Karl Stahr

Palagonite reconsidered; paracrystalline illite-smectites from regoliths on basic pyroclastics

Poorly crystalline authigenic alteration products of basic pyroclastics from the Golan Heights, Israel, were investigated by XRD, DTA, TGA, FTIR and chemical analysis. Modeling XRD patterns with the use of NEWMOD code provided a way to identify these clays as random interstratified illite/smectites (I/S) with ∼70% of illitic interlayers. Their characteristic features were very poor basal reflections, distinct hk bands, high CEC and low (∼2%) K2O content. Crystallite thickness distribution was found to follow Ergun’s model with a weight-average thickness of 2.7–2.8 layers. A new method was proposed to calculate the proportion of kaolinite and 2:1 minerals in their mixtures and the average crystallochemical formula of 2:1 minerals in the presence of kaolinite. The method starts from data of chemical analysis and TGA and assumes that the anionic frameworks of kaolinite and 2:1 minerals are exactly O10(OH)8 and O10(OH)2 respectively. The number of OH-groups per ten oxygens not bonded to H in the empirical formula of the mixture is used to evaluate the proportion of kaolinite. Formation of I/S in well-drained environments under humid mediterranean climatic conditions was attributed to long dry seasons. Interstitial water composition was shown to be consistent with authigenic formation of I/S.

Transport of trace elements in ecosystems of the Barhalde watershed in the southern Black Forest.

Concentrations of trace elements and macroelements in rainfall, canopy drip, runoff, and soil solution have been determined each week at four free-drained and three hydromorphic sites at an altitude of 1000–1300 meters above sea level in the very humid, cool Black Forest. Among these elements, the turnover of beryllium, cadmium, copper and lead are discussed in detail. Beryllium had the lowest input and the highest output of these four elements. It was primarily mobilized in the mineral topsoil, and only a small amount was readsorbed by humic acids or subsoil or taken up by plants. Lead concentrations were highest in precipitation, but only about 5 percent of the input appeared in the output. Cadmium, Cu, and Pb were all adsorbed by the humus and iron oxide accumulation horizons of podzols and Ockererde. Copper was adsorbed in all soils except podzols, and fixation of Cu was especially obvious in the Ockererde. Cadmium was not highly adsorbed in mineral soil. The recent increase in atmospheric input resulted in an enrichment and rise of turnover for Cd, Cu, and Pb throughout the watershed.

Palygorskite-cemented crusts (palycretes) in Southern Portugal.

In the Oriola depression of Southern Portugal near the town of Evora, field examinations revealed the presence of Tertiary sedimentary deposits that had the consistency of duricrusts. These duricrusts, occurring close to the land surface, were examined in the field as well as in the laboratory, with the objective of establishing their composition and formation. Micromorphological examinations showed that the duricrusts were composed of clasts of fine sand to fine gravel sizes cemented together by a matrix dominated by either palygorskite or carbonate. The matrix : clasts ratio varied from about 1 : 3 when the cement was carbonate, to 3 : 1 or higher when the matrix was palygorskite. Occasionally the ratio in the latter was even higher. The clasts consisted of quartz, feldspar, and some Mg-rich metamorphic minerals. The palygorskite matrix fibres were arranged in mats within which they had parallel orientation. The mats or ‘domains’, which had a length of 15–25 sm and a width of about 40 sm, showed random orientation. In analogy to the term ‘calcrete’ the term ‘palycrete’ is used for the palygorskite duricrusts. The palycrete, of an average thickness of 0.5 m, frequently rested directly on the Hercynian basement rocks, and was covered by a recent solum. In the B horizons of the solum, the palygorskite appeared to undergo recent weathering and transformation into smectite. The duricrusts were proposed to have formed by authigenic calcite or palygorskite, which filled the interstices between clastic particles that had been deposited on Hercynian basement rocks following their peneplanation in the early Tertiary. The proposed environment of deposition and formation was that of an intermittent playa-lake in a semi-arid, seasonal climate, where strong evaporative processes had been active. Alteration and weathering of the mafic minerals contained in some of the clasts, in addition to interstitial solutions rich in Si and Mg, had created the chemical environment required for palygorskite neoformation. From the state of weathering–disintegration of the palygorskite in the soils formed on the palycrete, it is inferred that the environment for palygorskite neoformation had ceased to exist after palycrete formation.

Mineral and elemental distribution in soils formed on the River Niger floodplain, eastern Nigeria

Studies of mineral distribution in soils provide vital information for understanding the genesis of the soil. We studied the soils formed on the floodplain of the River Niger to determine the occurrence, distribution, and weathering transformations of minerals in a soil chronosequence in eastern Nigeria. Five soil profiles representing 5 depositional stages were studied. The soils have aquic moisture regimes and an isohyperthermic temperature regime by Soil Taxonomy. Gleysation due to poor drainage is very dominant. The soils are low in pH, organic matter, and exchangeable cations. Plinthisation and ferralitisation resulting in high values of Fe2O3 and Al2O3 were observed in the coarse sand, while in the fine sand fractions, quartz and feldspar grains have accumulated with mica being next in abundance. The occurrence of expansible minerals and kaolinite in the clay fractions is as a result of transformation of mica and feldspars giving rise to these minerals. We postulate that the origin and abundance of K2O and MgO in the clay fractions were from the breakdown of the structural units of the expansible minerals, micas and feldspars. Illite undergoes a transformation process to expansible minerals, while kaolinitisation is the major process in the clay fractions. Principal component analysis shows that 23 mineral variables which relate with kaolinite and other silicate clays can be reduced to 5 principal components.

Clay Dispersion of Hardsetting Inceptisols in Southeastern Nigeria as Influenced by Soil Components

Abstract Hardsetting soil properties are undesirable in agricultural soils because they hamper moisture movement and soil aeration. The soils of the floodplain of Niger River in eastern Nigeria hardsets upon drying, following dispersion, puddling, and slaking during the waterlogged period. Ten soil samples collected from a depth of 0–20 cm were analyzed for their properties. The soils are classified as Fluvaquentic Eutropepts or Dystric Gleysol (FAO). The objective was to investigate the influence of some soil properties on water‐dispersible clay (WDC) of the soils, which is the precursor of the hardsetting process. The total clay content (TC) correlated significantly with WDC (r=0.94**), whereas the water‐dispersible silt (WDSi) was higher than its corresponding total silt content. The WDC showed a positive correlation with dithionite extractable Fe (Fed), Al (Ald), and oxalate extractable Fe (Feo) (r=0.75*, 0.89**, and 0.76* respectively). Exchangeable Mg2+ correlated significantly with WDSi (r=0.70). Principal component analysis of the soil variables indicates that 15 soil components, which influence WDC as hardsetting properties, were reduced to 5 orthogonal components. The parameters that influence hardsetting properties are exchangeable Na+, K+, Ca2+, Mg2+, Fed, Alo, and Feo. Other soil properties are kaolinite, smectite, illite, and WDC, including soil organic carbon (OC), electrical conductivity (EC), and ESP. Therefore, those soil properties, which explain hardsetting characteristics most, are exchangeable Na+, Fed, OC, Mg2+, and Alo. There are negative consequences on the erodibility, runoff, infiltration and tillage of the soils at both submerged and dry conditions due to clay dispersion, low OC, and hardsetting behavior of the soil.

Formation of mineral N (NH4+, NO3-) during mineralization of organic matter from coal refuse material and municipal sludge.

In 1994, the 14 hectare plateau of a coal refuse bank in Landsweiler-Reden (Southwest-Germany) was covered with a mixture consisting of 80% (v/v) refuse materials, 10% (v/v) composted wood and 10% (v/v) of sewage sludge as part of a reclamation project. The amount of sludge dry matter applied was approximately 450 Mg ha−1 to a depth of 2 m. The approximate amount of nitrogen (N) applied with the substrate was 20 Mg ha−1 (total N). From April 1996 until November 1997, contents of mineral nitrogen and nitrogen mineralization were monitored down to a depth of 2 m. Nitrogen mineralization was monitored by means of a modified buried bag procedure using a retrievable cylindrical receptacle. The contents of NH4+- and NO3−-N were largest at the beginning of the observation period, reaching a peak value of 650 kg ha−1 in May 1996. Then, mineral N stabilized in 1997 at a level of 200 kg N ha−1, with the soil profile below 150 cm contributing about 75% to this amount. Net nitrogen mineralization was characterized by the same depth distribution. Other than in surface horizons, mineralization activity at the bottom of the profile continued into 1997 with the same intensity as in 1996. Variability among replicate buried bag incubations was high (CV > 100% on several occasions). Nitrogen loss through leaching was estimated at 630 kg N ha−1 over the observation period, averaging at 360 kg N ha−1 a−1. The reclamation procedure used in this study may have the potential to contaminate ground water in hydrologically sensitive areas. Stickstoffumsatz in einem Rekultivierungssubstrat aus Bergematerial, Holzkompost und Klarschlamm 1994 wurde das 14 Hektar grose Plateau der Bergehalde Landsweiler-Reden im Zuge einer Rekultivierungsmasnahme mit einer Mischung aus 80 Vol.-% Bergematerial, 10 Vol.-% Holzkompost und 10 Vol.-% Klarschlamm bedeckt. Dabei wurden etwa 450 Mg ha−1 Klarschlamm bis in eine Tiefe von 2 m eingebaut. Die dabei ausgebrachte Gesamtstickstoffmenge betrug etwa 20 Mg ha−1. In diesem Substrat wurden Mineralstickstoffgehalte und die Stickstoffmineralisation wahrend des Zeitraumes von April 1996 bis November 1997 bis in eine Tiefe von 2 m beobachtet. Dies geschah mit Hilfe der „buried bag”-Methode unter Verwendung einer herausnehmbaren zylindrischen Brutkapsel. Die Gehalte an NH4+ und NO3− waren zu Beginn der Beobachtungsphase am hochsten, der Spitzenwert betrug 650 kg N ha−1 im Mai 1996. Der Mineralstickstoffgehalt stabilisierte sich wahrend des Jahres 1997 bei 200 kg N ha−1. Der Profilbereich tiefer als 150 cm hatte daran einen Anteil von 75%. Die Nettostickstoffminera lisation war durch einen gleichgerichteten Trend gekennzeichnet. Im Gegensatz zu den Oberflachenhorizonten war die Mineralisa tions aktivitat in den tiefen Bereichen des Profils im Jahr 1997 ebenso hoch wie im Jahr 1996. Die Variabilitat zwischen den Einzelinkubaten war hoch (Variationskoeffizient an mehreren Terminen > 100%, n = 20 pro Tiefe). Stickstoffverluste mit dem Sickerwasser wurden fur die gesamte Beobachtungsphase mit 630�kg N ha−1 (entsprechend 360 kg ha−1 a−1) geschatzt. Das hier benutzte Rekultivierungsverfahren kann daher nicht zur Anwendung in hydrologisch sensitiven Bereichen empfohlen werden.

Mineralogy and geochemical properties of some upland soils from different sedimentary formations in south-eastern Nigeria.

Geochemical and mineralogical properties of soil can be used to assess their agricultural productivity potential. Ten soils from 4 geological formations in the south-eastern Nigeria were studied. Soil samples were taken from typical A and B horizons from each soil. The soil properties assessed were the free forms of Fe and Al, particle size distribution, total elements, and clay mineralogy. The soils are deep and highly weathered. Crystalline Fe and Al were more dominant than amorphous or less crystalline forms. The geochemical properties of the soils are dominated by SiO2, Al2O3, and Fe2O3, whereas MgO, TiO2, and ZrO2 occur in moderate to low quantities. Other basic elements such as Na2O, K2O, and CaO are very low in the soils, with an insignificant role in their genesis. The low contents of these elements in the soil may be the cause of their low nutrient release and storage in the soil. Ferritisation, laterisation, and kaolinitisation are the major pedogenic processes in the soil. The dominant clay mineral in all the soils was kaolinite; other minerals present though less common were illite, vermiculite, and smectites. Based on elemental contents and clay mineralogy, the soils can be grouped into 3 distinct groups: those with only kaolinite, illite, and vermiculites; and those that also contain smectite. These groupings can indicate the agricultural fertility potential.

Auftreten und verbreitung von lösslehmbeimengungen in periglazialen schuttdecken des schwarzwaldwestabfalls

Abstract This work was done in three different research areas In order to determine the loess content in the periglacial strata, there has been taken a profile catena on gneis, granite and ignimbrite as solid rock. At first the rock material including the loess of the upper Rhine plain was described. The admixed loess in the layered solifluction profiles was qualitatively and quantitatively determined by its differentiating values By grain-size-distribution the “total loess” including far and local transport was calculated. Because the “far transported loess” differes in geochemical values and heavy minerals it was possible to select it from the local loess The maximum in loess content was found in the so called Hauptfolge (main series) of the Periglacial. The “Decksediment” (top layer) has got similar contents but is less important because of his minor thickness and smaller spread. The dense “Basisfolge” (basic series) is almost free of loess The amount of far transported loess in a distance of 1 km from the glacial terrace of the Rhine is about 1000 kg/m 2 (300 m above sea level). It decreases sharp into the mountains and reaches at 1000 m and 12 km from the plain the detection limit of about 30 kg/m 2 . The local component in contrary is not important on the lower slopes and has its maximum of 150 kg/m 2 at the mountains top (1300 m, 15 km). According to this features total loess has a minimum in an altitude between 800 and 1000 m. At the footslope of Black Forest loess accumulation was favoured at least at the end of the last glacial period. On the mountains kryoclastic silt production and local transport have been more important.

Genesis and diagenesis of paleosols from Pliocene volcanics on the Golan Heights

Pedogenesis and diagenesis of paleosols that are intercalated amid basalt flows of Late Pliocene age (∼ 3.7-3.1 m.y.B.P.) have been studied on the southwestern slopes of the Golan Heights. The data obtained suggest that environmental conditions resembled present-day ones, being characterized by a warm climate with seasonal moisture contrasts. All soils show evidence of redeposition as well as stratification of the parent material. On very low relief sites, vertisols with a large content of smectitic clay, influenced by aeolian deposition with a large content of smectic clay formed. Rubefaction took place, as well as clay translocation and possibly also carbonatisation. The burial of the soils by lava flows resulted in partial erosion and distinct fritting, indicated by compaction, cementation and hematization. After burial, various types of alteration affected the soils, such as clay illuviation, strong carbonatisation, and tectonic movements. Pedogenic features were preserved very well, but have subsequently been overprinted by diagenetic processes, especially carbonate precipitation. e414C ages of the carbonates indicate continuous rejuvenation by meteoric moisture. Persistence of smectite indicated that conditions affecting soil solution chemistry had not changed significantly since burial.

Zur pedochemie des berylliums — untersuchungen einer bodengesellschaft im gebiet des bärhaldegranits (südschwarzwald)

The profile distribution of Be is given for a toposequence of podzols, brown earths, stagnogley, forest bog and “Ockererde” (slope gley with infiltrated Al, Mn and Fe). Analysed were the parent rock, fine earth, four fractions of mineral soil (fine skeleton, sand, silt, clay) and the needles of spruce trees. Beryllium is involved in selective weathering processes of elements. Accordingly, the Be-content increases from the fine skeleton to sand, rock, silt and clay, progressively. Through pedogenetic enrichment, Be accumulates in the mica-rich silt fraction. Uptake of Be by spruce is very low even from these acid soils. The accumulation in the needles becomes greater with increasing age. The pedochemical behaviour of Be is very similar to that of Al. Be is incorporated very little in the organic matter cycle, and is therefore not enriched in the soil humus. The brown earth has lost Be, especially in the Ah-horizon. In the Ae-horizon of the podzol, loss of Be is even greater; the loss is partly offset by Be-enrichment in the B-horizon. In the profiles of depressions, the Be-content is high and is ascribed to lateral flow from the slopes. Be-enrichment is especially high in horizons with a pH of about 5. The Be-balance of the watershed indicates an export of about 10% of the original amount.