This study reports on the relationship between timing of initial hepatitis B virus (HBV) vaccine series and HBV antibody immunity in healthcare personnel (HCP) screened prior to employment. HCPs vaccinated as neonates were significantly more likely to have negative or indeterminate antibodies. An alternative screening approach is considered.

Fifteen iron oxide accumulations from the bottoms of two Finnish lakes (“lake ores”) were found to contain as much as 50% Fe. Differential X-ray powder diffraction and selective dissolution by oxalate showed that the samples consisted of poorly crystallized goethite and ferrihydrite. The crust ores of one lake had higher ferrihydrite to goethite ratios than the nodular ores of the other lake. The higher ferrihydrite proportion was attributed to a higher rate of Fe2+ supply from the ground water and/or a higher rate of oxidation as a function of water depth and bottom-sediment permeability.

Values of Al-for-Fe substitution of the goethites determined from unit-cell dimensions agreed with those obtained from chemical extraction if the unit-cell volume rather than the c dimension was used. In very small goethite crystals a slight expansion of the a unit-cell dimension is probaby compensated by a corresponding contraction of the c dimension, so that a contraction of the c dimension need not necessarily be caused by Al substitution.

The goethites of the two lakes differed significantly in their Al-for-Fe substitutions and hence in their unit-cell sizes, OH-bending characteristics, dehydroxylation temperatures, dissolution kinetics, and Möss-bauer parameters. The difference in Al substitution (0 vs. 7 mole %) is attributed to the Al-supplying power of the bottom sediments: the silty-clayey sediments in one lake appear to have supplied Al during goethite formation, whereas the gravelly-sandy sediments in the other lake did not. The compositions of the goethites thus reflect their environments of formation.

Storage of ferrihydrite in aqueous suspensions at 24°C and pHs between 2.5 and 12 for as long as three years resulted in the formation of goethite and hematite. The proportions and crystallinity of these products varied widely with the pH. Maximum hematite was formed between pH 7 and 8, and maximum goethite at pH 4 and at pH 12. The crystallinity of both products, as indicated by X-ray powder diffraction line broadening and magnetic hyperfine field values and distribution widths, was poorer, the lower the proportion of the corresponding product in the mixture. The existence of two competitive formation processes is suggested: goethite is formed via solution, preferably from monovalent Fe(III) ions [Fe(OH)2+ and Fe(OH)4−], and hematite by internal rearrangement and dehydration within the ferrihydrite aggregates. This concept relates the proportions of goethite and hematite to the activity of the Fe(III) ion species in solution, and implies that conditions favorable for the formation of goethite are unfavorable for that of hematite and vice versa.

Mixtures of magnetite and goethite were formed by the slow oxidation of mixed FeCl2-AlCl3 solutions in an alkaline environment at room temperature. The compositions of the products ranged from almost exclusively magnetite in Al-free systems to goethite only at Al/(Al + Fe) ≈ 0.3. The magnetic phase consisted of a partly oxidized (Fe2+/Fe3+ < 0.5), Al-substituted magnetite. The unit-cell edge length a of the magnetite decreased with increasing Al(Al ≈ 0–0.37 per formula unit, corresponding to 0–14 mole % Al) and decreasing Fe2+ in the structure as described by the empirical relationship α(A) = 8.3455 + 0.0693 Fe2+ - 0.0789 Al. A correlation between the experimentally determined a and that calculated from the unit-cell edge lengths of end-member magnetite, maghemite, and hercynite was highly significant (r = .96) although shifted by about 0.01 Å. Mössbauer spectra showed Al to have entered preferentially the tetrahedral rather than the octahedral sites at low Al substitutions (<0.15 per formula unit), perhaps because of steric reasons. With increasing Al substitution the crystal size of magnetite decreased and structural strain increased, indicating that the structure had a limited capability to incorporate Al under these synthesis conditions. The capacity of the goethite structure to tolerate more Al may explain why goethite replaced magnetite at higher Al concentrations.

A synthetic octahedral-site-vacancy-free annite sample and its progressive oxidation, induced by heating in air, were studied by powder X-ray diffraction (pXRD), Mössbauer spectroscopy, nuclear reaction analysis (NRA), Raman spectroscopy, X-ray fluorescence (XRF) spectroscopy, gas chromatography (GC), thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), and size-fraction separation methods. For a set heating time and as temperature is increased, the sample first evolves along an annite-oxyannite join, until all H is lost via the oxybiotite reaction (Fe2+ + OH− ⇌ Fe3+ + O2− + H↑). It then evolves along an oxyannite-ferrioxyannite join, where ideal ferrioxyannite, KFe3+8/3□1/3AlSi3O12, is defined as the product resulting from complete oxidation of ideal oxyannite, KFe3+2Fe2+AlSi3O12, via the vacancy mechanism (3 Fe2+ ⇌ 2 Fe3+ + [6]□ + Fe↑). A pillaring collapse transition is observed as a collapse of c near the point where ${\text{Fe}}^{2+}\text{/Fe}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$ and all OH groups are predicted and observed to be lost. Quantitative analyses of H, using NRA, GC, and Raman spectroscopy, corroborate this interpretation and, in combination with accurate ferric/ferrous ratios from Mössbauer spectroscopy and lattice parameter determinations, allow a clear distinction to be made between vacancy-free and vacancy-bearing annite. The amount of Fe in ancillary Fe oxide phases produced by the vacancy mechanism is measured by Mössbauer spectroscopy to be 11.3(5)% of total Fe, in agreement with both the theoretical prediction of 1/9 = 11.1% and the observed TGA weight gain. The initiation of Fe oxide formation near the point of completion of the oxybiotite reaction (${\text{Fe}}^{2+}\text{/Fe}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$) is corroborated by pXRD, TGA, Raman spectroscopy, and appearance of an Fe oxide hyperfine field sextet in the Mössbauer spectra. The region of Fe oxide formation is shown to coincide with a region of octahedral site vacancy formation, using a new Mössbauer spectral signature of vacancies that consists of a component at 2.2 mm/s in the [6]Fe3+ quadrupole splitting distribution (QSD). The crystal chemical behaviors of annite-oxyannite and of oxyannite-ferrioxyannite are best contrasted and compared to the behaviors of other layer-silicate series in terms of b vs. [D] (average octahedral cation to O bond length). This also leads to a diagnostic test for the presence of octahedral site vacancies in hydrothermally synthesized annite, based on a graph of b vs. Fe2+/Fe. The implications of the observed sequence of thermal oxidation reactions for the thermodynamic relevance of the oxybiotite and vacancy reactions in hydrothermal syntheses are examined and it is concluded that the oxybiotite reaction is the relevant reaction in the single-phase stability field of annite, at high hydrogen fugacity and using ideal starting cation stoichiometry. The vacancy reaction is only relevant in a multi-phase field, at lower hydrogen fugacity, that includes an Fe oxide equilibrium phase (magnetite) that can effectively compete for Fe, or when using non-ideal starting cation stoichiometries.

β-FeOOH (akaganéite) was prepared by slow hydrolysis of an FeCl3 solution. X-ray diffraction measurements gave refined unit-cell parameters of a=10·535 Å, c=3·030 Å.

Two doublets with δ(Fe)=0·39, ΔEQ=0·95, and δ=0·38, ΔEQ=0·55 mm s−1, respectively, can be fitted to the Mössbauer spectrum taken at room temperature.

Magnetically split Mössbauer spectra were registered at 135 and 4°K. These can be resolved into at least three superimposed sextets, corresponding to different Fe3+ sites in the β-FeOOH structure. At 4°K a three sextet model gives parameters of δ=0·36, ΔEQ=0·90, Hi=473; δ=0·35, ΔEQ=0·30, Hi=479; and δ=0·37, ΔEQ=−0·05 mm s−1, Hi=486kOe, respectively.

The complexity of the Mössbauer spectra of β-FeOOH limits the usefulness of this method as a tool for the identification of akaganéite in composite natural samples.

Mössbauer spectra of Fe2+Fe3+ and Fe2+Al hydroxycarbonates taken in the paramagnetic state were fitted using two Fe2+ and Fe3+ doublets each. These spectra can be interpreted in terms of an ordered cation arrangement in the pyroaurite-type structure. The inner Fe2+ doublet seems to be the outcome of excess Fe3+ in the samples studied. The outer Fe2+ doublet (quadrupole splitting ∼2·8 mm s−1, FWHM = 0·26 mm s−1) is relatively well-defined and can, together with the fact that this doublet disappears on oxidation, possibly serve to identify these compounds in natural systems.

Analysis of the near-infrared (NIR) spectral bands of phyllosilicates, together with the mid-infrared bands, enables testing and confirmation of band assignments for the structural OH vibrations. Spectral analyses of selected smectites and serpentine-kaolin minerals are presented here. The results of this study indicate that dioctahedral smectites may contain both in-plane and out-of-plane OH-bending vibrations, as suggested by Farmer (1974). In-plane bands occur near 800 ­ 915 cm–1, while the weaker out-of-plane vibrations occur near 600 ­ 700 cm–1 and are enhanced in dioctahedral smectites when the structure is disrupted by substitutions. Analysis of the OH-stretching vibrations and their NIR overtone bands is also presented for both smectites and serpentine-kaolin minerals. These overtones are more straightforward for serpentines than for kaolinite, and a strong overtone associated with the kaolinite OH-stretching band at 3620 cm–1 is found that supports its assignment as an OH-stretching band.

Mössbauer spectra of three natural ferrihydrites of different crystallinities were collected between 295 and 4·2 K. Optimal fits of the room-temperature spectra were obtained using distributions of quadrupole-split doublets; half-widths of the distributions (0·71–0·86 mm/s) increased, and maxima (at 0·62–0·78 mm/s) shifted to higher quadrupole splittings with decreasing crystallinity. Rather poorly-defined magnetically-ordered spectral components appeared and gradually replaced the superparamagnetic doublets as temperatures were reduced. Blocking temperatures between 115 and 28 K, derived from the relative areas under the doublets and magnetic sextets, indicated average particle sizes between ∼ 5 and 3 nm. The sextets were relatively broad and could be fitted with distributions of hyperfine fields. These distributions narrowed and their maxima shifted to higher fields as temperatures decreased; the influence of superparamagnetism was no longer apparent at 4·2 K.

Eight illites were studied by Mössbauer spectroscopy at room temperature and 4.2 K. On the basis of their Fe contents, these illites can be divided into an Fe-rich (>5 wt% Fe) and an Fe-poor (<1 to ∼3 wt% Fe) group. Mössbauer spectroscopy showed that the Fe-rich illites had lower proportions of divalent Fe than their Fe-poor counterparts. Slow paramagnetic relaxation was observed in the Fe-poor illites and must be accounted for when fitting the spectra. Two samples contained iron oxides that were superparamagnetic and thus, although contributing to the Fe3+ doublets, escaped detection at room temperature. Structural Fe3+ had a temperature-independent quadrupole splitting that was lower for the Fe-rich illites (0.59 mm/s) than that of the Fe-poor illites (0.73 mm/s). The Fe2+ quadrupole splittings were higher at 4.2 K than at room temperature, but the Fe-rich illites again had lower Fe2+ quadrupole splittings both at room temperature (2.69 vs. 2.88 mm/s) and at 4.2 K (2.96 mm/s vs. 3.08 mm/s). Distinction of Fe sites in the illites with cis- and trans-OH coordination was not possible. The presence of tetrahedral Fe3+ was observed only in the most Fe-rich sample (8.4 wt% Fe).

The mineralogy of the silt fraction of a 1.5 m-deep, well developed, intensely weathered, greyish soil profile from a toposequence on a tableland covered by agricultural crops in the upper valley of the Jequitinhonha river basin, Minas Gerais, Brazil, has been studied by X-ray powder diffraction, 57Fe Mössbauer spectroscopy at 298 K and 80 K, and vibrating sample magnetometry. Mössbauer data collected at room temperature indicated about 17 atom% of the iron content of the sample to be structural Fe2+ in phyllosilicates, which X-ray diffraction showed to be mainly halloysite and kaolinite. The magnetization curve also indicates the presence of a ferrimagnetic phase, tentatively identified by Mössbauer spectroscopy as maghemite (γ-Fe2O3).

These findings support a pedogenetic model for this soil profile, by which the remaining Fe2+ bearing minerals were first formed under relatively anoxic palaeo-conditions of an intense hydric regime. Subsequent drier local conditions, due to a much improved drainage, favoured intensive weathering, leading to the presently developed Oxisol. Even under the more oxidative conditions, part of the Fe2+ -containing phyllosilicates still remained in the profile, which is believed to impart the rather unusual greyish colour (Munsell 10YR 3/2) to this deep tropical soil.

Mine-drainage waters and associated precipitates from several active and abandoned lignite mines and mine dumps in the Sokolov Basin, northwestern Czech Republic, were sampled and analysed. The data showed considerable variations of effluent composition and pH that can generally be related to differences in the local microenvironments. Temporal changes such as seasonal fluctuations of precipitation, leading to variations of water infiltration through and runoff over mines and mine dumps, were also observed to noticeably affect effluent composition. These variations have led to a wide range of precipitates, the principal constituents of which are generally one or several of the ferric minerals jarosite, schwertmannite, goethite, ferrihydrite and lepidocrocite.

The present paper consists of two parts: a short review of the genesis and properties of the named minerals, and a study of mine-drainage precipitates formed under different local conditions in various lignite mines and mine dumps of the Sokolov mining district. We show that variations in mine-drainage precipitate mineralogy, such as the presence or absence of specific ‘key’ minerals, can serve as indicators for factors such as the pH and sulphate concentration, and thus — with certain limitations — for the genetic environment during precipitate formation. Such variations in composition are reflected, among other properties, in the precipitate colour, which can therefore be used for a rapid identification and classification — both in the field and by remote sensing — of regions that are potentially prone to acid mine drainage.

Mössbauer spectroscopy is the technique of recoil-free resonant emission and absorption of gamma rays. It has the advantage of being oblivious to all elements except the one under survey. In the case of materials formed on the earth’s surface, such as soils and clays, the only propitious element is Fe. Iron is the fourth most abundant element in the Earth’s crust, it is essential for life, and almost all environmental materials contain at least some Fe. It is also fortuitous that 57Fe Mössbauer spectroscopy is among the most straightforward to operate. 57Fe Mössbauer spectroscopy thus allows the characterization of iron speciation, and thereby of environmental conditions, over a wide range of concentrations, making it an extremely effective environmental probe.

Straightforward as it may seem, Mössbauer spectroscopy nevertheless has many pitfalls. Besides problems arising from the basic physics, complications can arise among other causes from imperfect crystallinity (small particle size), non-stoichiometry, interparticle effects and isomorphous substitutions.

In this paper a succinct review of the basic principles of Mössbauer spectroscopy is presented, followed by examples of Mössbauer spectra of minerals that are common constituents of clays and soils, and by more complex cases of soils, clays and fired clays.

Both aluminium substitution and poor crystallinity reduce the magnetic hyperfine field of goethite. Mössbauer spectra taken at 4·2 K show that the effect of poor crystallinity is similar to that of Al substitution, i.e. it reduces the saturation hyperfine field. A multiple correlation was found to exist between the magnetic hyperfine field at 4·2 K as a dependent variable vs Al substitution and crystallinity as independent variables. If a hyperfine field is to be interpreted with respect to either Al substitution or crystallinity, it is therefore necessary to have knowledge of the other variable.

XRD, DTA and IR patterns showed clay veins filling fissures in a granite of the Bayerischer Wald (eastern Bavaria) to consist mainly of hydrated halloysite of low crystallinity with traces of gibbsite, 2:1 (mixed layer) clay minerals and iron oxides. The halloysite forms thin plates which exhibit varying degrees and types of enrolment, resulting in platy, tubular and spheroidal crystals within the same sample. Concentrations of the trace elements Rb, Sr, Ba, Zr, Y, Ce, Pb, Zn and Cu indicate halloysite formation to have taken place via an aqueous phase under the influence of vadose waters circulating in fissures.

Kaolin mined from the Ipixuna deposit of Pará Pigmentos S.A. in the Capim river area of northern Brazil has been studied at various stages of beneficiation to determine the behaviour of Fe- and Ti-bearing minerals which can reduce the brightness of the product. X-ray diffraction and Mössbauer spectroscopy showed the principal pigmenting minerals to be hematite and goethite, with chemical analyses showing a distinct decrease of both the total Fe and Ti contents in the course of processing. The Ti contents were primarily reduced due to the removal of anatase during particle size fractionation and dithionite reduction. While the Fe content of the final product is structurally bound in kaolinite, Raman spectroscopy indicates the remnant Ti to be bound both structurally in kaolinite and in remnant anatase.

Five Fe–bearing dioctahedral smectites (three nontronites and two Fe-rich smectites) were purified using a variety of physical and chemical procedures. The structural formulae indicate one nontronite and one Fe-rich smectite to be montmorillonitic, whereas the other three smectites are beidellitic. Mössbauer spectra showed Fe to be exclusively trivalent and were fitted with three doublets, two of which had quadrupole splittings characteristic of Fe3+ in octahedral coordination, whereas the third had a distinctly lower quadrupole splitting. Although the position of the Si–O stretching band in the infrared spectra could reflect tetrahedral Fe3+, the lack of distinctive features prevented a definitive attribution of this component to tetrahedral Fe3+. The 18O/16O data suggest that fractionation of nontronite-water at ambient temperatures (1000 lnα = 23 ± 2‰) is lower than that of Fe-rich smectite (1000 lnα = 27 ± 2‰). The estimated formation temperatures of the samples are below 70°C.