Über die Aggregatdichte und deren mögliche Auswirkung auf den Bodenlösungstransport

On the bulk density of aggregates and its possible impact on the movement of soil solutions The bulk densities of the aggregate fractions 15-18 mm, 10-15 mm, 5-10 mm, and 3-5 mm from a Typic Hapludalf, an Aquic Hapludalf, and a Typic Chromudert, all used as cropland and grassland, and that of aggregates of the 3-5 mm fraction from a Typic Dystrochrept used for a farm manure and crop residue trial, lay between 1.8 and 2.0 g/cm³. Sampling was done down to depths of 85 cm, 70 cm, 55 cm, and 80 cm. respectively. The bulk density values increase in most cases with decreasing aggregate size and indicate the aggregate pore volumes to generally range from 25 to 35% b.v. This means that either soil aggregates often contain only fine pores or that fine and medium pores also act as inter-aggregate pores. As a consequence, movement and exchange of soil water and soil solution between inter- and intra-aggregate pores is severely restricted.     

Metal fluxes to Swedis forest lakes

Data on atmospheric deposition, transport via run-off water and contents in soil were used to estimate the fluxes of Zn, Cd, Cu, Pb, and Hg to Swedish forest lakes. The calculations refer to a hypothetical lake with a surface area of about 9% of the total catchment area. There are clear differences in the pathways and transport mechanisms for the different elements. The dominating pathway for the input of Zn and Cd to lakes is via run-off from the drainage area. About 60 to 95% of the total load comes from run-off, highest in the acidified areas. The acidification status of the soil is by far the most important factor regulating the mobility of these elements. The amounts of Hg and Pb deposited on the drainage area are mainly accumulating in the surficial soil layers. The transport of these elements is primarily associated with humic substances. About 30 to 50% of the total load of Pb and 25 to 75% of the total load of Hg to lakes originates from run-off. The transport mechanisms for Cu are similar to those of Pb and Hg, but due to the lower anthropogenic airborne load, the direct deposition is of less importance.     

Biodegradation measurements confirm the predictive value of the O:C‐ratio for biochar recalcitrance

Suitable predictors of degradability are sought to support the identification of biochars with large potential to increase C sequestration in soils. We determined the biodegradation of 9 chars from hydrothermal carbonization and pyrolysis in two agricultural soils. The 200‐ and 115‐day degradation correlated strongly with the O:C‐ and slightly with the H:C‐atomic ratio of 9 and 14 biochars, respectively. Highest temperature treatment and ash content did not show similar correlations.     

Die Bedeutung der Festigkeitsverteilung in Einzelaggregaten für den Wasser- und Stofftransport im Boden

Relevance of strength distribution within aggregates to the movement of soil water and soil solution Different transport processes exist not only between the total soil and single aggregates, but also within individual aggregates. To clarify the structure of single aggregates without thin-sectioning, resistance to penetration was repeatedly measured on the same aggregate at a predefined soil water tension. The aggregates were sampled from the G_{o 2} horizon of a Typic Fluvaquent (Φ 15-25mm) and from the B_{g 2} horizon of an Aquic Chromudert (Φ 30-50mm) and equilibrated with water tensions ranging from roughly OhPa to 1000hPa. The strength distributions within individual aggregates were calculated using penetration resistance values of all measurements on one aggregate at a single water tension. These distributions, as exemplified by those at 300hPa and 1000hPa. show that the aggregates are surrounded by a thin, but very strong mineral skin which may be discontinuous, especially for aggregates from the Aquic Chromudert soil. In these aggregates, slickenside-like friction planes were found to penetrate through the skin. The deviation in the skin composition from that of the inner-aggregate described in literature, together with the finding of its strength, suggest that the exchange of water and solutes between the inter-aggregate and intra-aggregate pores is strongly impeded. The weaker parts within the skin, however, must be interpreted as preferred pathways, perhaps resulting in some fingering within aggregates at the prevailing matrix potential. The significance of different pathways within aggregates for the general transport of matter in soils is briefly discussed.     

Die Neugestaltung der Forstwissenschaft in der Ostmark im Geiste des Nationalsozialismus

Ohne Zusammenfassung     

Forstmeteorologische Messungen in einem Eichenbestand

Ohne Zusammenfassung     

Phosphorus accumulation and leaching risk of greenhouse vegetable soils in Southeast China

Over-fertilization has caused significant phosphorus(P) accumulation in Chinese greenhouse vegetable production(GVP) soils. This study, for the first time, quantified profile P accumulation directly from soil P measurements, as well as subsoil P immobilization, in three alkaline coarse-textured GVP soil profiles with 5(S5), 15(S15), and 30(S30) years of cultivation in Tongshan, Southeast China. For each profile, soil samples were collected at depths of 0–10(topsoil), 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Phosphorus accumulation was estimated from the difference in P contents between topsoil and parent material(60–100 cm subsoil). Phosphorus mobility was assessed from measurements of water-soluble P concentration(PSol). Finally, P sorption isotherms were produced using a batch sorption experiment and fitted using a modified Langmuir model. High total P contents of 1 980(S5), 3 190(S15), and 2 330(S30) mg kg~(-1) were measured in the topsoils versus lower total P content of approximately 600 mg kg~(-1) in the 80–100 cm subsoils. Likewise, topsoil PSol values were very high, varying from 6.4 to 17.0 mg L~(-1). The estimated annual P accumulations in the topsoils were 397(S5), 212(S15), and 78(S30) kg ha~(-1) year~(-1). Sorption isotherms demonstrated the dominance of P desorption in highly P-saturated topsoils, whereas the amount of adsorbed P increased in the 80–100 cm subsoils with slightly larger P adsorption capacity. The total P adsorption capacity of the 80–100 cm subsoils at a solution P concentration of0.5 mg L~(-1) was 15.7(S5), 8.7(S15), and 6.5(S30) kg ha~(-1), demonstrating that subsoils were unable to secure P concentrations in leaching water below 0.5 mg L~(-1) because of their insufficient P-binding capacity.     

3D simulation of the permeability tensor in a soil aggregate on basis of nanotomographic imaging and LBE solver

Purpose  

The purpose of this hydropedological work is to investigate the feasibility of a method to calculate permeability of soil peds on the matrix pore scale resolution. This paper focuses on imaging of the intra-aggregate microstructure and, based on the three-dimensional (3D) images, quantification of the pore network connectivity and permeability tensor. Finally, lattice Boltzmann equation (LBE) simulations of Navier–Stokes flow in the thus derived pore network allow to compute the heterogeneous 3D flow velocity field.