Vereinfachte Bestimmung der Basenneutralisationskapazität (BNK) stark saurer Böden

Simplified method to determine the base-neutralizing capacity of strongly acidified soils The base-neutralizing capacity (BNC) is an important property to characterize acid soils. The BNC can be reliably determined by soil-base titrations (BNC_tit). But these methods are work-expensive, and a large amount of soil material is needed. Such a large amount of soil material is not available if the soil is sampled by a hand-auger (e.g. mapping, areal investigations). Known buffer methods require less soil material, but have some shortcomings. Therefore, the well known Schachtschabel-method with calcium acetate buffer was developed for the application to strongly acidified soils. BNC values measured by the developed calcium acetate method (BNC_ac) agreed nearly perfectly with BNC_tit values of 59 mineral soils. The BNC_ac slightly overestimated (< 10%) the BNC_tit of 10 samples of humus layers. Furthermore, small soil samples (down to 1 g soil), wide soil:solution ratios, and integration of pH (H₂O) measurements into the determination of the BNC_ac yielded reliable BNC_ac values. Thus, the BNC_ac-method may be recommended as a simple and reliable method to determine the BNC of acid soils, especially if only a small amount of soil material is available.     

Protonenpuffersubstanzen in Böden

Proton buffer compounds in soils A classification of solid soil buffer substances according to the type of proton accepting sites, viz. carbonate buffer, variable charge buffer, silicate buffer and hydroxide buffer is proposed. The buffer reactions are discussed in some detail and so are formation and transformation processes of buffer. An association of pH-ranges to various buffer compounds is hampered by an insufficient knowledge of the acid strength of the different functional groups.     

Regenwürmer als Bioindikatoren für Schwermetallbelastungen von Böden unter Freilandbedingungen

The use of earthworms in monitoring soil pollution by heavy metals Total heavy metal contents (HNO₃-soluble) and exchangeable fractions (Ca(NO₃)₂-soluble) of Pb, Zn and Cd were measured in soils, litter layers and earthworms (dry masses) from forest, arable and pasture sites in a transect of the main wind direction and varying distances (1.5, 5.4, 11.4, 15.6 km) to a lead smelter near Bad Ems, Germany. Additionally, cast materials of Lumbricus terrestris-individuals were collected from the surface of the pasture sites. In the observed area total soil contents of Pb and Cd exceeded the C-level and total contents of Zn the B-level of the “Netherland-list”. Heavy metal contents in soils and earthworms decreased with increasing distance to the smelter. Pb showed the best correlation. Correlation between total contents of Pb and Cd in soils and earthworms were significant (rs = 0.66; p < 0.05 and rs = 0.67; p < 0.01, respectively). The uptake of heavy metals by Lumbricus rubellus, L. terrestris and Aporrectodea caliginosa was metal specific rather than species specific with factors of accumulation being <1 (Pb), 2.7–7.6 (Zn) and 19.5–85.5 (Cd). The heavy metal contents of the observed cast materials signified the different transfer of elements from soil material via earthworm individuals to the faeces. In the cast materials the amounts of Pb were high and the amounts of Zn and Cd were low. This indicates a high accumulation rate for Zn and especially for Cd in the tissues of the observed earthworm individuals. The present data support the necessity of ecotoxicological threshold levels.     

Anthropogener Asbest in Böden

Anthropogenic Asbestos in Soils Fibers of different asbestos types as well as other fibrous minerals, e.g. zeolites, have been found as natural contamination of soils or quarries in numerous countries and regions. Epidemiological studies have shown that inhabitants of these regions have high incidence of calcified pleural plaques and malignant pleural mesotheliomas. Anthropogenic contamination of soils by asbestos as well as asbestos contamination of the soil-near air layer were measured in this study. Soils were contaminated with chrysotile and amphibole asbestos during and after industrial asbestos processing. Asbestos fiber contaminations in the range of 10⁶ to 10¹¹ fibers/g soil and fiber concentrations as high as 5 × 10⁵ fiber/m³ air were measured. Soil contamination by anthropogenic asbestos can produce high or very high contamination of water and of ambient air by very fine fibers and entail carcinogenic risk for the general population, mainly for the inhabitants in the neighbourhood.     

Schwermetallanreicherung in den Böden des Abwasserbehandlungsgebietes Braunschweig

The accumulation of heavy metals in the soils of the Braunschweig wastewater irrigation area The concentration of lead, zink and cadmium in the Ap-horizons and subsoils of sandy Podzols and Cambisols were investigated. As compared with same soils outside the irrigation area an accumulation of the heavy metals in the Ap-horizons of the older sprinkler irrigation plots was found. On the rill irrigation area the heavy metals also were concentrated in the subsoils.     

Nitratumverteilung in Böden durch Trocknung

Redistribution of nitrate in soil samples due to drying Soil core samples of 500 cm³ volume were dried at 105°C and divided into 0-1 to 1.0 cm thick layers. The nitrate content of layers from the evaporating upper and lower surface greatly increased as compared with the central parts of the core. This process may take place on drying soil samples in general and may create problems of homogenisation when dried soil samples are analysed on their nitrate content.     

Dicyandiamidabbau in Quarzsand und Böden

Breakdown of Dicyandiamide in quartz sand and soils Under different moisture conditions the breakdown of dicyandiamide (DCD) was investigated in quartz sand with metal oxides and in soils. 1. In quartz sand without metal oxides DCD did not change over 100 days. 2. In the presence of amorphous Fe(III)-hydroxide DCD was transformed to guanylurea after 5 days to 50% and after 40 days to 90%. The transformation rate depended on the kind of metal oxides and increased with low humidity. Other metabolites were not detected in quartz sand medium. 3. In two soils (pH 6.5, 6.3; sandy silty loam and sand) the breakdown of DCD to guanylurea followed the same pattern, but continued to ammonium. About 20–70% of the added amount was transformed within 100 days. 4. With increasing soil moisture the transformation of DCD to guanylurea was slower, but the further breakdown to ammonium increased. 5. As long as DCD was present the formation of nitrate was blocked.     

Schwermetallverteilung und Tongehalte in Böden

Heavy metal distribution and clay contents in soils . In soil profiles differing considerably in horizon pattern and parent material the contents of Mn, Zn, Cu and Co were correlated with those of clay (and CEC), of total Fe (and dithionite soluble Fe) and - after relation to clay - with C. The correlations with clay, CEC, Fe_t and Fe_d were in all cases positive and highly significant, though differing between the different metals and between the references. Deviations for all elements are due to lithogenic differences in soils from mesozoic sediments and for Mn also due to its lower pedogenic stability. The correlations with C were not significant, since O horizons were not yet investigated. The ‘mobility’ of the heavy metals ( = EDTA + NH₄O Ac-extractable in relation to total amount) in topsoils could be more correlated (negative) with the reserves than with other soil features. Relating the ‘immobile’ heavy metal contents to the other soil features considerably improved the correlations.     

Kurzfristige pH-Pufferung von Böden

Short-time pH buffering of soils Changes in pH of 60 soils after HCl addition were related to reaction time and soil characteristis. Between 80 and 100% of the added protons were taken up by the soils within a few seconds, resulting in the release of exchangeable Ca, Mg and Al in strongly acid soils. The decrease of proton activity between 0.25 and 30-70 h can be formally described as a diffusion process. pH buffering depended on soil pH and organic C content but not on clay content. Buffering decreased from pH 3.5 to about 6 and increased again up to pH 7. Increase of C_org increased buffering mainly from pH 6-7.     

Phosphatsorption einiger Böden in Bayern

Phosphate adsorption of some Bavarian soils . Phosphate adsorption isotherms were established in buffered (pH 4.6, 5.5, 7.0) and some in unbuffered (0.01 M CaCl₂) systems for 9 soil profiles, 6 of which represent loess soils in various stages of development. In the P-equilibrium concentration range of 0–10^?4 mole/l two to three ranges can be identified, each of which obeys the Langmuir equation. In the lowest concentration range (0–0.2·10^?4 mole/l) adsorption is linearly related to equilibrium concentration. For the different Langmuir ranges the adsorption maxima (b) increase and the adsorption coefficients (k) decrease with increasing equilibrium concentration. The maxima depend on buffer-pH in the order 5.5<4.6<7.0. A single point method similar to the one recently proposed by Bache and Williams (1971) was succesfully applied to obtain b from a single measurement using a significant correlation between b from complete isotherms and the ratio of P adsorbed to that in solution after the addition of a fixed amount of P (0.8–1,6 mg P/g of soil). The b-values in the equilibrium concentration range of 1–20·10^?4 mole/l depend mainly on soil pH (negative) and clay (positive) (multiple correlation coefficient r = 0.858). The common reason for this appears to be the amount of exchangeable Al which is also significantly correlated with b. During soil development the depth function of b changes due to decalcification, drop of pH and migration of clay and iron oxides.     

Schwefelformen in Waldböden SO2-belasteter Standorte des Fichtelgebirges

Sulfur fractions in forest soils of the SO₂-polluted Fichtelgebirge The sulfur status of a soil sequence (two Dystric Cambisols, Haplic Podzol, Eutric Cambisol) in SO₂-polluted coniferous and hardwood forests of the Fichtelgebirge (North-East Bavaria) is investigated. In the mineral soil layers S_t fluctuates between 37 to 943 ppm; 11–84% of S_t is S_p. Layers rich in clay contain up to 79%-S_E, whereas in sandy to silty substrates organic bound C?S-S dominates. The organic surface layers show 1.0–2.9‰ S_t, maximum in the Oh. 69–90% of S_t are C?S-S. S_p is low with a maximum in the L-horizons (9–19% of S_t). S_E is vice versa, because values increase from L (0–8% of S_t) to Oh (7–22% of S_t). The characterization of the sulfur status in a forest ecosystem by investigation of organic layers presumably is more reliable than the results of needle and mineral soil analyses.     

Differenzierte quantitative Erfassung der Nettoammonifikation durch Pilze und Bakterien in Böden unter verschiedenen Pflanzengesellschaften

Determination of ammonification rate by fungi and bacteria in soils with different plant societies. In soil samples of three sites in decidous forests with different plant-ecological and plant-sociological characteristics an attempt was made to determine the contributions of the saprophytic ammonifying fungi and bacteria by selective inhibition and by the use of a special incubation technique. The stimulation of the soil microflora was carried out by the addition of a universal-pepton as an easily degradable organic nitrogen. For the selective inhibition of fungi and bacteria the broad-spectrum antibiotics cycloheximide and streptomycinsulfate were used, which had been tested and found suitable by Anderson and Domsch (1973). The determinations of the produced fractions of inorganic nitrogen were conducted by the use of ion-specific eletrodes. During the short period of incubation lasting for a maximum of 8 hours, feasible for calculation, only the NH,-N-contents of the soil material increased while the contents of NO,-N and NO,-N did not change during this period. The average contributions of the ammonifying soil microflora was calculated as follows: site I 80 %by fungi/20 %by bacteria site II 80 % by fungi/20 % by bacteria site III 65 %by fungi/35 % by bacteria. A relationship between the contributions of ammonifying fungi and bacteria and ecological characteristics of the sites could not be found.     

Stickstoffdynamik von Böden mit Abwasserverrieselung

Nitrogen dynamic of soils with wastewater irrigation The nitrogen status of a Sandy Cambisol and a Loamy Luvisol of Berlin, which were flooded with wastewater over a period of 100 years were studied. The two-year examination of the water, redox and nitrogen dynamics showed great differences in nitrogen leaching and the intensity of nitrification and denitrification processes.     

Kalium-Dynamik und Kalium-Fixierung nordwestiranischer Böden

Dynamics and fixation of potassium in soils of North-West-Iran The following results were obtained from experiments conducted on two calcareous soils (A-horizon) and on two soil samples from fertilizer experimental plots (K₀ = control plot, K₅ = 1000 kg K₂O/ha) to study the dynamics and fixation of potassium in these soils: The K-exchange curve of K₅ sample when compared with K₀ sample showed that, as a consequence of high fertilizer dose, most of the specific adsorption sites for cations (particularly on illites and weathering products of illites) were occupied by K which, thus, resulted into lower K-adsorption as well as fixation. The shape of K-exchange curves of other three samples (Alluvial soil, 16, Brown soil 26 and K₀ sample, Fig. 5 and 6) indicates a typical bend at definite activity ratios. This bend in the exchange curves exists apparently in soils containing high content of illitic clay mineral fraction. This behaviour has been interpreted as a consequence of contraction of layers of illitic minerals which were formerly expanded due to loss of potassium. The K-desorption experiment, which then followed, showed that a major part of sorbed amounts of potassium could not be desorbed and remained fixed in the soil. Similar type bend as in the exchange curve was also observed in the potassium fixation curves (Fig. 6 and 7). Illite is the dominant clay mineral in all these soils which in Brown soil and K₀-sample is expanded at edges; the expansion goes back to 10 A on treatment with K which then does not expand again on saturation with Mg.     

Zur Bestimmung von Gips in Böden

On the determination of gypsum in soils The (020) X-ray reflection of gypsum at 7,56 Å is nearly specific and may be used for detection and quantitative measurement of the mineral in soil samples. By X-ray powder diffractometry gypsum can be detected as far down as 0,5% by weight. This limit may be extended down to 0,005% by concentration in the density fraction 2,1–2,5 g/cm³. For quantitative measurements references may be prepared from sample parts by dehydration of the original gypsum and adding known quantities of this mineral. So it is possible to compare samples of nearly identical grain size distribution, and mineral contents. This is important in the powder-diffractometrical quantitative measurement of a mineral with low hardness and good cleavage where mechanical stress during homogenisation lowers the intensities of X-ray reflections. Under comparable conditions for sample and reference, gypsum contents can be determined in the range of 0,5 to 20% by weight with an accuracy of ± 3% (relative).