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Impact of metabolites of the forest vegetation on the chemistry of throughfall
Skřivan, Petr ; Navrátil, Tomáš ; Vach, Marek ; Špičková, Jitka ; Fottová, D.
The chemistry of throughfall is a result of numerous processes that affect the concentrations of its individual components in the original wet precipitation above the tree crowns. The precipitation entering the tree crowns is generally enriched throughout its interactions with the above - ground part of the vegetation. The samples of open place precipitation and throughfall have been collected since 1989 in the region of Kostelec n. Č.lesy. The monitored area is situated predominantly in the Nature State Reserve Voděradské bučiny on the bedrock of the Říčany and Jevany granites. The exact evaluation of the impact of metabolites on the resultant concentration and fluxes of individual monitored elements in throughfall, based on mere comparison with the corresponding values in open place precipitation, is faced with several problems. First, the chemistry of throughfall reflects more the chemical composition of aerosol from lower parts of the atmosphere, as it is more or less effectively swept out by the above ground growth. The vegetation surface also entraps the reactive atmospheric gasses. Finally, the original precipitation solution is thickened through the evapotranspiration and it is enriched by the excluded and leached metabolites. The estimate of the extent of metabolic activity of the forest trees on the chemistry of throughfall was therefore limited on the comparison of a relative magnitude of normalised fluxes of individual elements in a given type of throughfall. The fluxes of individual elements in a beech- and spruce throughfall were normalised on the Na fluxes, with respect to the supposed zero metabolic share of Na in throughfall and to its predominantly natural sources in the atmospheric aerosol. The calculation of the enrichment factor Ef of the individual elements was then executed by means of the relation EfTFB,TFS (Me) = FBP Na / FTFB,TFS Na* FTFB,TFS Me / FBP Me, where EfTFB,TFS (Me) is the enrichment factor od the particular element in a given type of throughfall, FBP Na a FBP Me are the mean annual deposition fluxes of Na and the element Me on an open place, and FTFB,TFS Na a FTFB,TFS Me are the mean annual fluxes of Na and the element Me in throughfall. Values of the enrichment factor for the individual elements are presented in the article in the Tab. 1. Values higher than 1 should generally indicate the presence of metabolic products of the vegetation. The highest Ef values were found, after expectations, for the basic nutrients and significant essential elements, in a row of K > Mg > Mn > Ca. Together with these elements, significant impact of leached metabolites was also found for Rb, Sr and Ba. The enrichment of throughfall with rubidium is extraordinary high, probably even higher than that of its homologue potassium. Surprisngly high values of the Rb deposition fluxes in both tyes of throughfall certify the extensive input of this element through the root uptake of the forest vegetation, which is contingent on very close chemical characteristics of rubidium and potassium (ionic radii, electronegativity, ionic character of bonding of these alkaline metals in all their chemical compounds etc.). We have not found, however, similar pronounced paralell between Ca, Sr and especially Ba, which is even more abundant in the underlying rocks and soils than Sr.
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Recyclation and Transformation of Homocysteine as a Part of Detoxication Processes in the Cell
Přistoupilová, K. ; Přistoupil, T. ; Šenholdová, Z. ; Navrátil, Tomáš ; Heyrovský, Michael
The presented metabolic pathways explain how the transformation of homocysteine affects the detoxication processes in the human cell. On the one hand homocysteine is recycled to methionine; on the other hand it is transformed to cysteine. Both pathways are connected by B12 vitamin. Their relation to the thiodiglycolic acid (TDGA), which represents a part of the detoxication processes, is demonstrated on the scheme. The changes in TDGA concentration in urine were found to depend on the changes in redox equilibria (of vitamin B12, folic acid, homocysteine). Key Words: Thiodiglycolic acid, TDGA, vitamin B12, folic acid, metabolic pathways, homocysteine, detoxication.
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Změny koncentrace TDGA v moči jako možný marker metabolismu thiosloučenin
Přistoupilová, K. ; Přistoupil, T. I. ; Šenholdová, Z. ; Navrátil, Tomáš ; Heyrovský, Michael ; Fenclová, Z.
The new simple voltammetric method we described recently, proved already to be useful in determining thiodiglycolic acid (TDGA) levels in urine samples of people influenced by some chemicals, victuals and pharmaceuticals. The present pilot study is a continuation of our previous work devoted to test general feasibility of the method. We concentrated upon time dependent quantitative changes of TDGA excretion into urine of selected volunteers. The TDGA level in all morning samples was the highest in comparison with samples collected during the day. The TDGA level was dependent on the health condition of each person involved. However, a further marked increase of TDGA in the morning urine was observed individually, in general when vitamin B12 had been administered in the evening the day before. Vitamin B12 is known to play an important role in the metabolism of one- and two-carbon units, of homocysteine and of sulfhydryls in general. Certain differences in excretion course of TDGA.
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Anodic Stripping Voltammetry on Silver Composite Electrodes
Kopanica, M. ; Šebková, Světlana ; Navrátil, Tomáš
The influences of presence of various cations (Cd, Cu, Bi, Tl) and anions (chlorides) on the anodic stripping voltammetric determination of lead on silver composite electrodes were studied. It was found that the effect of underpotential deposition at these electrodes differs from that one produced by metallic silver electrode. Their use enables the direct determination in water samples without elimination of the presence of surface-active substances or of dissolved oxygen (LOD about 3 ug L-1).
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