Influence of palladium content dispersed in the TiO2 photocatalyst for degradation of volatile organic compounds in gas emission

Heterogeneous photocatalysis is highlighted to treat volatile organic compound (VOC) emission. Then, this work analysed the influence of palladium (Pd) content loaded in TiO₂ on n-octane and iso-octane photodegradation. For this, TiO₂ was loaded with Pd in different contents: 0.4%, 0.7%, and 1.0%. The samples were characterized, and the photodegradation experiments were conducted by Pd/TiO₂/UV process. The characterization analyses showed that the metal presence did not change the catalyst structure or its surface area; however, it reduced the bandgap energy. The photocatalytic results proved that palladium improved n-octane degradation from 62% (pure TiO₂) to 92.6% (0.4%Pd/TiO₂) and, iso-octane degradation enhanced from 59% (pure TiO₂) to 90.6% (0.7%Pd/TiO₂); all results were obtained in the space time of 39 s. Therefore, 0.4%Pd/TiO₂ and 0.7%Pd/TiO₂ showed better oxidation results to degradation n-octane and iso-octane, respectively. The kinetic model of pseudo-first order showed a good fit for the data of both VOCs. Heterogeneous photocatalysis with Pd/TiO₂ showed to be an adequate technique to reduce VOCs emission.

     

Spectral analysis unmasks synchronous and compensatory dynamics in plankton communities

Community biomass is often less variable than the biomasses of populations within the community, yet attempts to implicate compensatory dynamics between populations as a cause of this relationship often fail. In part, this may be due to the lack of appropriate metrics for variability, but there is also great potential for large-scale processes such as seasonality or longer-term environmental change to obscure important dynamics at other temporal scales. In this study, we apply a scale-resolving method to long-term plankton data, to identify the specific temporal scales at which community-level variability is influenced by synchrony or compensatory dynamics at the population level. We show that variability at both the population and community level is influenced strongly by a few distinct temporal scales: in phytoplankton, ciliate, rotifer, and crustacean communities, synchronous dynamics are predominant at most temporal scales. However, in phytoplankton and crustacean communities, compensatory dynamics occur at a sub-annual scale (and at the annual scale in crustaceans) leading to substantial reductions in community-level variability. Aggregate measures of population and community variability do not detect compensatory dynamics in these communities; thus, resolving their scale dependence unmasks dynamics that are important for community stability in this system. The methods and results presented herein will ultimately lead to a better understanding of how stability is achieved in communities.     

PUMP-CTD-System for trace metal sampling with a high vertical resolution. A test in the Gotland Basin, Baltic Sea

It is a great challenge to sample seawater across interfaces, for example the halocline or the redoxcline, to investigate trace metal distribution. With the use of 10l sampling bottles mounted to a wire or a CTD-Rosette it is possible to obtain a maximum vertical resolution of 5m. For the detection of small vertical structures in the vertical distribution of trace metals across the redoxcline, the CTD-Bottle-Rosette is not sufficient. Therefore, a PUMP-CTD-System was developed, which enables water sampling with high resolution (1m maximum) along a vertical profile. To investigate the suitability and possible contamination sources of this device two experiments were carried out in the Gotland Basin. The first experiment consisted of two separate profiles. The first profile was obtained with the CTD-Bottle-Rosette and the second with the PUMP-CTD-System. Both were taken from the bottom to the surface water layer. The second experiment was a combined profile obtained from the surface to the bottom with the PUMP-CTD-System attached to the CTD-Bottle-Rosette. Concentrations of dissolved Pb, Cd, Cu, Zn, Fe, Mn, Co and Ni from the "Niskin Bottles" and from the PUMP were measured and compared for each investigation. We demonstrate that it is useful to perform vertical sampling from lower to higher concentrations, e.g. surface to bottom in this environment, and that a longer flushing is required for sampling seawater in the anoxic bottom water. A comparison of the two systems for oxygen and hydrogen sulphide measurements showed an improvement of the precision and the quality of the sampling when using the PUMP. Thus, metal speciation at the oxic-anoxic gradient zone and on a high vertical resolution will be accessible. As concentrations of dissolved Pb, Cd, Cu, Zn, Co, Ni, Fe and Mn in seawater sampled with both devices were in the same range, we conclude that the PUMP-CTD-System is well suited to sample seawater for trace metal analyses.     

Strategies of maintaining the natural purification potential of rivers and lakes

Surface waters have a great impact on ecology and life of man. Because of their current use and exploitation, chemical and biological pollution, as well as physical changes of rivers and lakes are common. Natural self-purification potential helps to compensate harms to a certain degree. Proposals are given to detect restrictions of the purification potential in time as well as to support and to enhance the natural purification potential.     

Pillar building in the fiddler crab Uca beebei: evidence for a condition-dependent ornament

In the fiddler crab (Uca beebei) males build a small mud pillar next to their burrow which increases their attractiveness to females. Three hypotheses were tested to explain inter-male variation in pillar-building. (1) The benefits of pillar-building are density dependent. The experimental addition of vertical structures did not support this hypothesis as there was no change in the level of pillar-building. (2) There are two classes of males (pillar-builders and non-pillar-builders). This could either be due to an alternative mating strategy, or because pillar building is age or size-dependent. There was also no support for this hypothesis. (3) Pillar-building is an honest signal of male quality dependent on body condition. A food supplementation experiment was performed. Addition of food affected several aspects of male behaviour and resulted in a two fold increase in the number of pillars built between control and food treatments (P < 0.001). However, the percentage of males building pillars did not increase significantly. Pillar building in this species has been attributed to sensory exploitation. Our results indicate that a trait which may well have evolved through sensory exploitation also appears to be condition-dependent. We emphasise that showing that an ornament or behaviour is condition-dependent does not necessarily mean that it evolved through good gene processes. However, in terms of its current selective value, pillar building may be maintained through female choice because it acts as a signal of male condition.     

Verst?ndigungsprobleme durch anthropogene Eintr?ge? Der Infochemikalien-Effekt

Hintergrund Organismen k?nnen chemische Signale in ihrer Umgebung, sogenannte Infochemikalien, deuten und als Informationsquelle nutzen, um ad?quat auf ihre biotische und abiotische Umgebung zu reagieren. Diese chemische Kommunikation spielt eine entscheidende Rolle bei lebenswichtigen Aktivit?ten wie Fortpflanzung, Sozialverhalten, Nahrungsaufnahme, Verteidigung und Orientierung und ist damit essenziell für das überleben eines Individuums oder einer Art. Vorgehensweise Der Transfer der Kenntnisse über natürliche Infochemikalien aus der chemischen ?kologie auf die ?kotoxikologie führt zu der Beschreibung des Infochemikalien-Effekts. In einem zweiten Schritt werden M?glichkeiten zur Quantifizierung des Infochemikalien-Effekts entwickelt. Dazu wird die schrittweise Abfolge von der Geruchsemission bis zu den Reaktionen von Empf?ngerorganismen als Basis zu Systematisierung verwendet und geeignete Testans?tze, die sich in der Grundlagenforschung bew?hrt haben, vorgestellt.