Search results for " composition"
showing 10 items of 1437 documents
Water uptake and equilibrium sizes of aerosol particles at high relative humidities: Their dependence on the composition of the water-soluble material
1978
Equilibrium water uptake and the sizes of atmospheric aerosol particles have for the first time been determined for high relative humidities, i.e., for humidities above 95 percent, as a function of the particles chemical composition. For that purpose a new treatment of the osmotic coefficient has been developed and experimentally confirmed. It is shown that the equilibrium water uptake and the equilibrium sizes of atmospheric aerosol particles at large relative humidities are significantly dependent on their chemical composition.
Geochemical characteristics of waters in mineralised area of Peloritani Mountains (Sicily, Italy)
2009
Abstract This paper presents the results of a study on the geochemistry of waters circulating in the mineralised area of the south-eastern sector of Mt. Peloritani (north-eastern Sicily, Italy), aimed at basic understanding of the geochemical processes influencing their chemical composition. Chemico-physical parameters and data on 26 major and minor chemical elements are reported for 103 water samples. Water chemistry is mainly dominated by dissolution of carbonates and hydrolysis of aluminosilicate minerals. Total dissolved salts (TDS) range from 80 to 1398 mg/L. All the waters exhibit E H characteristic of an oxygenated environment. Excluding two samples, which show very high H + activity…
Changes of humic substances characteristics from forested to cultivated soils in Ethiopia
2006
The dynamics of the stable fractions of soil organic matter (SOM), the humic substances, has been rarely studied in tropical soils. We evaluated extraction yields, elemental composition, isotopic d 13 C abundance and solid-state 13 C NMR spectra of humic fractions isolated from five forested and cultivated soils in Ethiopia in order to assess the influence of deforestation and subsequent cultivation on the composition of humic fractions. In all locations, humic (HA) and fulvic (FA) acids, humin (HU) and a humic hydrophobic fraction extracted with an acetone–HCl solution (HE) were decreased as a result of deforestation and cultivation, but the magnitude of decrease was site-specific. While t…
Mineral Profile
2013
The identification of foods with protected designation of origin (PDO) has been a long-standing issue. Its detection provides valuable information to regulatory commissions (government and industries) which can regulate precise quality control procedures for their products. Authentication of food covers many different aspects, including characterization, mislabelling and misinformation regarding origin, and adulteration, which is defined as the process to reduce the quality or nature of a given substance by adding a foreign or an inferior substance and removing a vital element. Numerous methods have been developed as fingerprinting methodologies for PDO products. The analytical techniques c…
Uptake and release kinetics of134Cs by Goldfish (Carassius auratus) and137Cs by Zebra Fish (Brachydanio rerio) in controlled aquatic environment
1994
The uptake and release kinetics of134Cs by Goldfish (Carassius auratus) and137Cs by Zebra Fish (Brachydanio rerio) from aquatic media of different ionic compositions and temperature was studied in controlled laboratory conditions. The accumulation of radiocesium in the case ofBrachydanio rerio is observed to be strongly dependent on the potassium ion concentration of the aquatic medium, but in the case ofCarassius auratus this dependence is quite weak. The biological half-lives of the cesium isotopes incorporated into the fish investigated in the present work vary from 19 to 80 days and are influenced by the temperature and the ionic composition of the aquatic medium.
Ionic conductivity in monophasic Ag2xNa2(1 − x)ZnSiO4 materials with 0 ≤ x ≤ 1
1996
Abstract Solid solution samples Ag 2 x Na 2(1 − x ) ZnSiO 4 with 0 ≤ x ≤ 1 have been prepared by heat treating powder mixtures of Na 2 ZnSiO 4 and Ag 2 ZnSiO 4 at 300 °C and characterised by X-ray powder diffraction. The ionic conductivity of the solid solution has been determined as a function of composition and temperature by means of impedance measurements. The ionic conductivity of the mixed-mobile ion compositions (0 ≤ x ≤ 1) shows no substantial deviation from the mutually similar conductivities of the end compositions Na 2 ZnSiO 4 and Ag 2 ZnSiO 4 , and neither activation energy nor conductivity pre-factor varies significantly with composition. The results indicate that the mixed-alk…
Sicilian bottled natural waters: Major and trace inorganic components
2013
Sixteen bottled waters of various Sicilian brands, 11 natural mineral waters and five normal drinking waters, were analyzed for major and trace inorganic components by ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The bottled waters represent a variety of water types with significantly different compositions in terms of salinity, major components and trace elements. Chemically, they range from Ca–HCO3 and Ca–SO4 to Na–HCO3 types. Total dissolved solids ranges from 54 to 433 mg/L, total hardness from 25 to 238 mg/L CaCO3, and measured Na content from 5.7 to 57 mg/L. According to total dissolved ions, all the bottled waters were classified as…
Influence of Initial Water Content on the Wettability of Autoclaved Soils
2010
Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. This study, however, showed that autoclaving can cause a major change in soil hydraulic properties. For samples with intermediate water contents (10-35% v/v), it caused severe or extreme water repellency in three of four soil types tested, although no effect for initially low or high water contents was found. These findings have important implications for any experimental work involving soil autoclaving as a pr…
A preliminary approach to mineral intake in the Spanish diet established from analysis of the composition of university canteen menus
2012
Abstract The concentration of mineral elements in complete menus has in Spain been determined in order to establish the levels of essential and toxic elements and their contribution to the maximum recommended intake. Thirteen university canteen menus obtained from the Burjassot campus, in Valencia, were analysed to establish a first approach on mineral composition in the Spanish diet. The menus were composed of a mixture of cereals, meat, fish, vegetables, fruits and dairy products. Samples were crushed, homogenized and lyophilized, and 25 elements were determinated by inductively coupled plasma optical emission spectroscopy (ICP-OES) after digestion of samples in a microwave oven. Menu sam…
Surface composition analysis during the oxidation of ferrites: A necessity
1998
The cationic composition of a titanium ferrite (Fe 2.5 Ti 0.5 O 4 ) has been followed by XPS during its oxidation in cation deficient phases (without crystallographic transformation) in order to reveal a dynamic segregation phenomenon. Indeed, during this oxidation, an important modification of the chemical composition of the first layers of the material has been revealed: below 350 °C, the titanium ferrites surface becomes richer in iron and poorer in titanium. But, if the reaction is extended above 400 °C, some titanium can move to the surface. This phenomenon has been interpreted on the basis of the differences of mobility of the different ions which are present in the material. Finally,…