Die Dehydrogenase-Aktivität rezenter Unterwasserböden

The dehydrogenase activity in recent underwater soils The figures for present dehydrogenase activity (DHA) in recent carbonaceous underwater soils of small rivers usually are below those of neutral arable soils with a good nutrient status. No dependence was found between DHA and organic matter or nutrient contents. The amount of formazan formed by chemical reduction of triphenyl tetrazolium chloride (TTC), becomes more important with increasing depth, whereas DHA shows no distinct depth function.     

Die analytische Bestimmung der Dehydrogenaseaktivität in Unterwasserböden

The analytical determination of dehydrogenase activity in underwater soils The determination of dehydrogenase activity in recent underwater soils is often troublesome, because of lack of homogeneity of the fresh samples. Mainly the occurrence of very low redox potentials in the lower horizons causes chemical reduction of triphenyl tetrazolium chloride (TTC), which gives misleadingly high dehydrogenase activities. This could be eliminated by a toluene treatment preceding the TTC incubation, by which bacterial dehydrogenase production is inhibited and chemical TTC reduction can be determined. Homogeneity is increased by intensive stirring immediately before weighing the aliquots.     

Quantitative Erfassung der reduzierten Substanzen in Unterwasserböden

Quantitative determination of reduced substances in subhydric soils The determination of reduced substances is possible by rapid oxidation with a diluted potassium dichromate/sulfuric acid solution at room temperature, and subsequent titration with FeSO₄ solution. These values (meq/100 ml of fresh sample) show a nonlinear, negative correlation with redox potential, and increase with increasing content of organic material. Sulfides, expressed as FeS, amount to appr. 50 % of the reduction equivalents. Subhydric soils rich in nutrients show an increasing amount of reduced substances with increasing depth, whereas oligotrophic and mesotrophic soils give no distinct depth function.     

Die Sorption von Phosphat an carbonatreichen Unterwasserböden

The sorption of phosphate by underwater soils rich in carbonate The phosphate sorption isotherms for carbonate rich under water soils (Unterwasserboden) can frequently be linearized by a modified Freundlich-isotherm when one assumes that, because of previously sorbed phosphate, the concentration of the equilibrium soil solution, P_1,0 is greater than 0. However, in many cases, the character of the phosphate sorption can be adequately determined with only one phosphate addition (P_s,500). Both methods show that for dried samples from under water soils, the samples from reduced horizons have a higher P sorption than for the associated oxidized horizons. This can be explained by the presence of very sorption active ferrihydrite which has precipitated from previously biologically reduced material.     

Bestimmung der Harnstoffabbaurate in Land- und Unterwasserböden nach verschiedenen Methoden

Determination of urease activity by two different methods in some soils and underwater soils Two methods differing in microbial activity during incubation with urea were used for the determination of urease activity. The results obtained showed a better relationship with natural conditions such as pH, organic substance-, or clay content, if the microbial activity was not inhibited during incubation. This effect was found to be particularly pronounced in underwater soils, where addition of a bacteriostatic substance (toluene) resulted in practically uniform values that reflected neither bacterial nor nutrient status.     

Modellversuche zur Phosphatsorption von Unterwasserböden unter oxidierenden und reduzierenden Bedingungen

Model experiments on phosphate Sorption by river sediments under oxidizing and reducing conditions. During intensive reduction by sodium dithionite, phosphate sorbing river sediments often show a pronounced desorption of phosphate. Reoxidation by air causes an increase in phosphate sorption up to five times the original value, the height being linearly related to the ferric oxide content (Fe_d) of the sample. A possible explanation for this phenomenon is the oxidative precipitation of iron(III) oxides with high surface area being very active in phosphate adsorption.     

Analytische Bestimmung und Fraktionierung von Cu,Zn, Pb,Cd, Ni und Co in Böden und Unterwasserböden

Analytical methods for determination and fractionation of Cu, Zn, Pb, Cd, Ni, and Co in soils and underwater soils Using a wet oxidation procedure with mixtures of strong acids, even samples rich in both organic carbon and carbonate could be dissolved quantitatively in platinum crucibles. Fractionation of trace elements was performed by extraction with oxalate (boiling and at room temperature), and with EDTA. Analytical problems (mainly by contamination) could be eliminated by simple preventive arrangements.     

Simulation des Anionen-Transports in ungestörten Bodensäulen unter stationären Fließbedingungen

Simulation of anion transport in undisturbed soil cores under steady-state flow conditions Miscible displacement experiments with undisturbed soil columns were carried out in the laboratory. Objective of the experiments was to collect information about the transport of Cl^? and NO₃^? through field soils. The experiments were carried out with a forest soil and an agricultural soil. The flow velocity of the chloride and the nitrate solution was either 1 cm/day or 0,3 cm/day. Of each soil there were 5 replicates. The effluent of each of the columns was analyzed and the collected data were used for model calculations. It was found that the breakthrough curves of Cl^? and NO₃^? were similar in shape. For the well-aggregated forest soil the apparent diffusion coefficient was much larger than for the agricultural soil. For both soils practically all of the chloride could be recovered in the effluent, but for nitrate considerable losses within the soil column were noted. It was also found that the chloride breakthrough could be described with a simple convection-dispersion equation. However a reduction of the total pore space, accounting for anion exclusion, was needed. Furthermore it was observed that for nitrate an additional sink term in the convection-dispersion equation was needed to account for the observed nitrate losses. It appears that the transport of nitrate and chloride through the soils that were studied can be described mathematically, provided the anion exclusion space and the rate of nitrate losses are known. The nature of the anion exclusion and the nitrate transformation needs further study.     

Wasserspannungsabhängiger Eindringwiderstand von Modellböden

The resistance to penetration of model soils depending on water tension The device used for measuring resistance to penetration (Becher 1978b) allows to measure varying resistances corresponding to differences in texture, bulk density and moisture. Model soils consisting of varying layers of sand (0,2–0,5 mm) and silt (～ 10–60μm) were equilibrated with water tensions ranging from 20 to 600 cmH₂O. The resistances to penetration measured after equilibrium were significantly influenced by water tension corresponding to second power regressions. The extrema of these regressions being found between 250 and 350 cmH₂O water tension were always maxima for silt and in most of the cases minima for sand regardless of thickness and arrangement of the textural layers. Moreover, silt showed an overall higher resistance to penetration (30 kp/cm²) than sand (15 kp/cm²). The interaction between unwieldiness of soil particles, cohesive and adhesive forces, and rate of change of negative pore water pressure (= water tension) probably causes at the same tension the differences of friction and resistance to penetration as stated for sand and silt.     

Erodibilität repräsentativer Böden der Hallertau

Erodibility of representative soils of the Hallertau (South Bavaria) Differences between the USA and the Federal Republic of Germany in geology, soil types, and climate necessitate to verify the erodibility of the soils estimated according to Wischmeier and Smith (1978), when using the Universal Soil Loss Equation under local conditions. The erodibility of 5 representative soils of the region Hallertau within the so-called “Unterbayerisches Hügelland” was checked by measuring soil losses using a laboratory rainfall simulator. The estimated and measured erodibilities for two Aquic Hapludalfs from loess and one Ruptic-Alfic Eutrochrept from Tertiary sand compared very well as shown by coefficients of regression of 1. The estimated erodibilities for a Typic Eutrochrept and an Aquic Chromudert, both from Tertiary materials, however, underestimated the soil losses by a factor of 1.5. For all regressions the coefficients of correlation were 0.90. Due to the small number of soils checked, it is only possible to suggest causes for the observed deviations, particularly since the aggregate stability could not be the only property, as demonstrated by measurements.     

Periodische und aperiodische Veränderungen in den Eigenschaften junger Marschböden im Deichvorland

Periodical and aperiodical changes of properties of young marshland soils seawards the dike The changes of properties of young marshland soils searwards the dike were investigated (1.) throughout the year, (2.) after storm tides, long drought periods and intensive rainfalls, and (3.) in the course of the low-high tide cycle. - In each case the relative cation distribution of the saturation extract remained constant. The relative distribution of the mobile cations remained also constant within the low-high tide cycle, white it shows fluctuations with a deviation of up to 16 % from the mean Na-content within the oneyear investigation and up to 28 % after extreme climatic or storm tide conditions. The annual salt fluctuations were determined to be at least 60–80 %. The deviations from the mean salt content were at least 100 % after storm tides and long drought periods (extreme deviation of 370 % within the first 1–3 cm soil) and partly also after heavy rain. The redox conditions remained constant within the low-high tide cycle, whereas they differed to a small extent following extreme climatic or storm tide conditions. With values of 0.4–0.9 the soils showed a small spectrum of different Ca/Mg ratios. Moreover, the determined annual fluctuation of the Ca/Mg ratios showed that the Ca/Mg ratio is not a suitable classification criterion.     

Genese und Ökologie innerstädtischer Böden aus Bauschutt

Formation and ecology of rural soils from debris Within 30 years Rendzinas have developed on habitats of debris and rubbles in West-Berlin by accumulation of organic substances, carbonate impoverishing, slightly beginning acidity, and biogenic structuring. Their conditions for water, air, and nutrients were investigated for 2 years.     

Schadstoffpotential technogener Substrate in Böden urban-industrieller Verdichtungsräume

Potential of contamination of technological substrates in soils of urban and industrial environments The soils of urban and industrial environments are often present in form of anthropogenic Deposols made of natural and technological substrates. The admixture of technological substrates can be connected with the accumulation of contaminants. On the basis of extensive investigations in the central Ruhr area and literature studies the contamination level (parameters: As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, Benzo(a)pyrene, Σ PCB) of the different technological substrates is characterized. The volume of data permits to establish an assessment scheme for the contamination level of technological substrates with a five stage scale (very low, low, middle, high, very high).     

Torfeigenschaften und ungesättigte hydraulische Leitfähigkeit von Moorböden

Peat properties and unsaturated hydraulic conductivity of peat soils . Drainage of organic soils is closely connected with water supply of plants by the capillary fringe of the groundwater. Unsaturated flow of water was measured by the double-membrane apparatus described by Vetterlein, which was modified for experiments with undisturbed peat samples. The influence of decomposition, nature of peat, ash content, bulk density (consolidation) and flux direction on unsaturated flow of water in peat soils was determined. The correlation to unsaturated water conductivity decreased in the sequence: decomposition, flux direction, ash content, bulk density. A dependence on bulk density exists only below pF 2.