Interferences of carbonate quantification in municipal solid waste incinerator bottom ash: evaluation of different methods

Quantification of carbonate contents in fresh and weathered municipal solid waste incinerator (MSWI) bottom ash was performed using volumetric and gravimetric methods, Fourier Transform Infrared (FT-IR) spectroscopy and thermal analysis. Results differ considerably depending on the method applied. Volumetric measurement and thermogravimetry (TG) are based on the determination of CO₂ release by acid or thermal treatment, respectively. Interactions of CO₂ with the mineral matrix and de novo synthesis of carbonates during thermal analysis were observed. In order to find out the contribution of CO₂ released from residual organic matter, an additional experiment was carried out to demonstrate how the material is affected by the heating process in the course of thermal analysis. FT-IR spectroscopy as a non-destructive method seems to provide the most reliable quantitative results.     

Oxygen dynamics and transport in the Mediterranean sponge Aplysina aerophoba

The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba specimens with Clark-type oxygen microelectrodes (tip diameters 18–30 μm). Total oxygen consumption rates of whole sponges were measured in closed chambers. These rates were used to back-calculate the oxygen distribution in a finite-element model. Combining direct measurements with calculations of diffusive flux and modeling revealed that the tissue of non-pumping sponges turns anoxic within 15 min, with the exception of a 1 mm surface layer where oxygen intrudes due to molecular diffusion over the sponge surface. Molecular diffusion is the only transport mechanism for oxygen into non-pumping sponges, which allows total oxygen consumption rates of 6–12 μmol cm⁻³ sponge day⁻¹. Sponges of different sizes had similar diffusional uptake rates, which is explained by their similar surface/volume ratios. In pumping sponges, oxygen consumption rates were between 22 and 37 μmol cm⁻³ sponge day⁻¹, and the entire tissue was oxygenated. Combining different approaches of direct oxygen measurement in living sponges with a dynamic model, we can show that tissue anoxia is a direct function of the pumping behavior. The sponge-microbe system of A. aerophoba thus has the possibility to switch actively between aerobic and anaerobic metabolism by stopping the water flow for more than 15 min. These periods of anoxia will greatly influence physiological variety and activity of the sponge microbes. Detailed knowledge about the varying chemical microenvironments in sponges will help to develop protocols to cultivate sponge-associated microbial lineages and improve our understanding of the sponge-microbe-system.     

Reduced costs of mixed-species pairings in flycatchers: by-product or female strategy?

Heterospecific matings are generally assumed to be unconditionally disadvantageous due to reduced viability or fertility of hybrid offspring. For female collared flycatchers (Ficedula albicollis) mated to male pied flycatchers (Ficedula hypoleuca), the cost of heterospecific pair formation is reduced due to high levels of conspecific extra-pair paternity and a male-biased offspring sex ratio. In order to investigate whether these cost-reducing mechanisms are the result of female mating strategies, rather than being a by-product of species incompatibilities, we manipulated the plumage of male collared flycatchers before pair formation to make them resemble male pied flycatchers. Since species incompatibilities are absent in this design, any systematic effect of manipulation on sex ratio or paternity would indicate a role of female mating strategy. Paternity was determined by means of a likelihood approach that controls the errors made in assigning a chick to be ‘within-pair’ or ‘extra-pair’. Neither the sex ratio nor the male share of paternity was affected by the manipulation in a systematic manner. We therefore conclude that our experimental data provide no support for the suggestion that female behavioural strategies are markedly adjusted in response to formation of mixed-species pairs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Efficient welding conditions in magnetic pulse welding process

This study investigates the experimental research of the appropriated conditions for the magnetic pulse welding of AA6060T6 tubular assembly. Some welding tests were performed with two process parameters: the charging voltage and the width of the air gap between the two parts to be welded. A torsion-shear test, associated with the material fracture surfaces observation, gives an insight about the appropriateness of the welding conditions. The failure mode of the destructive test gives a dimensional criterion of the weld that is used as weld quality. It appears that the voltage does not strongly affect the weld quality for a low gap. It is possible to find an optimal gap range giving a high weld length. When the gap is too small, it is necessary to increase the pressure on the flyer, and some cracks appear in the material. Similarly, when the gap is too large, the high impact energy damages the welded interface.     

Risk-taking and environmental perception

This paper investigates the relationship between pupils' environmental perception (in terms of preservation and utilisation of nature) and personality (in terms of risk-taking). 713 secondary school pupils in Switzerland were investigated. Environmental perception was assessed via three factors: Preservation, Utilisation of Nature and Consideration for Conservation. Risk-taking was evaluated via six factors: Positive Risking, Ambivalence, Thrill in Gambling, Ineffective Control, Effective Control, and Anger Reaction. Analysis of the correlation matrix between Risk-taking and Environmental perception revealed three profiles (types): the high scorer on Preservation is the controlled and cautious gambler. The Utiliser (anthropocentric) profile is essentially a mirror image of the first: the Utiliser does not enjoy unpredictable risks, reacts with anger when risks fail and has little control over his/her own risk-taking behaviour. The Consideration for Conservation (ecocentric) profile assumes a position between these two profiles.     

Trait-mediated indirect effects of predatory fish on microbial mineralization in aquatic sediments

Sediment-dwelling zoobenthos stimulate the mineralization of organic matter and alter nutrient cycling by aerating the sediment via burrows, by feeding on detritus, and by redistributing particles. Here we experimentally revealed that abundant benthic chironomids (Chironomus riparius) can perceive predatory fish (Rutilus rutilus) via chemical cues (kairomones) and spend less time foraging at the sediment surface and more time hiding in their burrows. This predator avoidance behavior significantly increased the exposure of freshly deposited organic particles to oxygen by reducing their burial to subsurface layers and by enhancing the aeration of subsurface layers via burrow ventilation, conditions that together increased the rate of organic matter mineralization. These results demonstrate that predatory fish can exert trait-mediated effects on benthic communities that in turn alter basic ecosystem processes related to nutrient cycling.     

Characterization of slow pyrolysis biochars: effects of feedstocks and pyrolysis temperature on biochar properties

Biochars are increasingly used as soil amendment and for C sequestration in soils. The influence of feedstock differences and pyrolysis temperature on biochar characteristics has been widely studied. However, there is a lack of knowledge about the formation of potentially toxic compounds that remain in the biochars after pyrolysis. We investigated biochars from three feedstocks (wheat straw, poplar wood, and spruce wood) that were slowly pyrolyzed at 400, 460, and 525°C for 5 h (straw) and 10 h (woodchips), respectively. We characterized the biochars' pH, electrical conductivity, elemental composition (by dry combustion and X-ray fluorescence), surface area (by N adsorption), water-extractable major elements, and cation exchange capacity (CEC). We further conducted differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffractometry to obtain information on the biochars' molecular characteristics and mineralogical composition. We investigated trace metal content, total polycyclic aromatic hydrocarbon (PAH) content, and PAH composition in the biochars. The highest salt (4.92 mS cm) and ash (12.7%) contents were found in straw-derived biochars. The H/C ratios of biochars with highest treatment temperature (HTT) 525°C were 0.46 to 0.40. Surface areas were low but increased (1.8-56 m g) with increasing HTT, whereas CEC decreased (162-52 mmol kg) with increasing HTT. The results of DSC and FTIR suggested a loss of labile, aliphatic compounds during pyrolysis and the formation of more recalcitrant, aromatic constituents. X-ray diffractometry patterns indicated a mineralogical restructuring of biochars with increasing HTT. Water-extractable major and trace elements varied considerably with feedstock composition, with trace elements also affected by HTT. Total PAH contents (sum of EPA 16 PAHs) were highly variable with values up to 33.7 mg kg; irrespective of feedstock type, the composition of PAHs showed increasing dominance of naphthalene with increasing HTT. The results demonstrate that biochars are highly heterogeneous materials that, depending on feedstock and HTT, may be suitable for soil application by contributing to the nutrient status and adding recalcitrant C to the soil but also potentially pose ecotoxicological challenges.     

Glacier changes and related glacial lake expansion in the Bhutan Himalaya, 1990–2010

This paper discusses the recent retreat of glaciers and the changes in supraglacial lakes in the Bhutan Himalaya during the last two decades. We calculated the changes in clean and debris-covered glaciers and the formation, disappearance, and expansion of glacial lakes during the beginning of 1990s, 2000s, and 2010 using Landsat TM and ETM+ images. For this purpose, eight river sub-basins namely Wang Chu, Chamkar Chu, Dangme Chu, Kuri Chu, Mangde Chu, Mo Chu, Pho Chu and Northern Basin were considered. A retreating trend was found in the case of clean glaciers. Debris-covered glaciers in this region were found to have undergone an increase of about 29 %, and this increase was partially contributed by those expanded upstream. This increase in the debris-covered area is higher on the southern side of the Bhutan Himalaya. It is found that a number of moraine-dammed glacial lakes were formed during this period and can be potentially dangerous depending on the size, distance from the glacier and altitude. Most of the glacial lake formation and expansion occurred on the southern side of the Bhutan Himalaya.