Quantitative Mineralbestimmung in der Schlufffraktion von Böden auf der Grundlage der chemischen Analyse und unter Anwendung der Karl-Fischer-Titration. II. Ergebnisse bei Böden aus Geschiebedecksand,Geschiebemergel und Löß

Quantitative estimation of the mineralogical composition from silt-fractions of soils on the basis of the chemical analysis and by application of the Karl-Fischer-titration. II. Results obtained with soils from glacial sand, boulder marl and loess The contents of micas and feldspars were quantified in the silt-fractions from horizons of a podsolic brown earth developed on glacial sand and of lessives on loess as well as on boulder marl by using a method that has been described in detail in part I. Three components each of micas and of feldspars, namely muscovite (Ms), phlogopite (Phl), annite (Ann), orthoclase (Or), albite (Ab) and anorthite (An) were determined. The silt fractions of the three investigated soils are similar in their mineralogical composition. Feldspars are composed of equally high amounts of Or and Ab. Micas are dominated by the Ms-component. Apparently the mica content of the silt fractions is reduced during soil development, whereas no significant changes can be found for feldspars. The loss of micas is responsible for the decreasing potassium content of the silt fractions.     

Zur Genese der Marschböden. II. Kalksedimentation,Entkalkung

On the genesis of tidal marsh soils II. Carbonate sedimentation, decalcification A central problem of the tidal-marsh soils is the calcareous deposit of the parent material. On the basis of small-scale, systematic investigations it has been demonstrated in two “key areas” in the Weser tidal flats, that fluviatile and brackish soils are descended from calcareous or not-calcareous sediments. Soils buildet from calcareous sediments shows a low depth and a low rate of decalcification because of a high content of clay and bases as well a permanent high level of groundwater during the development of the soils.     

Die Ermittlung der Porengrößenverteilung aus der Körnung,dem Gehalt an organischer Substanz und der Lagerungsdichte

The estimation of pore size distribution from texture, organic matter content and bulk density Using regression analysis the dependence of the pore size distribution of soils on the compactness and percentage of organic matter, clay and silt was studied on 450 soil horizons. From the results nomograms for determination of the pore size distribution were constructed. The average deviation between pore size distribution as read from the nomograms compared and determined in the laboratory is ～ ± 3 Vol.-%.     

Die Bedeutung der K-Ca-Austauschisotherme für eine Beurteilung der K-Versorgung der Pflanzen bei Lößböden

K-Ca-exchange isothermes of soils from loess and the potassium supply of plants From 80 Ap-horizons of Luvisols and Phaeozems on loess from south of Hannover K-Ca-exchange isotherms and cation concentrations in saturation extracts were investigated. Though not K deficient these soils show a very wide range of available K. From the very high K-concentrations in the saturation extracts (up to 3 meq/1) of part of the soils it was concluded, that mass flow should be sufficient for plant needs of K. The only soil property varying the exchange isotherms seems to be the clay content (Fig. 4). In order to calculate available K from the exchange isotherms in the same way as available water from pF characteristics the isotherms were extended down to activity ratios, according to literature, marginal for plant uptake of K (Fig. 6). The estimated soil K content, sufficient for plant in loess soils, amounts to about half that considered marginal by the regional extension service. With the assumption that so called non exchangeable, but plant available K is essentially very slowly exchangeable, an experiment was performed at 80°C to accelerate the exchange and to establish a true equilibrium. The comparison between the new exchange curve and the 25°C curve (Fig. 8) seems to reveal additional 180–450 kg/ha · 30 cm bound with equal free energy of exchange as easily exchangeable K.     

Anorganische Schadstoffe in Böden Nordrhein-Westfalens. I. Möglichkeiten der Auswertung mehrmodaler Häufigkeitsverteilungen

Inorganic toxicants in soils of North Rhine-Westphalia. I. Evaluation of multi-modal frequency distributions In 335 soil samples from North Rhine-Westphalia the contents of 18 elements were quantified (total contents, mobilizable fraction (extraction with EDTA cocktail), mobile fraction (extraction with NH₄NO₃). An inspection of the resulting histograms revealed that the distribution of element contents in soils is not normal and even not log-normal. The appearance of several peaks indicates the existence of multi-modal distributions with various independent sub-distributions. Two methods for analysing such data sets are presented. The parametric approach assumes several single lognormal components, which are fitted by the Expectation Maximization Algorithm. In a nonparametric approach the Kernel Density Estimation is used. With this procedure five to ten concentration levels can be determined per element for our data set with corresponding groups of soil samples being characterized by common features (e.g., parent material, region of origin, specific source of pollution). This way, e.g., background concentrations for potentially toxic elements can be derived. The parametric approach is lacking sharpness of separation in the case of more than four subdistributions.     

Einflußgrößen der Schwermetallöslichkeit und -bindung in Böden

Solubility and retention of heavy metals in soils Model experiments were carried out under oxidizing conditions with soil samples from surface and subsurface horizons of different composition in order to investigate the solubility and retention of Cu, Zn, Cd, and Pb in soils. The solubility of heavy metals is mainly determined by ad- and desorption processes and complexation reactions of organic and inorganic ligands. Precipitation and dissolution of definite heavy metal compounds do not seem to govern the solution concentration in soils. An exception may probably be the formation of lead phosphate and zinc silicate under specific reaction conditions. The main factors which determine solubility and retention of heavy metals are total amount (except the proportion incorporated in the silicate structure) of the different metals, soil reaction, content of mobilizing and immobilizing organic substances, content of pedogenic oxides and clay minerals, and kind and concentration of salts and inorganic ligands. The results of the model experiments are used together with the results of other authors and general physico-chemical data to give an interpretation of the solubility behaviour of heavy metals in soils. The relations between heavy metal solubility, availability and mobility and possible procedures for melioration of soils contaminated with heavy metals are discussed.