A mechanistical model for the uptake of sulfonamides by bacteria

The uptake of sulfonamides into bacterial cells was simulated by a dynamic model to estimate bioavailability and steady-state accumulation of sulfonamides in the cells. Uptake of sulfonamides is modeled as diffusion-like transport of the neutral molecule and the ionic species. Speciation outside and inside the cell depends on the extra- and intracellular pH and the pK(a)-value of the antibiotic active SO(2)NH moiety. The ratio between intra- and extracellular sulfonamide concentration is used as a measure for potential sulfonamide accumulation in bacterial cells. Simulated ratios are in good agreement with experimental data for various sulfonamides with pK(a2) values ranging from 5.0 up to 11.8. Sensitivity analyses indicate that intracellular sulfonamide concentration depend significantly on the degree of ionization in the cytoplasm and the surrounding medium. No accumulation in the cell occurs, if the external pH exceeds the intracellular pH. For sulfonamides with large pK(a)-values the internal activity equals the activity in the extracellular solution. Highest accumulation is reached if the pH gradient from inside to outside the cell is large, which depends on the bacterial pH-regulation mechanisms. The pH-dependent intracellular accumulation of various sulfonamides correlates well with their observed antibiotic effect on selected bacteria.     

Ableitungskriterien für Geringfügigkeitsschwellen zur Beurteilung von Grundwasserverunreinigungen

Ohne Zusammenfassung     

Allocation plasticity and plant-metal partitioning: meta-analytical perspectives in phytoremediation

In this meta-analysis of plant growth and metal uptake parameters, we selected 19 studies of heavy metal (HM) phytoremediation to evaluate trends of allocation plasticity and plant-metal partitioning in roots relative to shoots. We calculated indexes of biomass allocation and metal distribution for numerous metals and plant species among four families of interest for phytoremediation purposes (e.g. Brassicaceae, Fabaceae, Poaceae, and Solanaceae). We determined that plants shift their biomass and distribute metals more to roots than shoots possibly to circumvent the challenges of increasing soil-HM conditions. Although this shift is viewed as a stress-avoidance strategy complementing intrinsic stress-tolerance, our findings indicate that plants express different levels of allocation plasticity and metal partitioning depending on their overall growth strategy and status as ‘fast-grower’ or ‘slow-grower’ species. Accordingly, we propose a conceptual model of allocation plasticity and plant-metal partitioning comparing ‘fast-grower’ and ‘slow-grower’ strategies and outlining applications for remediation practices.     

Analysing the influence of different street vegetation on traffic-induced particle dispersion using microscale simulations

Urban vegetation can be viewed as compensation to the environmental drawbacks of urbanisation. However, its ecosystem function is not well-known and, for urban planning, vegetation is mainly considered as an element of urban design. This article argues that planning practice needs to re-examine the impact of vegetation cover in the urban fabric given our evaluation of vegetation's effects on air quality, including the dispersion of traffic-induced particles at street level. Using the three-dimensional microclimate model ENVI-met?, we evaluate these effects regarding the height-to-width ratio of streets flanked by buildings and the vertical and horizontal density of street vegetation. Our results reveal vegetation's effect on particle dispersion through its influence on street ventilation. In general, vegetation was found to reduce wind speed, causing inhibition of canyon ventilation and, consequently, an increase in particle concentrations. Vegetation was also found to reduce wind speed at crown-height and to disrupt the flow field in close vicinity to the canopy. With increasing height-to-width ratio of street canyons, wind speed reduction increases and the disturbance of the flow impacts across a canyon's entire width. We also found that the effect is more pronounced in configurations with poor ventilation, such as the low wind speed, perpendicular inflow direction, and in deep canyons cases.     

Modeling Wetland Plant Community Response to Assess Water-Level Regulation Scenarios in the Lake Ontario – St. Lawrence River Basin

The International Joint Commission has recently completed a five-year study (2000–2005) to review the operation of structures controlling the flows and levels of the Lake Ontario – St. Lawrence River system. In addition to addressing the multitude of stakeholder interests, the regulation plan review also considers environmental sustainability and integrity of wetlands and various ecosystem components. The present paper outlines the general approach, scientific methodology and applied management considerations of studies quantifying the relationships between hydrology and wetland plant assemblages (% occurrence, surface area) in Lake Ontario and the Upper and Lower St. Lawrence River. Although similar study designs were used across the study region, different methodologies were required that were specifically adapted to suit the important regional differences between the lake and river systems, range in water-level variations, and confounding factors (geomorphic types, exposure, sediment characteristics, downstream gradient of water quality, origin of water masses in the Lower River). Performance indicators (metrics), such as total area of wetland in meadow marsh vegetation type, that link wetland response to water levels will be used to assess the effects of different regulation plans under current and future (climate change) water-supply scenarios.The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Research Articles

The metabolism of phenanthrene was studied both in cell suspension cultures of wheat (Triticum aestivum) and soybean (Glycine max), and in intact plants of the water mossFontinalis antipyretica. Metabolism in cell suspension cultures strongly differed between the monocotyle and the dicotyle plant. Only small amounts oftrans-phenanthrene-9,10-dihydrodiole and phenanthrene-9,10-dione were detectable in the wheat culture. Soybean cultures, in contrast demonstrated a strong turnover resulting in a 75% reduction of the initial phenanthrene concentration. Metabolites were phenanthrene-9,10-dione, not further characterized polar metabolites and bound residues. Intact plants ofFontinalis antipyretica metabolized only small amounts of phenanthrene. Data obtained from cell cultures did not provide information for the metabolic potential in intact plants. Therefore standardized tests with model systems like suspension cultures lead to inadequate assessment of the ecological risk of certain xenobiotics.     

Prioritizing the provision of urban ecosystem services in deprived areas,a question of environmental justice

The distribution of urban ecosystem services (UES) is often uneven across socioeconomic groups, leading to environmental justice issues. Understanding the distribution of UES across a landscape can help managers ensure an equitable distribution of services. While many past studies have focused on the distribution of green spaces in relation to socioeconomic variables, this research analyzes the distribution of UES provided by these green spaces. This research quantified air pollution removal, atmospheric carbon reduction, and surface runoff mitigation provided by urban trees in Strasbourg city (France). The provision of these three UES was studied at the census block scale by creating an index of UES delivery, which was contrasted with a constructed social deprivation index. Our results show that there is no significant association between the delivery of UES and social deprivation. Some deprived populations benefit from high UES delivery. Results also suggest that mapping associations between UES delivery and social deprivation should be integrated with future development plans to enhance the equitable distribution of UES. This study provides insights into the French context where studies about the distribution of UES at a small-area level remain lacking.     

When are overqualified employees creative? It depends on contextual factors

The research on perceived overqualification has mainly examined its negative consequences. Defined, employees who feel overqualified have surplus talent and thus can be excellent workers if managed properly; yet, empirical evidence in this domain is lacking. Building on person–environment fit theory, this research explored whether, when, and how employees who feel overqualified can engage in creative performance. The results of a multi‐source field study (N = 113 employees and 19 supervisors) supported theoretical predictions. Perceived overqualification was related positively to supervisor‐rated creative performance when these workers felt supported and appreciated and successfully negotiated developmental idiosyncratic deals. Opportunities to mentor others had an impact on the relationship between perceived overqualification and supervisor‐rated creativity, although the simple slopes were non‐significant. This study is novel in that it unpacked actionable steps that organizations can utilize to motivate this large segment of workforce to use their surplus qualifications constructively by, for example, engaging in creative performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Bewertung von diffusen Stoffeinträgen im Rahmen der nationalen Biodiversitätsstrategie

Background, aim and scope In 2007, the German government approved a national strategy on biological diversity. The strategy requires the integration of its quality targets and action targets into other policies. In addition to other pressure factors, area-wide diffuse substance discharges contribute considerably to the loss of biological diversity. Reducing these diffuse substance discharges to long-term ecologically compatible levels is one of the main action targets. This paper aims to provide an overview of preconditions for implementing this objective in terms of content as well as organization and to point out important deficits. Main focus To achieve this, the paper will discuss environmental monitoring and its implementation in Germany drawing on the targets of the national strategy on biological diversity. It will discuss the opportunities for the evaluation of the German and European biodiversity strategies using monitoring required in the execution of environmental laws and regulations as well as international substance-related indicators. Results Environmental monitoring in Germany and in Europe is characterized by a plurality of monitoring networks operated under different administrative competences and environmental sectors. Only a small part of the collected data is evaluated in a cross-media and cross-sectoral perspective even though the linking of the different data sets is technically possible. Discussion A key problem is that harmonized minimum requirements to monitor the reduction of diffuse substance discharges are missing. Without the implementation of a cooperative and harmonized monitoring approach and organizational guidelines, the reduction of diffuse substance discharges will not be verifiable. Environmental data as well as indicators are essential to evaluate the success of the national biodiversity strategy. Suitable monitoring concepts are available in the German Federal Republic and its Federal States, nevertheless, a political impulse for their implementation is missing. Recommendations and perspectives The national biodiversity strategy may reopen the discussion on the necessity of an integrated monitoring. A coordinated approach that refers both to the international indicator-discussion and to institutional obstacles and aims to develop a proposal for integrated monitoring data is necessary.