Determination of decamethylcyclopentasiloxane in river and estuarine sediments in the UK

Robust analytical procedures for the measurement of decamethylcyclopentasiloxane (D₅) in river and estuarine sediments and their application in determining environmental concentrations in the UK are presented for the first time in this work. Novel approaches to minimise commonly reported artefacts are utilised, improving the confidence in the concentrations of D₅ reported. Accelerated solvent extraction (ASE) and liquid–solid extraction methods are compared. Both methods use on-column injection gas chromatography/mass spectrometry (GC/MS). Measurements of D₅ concentrations in sediments sampled from the river Great Ouse and from the Humber estuary (UK) are also reported. ASE was suitable to measure concentrations of D₅ in sediments obtained from the river Great Ouse, UK (186–1450 ng g⁻¹, dry weight) and octamethyltetracyclosiloxane (D₄, 12–24 ng g⁻¹, dry weight). C₁₂ linear alkybenzene (C₁₂ LAB), which can be used as a chemical marker for sewage effluent related emissions, was also measured in this analysis. Liquid–solid extraction was optimised to provide more confidence in the lower D₅ concentrations measured in the Humber estuary, UK (49–256 ng g⁻¹, dry weight). A Limit of quantitation (LOQ) for D₅ of 57–110 and 4 ng g⁻¹ dry weight was determined for ASE and liquid–solid extraction, respectively.     

Uranium series disequilibrium in the coastal surface sediments and sea water of the Arabian Sea

Nearshore surface sediments from various locations of the West Coast of India were leached by saturated ammonium carbonate solution for the extraction of uranium isotopes. The reagent chosen was found to have high efficiency for leaching uranium isotopes without attacking the mineral core of the sediment particle. The activity ratios of²³⁴U/²³⁸U are in the range of 1.11 to 1.14 and the activity ratios of²³⁵U/²³⁵U are in the range of 0.045 to 0.047. The respective activity ratios in leachates, and residues after removal of surface organic matter from the sediment particles by treatment with hydrogen peroxide and 0.05M HCl, revealed disequilibrium between²³⁸U and²³⁴U only in the surface organic matter. The activity ratios of²³⁴U/²³⁸U and²³⁵U/²³⁸U have also been determined in some seawater samples from the Arabian Sea.     

Studies on the geochemical behaviour of uranium isotopes in Tuwa springs and Khari river sediments

High activities of radium were observed in the spring waters of Tuwa in Panchamahal district of Gujarat state. These determinations have led to further studies on geochemical behaviour of uranium in the surface sediments of this region. Labile uranium from the surface of the sediment particles is leached with saturated solution of ammonium carbonate. Uranium is chemically separated from the leachates by cellulose column chromatography. Unusually high activity ratios of²³⁴U/²³⁸U in the range of 2.3 to 2.77 were observed on the surface of the particles. The core of the particles exhibited a ratio of 1.00 indicating soluble²³⁴U fraction has migrated.     

Simple method for monomethylmercury determination in estuarine sediments

Several analytical methods have been proposed for determining monomethylmercury concentrations in sediments. We give an overview of the methods frequently used in the last few years, including matrix digestion, solvent extraction and preconcentration steps prior to quantification of MMHg by instrumental analysis. We propose a simple method to determine MMHg in estuarine sediments, involving alkaline digestion (KOH/methanol), toluene extraction and preconcentration of MMHg in dithizone. We performed separation as well as quantification by gas chromatography electron capture detection. Obtained and certified MMHg concentrations for international certified reference materials (AIEA-405 and CRM-580) showed no statistically differences (α=0.05). Low limits of detection, good repeatability and recoveries made this method a useful tool for rapid analyses of estuarine sediments. We applied this method to a sediment core collected in the Tagus Estuary, Portugal, giving a rapid vertical distribution of MMHg concentrations.     

Sampling representativity and homogeneity of river sediments

Statistical aspects of sediment sampling are discussed. Sampling sites at two selected rivers in East Germany were investigated using various sampling models. In the sediment samples the contents of 13 metals (As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se and Zn) were analyzed by means of atomic spectroscopy. Large differences in the contents of the analyzed metals were already found at small distances. The application of an overall error analysis shows that independent of the analyzed grain size fraction, sampling is the main source of variance. Two-dimensional variance analysis and a geostatistical method were applied because of homogeneity considerations. In contrast to the investigated longitudinal profiles, concentration gradients and spatial dependences of the metal contents were detected at the cross section. Finally, two approaches are described to determine the number of samples required for the representative assessment of loads. Weighting the result according to a critical value is shown as a way to reduce the expenditure of sampling.Dedicated to Professor Dr. K. Doerffel on the occasion of his 70th birthday     

Radionuclides in sediments of the Danube river

The trend of variation of sediment radiocontamination, expressed as a function of space and time, and specific accumulation of particular radionuclides in some investigated localities, are discussed on the basis of experimental results of gamma spectrometric analyses of artificial radionuclide contents.     

Screening of humic and fulvic acids in estuarine sediments by near-infrared spectrometry

Diffuse reflectance near-infrared spectroscopy (NIR) combined with partial least squares (PLS) data treatment has been employed for the rapid and nondestructive determination of sedimentary humic substances. Forty one samples of surface estuarine sediments, taken during distinct seasonal periods from different locations across Ria de Arousa (northwest of Spain), were scanned at wavelengths from 833 to 2,976 nm (12,000 to 3,360 cm⁻¹). Twenty four samples were randomly selected, from previous hierarchical cluster analysis of their NIR spectra, for the calibration set, and the 17 remaining samples were assigned to the validation set. NIR spectra of calibration samples were correlated to measured values of humic acids (HAs) and fulvic acids (FAs), which ranged from 1.53 to 28.17 mg/g and from 0.37 to 2.45 mg/g, respectively, using PLS regression and multiplicative scattering correction on the raw and first-derivative NIR spectra, respectively. Low root mean square error of prediction values of 4.3 mg HA/g sediment and 0.25 mg FA/g sediment were obtained. Good residual prediction deviation values of 1.16 and 1.2 were obtained for HA and FA, respectively, allowing the PLS models built to be considered as appropriate tools for screening purposes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Analysis of tributyltin in estuarine sediments and oyster tissue,Crassostrea virginica

An analytical method to determine tributyltin (TBT) in oyster tissue, Crassostrea virginica, and estuarine sediments is described. Recoveries of TBT from oysters range from 86 to 102% when samples are fortified at concentrations ranging from 22 to 890 μg kg^?1 (wet weight); recoveries from sediment range from 92 to 105% for samples fortified from 20 to 500 μg kg^?1 (dry weight). Feral oysters and natural sediments were analysed and shown to be contaminated with TBT. Oysters collected near a marina contained concentrations as high as 1.5 mg kg^?1 (wet weight).     

Contamination level of Danube river sediments

The paper presents a survey of the contamination level of the Danube river sediments along its course, between 849 km and 1162 km, during the period 1985–1988. Sampling was performed on several locations in the seasons with extreme hydrological conditions (spring, autumn).     

Radiocesium sorption-desorption processes in lake sediments

The kinetics of radiocesium sorption and desorption by cation solutions and the corresponding radiocesium distribution profiles in sediment cores were investigated. The results have shown that a significant percentage of radiocesium is adsorbed in the sediments during the first 3 d. Radiocesium reaches rapidly (< than 5 d) at a depth which does not exceed 3.5 cm. The desorption of radiocesium was found to depend on cation concentrations. Empirical laws are derived both for cesium adsorption and desorption.     

Behaviour of some organic micropollutants in river sediments and groundwater

Summary Organic micropollutants can reach the ground-water zone by various routes including direct contact with the surface water. River sediments play a substantial role, not only as a concentrating medium but also in their elimination of these substances. The behaviour of polycyclic aromatic hydrocarbons and halogenated compounds is investigated in laboratory experiments, filter plants, sediments and in the ground water. For analyses, Chromatographic methods (GC, TLC, HPLC) and mass spectrometry are employed. Statistical techniques such as principal component analysis and time series analysis are employed for data reduction and evaluation. The application of these methods together with empirical sorption and degradation experiments allow the influence of organic micropollutants on the ground water to be estimated.

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Verhalten einiger organischer Schadstoffe in Flußsedimenten und Grundwasser

Zusammenfassung Organische Schadstoffe können auf vielfache Art in den Grundwasserbereich gelangen, unter anderem durch unmittelbaren Kontakt mit Oberflächengewässern. Flußsedimente spielen in diesem Zusammenhang eine wesentliche Rolle als Medien zur Anreicherung, aber auch zur Eliminierung dieser Substanzen. Es wird berichtet über das Verhalten polycyclischer aromatischer Kohlenwasserstoffe und halogenhaltiger Schadstoffe in Laborversuchen, Filtereinrichtungen, Sedimenten und im Grundwasserbereich. Als Analysenverfahren werden chromatographische Methoden (GC, TLC, HPLC) sowie die Massenspektrometrie verwendet. Zur Datenauswertung werden statistische Verfahren wie die Hauptkomponentenanalyse und die Zeitreihenanalyse herangezogen. Diese Methoden ermöglichen es, gemeinsam mit empirischen Versuchen zum Sorptions- und Abbauverhalten, die Beeinflussung des Grundwassers mit organischen Schadstoffen abzuschätzen.

     

Radioisotopes of thirteen elements in intertidal coastal and estuarine sediments in the Irish Sea

A survey has been carried out of⁴⁰K,⁶⁰Co,⁹⁹Tc,¹⁰⁶Ru,¹²⁵Sb,¹²⁹I,¹³⁴Cs,¹³⁷Cs,¹⁵⁴Eu,²²⁶Ra,²²⁸Ra,²³⁷Np,²³⁸Pu,^239,240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm, and^243,244Cm activities in sediments from the Irish Sea. Several of these radionuclides were measured independently at two separate laboratories to enable the intercomparison of the results produced. The comprehensive data set generated allows the present spatial distributions of these radionuclides in coastal sediments to be examined in relation to sediment textural characteristics and by comparison with earlier survey, enables the temporal trends in their activities to be determined. In general all artificial radionuclides showed lower activities in sediments in response to falling discharges from Sellafield and relationships with either grain size, distance from Sellafield or both. Isotope ratios were similar to cumulative weighted activity ratios rather than present day values due to sediment mixing. Pu levels supplied evidence for the lag in response of sediment deposits with increasing distance from Sellafield due to sediment transport.     

Instrumental neutron activation analysis (INAA) of estuarine sediments

There has been an increasing interest in the consequences of the effectof discharge of effluents containing chemical elements into the marine environment.Here, we present the determination of a number of heavy metals in sedimentsfrom the Ribble Estuary in the north-west of England. Sediment cores wereobtained from the Ribble estuary and the cores were subdivided into 5 cm segmentswhich were then freeze dried. Part of the material so obtained was then usedto produce samples with particles of a given size range, since uptake of heavymetals by sediments is very particle-size dependent. Selected samples werethen reactor irradiated for instrumental neutron activation analysis. Theaims of this present study are to establish depth and longitudinal distributionsof heavy metals at selected site locations and to investigate the criticalsediment parameters that influence the uptake and retention of such contaminants.     

Characterization of estuarine sediments by near infrared diffuse reflectance spectroscopy

It has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63 μm grid. Spectra were scanned from 833 to 2976 nm, averaging 36 scans per spectrum at a resolution of 8 cm⁻¹, using chromatographic glass vials of 9.5 mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NIR spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area. pH, redox potential (Eh), carbon (C), nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3 mg g⁻¹ for H. Prediction errors for pH and Eh were 0.15 units and 37 mV, respectively, thus indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknown samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400 ng g⁻¹ Cd and 100 μg g⁻¹ Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes.     

Studies on thorium and uranium disequilibrium on the surface layers of the coastal sediments and their absolute concentrations in the sediments

Measurements of thorium and uranium isotopic activity ratios have been carried out with top layers of the sediments of the West coast of India in order to understand the behaviour and distribution of these isotopes in the coastal region. The southern part of the West coast contains a large amount of placer deposits while the northern region is free from such deposits.     

Determination of trace metals in estuarine sediments by graphite-furnace atomic absorption spectrometry

A simple and rapid acid digestion method for the decomposition of estuarine sediments is described. Quantitative recovery of Cd, Pb, Cu, Ni, Co, Be and Co is demonstrated. Sensitive, precise and accurate determination of these trace metals by graphite-furnace atomic absorption spectrometry in combination with the L'vov Platform provides an interference-free technique that permits calibration with simple aqueous solutions of metal standards. The accuracy of the method has been confirmed by analysis of two marine sediment reference materials, MESS-1 and BCSS-1.     

Precise determination of cadmium and lead isotopic compositions in river sediments

A method for the accurate determination of Cd and Pb isotope compositions in sediment samples is presented. Separation of Cd and Pb was designed by using an anionic exchange chromatographic procedure. Measurements of Cd isotopic compositions were carried out by multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS), by using standard-sample bracketing technology for mass bias correction and Pb isotopic ratios were determined by thermal ionization mass spectrometry (TIMS). The factors that affect the accurate and precise Cd isotope compositions analysis, such as instrumental mass fractionation and isobaric interferences, were carefully evaluated and corrected. The Cd isotopic results were reported relative to an internal Cd solution and expressed as the δ^114/110Cd. Five Cd reference solutions and one Pb standard were repeatedly measured in order to assess the accuracy of the measurements. Uncertainties obtained were estimated to be lesser than 0.11‰ (2s) for the δ^114/110Cd value. Analytical uncertainties in 2s for Pb isotopic ratios were better than 0.5‰. The method has been successfully applied to the investigation of Cd and Pb isotope compositions in sediment samples collected from North River in south China.     

Microanalytical determination of metallic constituents of river sediments

Summary The distribution of metallic constituents in torrential rivers as a function of the size particle cannot be frequently achieved by conventional analytical procedures, because of the lack of sufficient amounts of the fine fractions. For the study of river sediments in the Basque Country, microanalytical methods have been developed both for major (Na, K, Ca, Mg, Fe, Al, Si) and trace (Cu, Zn, Mn, Cr, Pb, Ni, Cd) components. Wet digestion in PTFE vessels at 140°C was done with 0.05 g sample using HNO₃-HClO₄-HF-H₃BO₃ or HNO₃-HClO₄, respectively. Further determinations were made by i) emission spectrometry (Na, K), ii) visible spectrophotometry (Al), iii) FIA (Fe, Si) and iv) AAS with flow spoiler (Ca, Mg, Cu, Zn, Mn) or graphite furnace (Cr, Pb, Ni, Cd). The proposed method has been checked with a standard sample obtaining mean values almost coincident with the certified ones and variation coefficients lower than 2% for major and 8% for trace components. Then it was applied to total samples and the fine fractions (<63 m) of 26 samples of sediments from three torrential rivers. Replicated values with analogous variation coefficients were obtained. Some considerations on distribution of major and trace constituents as a function of particle size are also included.     

Surface-analytical studies on environmental and geochemical surface processes.

The surface chemical compositions of solid samples from environmental and geological sources can differ from the bulk or average compositions, because of changes caused by adsorption, dissolution, oxidation, etc. Accordingly, analytical information on surface layers is important for a better understanding of the environmental chemistry involving solid surfaces. The rapid development of surface-analytical techniques has enabled us to probe the surface chemistry of environmental and geological solid samples of complex composition. This article demonstrates some examples of important items of information that can be obtained by applying surface-analytical techniques, such as X-ray photoelectron spectroscopy and secondary ion mass spectrometry, to environmental and geological samples. The surface analysis of fly ashes, soils, sediments and weathered silicate minerals is reviewed.