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Central European Geology
Authors: József Fekete, Csanád Sajgó, István Horváth, Zoltán Kárpáti, István Vetõ, and Magdolna Hetényi

Abstract

The geochemical facies of Hungarian thermal waters were the object of this study. Samples were separated into groups by relative ages (δ18O values). Mature and immature subgroups were formed on the basis of dissolved (semi)volatile organic compounds. The oldest (connate) waters form one group with a small number of samples. The subgroups containing different small molecular-sized soluble aromatics differ sharply in their chemical features (sodium, hydrogen carbonate, iodine, ammonium etc. content). The origin of the organic matter may differ in the subgroups as inferred by their different δ18O values and ten times greater halogen contents.

Our results show that the decomposition of organic matter produces small molecular-sized aromatic compounds and also influences the amounts of inorganic components in thermal waters, through the increase of feldspar hydrolysis and carbonate dissolution.

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A field experiment with microelement loads was set up on loamy-textured, calcareous chernozem soil formed on loess. The ploughed layer contained about 5% CaCO3 and 3% humus. The soil was well supplied with Ca, Mg, Mn and Cu, moderately supplied with N and K, and weakly supplied with P and Zn. The water table is at the depth of 15 m, the water-balance of the area is negative, and the site is drought-sensitive. Salts of the 13 examined microelements were applied at 4 levels in the spring of 1991.Treatments were arranged in split-plot design, in a total of 104 plots with two replications. Loading rates were 0, 90, 270 and 810 kg/ha per elements in the form of AlCl3, NaAsO2, BaCl2, CdSO4, K2CrO4, CuSO4, HgCl2, (NH4)6Mo7O24, NiSO4, Pb(NO3)2, Na2SeO3, SrSO4, and ZnSO4. Soil profiles of the control and the 810 kg/ha treatment were sampled in the 3rd, 6th and 10th year of the trial. The mixed samples, consisting of 5 cores/plot, were taken every 30 cm to the depth of 60 (1993), 90 (1996) and 290 (2000) cm. NH4-acetate + EDTA-soluble element content was determined. The scheme for vertical movement of soluble elements in soil profile as a function of time is shown in Fig. 1. The main conclusions of the study can be drawn as follows:

  1. 1. On contaminated soil with 810 kg/ha loading rates, As, Hg, Ni, Cu, Pb, Ba and Sr displayed no significant vertical movement. The movement of these elements is blocked in the soil-plant system: their accumulation in the above-ground plant parts usually remains below 5–10 mg/kg D.M., with the exception of Ba and Sr which showed a somewhat higher accumulation. On this soil the above elements do not seem to be dangerous contaminants either to soil, groundwater or plants. Extreme As and Hg loads, however, resulted in phytotoxicity in some plants.
  2. 2. Moderate extent of leaching occurs in the case of Zn and Cd, when they are enriched significantly. Their accumulation was moderate in the above-ground plant parts. Zn is not a dangerous pollutant either for soil, plants or groundwater at this site. Cd, however, is a very dangerous element from the human toxicological point of view and more extreme Cd loads also proved to be toxic for soil life, crops yield and quality.
  3. 3. Cr, Se, and Mo (in the form of chromate, selenate and molybdenate anions) exhibited great mobility in the soil and partly in the soil-plant system. Cr was hardly detectable in the above-ground floral parts. Its rapid leaching, however, can jeopardize groundwater quality. Se showed hyperaccumulation in all plant organs with high toxicity for all kind of crops. Mo also showed two or three orders of magnitude greater accumulation in plant parts, resulting in products unfit for animal or human consumption. Under our experimental conditions Cr(VI), Se, Mo can be classified as dangerous contaminants, since the anion forms remained stabile for a long time in this well-aerated calcareous environment.

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solubilities in subduction zone fluids Earth Plan. Sci. Lett. 124 119 129 . Kad. Balogh 1974

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14/1 120 131 Caroll, M.R., J.D. Webster 1994: Solubilities of sulfur, noble gases, nitrogen, chlorine, and fluorine in magmas. -- In: Caroll MR

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. J.D. Webster 1997 Chloride solubility in felsic melts and the role of chloride in magmatic degassing Journal of Petrology 38 1793

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evaluation of mineral solubilities and phase relations European Journal of Mineralogy 12 999 1014 . R. Varga

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. Környezetvédelmi talajvizsgálatok. Az összes és az oldható toxikus elem-, a nehézfém-, és a króm (VI) tartalom meghatározása (Environmental soil investigation. The total and soluble toxic elements, heavy metal, and chromium (VI) content determination). - Budapest

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.J. St. Arnaud 1979 Nature and distribution of secondary soil carbonates within landscapes in relation to soluble Mg ++ /Ca ++ ratios Canadian Journal of Soil Science

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Hungarian Standard MSZ 21470-50 (1998): Környezetvédelmi talajvizsgálatok. Az összes és az oldható toxikuselem-, a nehézfém- és a króm(VI) tartalom meghatározása (Environmental soil investigations. Determination of the total and soluble toxic element, heavy

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. 101 635 643 Montel, J., M. 1986: Experimental determination of the solubility of Ce-monazite in SiO 2 -Al 2 O 3 -K 2 O-Na 2 O melts at 800 °C, 2 kbar

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