Current state of heavy metal contents in Vienna soils

This study presents the current state of heavy metal contents in both urban and forest soils within the city area of Vienna, Austria. Based on a systematic survey of urban soils and on targeted sampling in forest areas, local and regional anomaly thresholds are derived using statistical methods and considering regional distribution patterns. For urban soils, local anomaly thresholds of elements Cu (60?mg/kg), Hg (0.5?mg/kg), Pb (100?mg/kg) and Zn (200?mg/kg) exceed national guideline values for uncontaminated urban soils and according to Austrian legislation fall into the category “anthropogenic contamination present but no damage to plants, animals or humans detectable”. In forest soils within the city, thresholds are very similar to reference values for similar geological settings outside the city, apart from higher concentrations of elements Cr and Ni (threshold values of 107 and 64?mg/kg, respectively). Grouping urban soils according to land use reveals that Cd contents are 25?% higher, Pb contents 36?% higher, in traffic and industrial areas than in parks and like Cu, Hg and Zn, these elements can be shown to be at least partly caused by anthropogenic contamination. A dependency between heavy metal concentrations in soils and underlying geological units is shown within the flysch zone at the western city margin where the contents of elements Co, Cr, Cu, Ni and V are controlled by geology and reveal distinct differences between geological units. In built-up areas, no clear dependency between heavy metal contents in soils and geology is evident as urban soils represent accumulations by anthropogenic activity rather than in situ weathering products of underlying sediments.     

Effects of wind-driven circulation on river intrusion in Lake Tegel: modeling study with projection on transport of pollutants

Prediction of mixing intensity of water masses in riverine Lake Tegel (Berlin, Germany) can be used to trace the fate of pollutants that enter the lake through several inflows. Because the contributions of each inflow have not yet been quantified and because the lake features complex bathymetry and numerous islands, a hydrodynamic circulation model with high spatial resolution and dynamic wind forcing is useful. We applied the two-dimensional version of the Princeton Ocean Model to separate the influences of wind and river discharge on the currents and mass transport in Lake Tegel. For model validation, we compared the simulation results with 1?year of electrical conductivity data, which was used as a conservative tracer to distinguish between water from the River Havel and water supplied by a smaller second inflow. Calculation of currents alone is insufficient to investigate water exchanges between rivers and lakes, especially when several islands create multiple pathways for river intrusion. Therefore, mass transport simulations are applied. Our calculations based on archetypical scenarios indicate that the proportion of (polluted) water from the River Havel in the main basin of Lake Tegel fluctuates with river discharge and wind, which either amplify or neutralize each other.     

Assessing the impacts of mountain biking and hiking on subalpine grassland in Australia using an experimental protocol

Mountain biking is an increasingly popular, but sometimes controversial, activity in protected areas. Limited research on its impacts, including studies comparing biking with hiking, contributes to the challenges for mangers in assessing its appropriateness. The impacts of mountain bike riding off trail were compared to those of hiking on subalpine grassland in Australia using a modification of a common trampling experimental methodology. Vegetation and soil parameters were measured immediately and two weeks after different intensities of mountain biking (none, 25, 75, 200 and 500 passes across slope, 200 pass up and down slope) and hiking (200 and 500 passes across slope). There were reductions in vegetation height, cover and species richness, as well as changes in species composition and increases in litter and soil compaction with riding. Riding up and down a moderate slope had a greater impact than riding across the slope. Hiking also affected vegetation height, cover and composition. Mountain biking caused more damage than hiking but only at high use (500 passes). Further research including other ecosystems, topography, styles of riding, and weather conditions are required, but under the conditions tested here, hiking and mountain biking appear to be similar in their environmental impacts.     

Derivation of correlations to evaluate the impact of retrofitted post-combustion CO2 capture processes on steam power plant performance

When integrating a post-combustion CO₂ capture process and CO₂ compression into a steam power plant, the three interface quantities heat, electricity and cooling duty must be satisfied by the power plant, leading to a loss in net efficiency. The heat duty shows to be the largest contributor to the overall net efficiency penalty of the power plant. Additional energy penalty results from the cooling and electric power duty of the capture and compression units.In this work, the dependency of the energy penalty on the quantity and quality of the heat duty is analyzed and quantified for a state-of-the-art hard coal fired power plant. Furthermore, the energy penalty attributed to the additional cooling and power duty is quantified. As a result correlations are provided which enable to predict the impact of the heat, cooling and electricity duty of post-combustion CO₂ capture processes on the net output of a steam power plant in a holistic approach.     

Application of lean flammability limit study and large eddy simulation to burner development for an oxy-fuel combustion system

Previously, we developed a model to predict lean flammability limit L and flame propagation velocity Sb for pulverized coal. In the present paper, we have extended the model to apply it in development of oxy-fuel combustion systems. The basic model consists of two particles. One of the two particles burns first, then, the other particle is ignited by the heat of combustion of the one burning particle. We analyzed at what distance the first burning particle could ignite the next particle, and how fast the first burning particle could ignite the next particle. The model was verified both for air and oxy-fuel combustion conditions. Next, a method to support burner development was examined by using the model. Local Sb and L near the ignition points of the burner could be analyzed from the concentration and temperature profiles of CFD results. Flame stability was judged by the calculated Sb and L profiles, and past results of blow-off limits obtained with actual- and pilot-scale experiments. A DS^®T-burner was developed by Hitachi Power Europe, and installed at the Schwarze Pumpe pilot plant. Combination of the technique and large eddy simulation was applied to confirmation of the system.     

Plant chemistry and insect sequestration

Most plant families are distinguished by characteristic secondary metabolites, which can function as putative defence against herbivores. However, many herbivorous insects of different orders can make use of these plant-synthesised compounds by ingesting and storing them in their body tissue or integument. Such sequestration of putatively unpalatable or toxic metabolites can enhance the insects’ own defence against enemies and may also be involved in reproductive behaviour. This review gives a comprehensive overview of all groups of secondary plant metabolites for which sequestration by insect herbivores belonging to different orders has been demonstrated. Sequestered compounds include various aromatic compounds, nitrogen-containing metabolites such as alkaloids, cyanogenic glycosides, glucosinolates and other sulphur-containing metabolites, and isoprenoids such as cardiac glycosides, cucurbitacins, iridoid glycosides and others. Sequestration of plant compounds has been investigated most in insects feeding or gathering on Apocynaceae s.l. (Apocynoideae, Asclepiaoideae), Aristolochiaceae, Asteraceae, Boraginaceae, Fabaceae and Plantaginaceae, but it also occurs for some gymnosperms and even lichens. In total, more than 250 insect species have been shown to sequester plant metabolites from at least 40 plant families. Sequestration predominates in the Coleoptera and Lepidoptera, but also occurs frequently in the orders Heteroptera, Hymenoptera, Orthoptera and Sternorrhyncha. Patterns of sequestration mechanisms for various compound classes and common or individual features occurring in different insect orders are highlighted. More research is needed to elucidate the specific transport mechanisms and the physiological processes of sequestration in various insect species.     

Verteilung und Abnahme von bodennahem Ozon in städtischen und ländlichen Regionen

The compilation of ozone data for the federal states of Hesse and Northrhine-Westphalia (NRW) in Germany indicated that the concentration of ozone level slightly decreased during the years 1990–1998. The average concentration of ozone over forest areas is significantly higher than over cities. Only the maximum figures in the years approached one another. However, values passing the legal thresholds (180 μg ozone/m³) were two to three-fold higher over forests than over cities. The ozone concentration in air is inversely proportional to the traffic density. It is suggested that the lower NOx concentration over the forest than over cities is involved in the maintenance of the higher ozone-concentration over forest areas. In the cities, the ozone is reduced by NO to almost zero at night, whereas it is reduced by only about 50% over forests with lower NO concentrations. This reduction is only partially compensated in connection with the photolysis of NO₂ and the subsequent oxidation of O₂ to O₃ during the day. The ozone situation is principally the same in the federal states of Hesse and Northrhine-Westphalia.     

Analyzing the Variability of Remote Sensing and Hydrologic Model Evapotranspiration Products in a Watershed in Michigan

The goal of this paper was to statistically explore the spatiotemporal performance of remotely sensed actual evapotranspiration (ETa) datasets and a remotely sensed ensemble in a region that lacks observed data. The remotely sensed datasets were further compared with ETa results from a physically based hydrologic model (Soil and Water Assessment Tool) to examine the differences and determine the level of agreement between the ETa datasets and the model outputs. ETa datasets were compared on temporal (i.e., monthly and seasonal basis) and spatial (i.e., landuse) scales at both watershed and subbasin levels. The results showed a lack of consistent similarities and differences among the datasets when evaluating the monthly ETa variations; however, the seasonal aggregated data presented more consistent similarities and differences during the spring and summer compared to the fall and winter. Meanwhile, spatial analysis of the datasets showed the MOD16A2 500 m ETa product was the most versatile of the tested datasets, being able to differentiate between landuses during all seasons. Furthermore, the use of an averaging ensemble was able to improve overall ETa performance in the study area. This study showed that the remotely sensed ETa products are not similar throughout the year, but the appropriate application periods for different ETa products were identified. Finally, spatial variabilities of the ETa products are more in tune with landuse and climate characteristics.