Trace Elements In Natural Waters Research Articles

Chemical characteristics and health risk evaluation of natural waters in the Du River Source National Nature Reserve: A case study in Zhushan County, Hubei Province, China

To study the distribution of trace elements in natural water of the Du River Source National Nature Reserve and to assess the water quality and health risks, Zhushan County in Hubei Province was selected as the study area. Element content in 361 natural water samples collected from Zhushan County were measured by ICP-MS, ICP-OES, and HG-AFS. The main anions and cations present in water samples from Zhushan County are Ca2+ and HCO3−. The water chemistry is predominantly influenced by the weathering of carbonate rocks. The water samples with high content of selenium (Se) (0∼82.9 μg/L, mean 4.6 μg/L) in natural water in Zhushan County are mainly distributed in the northern part of Zhushan. The strontium (Sr) content of 49.6% of the water samples (0.001–2.177 mg/L, mean 0.234 mg/L) reached the criteria of natural mineral water for drinking in China (Sr ≥ 0.2 mg/L), which is distributed throughout the county. The high content of metasilicic acid (H2SiO3) (0.026–35.910 mg/L, mean 12.598 mg/L) and zinc (Zn) (0∼407.218 μg/L, mean 12.406 μg/L) are concentrated in northern Zhushan County. 99.7% water samples were freshwater and 98.9% meet the criteria of “good” water quality. All of the natural water samples have low health risk and low heavy metal pollution. 6.1% water samples meet the criteria of Se-type mineral water, while 45.4% meet the criteria of Sr-type mineral water, and 4.4% water samples meet the criteria of “low sodium, high Se, and high Sr” mineral water. Zhushan County has the potential for Se-type mineral water and Sr-type mineral water development. The findings of this study hold immense significance for the public health implications of drinking water in Du River Source, thereby offering valuable insights for effective water resources management.

Final report for SIM.QM-S12: supplementary comparison for trace elements in natural water

Main textThe SIM Supplementary Comparison SIM.QM-S12 for Trace Elements in Natural Water was undertaken to assess and demonstrate the analytical capabilities of national metrology institutes (NMIs) and designated institutes (DIs) of SIM members (or other regions) for the accurate determination of trace elements in natural water at µg/kg levels.Evidence of successful participation in formal, relevant international comparisons is needed to document calibration and measurement capability claims (CMCs) made by NMIs and DIs.Seventeen NMIs and DIs participated. Participants were requested to evaluate the mass fractions, expressed in µg/kg, of arsenic, cadmium, lead and antimony in a natural mineral groundwater that was spiked with the respective elements. A variety of instrumental techniques including inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution ICP-MS (ID-ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), electrothermal atomic absorption spectrometry (ETAAS) and hydride generation flame atomic absorption spectrometry (HG-FAAS) were used by the participants for the determination.The NIST decision tree was used to assign the SCRV estimate for the proposed measurands and to calculate the degrees of equivalence of each national measurement standard following the IAWG Guidance on Using NIST Decision Tree for Comparison Reporting from 30 June 2023.Successful participation in SIM.QM-S12 demonstrates measurement for determination of elements in water matrices. Considering the IAWG Core Capability Matrix, this material falls into the matrix challenge called "Water/aqueous", which corresponds to the CCQM amount-of-substance category fresh water, and so will support CMCs for the metalloids and semi-metals at mass fraction levels below 50 µg/kg (As and Sb measurements) and transition elements at mass fraction levels below 50 µg/kg (except Hg) (for Cd and Pb measurements).To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Agro-ecological processes under conditions of biogeochemical imbalance of molybdenum in agrolandscapes of the Forest-Step zone

A special place in the theory and practice of landscape geochemistry belongs to biogeochemical zoning. Biogenic migration of substances and chemical elements can rightfully be considered one of the criteria for the typological classification of geochemical landscapes, which is the basis for building a map of geochemical landscapes of Ukraine. The scientific result of zoning is the recognition of spatial boundaries and areas of the territory consisting of connected components with uniform conditions of geochemical migration of chemical elements. With a long-term violation of the ratio between microelements, various diseases appear, which are called endemic, and the phenomenon itself — biogeochemical endemics. The latter most often occur due to a lack or excess of some threshold value of the concentration of microelements or a violation of the ratio of other micro­elements associated with it. On the basis of landscape-geochemical analysis and zoning, the authors defined the territory of the biogeochemical provinces of the Forest Steppe, where a lack of molybdenum content in the soil for normal plant development was found. In addition, the features of the molybdenum province are determined by low biogenic accumulation and intensive physicochemical dispersion of essential trace elements, increased mobility of most toxic trace elements in natural waters, and the absence of conditions for the formation of barriers of hydroamphoteric elements, including Mo2+. Also, in the territories of biogeochemical provinces, there is a high probability of the development of certain endemic phytopathologies and microelement diseases due to the imbalance of biogeochemical food chains.

Selenium quantification in wastewaters from selected coal-fired power plants and river waters in South Africa using ICP-MS

South Africa mainly relies on Eskom's coal-fired power plants for electricity generation. However, the use of coal causes several adverse environmental impacts, including the release of selenium into the hydrosphere. Selenium is an essential nutrient for humans, animals, and microbes, but excess selenium is toxic. This paper describes the determination of total dissolved selenium in wastewater from selected coal-fired power plants and river waters near coal-fired power plants in South Africa. A sensitive and robust inductively coupled plasma mass spectrometry (ICP-MS) method for determining total dissolved selenium in wastewater and river water was developed using a certified reference material (NIST SRM 1640a Trace Elements in Natural Water). The results agreed with the certified values, with percentage recoveries ranging from 92–96%. The method detection limit was 0.13 µg/L. Total Se concentrations in wastewater samples from Kriel and Lethabo Power Stations ranged between 4.86 and 8.53 µg/L, and in river water samples from the Olifants and Wilge Rivers, the concentrations ranged from 2.63–8.20 µg/L. These results indicate that the Se levels in the wastewater are too low to pose a health hazard to humans and livestock but pose an environmental threat to aquatic life. The low concentrations in the river samples also show that there may be slight Se pollution (regarding aquatic life) from the selected coal-fired power plants in South Africa. There may be slight Se pollution (with regards to aquatic life) from Duvha and Kendal Power Stations because an increase from 2–8 µg/L was observed in river water samples collected near these selected coal-fired power plants.

Development of a Sensitive Method for Cadmium Determination in Fish Tissue and Drinking Water Samples by FAAS Using SQT In Situ Atom Trapping.

A sensitive and robust trap method was developed for the determination of cadmium (Cd) by using a slotted quartz tube. Using this method at a sample suction rate of 7.4 mL/min for 4.0 min collection, a 1467-fold increase in sensitivity was obtained compared to the flame atomic absorption spectrometry method. Under the optimized conditions, a limit of detection of 0.075 ng mL-1 was obtained for the trap method. The interference effects of hydride-forming elements, transition metals, and some anions on the Cd signal were investigated. The developed method was evaluated by analyzing "Sewage Sludge-industrial origin (BCR no: 146R)", "NIST SRM 1640a Trace elements in natural water", and "DOLT: 5 Dogfish Liver". There was a good agreement between the certified and found values at the 95% confidence level. This method was applied successfully for the determination of Cd in drinking water and some fish tissue samples (liver, muscle, and gill) obtained from Muğla province.

Determination and speciation of methyl mercury and total mercury in fish tissue samples by gold-coated W-coil atom trap cold vapor atomic absorption spectrometry

A sensitive analytical technique was developed where gaseous mercury formed by sodium tetrahydroborate reduction is transported to and trapped on a resistively heated gold-coated Tungsten-coil atom trap for in situ preconcentration. This technique was applied successfully for determination and speciation of methyl mercury and total mercury in some fish tissue samples (liver, muscle and gill) obtained from Muğla province. The analytical parameters were optimized both for trap and no-trap studies. Under the optimized conditions, a limit of detection (LOD) of 6.0 ng/L was obtained. The precision was evaluated by relative standard deviation (RSD%) corresponding to 4.1% (n = 11). Accuracy of the proposed method was evaluated by analyzing “DOLT:5 Dogfish Liver”, “NIST SRM 1640a Trace elements in natural water” and “NIST 1946 Lake Superior fish tissues”. The measurements of the certified reference materials were in good agreement with the certified values at the 95% confidence level.

Ultra-Trace Determination of Arsenic by Platinum-Coated Tungsten Coil Hydride Generation (HG) Atomic Absorption Spectrometry (AAS)

A simple, rapid, and sensitive method for the determination of ultra-trace arsenic (III) is reported based on in situ trapping and revolatilization on a platinum (Pt) coated tungsten (W) coil atom trap. First, the analyte species in vapor form were transported by a mixture of Ar and H2 and trapped on the Pt-coated W-coil heated at 60 °C. Next, in the releasing step, the trap was resistively heated to 950 °C; the analyte species are revolatilized and transported to the quartz tube atomizer. The NaBH4 concentration, NaOH concentration, HCl concentration, trapping and releasing temperature, trapping time, and hydrogen and argon gas flow rates were optimized. Using these conditions, a limit of detection of 16 ng L−1 was obtained. The precision was evaluated by relative standard deviation corresponding to 4.8% at 1.0 μg L−1 (n = 11). The surface of the W-coil trap was coated with Pt using electrolytic deposition. Scanning electron microscopy-energy dispersive X- ray (SEM-EDX) analyses were performed to control the surface morphology of the trap. The same trap may be used for at least 350 atomization cycles without losing sensitivity. The accuracy of the proposed method was evaluated by analyzing NIST CRM 1640a (Trace Elements in Natural Water), EnviroMAT (Drinking water), and CRM-023 (Sandy Loam 7) certified reference materials. The measurements of the certified reference materials were in good agreement with the certified values at the 95% confidence level. The developed method was applied to the determination of As in drinking water samples from Muğla province.

A sensitive vesicle mediated dispersive liquid-liquid microextraction of parts per quadrillion levels of beryllium from seawater samples prior to graphite furnace atomic absorption spectrometry determination

A rapid and highly sensitive vesicle mediated dispersive liquid–liquid microextraction procedure is developed for the determination of parts per quadrillion level of beryllium in seawater and air filter samples for providing its natural background and contamination levels. In this procedure, dioctylsulfosuccinate, an anionic vesicular surfactant and acetylacetone are used as dispersing and chelating agents, respectively. At pH > 9.5, beryllium forms hydrophobic beryllium-acetylacetonate complex spontaneously at room temperature. This complex is selectively filled into the vesicular cavities of dioctylsulfosuccinate and is extracted into small chloroform phase from bulk aqueous phase. The beryllium present in the chloroform phase is back extracted with dilute nitric acid and is analyzed by graphite furnace atomic absorption spectrometry. This method is applied to groundwater, seawater, coal fly ash, air filter and sea sludge samples. Under the optimized conditions, the limit of detection, limit of quantification and linear dynamic range are 10 fg mL−1, 33 fg mL−1 and 40–500 fg mL−1 for seawater; 0.15 ng g−1, 0.5 ng g−1 and 0.4–4 ng g−1 for air filter and 1.5 ng g−1, 0.39 ng g−1 and 0.4–4 ng g−1 for coal fly ash, respectively. For 1 L seawater sample an enrichment factor of 954 is achieved. Coefficient of determination (R2) is found to be 0.997. The recoveries are in the range of 94–105% at 200–500 fg mL−1. The relative standard deviations are 20%, 11%, 8% for ppq, ppt and ppb levels of Be, respectively. The accuracy of the procedure is verified by analyzing NIST SRMs 1640 and 1640a trace elements in natural water.

Seasonal Variations in Proton Binding Characteristics of Dissolved Organic Matter Isolated from the Southwest Baltic Sea

The physicochemical characteristics of dissolved organic matter (DOM) strongly influence its interactions with inorganic species such as protons and trace elements in natural waters. We collected water samples at Boknis Eck, a time series station in the Baltic Sea with a low exposure to freshwater inputs, to investigate how seasonal fluctuations impact the proton binding properties of the isolated DOM. We used potentiometric titrations to assess the binding properties of solid-phase extracted DOM (SPE–DOM) over a seasonal cycle. We report and critically analyze the first NICA parameters estimates of carboxylic-like and phenolic-like sites for brackish water SPE–DOM. The total amount of functional groups (QmaxH,tot) showed no seasonal fluctuations and an average value of 136 ± 5.2 mmol·mol C–1. The average proton affinity (logKH) and binding site heterogeneity (m) showed a relatively minor variability for samples obtained between April and September, when the water remained stratified. These results contribute to a better understanding of the ion binding characteristics of DOM in natural brackish waters.

Dynamics of microelements (B, Al) in the water samples from the Prut river during the 2020 year

The purpose of this research was to study the dynamics of microelement content, the correlation between the main forms of migration of microelements (B, Al) - dissolved and suspended forms, except colloidal, and to study their seasonal variation. The main form of migration of the metalloid B in the waters of the Prut river is the dissolved one, while the migration form of Al is the suspensions. In this research, the content of the mentioned microelements was investigated in the water samples collected from the Prut River in 2020 (winter, spring, summer, and autumn) from 7 collection points. The microelements were determined using atomic absorption spectrophotometry (Perkin-Elmer AAnalist 400 atomic absorption spectrophotometer). The importance of determining trace elements in natural waters is determined by a number of issues, including the need to monitor the environment and assess environmental risks and assess their influence on living systems. The results of studying these forms of migration (dissolved and suspended) allow us a fuller understanding of their role in the migration of microelements in aquatic ecosystems in the system "water-suspensions-underwater deposits-hydrobionts".

The Forms of Occurrence of Trace Elements in Natural Waters of the Aquatic Formations of the Moscow Canal and the Volga–Baltic System

The Forms of Occurrence of Trace Elements in Natural Waters of the Aquatic Formations of the Moscow Canal and the Volga–Baltic System

Methodology development and optimization for direct quantification of total selenium concentration in mine water by total-reflection X-ray fluorescence spectrometry

Methodology for direct quantification of total selenium (Se) concentration in mine water by total-reflection X-ray fluorescence (TXRF) spectrometry was developed and optimized. Inductively coupled plasma – mass spectrometry (ICP-MS), as a recognized standard test method, was used as a benchmark for results verification. Preliminary measurements with aqueous multi-element standard solutions showed that Se concentration can be accurately determined down to 10 ng/g by using a single-drop of solution (10 μL) and a measurement time of 600 s. Quantification of lower Se concentration below 10 ng/g was subsequently optimized, also with aqueous multi-element standard solutions. Improvement in detection limit was accomplished by increasing amount of sample deposition as well as increasing measurement time. TXRF analysis of SRM1640a, Trace Elements in Natural Water, was also performed for accuracy check. The developed methodology was applied to analyze five raw mine water samples (MW-1, MW-2, MW-3, MW-4 and MW-5) collected from anonymous mine site locations. TXRF analysis was performed on the as-received samples directly without filtration, dilution and digestion. Samples were prepared as single-drop specimens and analyzed using a measurement time of 600 s. Se and fifteen other elements were detected in varying degree in the as-received samples. Se concentrations quantified by TXRF were 256.5 ± 22.5, 88.4 ± 1.4 and 61.3 ± 2.8 ng/g for mine water samples MW-1, MW-2 and MW-3, respectively, compared to 255.3 ± 5.6, 87.3 ± 2.6 and 59.7 ± 3.5 ng/g by ICP-MS. No clear Se-Kα peak above background was observed for samples MW-4 and MW-5. Increasing amount of sample deposition by preparing triple-drop specimens and using a longer measurement time of 1800 s, allowed a Se-Kα peak to emerge above the background for MW-4, but not MW-5. Se concentration in MW-4 quantified by TXRF was 4.9 ± 0.5 ng/g, compared to 6.7 ± 0.7 ng/g by ICP-MS, which represents an agreement within three standard deviation values between the two techniques. For sample MW-5, even after using triple-drop specimens and increasing the measurement time to 1800 s, Se concentration could not be determined because a Se-Kα peak was not detected by TXRF, compared to the Se concentration of 0.83 ± 0.1 ng/g obtained by ICP-MS. Overall, our analysis results showed that the TXRF technique can be used for direct analysis of total Se concentration in raw mine water samples down to ng/g range, providing high-quality, accurate and repeatable analysis comparable to ICP-MS while requiring much simpler sample preparation.

Determination of heavy metal ions by energy dispersive X-ray fluorescence spectrometry using reduced graphene oxide decorated with molybdenum disulfide as solid adsorbent

Reduced graphene oxide (rGO) decorated with molybdenum disulfide (MoS2) was synthesized by hydrothermal method. The physicochemical properties of the nanoadsorbent were characterized by different spectroscopic techniques, namely Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). MoS2-rGO was used as a solid nanoadsorbent in a dispersive micro-solid phase extraction (DMSPE) for the preconcentration of heavy metal ions from different types of waters prior to energy dispersive X-ray fluorescence spectrometry (EDXRF) determination. To optimize extraction process parameters such as sample pH, contact time and sample volume, were examined. The determined adsorption capacities for Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) ions were 242, 112, 145, 417, 550 and 498 mg g−1, respectively. Under optimal conditions (pH = 6.5, sample volume 50 mL, and sonication time of 10 min) the calibration curves showed linear response between analytes concentration and intensity of fluorescence radiation in the range 1–200 ng mL−1 for Cr(III), Cu(II), Zn(II) and Pb(II) ions, and 1–100 ng mL−1 for Co(II), Ni(II) ions. The limits of detection were 0.11, 0.12, 0.10, 0.07, 0.08, and 0.09 ng mL−1 for Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The precision of the method determined at two concentration levels, e.g. 2 and 20 ng mL−1 varied from 3% for Cu(II) to 5.1% for Co(II) and 1.4 for Cu(II) to 3.6% for Ni(II), respectively. The DMSPE-EDXRF procedure was suitable for determination of target analytes at ultra-trace level even in high salinity samples. The accuracy of the method was proved using certified material NIST 1640a (Trace elements in natural water). The ‘greenness’ of the procedure was calculated with the Analytical Eco-Scale tool.

СОДЕРЖАНИЕ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ В ПОЧВАХ И ПОВЕРХНОСТНЫХ ВОДАХ ПЛОСКОГОРЬЯ УКОК (ЮГО-ВОСТОЧНЫЙ АЛТАЙ)

Актуальность исследования обусловлена слабой изученностью химического состава почв и поверхностных вод плоскогорья Укок, являющегося объектом всемирного наследия ЮНЕСКО. Цель: изучить уровни содержания химических элементов в почвах и поверхностных водах центральной, южной и юго-восточной части плоскогорья Укок и дать эколого-биогеохимическую оценку этой малоизученной территории. Объекты: основные типы почв (криоаридные и горные лугово-степные, горные луговые, горные тундровые) и поверхностные воды (реки Жумалы, Калгуты, Аргамжи, Ак-Алаха, Тархата и озеро Укок) плоскогорья Укок (Республика Алтай, Российская Федерация). Методы. Содержание металлов в почвах определено методом эмиссионного спектрального анализа в Институте геологии и минералогии СО РАН, общее содержание микроэлементов в природных водах – в химико-аналитическом центре ИВЭП СО РАН спектрометрическим методом с использованием электротермической атомизации. Результаты. Представлен химический состав различных типов почв и поверхностных вод высокогорного плоскогорья Укок. Уровни содержания химических элементов в почвах плоскогорья не превышают их кларков в почвенном покрове и соответствуют их концентрациям в горно-тундровых почвах Алтая. Исключением являются почвы и почвообразующие породы над Калгутинским W-Mo-V-Cu месторождением, где отмечается аномально высокое содержание вольфрама – до 30–60 мг/кг. С ореолами рассеяния и воздействием отвалов штольни и хвостохранилища обогатительной фабрики этого месторождения мы связываем повышенное содержание Cu в водах реки Калгуты – 16 мкг/дм3 и в почвах бассейна. Почвы плоскогорья отличаются невысоким валовым содержанием P и Са, но обогащены калием – его содержание превышает 2 % в большинстве образцов. Концентрация фосфора в почвах плоскогорья Укок возрастает с запада на восток, от выровненной (центральной) части к горным окаймлениям, что обусловлено фосфоритоносностью коренных пород Алтае-Саянской горной страны. Низкие значения элювиально-аккумулятивных коэффициентов большинства металлов в изученных почвах плоскогорья могут служить показателем отсутствия на данный момент здесь выраженного антропогенного загрязнения. Содержание большинства элементов в почвах увеличивается c глубиной. В горно-тундровых торфянистых почвах под ерником обнаружена биогенная аккумуляция Mn. Для степных почв отмечено некоторое накопление в поверхностных горизонтах Zn, Cr, V и Ni. Наиболее равномерным распределением отличается Pb и Zn. Исходная неоднородность моренных и озерно-ледниковых отложений определяет разнообразие внутрипрофильного распределения металлов в почвах, на них сформированных. Не выявлено четкой зависимости содержания большинства макро- и микроэлементов в поверхностных водах от уровня их концентраций в почвах. Тем не менее отмечено повышение интенсивность водной миграции железа в заболоченных ландшафтах Бертекской части бассейна реки Ак-Алаха, в водах которой обнаружено его наиболее высокое содержание.

On-line sample treatment coupled with atomic spectrometric detection for the determination of trace elements in natural waters

This review discusses the application of on-line strategies for sample treatment prior to atomic spectrometric detection.

Graphene oxide covalently modified with 2,2′-iminodiacetic acid for preconcentration of Cr(III), Cu(II), Zn(II) and Pb(II) from water samples prior to their determination by energy dispersive X-ray fluorescence spectrometry

A novel adsorbent, graphene oxide modified with 2,2′-iminodiacetic acid (GO-IDA), was synthesized by nucleophilic substitution of dimethyl-2,2′-iminodiacetate hydrochloride to the surface of graphene oxide (GO). It was applied in the dispersive micro-solid phase extraction (DMSPE) for the simultaneous preconcentration of selected heavy metal ions from water samples prior to determination by Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). The experiments show that at pH 6.5 GO-IDA can be used for quantitative adsorption of Cr(III), Cu(II) Zn(II) and Pb(II) ions from water samples. The adsorption capacities of GO-IDA towards Cr(III), Cu(II), Zn(II) and Pb(II) ions are found to be 117.1, 108.4, 119.6, and 80.7 mg g−1, respectively. The experimental data are fitted better by the Langmuir model than by the Freundlich model. Under optimal preconcentration conditions the linear response between analyte concentration and fluorescence radiation intensity was observed within 1−200 ng mL−1 for Cr(III) and Cu(II), 1−140 ng mL−1 for Zn(II), and 1−100 ng mL−1 for Pb(II) ions. The uncertainty of the developed method does not exceed 4.3%. The detection limits are 0.11, 0.06, 0.07 and 0.08 ng mL−1 for Cr(III), Zn(II) Cu(II) and Pb(II), respectively. The enrichment factors obtained for the 50 mL sample volume are in 450−1465 range. The DMSPE-EDXRF procedure was applied for the determination of Cr(III), Cu(II), Zn(II) and Pb(II) ions in different types of water samples. The accuracy of the procedure was verified by the analysis of Certified Reference Material: NIST 1640a (Trace elements in natural water).

Rapid on-line solid phase enrichment using polytetrafluoroethylene beads for chromium speciation in contaminated real water samples

Due to unchecked disposal of industrial wastes into surrounding areas, the pollution of water bodies with heavy metal toxicants has become an environmental menace. The toxicity of chromium species depends on its oxidation states, and thus regular monitoring of environmental water sources vulnerable to pollution is a must. In this regard, an on-line method for chromium speciation and determination using FAAS has been proposed. The flow-injection preconcentration mini-column containing polytetrafluoroethylene beads was used as the solid phase extractant, and chromium speciation was done by complexing Cr(III) and Cr(VI) with thiosemicarbazide chelating agent. The figures of merit for Cr(III) and Cr(VI) obtained were 61 and 56 (preconcentration factors); 0.13 and 0.14 µg L−1 (detection limits); 1.6 and 1.3% (R.S.D.). The optimized method for chromium speciation was successfully applied to industrial and Yamuna River water samples. The method validation was carried out using SRM 1640a (Trace Elements in Natural Water, NIST), and recovery > 95% was obtained.

地球表層物質による微量元素とり込み過程とそのモデル化

Clay minerals, metal oxyhydroxides, and carbonates are important earth surface materials, which are secondary minerals formed from primary minerals with water and atmosphere under earth surface conditions. These minerals usually possess a high surface area and are highly reactive to foreign dissolved species; therefore, they play important roles as sorbents for trace elements in natural water. Predicting distributions of trace elements between solution and mineral phases is important for understanding migration and accumulation behaviors of toxic and useful elements on the earth surface. To predict distributions, it is required to elucidate the chemical processes governing the sorption of trace elements on or in minerals, and to model chemical processes quantitatively. The important chemical processes governing the sorption of trace elements by earth surface materials are adsorption, surface precipitation, ion exchange, mineralization, and coprecipitation. The current understanding of these chemical processes as revealed from laboratory experiments is reviewed, as well as current approaches to modeling.

Determination of labile species of As(V), Ba, Cd, Co, Cr(III), Cu, Mn, Ni, Pb, Sr, V(V), and Zn in natural waters using diffusive gradients in thin-film (DGT) devices modified with montmorillonite.

A binding phase based on the clay mineral montmorillonite (MT) was used as a sorbent in this work, which employed diffusive gradients in thin-film (DGT) devices to determine the lability of trace elements in natural waters. Montmorillonite exhibits low cost, wide availability, ease of handling, high ion-exchange capacity, and reusability. As(V), Ba2+, Cd2+, Co2+, Cr(III), Cu2+, Mn2+, Ni2+, Pb2+, Sr2+, V(V), and Zn2+ were quantitatively sorbed by MT and eluted with 1.0molL-1 HNO3, which provided efficiency above 70% of recovery. Validation tests were performed with synthetic solutions. The recovery of known concentrations ranged from 83 to 110%. The performance of modified DGT was compared with conventional DGT devices in experiments lasting 6 and 48h. The results obtained with both DGT devices showed no significant differences with 95% confidence. DGT samplers with MT were deployed in the determination of labile forms of the elements in water samples from Iguaçu River (Paraná, Brazil). The measured masses of elements in MT for various durations showed good fit to a theoretical line, indicating that the results agreed with the principle of the DGT technique. The concentrations of labile species in the sample proceeded as follows; Sr > Cd > Ba > Cu > Cr > Mn > Zn > Pb. The results suggest that DGT devices with MT are an effective alternative for speciation analysis of a wide range of elements (cations as well as anions) in natural waters.

Online Preconcentration Procedure for Chromium Speciation and Determination in Industrial Water Samples Using Flame Atomic Absorption Spectrometry.

An online preconcentration system based on solid-phase extraction was developed for speciation and determinations of Cr in industrial water samples using flame atomic absorption spectrometry. A minicolumn packed with Amberlite XAD-16 loaded with salicylic acid was used to preconcentrate chromium species. All flow and chemical parameters that influence sorption were studied. The preconcentration factor and detection limit for the preconcentration time of 120 s were 79 and 0.10 μg L-1, respectively. The concentration of Cr(VI) species was calculated by the difference of the total Cr and Cr(III). The relative standard deviation (RSD) (five replicate of measurements) for 50 and 100 μg L-1 Cr(III) solution was 1.2 and 1.0% respectively. The accuracy of the method was verified by analyzing a standard reference material (NIST SRM 1640a, trace elements in natural water). The proposed preconcentration method was successfully applied to the determination of Cr species in industrial water samples with satisfactory results.