Mixing of different mineral soil layers by endogeic earthworms affects carbon and nitrogen mineralization

The effect of the endogeic earthworm species Octolasion tyrtaeum (Savigny) on decomposition of uniformly ¹⁴C-labelled lignin (lignocellulose) was studied in microcosms with upper mineral soil (Ah-horizon) from two forests on limestone, representing different stages of succession, a beech- and an ash-tree-dominated forest. Microcosms with and without lower mineral soil (Bw-horizon) were set-up; one O. tyrtaeum was added to half of them. It was hypothesised that endogeic earthworms stabilise lignin and the organic matter of the upper mineral soil by mixing with lower mineral soil of low C content. Cumulative C mineralization was increased by earthworms and by the addition of lower mineral soil. Effects of the lower mineral soil were more pronounced in the beech than in the ash forest. Cumulative mineralization of lignin was strongly increased by earthworms, but only in the beech soil (+24.6%). Earthworms predominantly colonized the upper mineral soil; mixing of the upper and lower mineral soils was low. The presence of lower mineral soil did not reduce the rates of decomposition of organic matter and lignin; however, the earthworm-mediated increase in mineralization was less pronounced in treatments with (+8.6%) than in those without (+14.1%) lower mineral soil. These results indicate that the mixing of organic matter with C-unsaturated lower mineral soil by endogeic earthworms reduced microbial decomposition of organic matter in earthworm casts.     

Correlation of acrylamide generation in thermally processed model systems of asparagine and glucose with color formation, amounts of pyrazines formed, and antioxidative properties of extracts

The relations between the formation of acrylamide and color, pyrazines, or antioxidants in an asparagine/d-glucose browning model system under various conditions were investigated. The highest level of acrylamide was produced in the asparagine/glucose (1:3) system heated at 170 degrees C for 30 min (2629 microg/g asparagine). Color intensity increased with temperature and heating time. The formation of pyrazines increased steadily with an increase of temperature (140-170 degrees C) and heating time (15-60 min). Antioxidant formation varied among the samples heated under different conditions. A clear correlation between formation of acrylamide and browning color was obtained. The formation of acrylamide was linearly correlated with the formation of total pyrazines during the initial stages of the Maillard reaction. No obvious correlation between formation of acrylamide and antioxidants was observed. However, excess amounts of asparagine increased the formation of antioxidants, whereas excess amounts of glucose reduced its formation.     

Changes in the succession and diversity of protozoan and microbial populations in soil spiked with a range of copper concentrations

We studied microbial and protozoan activity, diversity and abundance as affected by Cu²⁺ amendments ranging from 0 to 1000 μg g⁻¹ over a 70-day period. At the end of the experiment the microbial population size, as indicated by substrate-induced respiration, had normalized for all Cu²⁺ concentrations, but 1000 μg g⁻¹. Protozoan abundance was negatively affected by Cu²⁺, although, only in the first few weeks. A more detailed analysis of the individual components that make up the microbial and micro-faunal populations (phospholipid fatty acid (PLFA) profile and protozoan morphotypes), however, yielded a somewhat more complex picture. For the three highest Cu²⁺ amendments (160, 400 and 1000 μg g⁻¹), there still was a significant reduction in number of differentiable protozoan morphotypes. The bacterial PLFA pattern suggested a shift from Gram-negative towards Gram-positive bacteria for the high amendments, a process where protozoan grazing most likely played a significant role. The ratio of the trans/cis isomers of the 16:1ω7 fatty acid indicated that Cu²⁺, even at low and medium concentrations, induced physiological changes in the microbial population. The relatively slight changes in total microbial and micro-faunal abundance and activity, also at the highest Cu²⁺ concentrations, probably reflected the ability of the community to compensate for loss of taxa by functional substitution.     

Aspects of phytoremediation of organic pollutants

Phytoremediation is a quite novel technique to clean polluted soils using plants. In theory, phytoremediation methods are cheap, are accepted by the public and, compared to physical or chemical approaches, are ecologically advantageous. Until today, however, there are only a few examples of successful applications. One reason is that the processes involved are complex, and a full clean up may require many years. Plants affect the water balance of a site, they change redox potential and pH, and stimulate microbial activity of the soil. These indirect influences may accelerate degradation in the root zone or reduce leaching of compounds to groundwater. Compounds taken up into plants may be metabolised, accumulated, or volatilised into air. Based on these processes, several phytoremediation methods have been developed: Phytoextraction, rhizofiltra-tion, phytostabilisation, rhizo and phytodegradation, pump and tree, land farming, phytovolatilisation, hydraulic control and more. Already in use are plants (and here willow, poplar and grass) for the degradation of petroleum products, aromatic hydrocarbons (BTEX), chlorinated solvents, explosives and cyanides. However, phytotoxicity and pollutant mass balances were rarely documented. Often, the success of the projects was not controlled, and only estimates can be made about the applicability and the potential of phytoremediation. This lack of experience about possibilities and limitations seems to be a hindrance for a broader use of these techniques.     

Quantitative Mineralbestimmung in der Schlufffraktion von Böden auf der Grundlage der chemischen Analyse und unter Anwendung der Karl-Fischer-Titration. I. Verfahren

Quantitative estimation of the mineralogical composition of silt fractions of soils based on both, chemical analysis and application of Karl-Fischer-titration. I. Method This paper describes a method for calculating the mineralogical composition of the silt fractions of soils. The chemical analysis and the temperature dependence of water release are used for determining micas and feldspars, each in three components in a relatively short procedure. The release of water was measured by Karl-Fischer-titration at controlled temperatures. At temperatures above 550°C the water release of the particle size fractions correlates with their content of micas. The quantity of micas can be obtained from the amount of released water and the results of the chemical analysis. The influence of kaolinite, amphibole and the fluoride content on the calculation is described. By considering the potassium content of the mica fraction results of the chemical analysis are used to quantify feldspars.     

Statistical Modeling of the Partitioning of Nonylphenol in Soil

Partition coefficients K _P of nonylphenol (NP) in soil were determined for 193 soil samples which differed widely in content of soil organic carbon (SOC), hydrogen activity, clay content, and in the content of dissolved organic carbon (DOC). By means of multiple linear regression analysis (MLR), pedotransfer functions were derived to predict partition coefficients from soil data. SOC and pH affected the sorption, though the latter was in a range significantly below the pK_a of NP. Quality of soil organic matter presumably plays an important but yet not quantified role in sorption of NP. For soil samples with SOC values less than 3 g kg^?1, model prediction became uncertain with this linear approach. We suggest that using only SOC and pH data results in good prediction of NP sorption in soils with SOC higher than 3 g kg^?1. Considering the varying validity of the linear model for different ranges of the most sensitive parameter SOC, a more flexible, nonlinear approach was tested. The application of an artificial neuronal network (ANN) to predict sorption of NP in soils showed a sigmoidal relation between K _P and SOC. The nonlinear ANN approach provided good results compared to the MLR approach and represents an alternative tool for prediction of NP partitioning coefficients.     

Comparison of the chemical composition of extracts from Scutellaria lateriflora using accelerated solvent extraction and supercritical fluid extraction versus standard hot water or 70% ethanol extraction

The aqueous extract of American skullcap (Scutellaria lateriflora L. (S. lateriflora), Lamiaceae) has been traditionally used by North American Indians as a nerve tonic and for its sedative and diuretic properties. Recent reports stated that flavonoids and possibly amino acids are responsible for the anxiolytic activity. As a part of our search for environmentally friendly solvents to extract the active components from medicinal plants, we used S. lateriflora in a comparison of accelerated solvent extraction (ASE) using water, and supercritical fluid extraction (SFE) using CO2 and 10% EtOH as modifier, at different temperatures. Flavonoids and amino acids were quantified by HPLC-UV and HPLC-MS, respectively. The flavonoid content was compared with conventional extraction methods (hot water extraction and 70% ethanol). The use of ASE at 85 degrees C with water as solvent gave the best results for flavonoid glycosides and amino acids, whereas SFE gave higher yields of flavonoid aglycones. However, the results obtained for total flavonoids were not significatively superior to hot water extraction or 70% aqueous EtOH extract.