation and the possible influence of climatic factors on the distribution of speciation were determined.

Ecosystem metabolism regulates seasonal bioaccumulation of metals in atyid shrimp (Neocaridina denticulata) in a tropical brackish wetland

Natural dissolved organic matter (DOM) forms the base of aquatic food webs and is a key environmental factor that affects the bioavailability of metals for aquatic organisms. Aquatic communities are naturally exposed simultaneously to environments containing a mixture of metals and varying DOM levels and compositions. However, the exact effect of DOM on metal bioaccumulation is difficult to predict due to temporal and spatial variations in sources, production, and consumption of DOM, and to interactions between DOM and metals. Ecosystem metabolism describes the process of organic carbon production and consumption and, therefore, the trophic status of ecosystems. However, whether and how ecosystem metabolism determines the seasonality of metal bioaccumulation remains unclear. The present study used in-situ water quality sondes and discrete field samplings to establish the relationship between the seasonality of ecosystem metabolism; related environmental and limnological regulators; the metal speciation and concentration in bulk water and sediments; and their metal bioaccumulation. The target population consisted of atyid shrimp (Neocaridina denticulata) in a brackish constructed wetland in tropical Taiwan was sampled between August 2014 and November 2015. Metal bioaccumulation displayed distinct seasonal patterns that peaked in summer (Cu, Cd, Cr, Zn, Mn, and Se) or winter (Pb and Ni). The in situ production (gross primary production) and heterotrophic consumption (ecosystem respiration) of organic matter significantly decreased with increasing waterborne DOM levels in this heterotrophic wetland. Both dissolved free metals bioavailable for respiratory surfaces (As, Zn, Cu, and Cr) and insoluble metals available for dietary intake (Mn and Ni) decreased with increasing DOM, as well as with decreasing gross primary production and ecosystem respiration. Seasonal variations of metal bioaccumulation also paralleled the transition in wetland trophic status, which reflected the effect of potential qualitative changes in the wetland DOM pool. Bioaccumulation of most metals displayed strong correlations with gross primary production, ecosystem respiration, and wetland trophic status. Our findings demonstrated that ecosystem metabolism can play a key mediating role in the seasonality of metal bioaccumulation in atyid shrimp, as it links the variation and interaction between DOM level/source, the speciation/bioavailability, and the uptake efficiency for metals by aquatic organisms. This study contributes to the temporal-specific risk assessment of aquatic metal exposure in regional environmental settings. It also reveals ecosystem-specific spectra in the context of changes in climate and environment.

Major, trace and rare earth elements geochemistry of geothermal waters from the Rehai high-temperature geothermal field in Tengchong of China

Major and trace elements geochemistry of high-temperature geothermal waters are important for understanding the subsurface transport and transfer of mass during groundwater circulation. The major constituents and trace elements, including rare earth elements, are discussed to reveal the source of elements and the hydrogeochemical processes occurring in the geothermal waters in the Rehai high-temperature geothermal field in Southwest China. Neutral-alkaline bicarbonate geothermal waters and acid sulfate waters are observed in Rehai due to different genesises. The bicarbonate waters contain higher concentrations of Na, K, Cl, HCO3, Li, Be, F, Sc, Ti, V, Cr, Ga, Rb, Nb, Sb, Cs, W, Tl, Zr and Si and less SO4 than the sulfate waters. The hydrogeochemical analyses show that the recharge of magmatic fluids, mixing with cold water and water-rock interaction affect the concentration of the elements. The geothermal waters and host rock REE chondrite-normalized patterns and the Eu anomalies are inherited from the host rock signature. Negative Ce anomalies may result from oxidative scavenging process of Ce and/or adsorbtion by the precipitation of Fe oxyhydroxides. T, TDS, pH and Fe/Mn minerals all affect the REE concentrations of geothermal waters. Calculations of REE speciation show that in the alkaline waters, Ln(CO3)2- is the major speciation. In the neutral waters, Ln(CO3)2- and LnCO3+ are the main speciation. In the weak acid waters, LnCO3+ is the main speciation and LnSO4+ are the major speciation in the strong acid water.