Dissolution of resistate minerals containing uranium and thorium: Environmental implications

Summary Minerals in the soil range from those that easily weather to those that are very resistant to the weathering processes. The minerals used in this study are referred to as “resistates” because of their resistance to natural weathering processes.¹ It is also known that there are some resistate minerals that have a tendency to contain uranium and thorium within their crystal structure. These resistates can contain as much as 15-20% of the total uranium and thorium present in the soil.⁹ Do resistates dissolve in acids, particularly in the HF/HNO₃ procedures, if not what can be done to the HF/HNO₃ process to dissolve more of the resistate minerals? How would these acid techniques compare to the fusion method used for mineral dissolution? Could the resistate minerals contain considerable amount of uranium and thorium? These were the questions addressed in this research. The comparative data indicate that the use of H₂SO₄ in the dissolution process resulted in ~25% overall increase in the minerals dissolving therefore resulting in a higher yield of extracted uranium and thorium.     

Bridging the gaps in analytical atomic absorption spectrometry

The techniques of analytical, valence electron, atomic spectrometry (absorption, fluorescence and emission), by themselves, are mainly for the determination of the amount of an element in a sample which has been prepared as a . For a large fraction of trace element analysis such an approach is satisfactory. However, there are some other very important requirements in trace element analysis not now adequately being addressed by analytical atomic spectrometry. A selection of these, familiar to the present writer, will be covered in this presentation. Some interesting initiatives to “bridge the gaps” are now being made. The topics to be discussed are; elemental speciation, direct analysis of solids, elemental and natural isotope analysis using plasma sources, micro analysis by laser probe and vapour generation approaches to improved detection limits. This is not intended to be an exhaustive review of these subject areas but will present material of interest together with recently published key papers. Greatest emphasis is given to the very important topic of speciation.     

Long range transport of biomass aerosol to Greenland: Multi-spectroscopic investigation of particles deposited in the snow

Summary Results are given from the NIST component of a pilot (“winter-over”) study of seasonal patterns of natural and anthropogenic species in air and snow transported to Summit, Greenland. Central to this research is the quantitative apportionment of fossil and biomass particulate carbon, based on advanced (micromolar) ¹⁴C accelerator mass spectrometry (AMS) applied to remote snow samples containing as little as 9 µg C/kg. The measurements were made practicable through stringent attention to the nature and sources of the isotopic-chemical blank, resulting in a blank reduction from »5 µg C to <0.5 µg C. An important result of this work is the first evidence of a seasonal pattern in biomass-C particles in Greenland snow. Although ¹⁴C AMS data serve to resolve fossil and biomass carbon quantitatively, a deeper understanding of the aerosol sources and character demands a multidisciplinary approach. This is illustrated with “multi-spectrometric” macro- and micro-analytical data for two cases involving substantial incursions of biomass aerosol to the Summit, Greenland snow.     

Adsorption of NOM onto Activated Carbon: Effect of Surface Charge, Ionic Strength, and Pore Volume Distribution

Adsorption of natural organic matter (NOM) onto seven activated carbons with a wide range of surface properties was studied at high and low ionic strength over a range of pH values. From adsorption isotherm studies it was found that, for six of seven carbons, at low surface concentrations, increased ionic strength decreased NOM adsorption. As the surface concentration increased, the adsorption isotherms converged and intersected, after which the addition of salt resulted in increased adsorption. This “crossover point” marked a change in the adsorption mechanism from the “screening reduced” to the “screening enhanced” adsorption regimes. The adsorption mechanisms are extremely complicated and appear attributable to various factors, including electrostatic forces, pore volume distribution, and chemical interactions between the NOM and the surface functionalities on the carbon surfaces.     

Supercritical Drying Applied to Natural “Gels”: Allophanic Soils

Allophanic soils behave as gels during a classical drying with an important irreversible shrinkage which can modify the soil physical properties. These soils are interesting in terms of mitigation of the greenhouse effect (C sequestration) and the knowledge of the true soils features are of importance. Like for silica gels, we use the CO₂ supercritical drying procedure (SCD) to control the drying step. The objective is to preserve the structural and textural properties of the soils, which can be affected by the classical drying. We show also that despite the necessary solvent exchange and high pressure of the supercritical drying, the chemical composition and the allophanic features are not strongly affected.The textural properties such as specific surface area are higher for the supercritical dried samples compared to the classical dried samples, indicating the preserving effect of the SCD and showing the interest of the application of this drying method to this natural and complex “gels”. With these data, we show possible effects of the specific surface area on the C and N content of the allophanic soils.     

On the role of environmental reference materials in the development of horizontal standards for environmental protection

The need for standardisation and harmonisation of measurements increases with the progress of the European integration process. One of the areas for which the need for harmonisation has been emphasised is the protection of the soil compartment. While knowledge of problems associated with soils is increasing in Europe, based on soil surveys, monitoring systems and data networks, the corresponding (analytical) data is not often comparable, which limits its value for policy development. In this context, the European Commission has invited the Member States to investigate the possibility for a harmonisation of European standards in the fields of soil, sludge and biodegradable waste (compost). Furthermore, the development of new reference materials for both the validation of these new methods and their successful implementation on a routine basis is required. This paper shows some selected examples for which the development of horizontal standards may be worth investigating. In addition, it discusses and proposes the vehicle of (C)RMs for the implementation of a common measurement system for soil, related to these horizontal standards. It also raises some open questions and sheds light on future perspectives and challenges.Presented at BERM-9 – 9^th International Symposium on Biological and Environmental Reference Materials, June 15–19, Berlin, Germany     

A tensiometric study of diamond (111) and (110) faces

Tensiometric contact angle measurements of diamond surfaces in both the air:water and octane:water systems reveal moderate hydrophobicity, as might be expected of a surface with a minority of oxygen-containing groups. High-temperature reaction with oxygen or hydrogen leads to large changes in the contact angles. Spectroscopic methods show a “one-third” coverage by oxygen. The response to pH and adsorption of ferric ion suggests that the oxygen is present as an hydroxyl group. Steric resistance to higher oxide coverage, because of the small lattice constant of the crystal, may be an explanation for the natural hydrophobicity of the diamond surface.     

Application of receptor models to airborne particulate matter

The human activities in their various aspects cause a change in the natural air quality. This change results more marked in very populated and in high industrialized areas. Some pollutants emitted are typical of a particular activity. Each source of pollution is identified by its profile in the composition of the emissions in the environment. Multivariate receptor models can be used in order to apportion pollutants to the different sources assessing the contribution of each source to the total pollution.This paper deals with the application of Absolute Principal Component Scores (APCS) receptor model to data obtained from the automatic network of air quality monitoring in the city of Bari (South Italy). The parameters monitored by automatic networks, as bihourly values, are PM₁₀, NO_x, CO, Benzene, Toluene, Xilene. The data shown in this paper concerning 1 month almost of sampling in different monitoring stations of Bari Municipality during the period of time from January 2005 to April 2006. Moreover preliminary results obtained applying the APCS model to daily PM_2.5 samples collected during SITECOS PRIN project are shown. The results concerning data collected in corso Cavour (Bari) during the month of October 2005.The results obtained by APCS receptor model seem to suggest a poor contribution of the “vehicular traffic source” and a relevant contribution of the “secondary particulate source” to particulate matter concentrations.     

Synthesis and interfacial properties of sophorolipid derivatives

Biosurfactants made by fermentation from renewable resources provide “environmental friendly” processes and products. A natural sophorolipid mixture was produced by the yeast Candida bombicola when cultured on glucose and oleic acid. The sophorolipid mixture was chemically modified to form the corresponding sophorolipid alkyl (methyl, ethyl, propyl, and butyl) esters by reaction with the corresponding sodium alkoxides. Interfacial properties of these surfactants, such as surface tension reduction, aggregation, and adsorption, were systematically studied. It was found that the critical micelle concentration of sophorolipid esters decreases to about 1/2 per additional one CH₂ group to the alkyl ester moiety. Interestingly, these surfactants were found to adsorb strongly on alumina but weakly on silica. They have properties that make them attractive candidates for uses in detergents, cosmetics, soil remediation, and enhanced oil recovery.     

The dual trend in histatins research

We review histatins (Hsts) in order to encourage development of analytical platforms to clarify obscure points in knowledge of this family of antimicrobial and antifungal peptides. To explain the present interest, we outline the number and the nature of Hsts and their known functions (i.e. antimicrobial action, wound closure, biomarkers of stress, satiety, body mass and incipient Alzheimer’s disease, and diagnosis and treatment of addiction, including to cocaine).The two aspects of research on Hsts (i.e. their natural effects on living organisms and their potential use for medical applications, including as biomarkers) make it necessary to develop new analytical methods. The variety of matrices in which Hsts exist (e.g., saliva and tooth-surface-protein pellicle) make it essential to develop new sample-preparation steps and to improve identification and quantitation steps as analytical instrumentation evolves.In this context, metabolomics studies could be of great interest, as contributions of analytical chemists could be one of the keys to achieving the role that they deserve within “-omics” research.     

Recent advances in NADH electrochemical sensing design

NADH electrochemical sensor development has been one of the most studied areas of bioelectroanalysis because of the ubiquity of NAD(P)H based enzymatic reactions in nature. The different solutions proposed are still far from the realisation of the “ideal” NADH sensor and the research area is still challenging. The principles and the recent approaches in NADH electrochemical sensing design are reported in this review. An overview of selected examples and novel sensor materials for the electrocatalysis of NADH is given with emphasis on the appropriate design to obtain improved performances. The literature data taken in consideration has been grouped depending on the strategy used in: surface modified electrodes for NADH sensing, surface redox mediated NADH probes, and bulk modified electrodes for the electrocatalytic oxidation of NADH. A list of already reported dehydrogenase-based biosensors is also given.     

The environmental challenge for analytical sciences

In this paper the major elements of the European Union’s policy on environmental protection and sustainable development and the resulting challenges for analytical sciences are presented. The priority issues dealt with are:

Investigation of Trace Metals Content and Carbon Isotopic Composition on the Soil Leaf-Fruit Chain from Some Transylvanian Areas

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Isotopic Ratio Mass Spectrometry (IRMS) were used in this study to trace heavy metal and isotopic content of soil into the fruit juices. This work presents a preliminary study on the carbon isotope signature and trace metal content investigated on the soil-plant-fruit pulp chain. The samples were collected from Transylvanian areas. Our results for fruit juices are compared with allowable limits for drinking water in the United Kingdom (NS30). The results for soil samples were compared with the maximum value reported for normal range values of natural soils cited by the EEA (European Environment Agency) report. The results obtained for δ¹³C values on the soil - leaf - fruit pulp chain for grape, pear, and apple samples show depletion in ¹³C isotope, as the trend of the values reported in literature for the soil–leaf–fruit chain.     

Conventional and unconventional infrared spectrometry and their quantitative interpretation

In condensed matter, optical properties can be described by a dielectric function (DF), and the structures observed in spectra are then related to the poles and zeros of the DF. As an example, model functions are calculated by a fit to measured spectroscopic data for polystyrene and silica. The first material shows weak, narrow bands and the latter strong, broad bands and a negative real part of the DF.Based on these model DFs, spectra are simulated which are expected to be obtained by “conventional” methods such as transmittance or reflectance measurements, or by “unconventional” methods such as reflectance at oblique incidence, diffuse reflectance, photoacoustic spectroscopy and attenuated total reflectance. A variety of simulated, typical spectra are plotted as a small “atlas”. Conditions are discussed that allow a straightforward procedure for interpreting the spectra quantitatively, i.e., the evaluation of the resonance frequency and the concentration of the oscillators under consideration.It is shown that for systems characterized by weak, narrow oscillator lines, mostly an intuitive interpretation is possible, looking only at the position and strength of “lines” in the spectra. Materials showing strong polar vibrations, however, require more sophisticated procedures for interpreting the spectra.     

Effect of Inorganic Ions on Oleate Adsorption at a Nigerian Hematite–Water Interface

Using “pure” natural hematite selected from a high silica Nigerian hematitic ore, oleate adsorption densities at the hematite–water interface were determined in the presence of various inorganic ions (anions and cations) of different charges and at varying concentrations. Adsorption density was determined using electrical conductivity measurements. The specific surface area of the hematite particles was determined using the method of adsorption of paranitrophenol in aqueous solution. Inorganic ions in solution depressed oleate adsorption at the aqueous hematite surface. The charge of the ion proved to be the dominant factor determining the depression of oleate adsorption. Ionic strength also was an influence, up to a limiting value at which monolayer oleate coverage of the hematite surface occurred. The inorganic ions in solution are considered to function through nonspecific adsorption in the diffuse region of the electric double layer.     

Levels of cadmium and lead in blood: an application of validated methods in a group of patients with endocrine/metabolic disorders from the Rome area

Lead (Pb) and cadmium (Cd) are environmental pollutants, known to cause adverse health effects in humans even following long-term exposure to low doses. These metals, individually or in combination with other persistent environmental contaminants, have been claimed to have the potential to cause alterations in the function of the endocrine system. Human exposure to Pb and Cd is generally assessed by monitoring their concentrations in blood, taking into account the influence of various factors, such as age, gender, smoking habit, occupation, alcohol consumption, diet and air pollution. Following the phase-out of leaded gasoline in the European Union and improvements in food-packaging and contamination control, a decrease in blood Pb levels of the general population has been observed in several European countries and the USA. We report the preliminary results of a study, performed within the framework of the project “Human Exposure to Xenobiotics with potential Endocrine Activities: Evaluation of Reproductive and Developmental risks”. We measured the concentrations of Cd and Pb in the blood of a group of patients with endocrine/metabolic disorders. The analytical procedures, based on atomic absorption spectrometry, were validated according to the EURACHEM guidelines. The median values and ranges were 0.48 μg l⁻¹ (0.20–1.73 μg l⁻¹) and 21.8 μg l⁻¹ (12.0–65.7 μg l⁻¹) for Cd and Pb, respectively; the Cd levels were significantly higher in smokers. Overall, the concentrations of Cd and Pb found in our series of patients were comparable to levels currently expected in the general population.     

Recent developments and applications of NSE in soft matter

Neutron Spin Echo is probably the youngest spectroscopic method in neutron scattering. After a brief introduction I will try to give a short account of recent progress on the instrumentation. Through some recent examples I will illustrate that NSE is a powerful tool in colloid science applied to both “old” and recent problems. With new instrumentation we will be able to tackle new problems and one of those areas in which there has been recently exciting progress is the field of surface science.     

Diffuse reflectance spectroscopy of powders

Diffuse reflectance (DRIFT) spectra in the mid-IR region, especially of inorganic powders, often reveal inverted or derivative-like structures (“reststrahlen” bands) which make their straightforward interpretation in terms of the Kubelka-Munk theory difficult. A simulation technique based on a combination of single scattering (Mie theory) and radiative transfer (with Kubelka-Munk as a special case) is reported that allows measured DRIFT spectra to be described without use of any free “fit” parameters. The results for silica glass microspheres and silicon carbide powder show that not specular reflectance but prominent structures in the single particle scattering cross-section are responsible for the reststrahlen features which cannot be suppressed even by diluting the powder in an excess of KBr. The efficiency of a “blocker” device in DRIFTS is also discussed.     

Phase-death mode in two-coupled chemical oscillators studied with reactors of different volume and by simulation

The behavior of the phase-death mode (cessation of oscillations and transition to a steady state) in the two-coupled Belousov–Zhabotinsky reactions is studied in the asymmetric coupling. In an experiment, the types of synchronized modes and their regions were investigated as an extension of our previous study. This experiment is compared to a simulation using the two-coupled three-variable Oregonator models. The results confirm that the phase-death mode changes from “bistable” to “monostable” and reveal the stable region of the latter.