Improvements of nano-SiO2 on sludge/fly ash mortar

Sewage sludge ash has been widely applied to cementitious materials. In this study, in order to determine effects of nano-SiO(2) additives on properties of sludge/fly ash mortar, different amounts of nano-SiO(2) were added to sludge/fly ash mortar specimens to investigate their physical properties and micro-structures. A water-binding ratio of 0.7 was assigned to the mix. Substitution amounts of 0%, 10%, 20%, and 30% of sludge/fly ash (1:1 ratio) were proposed. Moreover, 0%, 1%, 2%, and 3% of nano-SiO(2) was added to the mix. Tests, including SEM and compressive strength, were carried out on mortar specimens cured at 3, 7, and 28 days. Results showed that sludge/fly ash can make the crystals of cement hydration product finer. Moreover, crystals increased after nano-SiO(2) was added. Hence, nano-SiO(2) can improve the effects of sludge/fly ash on the hydration of mortar. Further, due to the low pozzolanic reaction active index of sludge ash, early compressive strengths of sludge/fly ash mortar were decreased. Yet, nano-SiO(2) could help produce hydration crystals, which implies that the addition of nano-SiO(2) to mortar can improve the influence of sludge/fly ash on the development of the early strength of the mortar.     

Control of GHG emission at the microbial community level

All organic material eventually is decomposed by microorganisms, and considerable amounts of C and N end up as gaseous metabolites. The emissions of greenhouse relevant gases like carbon dioxide, methane and nitrous oxides largely depend on physico-chemical conditions like substrate quality or the redox potential of the habitat. Manipulating these conditions has a great potential for reducing greenhouse gas emissions. Such options are known from farm and waste management, as well as from wastewater treatment. In this paper examples are given how greenhouse gas production might be reduced by regulating microbial processes. Biogas production from manure, organic wastes, and landfills are given as examples how methanisation may be used to save fossil fuel. Methane oxidation, on the other hand, might alleviate the problem of methane already produced, or the conversion of aerobic wastewater treatment to anaerobic nitrogen elimination through the anaerobic ammonium oxidation process might reduce N2O release to the atmosphere. Changing the diet of ruminants, altering soil water potentials or a change of waste collection systems are other measures that affect microbial activities and that might contribute to a reduction of carbon dioxide equivalents being emitted to the atmosphere.     

Characterizing effects of uncertainties in MSW composting process through a coupled fuzzy vertex and factorial-analysis approach

A coupled fuzzy vertex and factorial-analysis approach was developed in this study for systematically characterizing effects of uncertainties in a municipal solid waste composting process. A comprehensive composting process model was also embedded into the system framework and used to address substrate decomposition and biomass growth, as well as the interactions between moisture contents, temperatures, and oxygen concentrations. The applicability of the proposed method was verified through a custom-made pilot-scale composting system. Results from fuzzy simulation indicated that the fuzzy vertex method could effectively communicate implicit knowledge into dynamic simulations and thus provide valuable information for enhancing composting process control under uncertainty. The factorial analysis was effective in quantifying the proportion to which the uncertainty of each single or interactive effect of model parameters contributes to the overall uncertainty of the system outcomes. Thus, sensitive parameters that may lead to errors or unreasonable predictions can be determined. The proposed study system could not only be used in characterizing combined effects of uncertainties for composting processes, but was also applicable to many other environmental modelling systems.     

Characterization of food waste generators: a Hawaii case study

Information on food waste disposal and on recycling methods and recycled amounts is reported. Data were obtained from a mail and phone survey of all licensed food establishments in Hawaii conducted in 2004 and 2005. Of 8253 licensed food establishments, 5033 completed surveys. It was found that relationships exist between food establishment size (measured by the number of meals served per day or the number of employees) and the amount of food an establishment recycled; establishment type and recycling behavior; and establishment type and amount recycled. The amount of food waste recycled in the state of Hawaii was estimated to be 264,000 L/day and annual food waste generation was estimated to be 336,000 tonnes.     

Mechanical properties of concrete containing a high volume of tire-rubber particles

Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of a uniaxial compressive strain control test conducted on hardened concrete specimens indicate large reductions in the strength and tangential modulus of elasticity. A significant decrease in the brittle behavior of concrete with increasing rubber content is also demonstrated using nonlinearity indices. The maximum toughness index, indicating the post failure strength of concrete, occurs in concretes with 25% rubber content. Unlike plain concrete, the failure state in rubberized concrete occurs gently and uniformly, and does not cause any separation in the specimen. Crack width and its propagation velocity in rubberized concrete are lower than those of plain concrete. Ultrasonic analysis reveals large reductions in the ultrasonic modulus and high sound absorption for tire-rubber concrete.     

Natterer’s bat (Myotis nattereri Kuhl, 1818) hawks for prey close to vegetation using echolocation signals of very broad bandwidth

We present a hitherto unknown prey perception strategy in bats: Myotis nattereri (Vespertilionidae, Chiroptera) is able to perceive prey by echolocation within a few centimeters of echo-cluttering vegetation, by using frequency-modulated search signals of very large bandwidth (up to 135 kHz). We describe the species’ search behavior and echolocation repertoire from the field and from experiments in a flight tent. In the field, bats varied signal parameters in relation to their distance from vegetation and usually flew close to vegetation. In the flight tent, M. nattereri detected and localized prey by echolocation alone as close as 5 cm from vegetation. Apparently, the bats were able to tolerate some overlap between prey and clutter echoes. Passive prey cues (vision, olfaction, prey-generated sounds) were not used in prey perception. The bats selected prey by size. The animals performed aerial catches and produced approach sequences typical for aerial hawking bats, but were able to do so within a few centimeters of the substrate. M. nattereri thus has access to silent, suspended prey very close to vegetation (e.g., spiders, and caterpillars on threads). Received: 29 September 1999 / Received in revised form: 12 February 2000 / Accepted: 12 February 2000     

Aggression and resource sharing among foundresses in the social wasp Polistes dominulus: testing transactional theories of conflict

Tug-of-war models of within-group conflict predict that the frequency of conflict will be positively related to the degree of reproductive sharing within the group; in contrast, a negative relationship supports transactional models, in which reproductive payments among group members limit the degree of within-group selfishness. We tested predictions of the tug-of-war and transactional models by examining cofoundress interactions during the founding (preworker) phase of colony development in 30 naturally nesting colonies of the paper wasp Polistes dominulus. We found that the mean rate of foundress aggression and the mean probability of food sharing were significantly negatively associated, which supports the prediction of the transactional, not the tug-of-war model. Further, cofoundress aggression significantly increased over the founding phase (independently of temperature), while the fraction of aggression initiated by the dominant (alpha) foundress significantly decreased over this period. We show that both of these results are predicted by the transactional model of within-group conflict. Interestingly, the alpha’s rate of aggression was significantly positively temperature dependent, while the beta’s was not. This indicates that the alpha’s aggression level may often be near her physiological maximum, while the beta’s aggression is limi- ted by other factors, contradicting the prediction of the tug-of-war model. Moreover, the alpha’s aggression was significantly positively temperature dependent only in the second half of the founding period, as predicted by the transactional model since this is when there is least reproductive sharing. Finally, our results indicate that the alpha’s level of aggression depends on the resources controlled by the beta. Received: 18 January 2000 / Revised: 19 June 2000 / Accepted: 24 June 2000     

Assessing the Geographic Representativeness of Genebank Collections: the Case of Bolivian Wild Potatoes

Abstract: Genebank collection databases can be used for ecogeographical studies under the assumption that the accessions are a geographically unbiased sample. We evaluated the representativeness of a collection of wild potatoes from Bolivia and defined and assessed four types of bias: species, species-area, hotspot, and infrastructure. Species bias is the sampling of some species more often than others. Species-area bias is a sampling that is disproportionate to the total area in which a species is found. Hotspot bias is the disproportionate sampling of areas with high levels of diversity. Infrastructure bias is the disproportionate sampling of areas near roads and towns. Each of these biases is present in the Bolivian wild potato collection. The infrastructure bias was strong: 60% of all wild potato accessions were collected within 2 km of a road, as opposed to 22%, if collections had been made randomly. This analysis can serve as a guide for future collecting trips. It can also provide baseline information for the application of genebank data in studies based on geographic information systems.     

Life under Arctic sea ice – reproduction strategies of two sympagic (ice-associated) amphipod species, Gammarus wilkitzkii and Apherusa glacialis

The reproductive strategies of two gammaridean amphipod species, Gammarus wilkitzkii and Apherusa glacialis, that permanently inhabit the Arctic sea ice were investigated. G. wilkitzkii reaches sexual maturity at an age of 2 years and produces 128 ± 54 eggs fem.⁻¹ yr⁻¹. Mating takes place during fall and winter, and the development of the large eggs (0.60 to 0.80 mm diam.) lasts 6 to 7 months. The sex ratio of G. wilkitzkii was dominated by males in a proportion of 1.5:1. In vivo studies showed that juveniles are released in batches from the brood pouches of the females during April and May. A. glacialis reaches sexual maturity at the age of 1 year and produces 555 ± 151 eggs fem.⁻¹ yr⁻¹. The eggs are between 0.18 and 0.23 mm in diameter, and are the smallest known for gammaridean amphipods. Eggs are kept in packages of two to eight in the brood pouches of females. The sex ratio of A. glacialis was dominated by females in a proportion of 3:1. The high fecundity of both amphipod species, the release of juveniles in batches over a period of time, a high proportion of females (A. glacialis), and an elongated life-span with multiple spawnings (G. wilkitzkii) are discussed as possible adaptations to the specific and highly variable conditions under Arctic sea ice. Received: 29 December 1999 / Accepted: 8 March 2000     

Occurrence of the semi-catadromous European eel Anguilla anguilla in the Baltic Sea

Strontium (Sr) and calcium (Ca) contents in the otoliths of yellow and silver European eels [Anguilla anguilla (L.)] collected from coastal waters of the Baltic Sea and a freshwater lake in Sweden were examined by wavelength dispersive X-ray spectrometry with an electron microprobe. The mean Sr/Ca ratios from elver check to otolith edge were significantly higher for the eels from coastal waters (5.39 ± 1.09‰) than for those from the lake (0.71 ± 0.89‰). The evidence indicates that European eels in the Baltic Sea do not necessarily migrate into freshwater streams during the growth phase. Received: 30 September 1999 / Accepted: 6 April 2000