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Phosphorus dynamics in a small eutrophic Italian lake.
No full textPhosphorous dynamics within Lake Sirio (NW Italy) were investigated, considering both water and sediments.
The total phosphorus (TP) concentration in the water is about 79 ug•l-1 after the winter mixing, that is in homogeneous conditions; then TP content increases up to 360 ug•l-1 in late autumn in the deep hypolimnium (30–45 m). This deep lake portion accounts for only 1/12 of the water volume.
Sediment sampled at depths of 20 and 33 m contains less than 2,000 mg•kg-1 of TP, whereas cores from the deepest sediments (46 m) display TP values of 2,000–4,000 mg•kg-1 at the water-sediment interface, increasing with depth to 16,000 mg•kg-1 at about 60–100 cm. In these deep sediments the main chemical form is the Al-Fe-Mn bound P (about 90% in the high TP cores) and Fe and Mn are also highly enriched (3 and 9 times more than in the shallow sediments respectively). The P-Fe association is confirmed by SEM-EDS and XRD analyses.
The vertical distribution of the P content in the water column is consistent with its release from sediments, but in this hypothesis an unrealistic P release rate from 8.1 g m-2y-1 to 3.0 g m-2y-1 was estimated. A more complex model is therefore proposed, involving a process of P concentration in the sediments of the central (deepest) part of the lake, and a short term sediment-water exchange. The TP vertical variability and speciation in the cores suggests a change in the sediment retention capacity, connected to the lake shift to more eutrophic conditions
Multivariate statistical and GIS-based approach to identify heavy metal sources in soils
No full textThe knowledge of the regional variability, the background values and the anthropic vs. natural origin for potentially harmful elements in soils is of critical importance to assess human impact and to fix guide values and quality standards. The present study was undertaken as a preliminary survey on soil contamination on a regional scale in Piemonte (NW Italy). The aims of the study were: (1) to determine average regional concentrations of some heavy metals (Cr, Co, Ni, Cu, Zn, Pb); (2) to find out their large-scale variability; (3) to define their natural or artificial origin; and (4) to identify possible non-point sources of contamination. Multivariate statistic approaches (Principal Component Analysis and Cluster Analysis) were adopted for data treatment, allowing the identification of three main factors controlling the heavy metal variability in cultivated soils. Geostatistics were used to construct regional distribution maps, to be compared with the geographical, geologic and land use regional database using GIS software. This approach, evidencing spatial relationships, proved very useful to the confirmation and refinement of geochemical interpretations of the statistical output. Cr, Cc and Ni were associated with and controlled by parent rocks, whereas Cu together with Zn, and Pb alone were controlled by anthropic activities. The study indicates that background values and realistic mandatory guidelines are impossible to fix without an extensive data collection and without a correct geochemical interpretation of the data
Crystal-chemical interpretation of crystallographic anomalies in lunar plagioclases
No full textUnit-cell dimensions of lunar plagioclases, γ in particular, notably differ from those of terrestrial plagioclases with the same An-content inferred from Ca/Ca + Na + K or Ca/8O.
It is shown that this crystallographic anomaly is a consequence of the chemical anomalies affecting lunar plagioclases.
In particular it is a consequence of the presence of □ [Si₄O₈] in solid solution. This molecule influences the composition of the framework, to which the γ angle is strongly related.
On the basis of these results some data on the thermal state of lunar plagioclases are briefly discussed.Les paramètres réticulaires des plagioclases lunaires, en particulier γ, diffèrent de façon notable de ceux des plagioclases terrestres ayant la même teneur en anorthite d'après le rapport Ca/Ca + Na + K ou Ca/8O.
On montre que cette anomalie cristallographique provient d'anomalies chimiques affectant les plagioclases lunaires, notamment de la présence de □ [Si₄O₈] en solution solide. Cette molécule joue un rôle dans la charpente de feldspath, dont dépend l'angle [γ].
On discute brièvement quelques données sur l'état thermique des plagioclases lunaires.Bruno Emiliano, Facchinelli Aurelio. Crystal-chemical interpretation of crystallographic anomalies in lunar plagioclases. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 98, 2-3, 1975. pp. 113-117
Assessment of Chromium release from steel manufacturing waste
No full textIndustrial waste of different origins has been dumped for decades (1950–1980) in a landfill of 150,000m2 area, a few km from the centre of Torino (NW Italy). A large portion of this landfill, estimated to be in the order of 1,100,000m3 and extending over a surface of 55,000m2, is composed of steel manufacturing waste.
This study discusses an investigation of this waste mass in order to assess the total Cr concentration and solubility, identify the main Cr-bearing phases and estimate the release of Cr to rainwater leaching through the material and the consequent
contamination of groundwater
Post-depositional processes in lake sediments traced by heavy metals and radionuclides: a case study from Lake Sirio (Ivrea, Northern Italy)
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Correlations between the unit˗cell dimensions and the chemical and structural parameters in plagioclases and alkaline-earth feldspars
No full textIn a previous paper we have given experimental evidence of the existence of a metastable feldspar-like solid solution Ca₁₋ₓ⎕ₓ.Al₂₋₂ₓSiAl₂₊₂ₓO₈ (0 < x < 0.17 and 1 < Si/Al < 1.4). Chemical and structural features of lunar calcic plagioclases show the presence of the same solid solution in natural samples. We have compared the lattice changes in this solid solution with the unit-cell variations in plagioclases in the range An₁₀₀-An₆₇ (1 < Si/Al < 1.4) in order to get informations about the correlations between individual chemical parameters and individual unit-cell parameters. A comparison with the behaviour of other feldspars and substituted feldspars analogues allows us to emphasize the usefulness of taking in to account the coordination of the non-tetrahedral cation to give a structural interpretation of the correlations between the structural state, the chemical composition and the lattice constants in feldspars.Lors d'un précédent travail, on a mis en évidence expérimentalement l'existence d'une solution solide métastable dans les feldspaths Ca₁₋ₓ⎕ₓ.Al₂₋₂ₓSiAl₂₊₂ₓO₈ (0 < x < 0,17 et 1 < Si/Al < 1,4). Les caractéristiques chimiques et structurales des plagioclases calciques lunaires indiquent la présence d'une même solution solide dans les échantillons naturels. On a comparé les modifications du réseau dans cette solution solide avec les variations de dimensions de la maille des plagioclases dans le domaine An₁₀₀-An₆₇ (1 < Si/Al < 1,4) afin d'obtenir des informations sur les corrélations entre paramètres chimiques et paramètres cristallins. Une comparaison avec le comportement d'autres feldspaths et de feldspaths analogues substitués permet de mettre en évidence l'intérêt de prendre en considération la coordination du cation non tétraédrique pour donner une interprétation structurale des corrélations entre l'état structural, la composition chimique et les constantes du réseau dans les feldspaths.Bruno Emiliano, Facchinelli Aurelio. Correlations between the unit˗cell dimensions and the chemical and structural parameters in plagioclases and alkaline-earth feldspars. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 97, 2-5, 1974. Les solutions solides en minéralogie. Colloque international du C.N.R.S. n° 234. 27-30 mai 1974, Orléans, France
Experimental studies on anorthite crystallization along the join CaAl2Si2O8-SiO2
No full textCrystallization of anorthite along the join CaAl₂Si₂O₈-SiO₂ under hydrothermal and dry conditions has led to the following conclusions :
1) there is a partial solubility in the solid state of silica in anorthite up to a maximum limit of 15 wt % ;
2) the solid solution is metastable and the solubility limits vary according with the conditions of synthesis ;
3) lattice constants of the «anorthite-like phases », crystallizing within the solubility field, vary continuously with increasing concentration of SiO₂ in solid solution ; the trend of this variation is closely analogous to that observed in plagioclases in the range An100-An65.
From the points listed above it is possible to assume that, within the solubility field, crystallization of a feldspar-like phase occurs and its formula is Ca1-x□xAl2-2xSi2+2xO8.
Some consideration are put forward on the crystal chemical problems about this solid solution and on its metastability and limits. Some petrological implications are discussed.La cristallisation d'anorthite le long d'un joint CaAl₂Si₂O₈-SiO₂ sous les conditions hydrothermales et sèches a conduit aux conclusions suivantes :
1) il existe une solubilité partielle de la silice dans l' anorthite. Elle peut atteindre jusqu'à 15 % en poids de SiO₂ dans l' anorthite.
2) la solution solide résultante est métastable. Les limites de la solubilité varient selon les conditions de la synthèse.
3) les paramètres de la maille d'une phase du type anorthite, cristallisée dans le domaine de solubilité de la silice, varient d'une façon continue avec la teneur croissante de SiO₂ dans la solution solide. Cette variation est très analogue à celle qu'on observe sur les plagioclases entre An100 et An65.
De ces observations, on peut supposer que, dans le domaine de solubilité de la silice, une phase du type feldspath peut cristalliser, dont la composition s'exprime par la formule : Ca1-x□xAl2-2xSi2+2xO8.Bruno Emiliano, Facchinelli Aurelio. Experimental studies on anorthite crystallization along the join CaAl2Si2O8-SiO2. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 97, 6, 1974. pp. 422-432
Gamma dose rate calculation and mapping of Piemonte (North-West Italy) from gamma spectrometry soil data
No full textIn this study the air gamma dose rate map of Piemonte, a region in the North-West of Italy, was produced from gamma spectrometry soil data. Soil samples collected in 110 different sites of Piemonte were analysed with Hyperpure Germanium (HPGe) detectors (30% relative efficiency), which allow the evaluation of the activity concentrations of natural radionuclides and Cs-137. Then, using the available mathematical models, the gamma absorbed dose rate in air due to radionuclides was calculated. The contribution of the cosmic radiation to the total absorbed dose rate, which depend on the site altitude was also evaluated and added to the soil contribution. Finally, the map of the whole region was obtained by fitting the dose rate values of the different sites with kriging algorithms
Dendroanalytical monitoring of atmospheric pollution with LA-ICP-MS: a case study from Villadossola (VCO, Italy).
No full textTree rings yearly formed in wood are a wide and complex source of data, potentially offering hints on the impact of atmospheric pollution. Dendroanalysis, the method of analysing tree-rings for trace metal pollution, is based on the assumption that element concentrations in wood represent the availability of those elements in the environment in which the tree has grown. Tree ring counting combines the chronological information to the chemical data, providing a potentially powerful tool for precise dating of atmospheric pollution events.
While root uptake is generally recognised, trace element assimilation through leaves is still questioned, especially in the case of superior plants. Therefore changes in xylem chemistry would reflect both changes in exposure to metal deposition and changes in soil chemistry. Unlike deciduous plant leaves, conifers needles have a life span of several years, rendering these plants more sensitive to atmospheric pollution. In addition, previous studies already acknowledged pine needles as environmental indicators (Dongarrà et al., 2003).
To test the applicability of dendroanalysis for retrospective environmental monitoring, the site of Villadossola has been selected, where a serious atmospheric pollution event, due to uncontrolled emissions of black smokes from a smelter, was documented in 1989-1990. Air quality data produced in the 1990's indicate that the main emitted pollutants were Cd, Zn, Pb, Mn, Ni e Cu (ARPA Piemonte, 1990). In addition, in 1995, an investigation on the heavy metals content in soils surrounding Villadossola allowed to estimate the deposition, evaluate the bioavailability and calculate the migration rate within the soil (Facchinelli et al., 2003).
Wood cores from 8 conifer trees, ranging in age from 23 to 77 years were sampled with a Pressler borer at about 300 m from the emission source. Tree ring analyses are performed at the CNR-IGG, Pavia, using a Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). This technique offers the potential for quick and non-destructive analysis, with minimal sample preparation and high spatial resolution. The selected analytical spot dimensions (80 microns) allow repeated measurements to be performed on the same ring.
Preliminary results are obtained on a core extracted from a 66 years old Pine tree (Pinus nigra) (Folin C., 2004). The analysed elements are: Li, Be, Mg, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Y, Mo, Cd, Sn, Sb, Cs, La, Ir, Pt, Au, Hg, Pb, Th, U. As no internal standard is presently available, all signals are normalised to Mg, an essential macronutrient whose concentration has been determined by ICP- AES after acid dissolution. Repeated analysis of the same ring showed a good analytical reproducibility for all elements.
Temporal trends indicate that several heavy metals (Cu, Pb, Ni, Mn, Zn, Cd) are significantly above background levels. Pb, Cu and Ni show peaks exactly corresponding to the years of documented smoke emission, testifying for a strong foliar uptake for these elements. Cd, Zn and Mn also show significant enrichments, although not perfectly coinciding. These discrepancies are likely due to translocation mechanisms within the wood.
Statistical data treatments (factor and cluster analyses) also confirm the association of these elements.
Results clearly show the importance of foliar adsorption as a metal uptake mechanism and indicate that LA-ICP-MS can be considered, in our case, a valid analytical technique for precisely dating circumstanced atmospheric pollution events. The comparison with results obtained on other conifer wood samples, currently ongoing, will allow evaluating the response of these living organisms to environmental pressure and verifying their reliability for retrospective environmental monitoring
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