Effects of temperature regime on the respiratory activity of developmental stages of Lumbricus rubellus (Lumbricidae)

Rates of carbon dioxide production of cocoons, juveniles and matures of Lumbricus rubellus were measured at five constant (2°C, 5°C, 10°C, 15°C, 20°C) and three diurnally fluctuating temperature regimes (0–10°C, 5–15°C, 10–20°C) covering the whole range of temperature conditions experienced by this species in forests in Central Germany. Respiration rates of developmental stages significantly increased with temperature both under constant and fluctuating regimes. Overall, at constant temperature regimes Q₁₀ values for cocoons, juvenile and mature earthworms were 1.6, 2.7 and 2.0, respectively. At fluctuating temperature regimes Q₁₀ values were generally higher with 2.4, 3.6 and 3.5 for cocoons, juvenile and mature earthworms, respectively. At the same mean temperature respiration rates at fluctuating regimes exceeded those at constant regimes in all developmental stages.     

Combined influence of NaCl and sucrose on heat-induced gelation of bovine serum albumin

The combined influence of a strongly interacting cosolvent (NaCl) and a weakly interacting cosolvent (sucrose) on the heat-induced gelation of bovine serum albumin (BSA) was studied. The dynamic shear rheology of 4 wt % BSA solutions containing 0 or 20 wt % sucrose and 0-200 mM NaCl was monitored as they were heated from 30 to 90 degrees C at 1.5 degrees C min(-)(1), held at 90 degrees C for 120 min, and then cooled back to 30 degrees C at -1.5 degrees C min(-)(1). The turbidity of the same solutions was monitored as they were heated from 30 to 95 degrees C at 1.5 degrees C min(-)(1) or held isothermally at 90 degrees C for 10 min. NaCl had a similar effect on BSA solutions that contained 0 or 20 wt % sucrose, with the gelation temperature decreasing and the final gel strength increasing with increasing salt concentration and the greatest changes occurring between 25 and 100 mM NaCl. Nevertheless, the presence of sucrose did lead to an increase in the gelation temperature and final gel strength and a decrease in the final gel turbidity. The impact of NaCl on gel characteristics was attributed primarily to its ability to screen electrostatic interactions between charged protein surfaces, whereas the impact of sucrose was attributed mainly to its ability to increase protein thermal stability and strengthen the attractive forces between proteins through a preferential interaction mechanism.     

Spatial changes of soil solution and mineral composition in the rhizosphere of Norway‐spruce seedlings colonized by Piloderma croceum

Ectomycorrhizae (ECM) or the root‐fungal association in forest ecosystems provide a unique soil microenvironment where soil properties and processes differ from the bulk soil. In this study, we would like to better understand the role of ECM systems in mineral weathering and its implications to soil formation and nutrient cycling in forest ecosystems. Specifically, we would like to document the spatial variations in the composition of soil solution and mineralogy of the rhizosphere as influenced by the ECM of Norway spruce + Piloderma croceum. Two‐month‐old seedlings of Norway spruce (control and colonized by P. croceum) were cultivated in special rhizotrons designed to allow spatial collection of soil solution. We used A and C horizons of a Dystric Cambisol collected from Höglwald forest near Munich. Micro suction cups (5 mm x 1mm) were installed in colonized and control rhizotrons, and soil solution was collected from September to November 2000. Our results show that the concentrations of NH , Ca²⁺, and Mg²⁺ in the soil solution were lower in <1.0 cm than in >3.0 cm distance from the roots of Norway spruce, due to the possible range of influence of Piloderma mycelium reaching about 2–3 cm from the surface of the mycorrhizal root. In the rhizotron with soil from the A horizon, a higher phosphorus content in Piloderma‐colonized seedlings was observed. X‐ray diffraction data indicate that chlorite and possibly mica are being transformed to 2:1‐expanding clay minerals (probably smectite) within <1.0 cm distance from roots. The spatial variations in soil solution composition and mineral transformation are likely to be due to Piloderma colonization and concentrated mycelial growth within <1.0 cm distance from the roots. This is also evident in more intricate growth of mycelia on surfaces of micaceous minerals as compared to quartz. We assume that Piloderma modifies soil solution and mineralogy through acquisition of essential elements for its own survival and/or for the uptake by plant roots. However, the presence of spontaneous infection with wildtype ECM in the control plots may have altered the influence of Piloderma and must be taken into consideration when interpreting our results.     

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.     

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.     

Little effect of forest age on oribatid mites on the bark of trees

This study investigates the effect of forest age (20-, 50-, 160-year-old, and primeval forest) on oribatid mite communities on the bark of oak trees in the National Park Pusza Białowieża in eastern Poland. We hypothesized that oribatid mite diversity on bark peaks at forests of intermediate age and that the number of parthenogenetic species of oribatid mites is highest in young stands. In contrast to these hypotheses, the diversity, density, number of juveniles, community structure and the mode of reproduction of oribatid mite species were not significantly affected by forest age. None of the oribatid mite species occurred exclusively on trees of a specific age. The results suggest that oribatid mite communities on the bark of trees are minimally affected by tree harvesting regimes. In contrast to oribatid mites in soil, communities on bark appear to be less sensitive to disturbances.     

In vitro bioaccessibility of soil-bound polycyclic aromatic hydrocarbons in successive digestive compartments in cows

Ruminants, which have a central place in the food chain, ingest soil that may contain pollutants. The bioaccessibility of three different polycyclic aromatic hydrocarbon compounds from soil was studied using an in vitro model based on the digestive tract of cows. For this purpose, pasture soil was spiked with (14)C radio-labeled compounds, aged, and then exposed to conditions which simulated the digestive compartments of the rumen, abomasum, and intestines. Our results show that aging generally reduced the bioaccessibility of all the compounds tested. Total bioaccessibilty in the first digestive compartment, i.e., the rumen, depended on the considered compound: elevated for phenanthrene (17-24%), moderate for pyrene (6.6-8.1%), and low for benzo[ a]pyrene (2.3-3.6%). Bioaccessibility was very low in abomasal acidity (generally <2%) and intestinal colloids (<8%). The liquid phases of intestinal medium successfully extracted compounds from freshly contaminated soil (25-28%), but the bioaccessibilty dropped markedly after aging (17% for phenanthrene and <9% for the more lipophylic compounds). Total bioaccessibilty in this in vitro model ranged from 11% for benzo[ a]pyrene in aged soil to 58% for phenanthrene in freshly contaminated soil, and the bioaccessibility of this latter compound was always higher compared to pyrene or benzo[ a]pyrene. Residual soil contained around half of the initial load, the highest residual levels being of benzo[ a]pyrene, which confirms the observed bioaccessibility.     

Die Oberflächenladung der Ton-Humusfraktion aus Schwarzerden als Funktion von pH und Ca-Konzentration

Surface charge of clay-humus fractions from Chernozems as a function of pH and Ca-concentration The charge characteristics of clay-humus fractions from A-horizons of several Chernozems as a function of Ca concentration and pH of the soil solution was investigated. The surface charge was measured by titration with charge compensating polyelectrolytes; the endpoint was at zero potential. A logarithmic dependence of the surface charge [mol_c/kg] on the Ca concentration of the soil solution in the range ? 2 mmol/L was observed. The influence of pH on the surface charge was almost linear over a wide range of pH-values, the change in pH-dependent charges being most pronounced for the horizons with low Ca saturation on the exchange sites. It was also found that the competition between protons and Ca ions for the exchange sites leads to a distinct decrease of the influence of Ca concentration on the surface charge in acid environment. The reason for slaking of the soil surface and of the displacement of clay-humus particles in Chernozems could be attributed to an increase in surface charge with decreasing Ca concentrations after leaching of lime. According to the present findings the drop in mobility of the clay-humus fractions during acidification could be explained by a charge compensating effect of protons and aluminium ions.     

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.