The hazardous effects of arsenic are closely linked to its speciation and interaction with different soil minerals, which influence both As mobility and bioavailability. Adsorption onto iron ...(oxyhydr)oxides is one of the main processes controlling the partitioning of arsenite As(III) and arsenate As(V) between aqueous and solid phases. Arsenic retention can be affected by changes in soil pH and the presence of competing anions, like phosphate. Although competition with inorganic phosphorus (P) for sorption sites on mineral surfaces has been widely studied, little is known about the interactions with organic P (Po) compounds, in particular inositol phosphates, even though they may represent a large fraction of total soil P. We quantified the effects of myo‐inositol hexaphosphate (InsP6) on the adsorption and retention of As(III) and As(V) on goethite as influenced by pH, the order of anion addition, and residence time. The efficiency of InsP6 in displacing adsorbed As(III) decreased with increasing pH values and interaction time, which may be attributed to the increase in bonding strength of the As(III) complexes on the surface of goethite. Adsorption and retention of As(V) by goethite generally decreased with increasing pH, particularly in the presence of InsP6 due to the similar pKa values and the competition for the same binding sites. The addition of InsP6 before, together with, or after adsorption of As(III) and As(V) strongly reduced the amounts of sorbed As, suggesting that the addition of Po–rich matrices to As‐contaminated soils may strongly enhance As mobility.
Today, artworks partially or completely made of plastic materials can be found in almost all international museums and collections. The deterioration of these objects is now becoming evident mainly ...because these synthetic materials are not designed for a long life and the characterization of their state of conservation can help curators and conservators. In this research we investigated the applicability of a portable attenuated total reflection (ATR) infrared spectrometer for the non-invasive characterization and for monitoring the degradation of plastics used in modern and contemporary art. Several polypropylene and polycarbonate samples were artificially aged in solar box, simulating about 200 years of museum light exposure, and they were monitored with the portable ATR, creating an infrared library of the conservation state of plastics. Through the use of chemometric techniques like principal component analysis–linear discriminant analysis and partial least square—discriminant analysis, we built a robust degradation model of each material that can be used to predict and classify the degradation state of artworks and to identify the priority of intervention in the museum collections. Portable ATR coupled to multivariate statistics can be employed for taking care of plastic artworks as it is non-invasive, the analysis is very fast and it can be performed directly in situ.
This work presents a comprehensive picture of As adsorption on a range of soil colloidal particles in comparable conditions of pH and ionic strength to allow a direct comparison of the surface ...interactions, including surface charging phenomena. The highest adsorption capacity for arsenite As(III) was shown by the iron minerals, with a clear shift in the surface charge. Pure ferrihydrite could retain over 5.3 μmol m‐2 of As(III); the adsorption density was reduced to 3.36 μmol m‐2 when ferrihydrite was a covering film on kaolinite surfaces. Goethite adsorbed up to 2.3 μmol m‐2, but this amount was nearly halved on Al‐substituted goethite and was much lower for hematite. Arsenite adsorption on a poorly ordered Al hydroxide was lower than on poorly ordered and crystalline Fe (hydr)oxides, and its adsorption on gibbsite, kaolinite and calcite was almost negligible. When arsenate As(V) was added, a similar adsorption capacity for surface unit was shown by both Fe and Al minerals and, differently from As(III), As(V) was adsorbed also on kaolinite and calcite. The adsorption of As(V) on all adsorbents and of As(III) on Fe minerals were observed to be exothermic reaction. The differences in the affinity for As(III) and As(V) adsorption shown by the different soil components were explained in terms of differences in Lewis hardness/softness of adsorbate and adsorbents. These results provide a comparison between possible adsorbents to be used for remediation, and also to assess the As adsorption capacity of soils from their composition.
Helicobacter pylori
is a Gram negative bacterium most frequently associated with human gastrointestinal infections worldwide. The increasing occurrence of antibiotic-resistant isolates of
H. pylori
...constitutes a challenge. The eradication of the microorganism is currently being considered a “high priority” by the World Health Organization (WHO). In this context, bioactive compounds found in natural products seem to be an effective therapeutic option to develop new antibiotics against the pathogen. In this study, we investigated the effect of asclepain cI, the main purified proteolytic enzyme of the latex of petioles and stems from
Asclepia curassavica
L. (Asclepiadaceae), a South American native plant, against
H. pylori
; in order to obtain a natural therapeutic adjuvant and a safe nutraceutical product. Asclepain cI showed antibacterial activity against reference strains and drug-resistant clinical isolates of
H. pylori in vitro
. A range of minimal inhibitory concentration (MIC) from 1 to 2 μg/ml and minimal bactericidal concentration (MBC) from 2 to 4 μg/ml was obtained, respectively. The action of asclepain cI on the transcription of
omp
18,
ure
A,
fla
A genes showed a significantly decreased expression of the selected pathogenic factors. Furthermore, asclepain cI did not induce toxic effects at the concentrations assayed. Asclepain cI could be considered a highly feasible option to be used as a natural therapeutic adjuvant and a safe nutraceutical product against
H. pylori
.
Soil science research has probably underestimated the significance that short-term, episodic cycles of reduction and oxidation has had on phosphorus (P) reactivity. Here, the effects of eleven pulsed ...reduction-oxidation (including wet-dry) cycles on soil P dynamics are compared for 12 soils having contrasting properties and all overfertilised with respect to P. The laboratory based incubation conditions attempted to simulate transient waterlogging of the soil profile and involved repeated sampling and analysis of both the solution and solid phase P forms. An initial increase in P concentration in solution that occurred up to and including the fourth full cycle was followed by a sharp decline in concentration for all but one soil. Accompanying changes in the main extractable forms of P, which appeared to be cumulative, could be summarised as a general decline in the organic P fraction and an overall increase in amorphous associated inorganic forms of P. The fact that up to 60% of the total soil P was demonstrated to change its sensitivity for a particular extractant suggests that these operationally defined P forms are susceptible to transformation as a consequence of changing environmental conditions. There was also a suggestion that certain of the changes in P forms were irreversible. While the laboratory conditions imposed do represent extreme conditions the soils only experienced cyclic changes in their moisture regime. If timing and frequency of intense precipitation events are likely to increase, as predicted in many climate change scenarios, then these results suggest that the effects of episodic redox pulses may have implications for P cycling in agricultural soils.
► Pulsed reduction favours P release with respect to continuous flooding. ► Pulsed reduction reallocates more than half of the total P to more labile fractions. ► Type and timing of irrigation, OM and watertable influence P release. ► Maintaining efficient field drainage systems reduce the risk of P solubilisation.
Large areas of the southern European countries possess a Mediterranean climate, which influences soil properties, land use, fertilizer application practices and pathways of phosphorus (P) loss from ...agricultural soils. On average, inputs of fertilizer P exceed P exports from the agricultural areas in these countries; however, large differences in P surplus/deficit and soil P test values exist among regions. Losses of P in drainage water are modest except in some irrigated areas and in those regions where intensive animal production is concentrated. Losses of P in runoff water, whether as dissolved reactive or particulate P, can be substantial as a result of the significance of erosive processes under the land uses typical of the Mediterranean region, where extreme rainfall events contribute disproportionately to such losses. Eutrophication due sensu lato to agricultural P sources affects a relatively high proportion of rivers, lakes and reservoirs. The typical Mediterranean climate and patterns of land use result in marked seasonality in the concentration of P in surface waters. Despite the growing number of studies conducted, the contribution of agricultural P to eutrophication in southern European countries remains largely unassessed and thus warrants pertinent research at the soil, field and catchment scales.
Accumulation of surplus phosphorus (P) in the soil and the resulting increased transport of P in land runoff contribute to freshwater eutrophication. The effects of increasing soil P (19-194 mg ...Olsen-P (OP) kg⁻¹) on the concentrations of particulate P (PP), and sorption properties (Qmax, k and EPCo) of suspended solids (SS) in overland flow from 15 unreplicated field plots established on a dispersive arable soil were measured over three monitoring periods under natural rainfall. Concentrations of PP in plot runoff increased linearly at a rate of 2.6 μg litre⁻¹ per mg OP kg⁻¹ of soil, but this rate was approximately 50% of the rate of increase in dissolved P (< 0.45 μm). Concentrations of SS in runoff were similar across all plots and contained a greater P sorption capacity (mean + 57%) than the soil because of enrichment with fine silt and clay (0.45-20 μm). As soil P increased, the P enrichment ratio of the SS declined exponentially, and the values of P saturation (Psat; 15-42%) and equilibrium P concentration (EPCo; 0.7-5.5 mg litre⁻¹) in the SS fell within narrower ranges compared with the soils (6-74% and 0.1-10 mg litre⁻¹, respectively). When OP was < 100 mg kg⁻¹, Psat and EPCo values in the SS were smaller than those in the soil and vice-versa, suggesting that eroding particles from soils with both average and high P fertility would release P on entering the local (Rosemaund) stream. Increasing soil OP from average to high P fertility increased the P content of the SS by approximately 10%, but had no significant (P > 0.05) effect on the Psat, or EPCo, of the SS. Management options to reduce soil P status as a means of reducing P losses in land runoff and minimizing eutrophication risk may therefore have more limited effect than is currently assumed in catchment management.
Raman scattering experiments on LaFeAsO with distinct antiferromagnetic (TAFM=140 K) and tetragonal-orthorhombic (TS=155 K) transitions show a quasielastic peak (QEP) in B2g symmetry (2 Fe tetragonal ...cell) that fades away below ∼TAFM and is ascribed to electronic nematic fluctuations. A scaling of the reported shear modulus with the T dependence of the QEP height rather than the QEP area indicates that magnetic degrees of freedom drive the structural transition. The large separation between TS and TAFM in LaFeAsO compared to BaFe2As2 manifests itself in slower dynamics of nematic fluctuations in the former.
The pH and the nature of electrolytes are important factors affecting the sorption of anions by soil components. The effects of pH, K, and Ca on the interaction of inositol hexaphosphate (IHP) and ...inorganic phosphate (Pi) with goethite were investigated by sorption experiments. Laser Doppler Velocimetry‐Photon Correlation Spectroscopy was employed to determine zeta potential (ζ) and particle size before and after sorption. In the presence of KCl, the amount of adsorbed P decreased, with increasing pH, from 4.5 to 0.18 μmol P m−2 for IHP, and from 2.5 to 0.67 μmol P m−2 for Pi. A more pronounced decrease was observed in the amount of IHP adsorbed compared with Pi, because of the higher negative charge of IHP and to the lower tendency of phosphate groups of IHP to neutralize the OH− released from the surface during adsorption. In CaCl2, sorption increased from 4.5 to 4.9 μmol P m−2 for IHP, and from 2.7 to 4.8 μmol P m−2 for Pi with increasing pH. For both P compounds, however, the sorption increased even beyond the maximum adsorption capacity of the mineral. At the used concentrations of anions and Ca2+ and in a pure system, the reaction with goethite may involve adsorption at low pH, but precipitation of Ca salts at pH >5 must be taken into account. The sorption of IHP caused a high change of the surface charge that became negative at all pH values in K+, causing dispersion of particles, while in Ca2+ the slightly negative phosphated surface determined particle aggregation.
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