1,085 research outputs found
Soil REE patterns as tracers of the emplacement of metal-rich anthropogenic materials. A case study in Moa (Cuba)
No full textPurpose: Are rare earth element (REE) patterns employable as tracers in human interventions of bulk soil disturbances, when high concentrations of metals are involved in the in situ soil disturbance? In terms of bulk soil disturbance, it is difficult to distinguish between bulk soil disturbances and emplacement of new earthen material. Chemical fingerprinting, in particular REE plus yttrium, is applied across many fields, but predominantlyin tracking the sources of potential environmental contaminants. Materials and methods: The REE normalised patterns (HNO 3 :HF:HCl 3:1:1 digestion, ICP-MS) of two Calcaric Cambisols were compared with those of a Geric Ferralsol (Novic, Technic) originated from selective overburden of nickel mining (20°40′ N, 75°35′ W). Results and discussion: The sum of REE, including Y and Sc, ranged between 48 and 101 mg kg −1 . Principal component analysis (PCA) shows a discriminant role of REE. REE signature normalised to the upper continental crust shows slight positive Eu and negative Ce anomalies in the case of both Calcaric Cambisols, while the Geric Ferralsol shows anomalous patterns with the same anomalies plus a slight positive anomaly of Y, as a consequence of the addition of mining by-products. Conclusions: Here, we show that REE patterns of the individual horizons of a soil have characteristics that allow us to distinguish undisturbed from soils mixed with other soil materials, including those with different pH values and high metal contents (e.g. Cr, Mn, and Ni ≥ 0.5%, Fe ≫ 5 wt%). Our results demonstrate, by using soils with contrasting characteristics, that their origins can be traced via the patterns of their REEs, even in the presence of high concentrations of other metals. In perspective, when background maps of all REE elements in soils are available worldwide on an appropriate scale, this enables us to obtain a level of discriminatory detail on a local scale
A rapid method of screening ceramic artefacts to reject unlikely hypotheses of provenance
No full textThis study was aimed at testing a cost‐effective method based on comparing the rare
earth element patterns in artefacts of known origin with patterns of potential raw
materials, thus allowing the restriction/exclusion of working hypotheses on
provenance, and consequently a better focus of research funding. The method
targets ceramics/materials of terrigenous origin. Lanthanoids and yttrium patterns
were determined in 26 wine amphorae that had a well‐established geographical origin
from the Nuovo Mercato Testaccio in Rome, and these patterns were compared to
plausible terrigenous materials from various ancient Roman regions. The point was
not to pinpoint the origins of the material, but rather to rule out possible areas of
origin. On both a national and a regional scale, we were able to exclude some regions
of origin for these amphorae that would otherwise have been largely plausible. This
method does not require sampling from already known kiln/extraction sites.
Moreover, if maps of all rare earth elements in soils become available on a regional
scale, it could be possible to obtain a level of discriminatory detail in the range of a
few tens of kilometres
Removal of Pesticide Oxadixyl from an Aqueous Solution
No full textThe mycelium of Phomopsis helianthi (Ascomycete) was hydrolyzed with boiling NaOH to give an insoluble fraction composed of chitosan and glucans. The biomass obtained was tested as an agent for the removal of pesticides from an aqueous solution. Oxadixyl, which has a solubility in water of 3400 mg L−1, has been chosen as a hydrophilic organic contaminant model.
The new, cheap material was demonstrated to recover up to 6 mg of oxadixyl per gram of adsorbent. The experimental data show an excellent correlation with the Langmuir isotherm model
Captazione di metalli pesanti da un substrato con plantule di Opuntia ficus-indica Mill..
No full textComputational Study on the Gas-Phase and Aqueous Solution Acidity of Nicotine
No full textDielectric continuum solvation models (1), recently introduced in the routine of computational
chemistry, have allowed organic chemists to afford solvation free energies, thus getting a closer
insight on the real thermodynamics of chemical reactions in solution. Hydron transfer reactions are
by far the most studied due to their importance both in physico-chemical systems and in synthetic
applications.
Since, on the other hand, molecules have almost always a notable molecular flexibility, each
computational assessment should certainly address an accurate conformational analysis of each
species involved in the chemical equilibrium. This rather annoying and troublesome complication has
been automated and made simpler to unravel by using the application called RotAnal (Rotational
Analysis), still in steady development at our laboratories. RotAnal is a smart front-end program that
performs a conformational sampling, pruning, refinement and analysis through an original, multistep
procedure, through any of the most widely used quantum computing packages like GaussianTM and
FireflyTM, and MPI parallel computing across a PC cluster in Microsoft WindowsTM environments
(2).
Alkaloid nicotine has been selected in the present pilot study as a convenient model due both to the
simplicity of their structure and phase space and the easy availability of the experimental aqueous
sequential ionization pKa’s (3).
Calculations performed up to different theoretical levels of theory (Hartree-Fock, Kohn-Sham DFT)
both in vacuo and in PCM aqueous solution have provided us with the relative and absolute pKa’s.
Results show that asserting about hydronation sites of real-chemistry bases grounded mainly upon
the empiric rules of introductory organic chemistry should be treated with caution.
A population analysis based on the Natural Bond Orbital (NBO) paradigm (4) has also allowed us to
correlate the torsional preferences with the presence of stabilizing interactions between filled and
empty orbitals through hyperconjugation effects
An anthropic soil transformation fingerprinted by REY patterns
No full textThis Focus article deals intentionally with modern soil disturbance in situ. This is of interest to archaeologists
as after disturbances, both short- and long-term, pedogenesis (re-)starts obliterating previous
signs. Soil modifications induced by human activity may be linked to pedogenetic evidence for disturbance
with archaeological evidence for the cultural activities. We contrasted two 750-m3 soil pedons, an
Anthrosol and a Kastanozem, from which the Anthrosol is derived, using 77 descriptors of soil properties
which have been utilized in archaeological studies (pedo-morphological, routine laboratory, biochemical,
metals and rare earth elements plus yttrium, REY) with the aim of identifying a group of descriptors able
to sort the occurrence of human interventions. But, which one is more promising? Our findings indicate
that by the use of rare earth spatial patterns it is possible to classify the occurrence of human interventions,
in the case of emplacement of new parent material in respect to bulk soil disturbance in situ
Rimozione del pesticida oxadixyl da una soluzione acquosa
No full textIl micelio di Phomopsis helianthi, un Ascomicete, è stato trattato con NaOH all'ebollizione ottenendo una frazione insolubile essenzialmente composta da chitosano e glucani. Il materiale ottenuto è stato valutato come agente per la rimozione di pesticidi da una soluzione acquosa. Il pesticida usato nella presente sperimentazione è l'oxadixyl, il quale ha una solubilità in acqua pari a 3.4 g/L. L'efficienza della biomassa è stata provata usando 20, 40 ed 80 mg di materiale fino ad una concentrazione di 3 mM. La biomassa risulta in grado di recuperare fino a 6 mg di oxadixyl per grammo di materiale assorbente. l risultati sperimentali mostrano un'ottima correlazione nell'ambito del modello delle isoterme di Langmuir
Challenges in developing reliable phosphorus predictive models: Unpredictable release under soil redox changes
No full textPhosphorus (P), crucial for plant nutrition, is unevenly distributed in the Earth's crust, necessitating its supplementation in agriculture through fertilizers. However, excessive use can lead to water pollution. Our research focuses on the P adsorbing complex, investigating P release due to flooding, using 12 well-characterized soils with contrasting properties. Our research measures directly the P-adsorbing complex using adsorption/desorption isotherms. We observed that the P concentration in the solution —sufficient to prevent desorption yet low enough to avoid further sorption by the soil— decreases when the soil undergoes complete reduction (anoxia). When grouped by similarity, calcareous soils exhibit higher maximum P adsorption capacities (Xmax) under alternating reducing conditions (ARC) compared to continuous reducing conditions (CRC). In slightly acidic soils, CRC leads to a wider spread in Xmax values than ARC. For acidic, organic matter-rich soils, ARC results in the highest Xmax values (123 mmol P kg−1 soil) compared to CRC, whereas in acidic, light-textured soils, CRC shows significantly higher mean Xmax values than ARC. Nevertheless, we were unable to develop a predictive model for soil P desorption based on key intrinsic properties and climate. When an environmental or anthropogenic transformation induces anoxia, the P released does not follow a predictable pattern
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