Verhalten von PAK im system boden/Pflanze

The results of lysimeter experiments conducted since 1991 dealing with the behavior of PAH in soil/plant systems demonstrate that the PAH pollution to cultivated plants may be caused by both atmospheric deposition and by the soil-to-plant transfer observed in contaminated sites. In the latter, a “direct contamination” of plant surfaces with PAH-loaded soil particles and the subsequent PAH turnover by desorption/adsorption processes is seen to dominate—at least for the most relevant PAHs toxic to humans, benzo(a)pyrene and dibenz(a,h)anthracene. Leafy vegetables growing close to the soil surface are therefore endangered most by a PAH contamination of the soil. The soil-to-plant transfer via “direct contamination” can be reduced to a high degree by covering the contaminated soil with different mulch materials. Systematic PAH transfer via root uptake could not generally be observed. From the reported results, a trigger value in the soil of 1 mg·kg^?1 for benzo(a)pyrene is proposed to make a judgement on PAH contaminated soils with regard to the soil-to-plant transfer pathways. Soils with excessive concentrations of benzo(a)pyrene demand special attention when considering the recommendations for the growth and consumption of cultivated vegetables. The “soil”as well as the “deposition pathways” must be integrated into a complete risk assessment of locations with food plant production, especially in urban areas.     

Organic residue decomposition: The minicontainer-system a multifunctional tool in decomposition studies

The Minicontainer-test, first described by Eisenbeis (1993), was designed to study the kinetics of organic residue decomposition at a microsite level. It is derived from the litterbag technique and consists of polyethylene minicontainers (volume about 1.5 cm³) filled with a test substrate (litter, straw, cellulose, etc.). The minicontainers (MCs) are closed at either end with plastic gauze discs of variable mesh size (e.g. 20 μm, 250 μm, 500 μm or 2 mm). A definite number of such units are inserted into PVC-bars, which can be implanted into the soil horizontally or vertically, or be exposed on the soil surface horizontally. The bars are very stable and can be exposed in different environments for months to years. If required, the bars can be removed temporarily and stored, e.g. during soil cultivation. Should fresh litter be used, two phases of decomposition can be distinguished: a fast initial phase, which can be mainly related to the effect of leaching, and a second slow phase depending mainly on the activity of soil organisms and litter quality. Several questions can be addressed to investigations using MCs, e.g. 1) parts of the soil fauna which are involved in decomposition (nematodes, microarthropods, and smaller specimens of the macrofauna, e.g. enchytraeidae, diplopods and dipteran larvae) can be extracted from the litter substrate using a miniscale high gradient extractor, 2) the organic mass loss of litter can be determined, 3) microbial biomass (C_mic, N_mic) can be assessed by fumigation extraction and 4) microbial activity (respiration) in the test substrate can also be assessed by use of standardised methods. Compared to litterbag studies, the larger number of small replicate units improves the statistical evaluation. Until today the Minicontainer-test has been applied in forestry and agriculture, e.g. studying the effects of liming, soil restoration and the application of insecticides, e.g. Diflubenzuron (Dimilin) and Btk (Bacillus thuringiensis var.kurstaki).     

Boosting large-scale river connectivity restoration by planning for the presence of unrecorded barriers

Conservation decisions are invariably made with incomplete data on species’ distributions, habitats, and threats, but frameworks for allocating conservation investments rarely account for missing data. We examined how explicit consideration of missing data can boost return on investment in ecosystem restoration, focusing on the challenge of restoring aquatic ecosystem connectivity by removing dams and road crossings from rivers. A novel way of integrating the presence of unmapped barriers into a barrier optimization model was developed and applied to the U.S. state of Maine to maximize expected habitat gain for migratory fish. Failing to account for unmapped barriers during prioritization led to nearly 50% lower habitat gain than was anticipated using a conventional barrier optimization approach. Explicitly acknowledging that data are incomplete during project selection, however, boosted expected habitat gains by 20–273% on average, depending on the true number of unmapped barriers. Importantly, these gains occurred without additional data. Simply acknowledging that some barriers were unmapped, regardless of their precise number and location, improved conservation outcomes. Given incomplete data on ecosystems worldwide, our results demonstrate the value of accounting for data shortcomings during project selection.     

Hands on explosives: Safety testing of protective measures

Several attempts have been made to test the suitability of protective measures for the handling of explosives. We investigated the suitability of safety gloves and a combined safety helmet and face shield. In the presented studies, three different experimental setups were used to simulate the effects of an explosion of a primary explosive in a glass flask on the glove or helmet protected body. Depending on the experimental setup, the fragment effects were evaluated and compared. Furthermore, the fragment distribution of an explosion inside a glass flask was investigated. The explosion of 1 g of lead azide in a 10 mL flask yielded approximately 14,000 glass fragments. However, most of the shards were accelerated down- and side-wards and only few upwards. Holding a flask on its neck (instead of its bottom) is therefore a simple but effective way of diminishing the risk of injury, when handling explosives. The safety helmet/face shield performed very well, by shielding the face from all fragments. Furthermore, it could be proven that DIN and EN standard testing procedures for gloves are unsuitable to simulate the effects of a respective explosion.In this article, the progress in the development of realistic testing procedures for the testing of gloves for the protection against fragmentation effects of glassware in situations involving explosions is reported and the results and methods of previous tests are summarized.     

The Researcher's Notebook: Mission and scope

Order and simplification are the first steps toward the mastery of a subject—the actual enemy is the unknown.

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An oligarchy of nest-site scouts triggers a honeybee swarm’s departure from the hive

Animals that travel in groups must synchronize the timing of their departures to assure cohesion of the group. While most activities in large colonies of social insects have decentralized control, certain activities (e.g., colony migration) can have centralized control, with only a special subset of well-informed individuals making a decision that affects the entire colony. We recently discovered that a small minority of individuals in a honeybee colony—an oligarchy—decides when to trigger the departure of a swarm from its hive. The departure process begins with some bees producing the worker-piping signal (the primer for departure) and is followed by these bees producing the buzz-run signal (the releaser for departure). In this study, we determined the identity of these signalers. We found that a swarm’s nest-site scouts search for potential nest cavities prior to the departure of the swarm from its hive. Furthermore, we found that the predeparture nest-site scouts are the sole producers of the worker-piping signal and that they are the first producers of the buzz-run signal. The control of the departure of a honeybee swarm from its hive shows how a small minority of well-informed individuals in a large social insect colony can make important decisions about when a colony should take action.     

Self‐management perceptions and practices: a structural equations analysis

Self‐management has many potential benefits for organizations. However, application of self‐management to organizational settings has been hampered by lack of theoretical frameworks for self‐management specifically applied to work settings and by a corresponding dearth of psychometrically sound measures. This paper presents results of structural equations modeling of measures of self‐management anchored in a revised version of the Brief and Aldag (1981) model of the self in organizational behavior. Using confirmatory factor analysis procedures (CFA), two a priori measures of self‐management are examined. Results point to two relatively distinct facets of self‐management, each of them composed of four relatively independent subscales. Finally, a structural model evidencing a pervasive set of relationships between self‐management perceptions and self‐management practices is provided. Copyright © 1999 John Wiley & Sons, Ltd.     

Justice constructs,negative affectivity,and employee deviance: a proposed model and empirical test

This study tests a model that uses organizational justice variables and the personality trait of negative affectivity to explain two forms of deviant employee behavior. Prior research suggests that deviance can be directed interpersonally or against organizations. We propose a model that links unfavorable perceptions of distributive, procedural, and interactional justice, as well as the dispositional trait of negative affectivity, to both types of deviant acts. To test the model, a survey was distributed to employees from a government agency and an international manufacturer of paper products. Responses to the survey were analysed using structural equation modeling to evaluate the fit of the theoretical model to the data. Results showed that the model fits the data well and that nearly all of the hypothesized relations among constructs were supported. Implications of the results for the prediction and control of deviant behavior are discussed and future research directions are offered. Copyright © 1999 John Wiley & Sons, Ltd.