Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 184

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 10 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  trace element
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 10 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The experiment was conducted in order to determine the concentration of fluorine in cow's milk and human breast milk. Milk samples were tested for fluoride concentration. After fractioning, free fluorine and protein-bound fluorine was tested by using ion-selective electrode. It was determined that the concentration of fluorine in tested human breast milk was higher than in cow's milk. The fluorine appeared mainly in free form and only a small fraction was bound to proteins. Complete concentration of fluorine was higher in human breast milk than in cow's milk.
The trace elements Cu, Cr, Co, Zn, Pb, V, Mo, Ni, Be, Sn, W, Zr, Ag, Sb, As, Bi, Ba, Sr, Ga, Y, Nb and La are reported from the ash of two nematodes, Ascarops strongylina and Ascaris suum from pigs, following analysis by emission spectroscopy.
The aim of this work was to determine the content of Mn, Zn, Cu, Pb, Cr, Ni and Cd in auto- and semihydrogenic soils of Bialowieza National Park and to find relationships between their occurrence and litho- and pedogenic features of these soils. Basing on geometric mean contents of the elements studied a quantitative series of their occurrence was established as follows: Mn (297) >Zn (29) >Cr (16) >Pb (12) >Ni (10) >Cu (8.0) >Cd (0.29) mg kg-1 d.w The distribution of the above trace elements in soil profiles is linked to the direction of progress of the soil forming processes and, to some extent, to the variability of soil texture (especially in not completely developed soils). In general, the mineral-organic (A) horizons were least abundant in Cr, Ni, Cu, Zn and Cd, followed by the illuvial (Eet) and bedrock (C) horizons of the soils studied. Statistical analysis shown a significant correlation between contents of Cr, Ni and Zn and clay and colloidal particle amounts as well as between the content of Pb and the amount of organic carbon
Background. Fish are often used as indicators of pollution levels in water environments. The omnivorous chub inhabiting rivers of Europe, including their more polluted parts, is a potentially suitable indicator. The information published, however, on the metal accumulation in the tissues of chub living in varyingly polluted waters (both polluted and unpolluted environments) is scarce. The presently reported study was conducted to examine the metal concentrations in selected tissues of chub living in a natural submontane river. Materials and Methods. Sediment samples (0–5 cm layer) and chub, Leuciscus cephalus (L.), were collected from the upper (stations 1–4) and lower (stations 5–8) sections of the Biała Tarnowska River in summer 2003. Fish age was determined from the otoliths. The AAS method was used to determine metal concentrations (Cd, Pb, Cu, and Zn) in sediment and chub tissues (spleen, liver, and muscle). Results. According to the values of the geochemical index (Igeo), the river sediments were not polluted by Pb, Cu, and Zn, while in various degrees polluted by Cd. Despite the low metal concentrations, the mean Cd and Cu concentrations were higher (c. 2× and 4×, respectively) in the upper part of the river compared to the lower section, while concentration of Pb and Zn were similar in the two areas. Chub accumulated the greatest amount of Cu in the liver, while the bulk of Cd, Pb, and Zn was found in the spleen. In the upper part of the river, elevated concentrations of trace elements in selected tissues of chub were found: Cu (spleen, muscle), Cd (spleen), Zn (muscle). The pollution status of the river, on the basis of trace element contents in the sediment, was also determined. Conclusion. The obtained results indicated tissue-specific metal accumulation in chub. Selected chub tissues are sensitive to Cd and Cu contents in the river sediment.
Disturbances of mineral metabolism are one of the many complications observed in patients with renal failure. Fluids used in dialysotherapy may introduce elements to a patient’s body. On the other hand, some trace elements may be removed. Dialysis fluids contain chlorides of calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), but they may also be contaminated by toxic metals. In the first part of our work the amounts of Mg, Ca, zinc (Zn), and iron (Fe) were determined in samples of hemodialysis fluids just before and after a dialyzer. The concentration of copper (Cu), aluminium (Al), lead (Pb), cadmium (Cd), and chromium (Cr) were measured by the atomic absorption spectrometry method (AAS) in a graphite furnace (GFAAS) in the same dialysates. The average concentration of Cu in dialysis fluids before and after dialyzer was 13.51 and 10.51 μg L-1 respectively, Al – 8.72 and 7.88 μg L-1, Pb – 24.03 and 22.81 μg L-1, Cd – 1.09 and 1.07 μg L-1, Cr – 5.91 and 6.28 μg L-1. Except for Cr (p < 0.05), the comparison of concentrations of all the measured elements before and after haemodialysis did not show any significant differences. Positive significant correlations between the element concentration before and after a dialyzer were found for Al (r = 0.33030 and Cd (r = 0.7496). In the samples of dialysis fluids of patients who had been dialyzed for less than one year, a negative balance of elements was found, except Pb. The balance was positive in patients who had been dialyzed for more than a year. Our findings also show statistically significant negative correlation between duration of dialysis treatments and Al concentration. Statistically, the examined dialysis fluids seem to be safe for dialyzed patients. However, individual data show that it is important to control elemental levels in dialyzates used for many years to prevent some complications in these patients.
Long-term application of fertilizers can change the chemical composition of the soil environment. Our objective has been to determine total amounts of trace elements (Cu, Mn, Zn, Cd and Pb) in the top layer of soil after 34 years of annual applications of organic and mineral fertilizers. The first experiment was set up in 1972 on lessive soil, while the second one was started in 1973 on brown soil. The same crops were grown in both experiments. Bovine manure and slurry were applied in the first experiment, while the other one involved the application of swine manure and slurry. Slurry was applied at two different doses. One dose of slurry was applied together with manure and mineral fertilization in amounts balanced according to nitrogen. The other dose of slurry was determined so that it brought to soil the same amount of organic carbon as introduced with a manure dose. Manure and slurry were also applied in combination with phosphorus and potassium fertilizers in amounts equal half the content of these components used delivered through exclusive mineral fertilization. The total metal content was assessed using the atomic absorption spectrometry method, with prior mineralization in a 1:1 mixture of nitric and chloric acid. The application of fertilizers over many years increased the content of trace elements. The actual effect varied between the analyzed soil types, depending also on the type of fertilizer and the dose of slurry. The average content of Cu, Cd and Pb was 13.8% higher in lessive than in brown soil, while the amount Mn was lower by as much as 32.7%. Among the doses balanced with respect to nitrogen, the effect of manure caused an increase in the Mn, Zn and Ni content in lessive soil, as well as Cu and Pb in brown soil compared to the application of the slurry dose balanced with manure according toorganic carbon. Mineral fertilizers did not increase the content of the analyzed metals as much as manure, with the exception of Cu and Pb in lessive soil and Ni in brown soil.
The aim of this study was: (a) to estimate the concentration of selenium in plasma of 136 residents (59 men and 77 women) of the Gdansk region, northern Poland, aged 19-70; and (b) to compare the obtained results with data corresponding to healtly populations living in different European countries. Selenium in plasma was determined by atomic absorption spectrometry using the hydride generation method. The mean selenium concentration in plasma of the investigated persons was: 72.3 +/- 14.1 mug/l, in men 75.9 +/- 12.8 mug/l, in women 69.5 +/- 14.7 mug/l. No age-dependent differences in plasma selenium were found in the investigated population. In 22% of the investigated persons the selenium level in plasma was lower than 60 mug/l. The obtained results indicate that a significant part of this population is deficient in selenium and should be supplemented with this element.
The analysis of river and lake sediments indicates that the physical, chemical, biochemical and geochemical processes that influence the fate of toxic compounds and elements in sediments are numerous and complex (for example: sorption – desorption, oxidation – reduction, ion-exchange, biological activity). Due to the above-mentioned general statement, only a long term and complex research programme can lead to satisfactory answers to the questions relating to possible changes of water and environmental quality in the future. The aim of our study consisted in physical and chemical characterisation of sediments in in-depth profiles taken from the Dobczyce reservoir in southern Poland that is a main source of drinking water for the city of Kraków. Due to morphological reasons, 7 layers of sediment samples were distinguished from the ground level to about 90 cm below (total thickness of the sediments in the sampling site). Analysis of grain size distribution and application of x-ray diffraction method, enabled mineralogical description of sediments. The use of proton-induced x-ray emission (PIXE) and atomic absorption spectrometry (AAS) revealed elemental composition of the samples (Al, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn). Concentrations of natural ⁴⁰K and artificial ¹³⁷Cs radionuclides were determined by the use of gamma spectrometry. The following facts were established: 1) the oldest (deepest) and newest, recently deposited layers of sediments are similar in their physical and chemical properties. It means that the inflow of contaminants and biogenic compounds to the reservoir has changed little since it was constructed and filled with water; 2) the severe flood in 1997 changed significantly sediment composition and, in fact, led to purification of sediments in the Dobczyce reservoir.
We have reviewed available data from our and other laboratories relevant to the effects of single and repeated intoxication with mercury on the metabolism of several elements in animal bodies. Additionally, emphasis has been placed on the influence of zinc and selenium on mercury toxicity. The data indicate that mercuric chloride and methyl mercury affect quite differently the distribution pattern and concentrations of trace elements in animal organs. Moreover, it should be stressed that mercury intoxication decreases bone radiocalcium and thyroidal radioiodine levels which correlated with the size of mercury doses. The disturbances were chiefly attributed to impairments of the gastrointestinal absorption in mercury intoxicated rats. Moreover, haemodynamic alterations and mercury trace ele- ments-metallothionein complexes may also result in these disturbances. The effect of zinc on mercury toxicity is not uniquivocal. In contrast, the ability of selenium to decrease mercury's deleterious effect in animals is well recognised.
According to the valid STN, a semi-product is as a suitable manure containing magnesium and calcium after removing the fraction above 0.5 mm. On average, the semi-products and raw materials analysed contain 86.64% MgC03 and 8.30% CaC03, which corresponds to 46.46% MgO and 4.65% CaO. They are also suitable for organic agriculture, which demands sufficient contents of magnesium in farm products. An essential portion of magnesium is bound in carbonates, complemented by magnesium in silicate forms. The products have relatively high contents of manganese (1643,68 mg kg-1), although its mobilisable percentage is barely 0.3%. Other controlled microelements (Cu, Zn, Co) are also present in forms unsuitable for vegetables.
The most important enzymatic mechanisms which protect an organism against oxidative stress are superoxide dismutase (SOD), peroxidase (Px), e.g. glutathione peroxidase (GSH-Px) and ascorbate peroxidase, catalase and glutathione reductase. Their activity depends on many trace elements. Enzymatic mechanisms, functioning under physiological conditions, prevent the spread of free radical reactions. New and reoccurring metabolic and infectious diseases of cattle emerge when there is a disproportion in the balance between reactive oxygen species and antioxidative enzymatic barrier.
In this paper the analytical methods and procedures were chosen for determining Hg, Be, Pb, Cd, As, Ni, Cr, Zn, Mo and Cl, Br in ashes, fly ashes and slags of hard coals. For Hg CV AAS, for As GFAAS and for other elements, FAAS methods were recommended.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 10 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.