Determination of water-soluble forms of oxalic and formic acids in soils by ion chromatography

Carboxylic acids (CA) play an important role in the chemical composition origin of soils and migration of elements. The content of these acids and their salts is one of the important characteristics for agrochemical, ecological, ameliorative and hygienic assessment of soils. The aim of the article is to determine water-soluble forms of same carboxylic acids - (oxalic and formic acids) in soils by ion chromatography with gradient elution. For the separation and determination of water-soluble carboxylic acids we used reagent-free gradient elution ion-exchange chromatography ICS-2000 (Dionex, USA), the model solutions of oxalate and formate ions, and leachates from soils of the Kola Peninsula. The optimal gradient program was established for separation and detection of oxalate and formate ions in water solutions by ion chromatography. A stability indicating method was developed for the simultaneous determination of water-soluble organic acids in soils. The method has shown high detection limits such as 0.03 mg/L for oxalate ion and 0.02 mg/L for formate ion. High signal reproducibility was achieved in wide range of intensities which correspond to the following ion concentrations: from 0.04 mg/g to 10 mg/L (formate), from 0.1 mg/g to 25 mg/L (oxalate). The concentration of formate and oxalate ions in soil samples is from 0.04 to 0.9 mg/L and 0.45 to 17 mg/L respectively

The Choice of Conditions for the Determination of Vanadium, Chromium and Arsenic Concentration in Waters by ICP-MS Using Collision Mode

Inductively coupled plasma mass spectrometry (ICP-MS) is a popular method for the analysis of waters with various matrices and salinity. One of the difficulties of routine measurements by ICP-MS is spectral interferences conditioned by polyatomic ion formation in the plasma. The detection of the background concentration of such elements as vanadium, chromium and arsenic in natural waters by ICP-MS is complicated because of the polyatomic interferences, having the same mass-to-charge ratio. Thus, the purpose of this article is to determine the optimal rate of helium flow for the effective correction of polyatomic interferences of vanadium, chromium and arsenic and the reduction of their detection limits in Cl-rich waters. This research has been carried out using an inductively coupled plasma mass spectrometer NexION 300D with a universal cell technology (UCT) (PerkinElmer, USA) and three model solutions. For the detection of vanadium, chromium and arsenic content in chloride matrix water by ICP-MS, a collision mode is preferable for polyatomic interference correction. The optimal helium flow rate for this purpose is 2.5 ml/min. Under these conditions, the detection limit of vanadium, chromium and arsenic decreases by order of two

Size fractionation of trace elements in the surface water and groundwater of the Ganjiang River and Xiushui River basins, China

The research of trace element behaviour and size fractionation is significant to understand the processes in the water-rock system. Moreover, the aqueous speciation of trace elements is strongly related to their distribution and toxicity. In this research, trace elements behaviour and their size fractionation are investigated in the natural water (the surface water and shallow groundwater) of the Ganjiang River and Xiushui River basins. Trace element concentrations were measured by ICP-MS. The authors estimated the size fractionation of the trace elements between suspended forms (>0.45 [mu]m) and dissolved fractions, which included truly dissolved (1 kDa) and colloidal particles (0.45 [mu]m-1 kDa)), after filtration through a 0.45 [mu]m acetate cellulose membrane filter. The distinct features of the trace element size fractionation were identified. The size fractionation of the trace elements under different conditions (in the surface water and shallow groundwater) was studied

Chemical composition of natural waters of contaminated area: The case for the Imandra Lake catchment (the Kola Peninsula)

The study of the current chemical composition of natural waters in the eastern and western parts of the Imandra Lake catchment was performed using ion chromatography, potentiometry and inductively coupled plasma mass spectrometry. It was found that the content of trace elements in the surface water is considerably higher than that in the groundwater. The nickel and copper concentrations exceed the background levels over 19 and 2 times respectively in groundwater, and 175 and 61 times in the surface waters. These data show that the Severonikel influences negatively air and surface water

Study of Aqueous Chemical Forms of Silicon in Organic-rich Waters

The study of silicon species in organic-rich waters is a very significant problem. This type of waters is widely spread all over the world. It is characterized by a high content of humic substances, high color of water and low pH. In this regard, a certain determination of silicon concentration in this type of waters is impossible without a preliminary investigation of silicon species. The aim of this research is therefore an investigation of the ratio of silicon dissolved forms in organic-rich waters depending on the silicon concentration and the acidity of the water. The study of pH influence on silicic acids and a silicon-humic matter interaction was carried out using model solutions and natural bog waters (Tomsk region). It has been found that the degree of polymerization of silicic acids essentially depends on the acidity of a solution. Scanning of spectrophotometric measurements has shown that silicon does not form stable complexes with fulvic and humic acids in weak-acid media (рН 3-4). Studying the bog waters of Tomsk Region has shown that they (рН=3.66-3.80) contain only monomeric-dimeric and polymeric forms of silicic acids

Uranium and thorium behavior in groundwater of the natural spa area "Choygan mineral water" (East Tuva)

The natural spa area "Choygan mineral waters", a unique deposit of natural carbon dioxide mineral waters in Siberia, is located in the Eastern Sayan Mountains. There are 33 spring discharges in this area. Spring waters are mainly of HCO[3]-Na-Ca type. TDS varies from 300 mg/L to 2600 mg/L, the temperature ranges from 7 °С (in spring 33) to 39 °С (in spring 12), pH varies from 5.9 to 8.3, and the value of the oxidation-reduction potential is from -170 mV to 236 mV. All studied waters were divided into two groups according to their temperature and geochemical conditions: cold fresh water in oxidizing environment and warm slightly brackish water in reducing environment. The uranium concentration varies from 0.7 to 14 [mu]g/l and the thorium concentration varies from 0.001 to 0.33 [mu]g/l in the studied waters. The predominant uranium complexes are (UO[2](CO[3])[3]){4-}, (UO[2](CO[3])[2]){2-}, UO[2]CO[3], (UO[2](PO[4])[2]){4-} in the waters in oxidizing and reducing environments. It was found that acid-alkaline and oxidizing-reducing conditions were the determining factors for uranium behavior and speciation in the studied waters. The pH conditions are determining factors for thorium behavior and speciation in the studied waters. In slightly acidic water the predominant thorium species is negatively charge complex (ThCO[3](OH)[3])- (more than 95 %)

Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper

Ggeochemistry of groundwater in Tashkent artesian basin (Republic of Uzbekistan)

Water resources play a significant role in the economic development of Tashkent oblast (Republic of Uzbekistan), groundwater is used for drinking water supply in urban and rural population, production and technical needs and irrigation. In this regard, the research of features of groundwater chemical composition formation in Tashkent artesian basin is of great importance for forecasting the changes in its quality. The main aim of the study: to investigate the features of groundwater chemical composition formation in Tashkent artesian basin according to the analysis of water-rock interaction evolution.The methods used in the study: Methods of equilibrium thermodynamics were used for comprehensive study of the groundwa ter-rock equilibrium conditions. Traditional methods were used to determine the groundwater chemical composition. The results: The authors have studied the features of groundwater chemical composition in Tashkent artesian basin and have determined the regularities in behavior of the basic ions at mineralization increase. The investigation of groundwater equilibrium showed that all examined waters achieve montmorillonite saturation and some waters are saturated with calcite. Despite the high sulfate content in waters the saturation with sulfate minerals is not observed. These results allowed the authors to distinguish two geochemical water types such as siliceouscalcium (magnesium) and calcium carbonatesiliceous, differ in pH and basic ions content

Calculation of deep temperatures of thermal waters in Eastern Tuva

Relevance of the work is caused by the presence of a wide variety of geochemical geothermometers used to assess depth of temperatures, and reliability of their application to various chemical types of thermal waters. The main aim of the study is to establish the applicability of the method for estimating deep temperatures of thermal waters circulation using geothermometers for different chemical types on the example of the Eastern Tuva springs. Methods of research. Chemical composition analysis of the waters was carried out in the accredited research laboratory of hydrogeochemistry of TPU. Traditional methods were used to conduct a complete chemical analysis. Geochemical geothermometers and calculation of a mineral saturation index as a function of temperature in PhreeqC package were used to estimate the deep temperatures. Results. The assessment of the temperature conditions of the Eastern Tuva hydrothermal systems shown silicon geothermometers predicted more reliable reservoir temperatures for all thermal waters in question compared to other geothermometers independently of chemical types of water. The choice of this or that geothermometer is determined by the chemical type of water, equilibrium in the water-rock system and concentration of the main elements. Almost all geothermometers showed good convergence of results for sulfate and hydrocarbonate waters of Tarys and Ush-Beldir, the predicted reservoir temperatures are 120 and 130 °C at a depth of 4,5 and 4,8 km, respectively. The same temperature values were obtained by the saturation index approach over a range of temperatures. Determination of reliable deep temperatures for the Choigan hydrocarbonate waters with help of cationic geothermometers proved to be difficult. In this case, the silicon geothermometer provides a reliable estimate of the reservoir temperature for waters with high cation concentrations. The value of the temperature obtained from the silicon geothermometer was confirmed by another method of temperature determining - using saturation indices - and it is about 100 °С, while the depth of formation is estimated at 3 km

Isotopic composition ([delta]{18}O and [delta]D) of the shallow groundwater in the Poyang Lake basin

The article is focused on the identification of evaporation and other natural processes which affect the isotopic composition of shallow groundwater in the Poyang Lake basin, such as water-rock interaction and mixing of the shallow groundwater and surface water. For this purpose the dual isotope approach ([delta]D–H[2]O and [delta]{18}O–H[2]O) was used. The samples were collected from domestic wells around the Poyang Lake. The value of [delta]D obtained for the shallow groundwater ranges from -21.5 to -42.6/. The [delta]{18}O value varies from -3.5 to -7.1/. It was found that the shallow groundwater of the Poyang Lake catchment is of meteoric origin. The influence of evaporation on the isotopic composition of shallow groundwater is negligible and observed mainly during the dry season. The deviation from the local meteoric water line, especially during the rainy season, may be explained by the processes in the water-rock system, but this issue is required further research