Azo-dyes photocatalytic degradation in aqueous suspension of TiO2 under solar irradiation

The photodegradation of two common and very stable azo-dyes, i.e. methyl-orange (C₁₄H₁₄N₃SO₃Na) and orange II (C₁₆H₁₁N₂SO₄Na), is reported. The photocatalytic oxidation was carried out in aqueous suspensions of polycrystalline TiO₂ irradiated by sunlight. Compound parabolic collectors, installed at the “Plataforma Solar de Almería” (PSA, Spain) were used as the photoreactors and two identical reacting systems allowed to perform photoreactivity runs for the two dyes at the same time and under the same irradiation conditions. The disappearance of colour and substrates together with the abatement of total organic carbon content was monitored. The main sulfonate-containing intermediates were found to be in lower number in respect to those obtained under artificial irradiation. In particular there were no more evidence of the presence of hydroxylated transients. The dependence of dye photooxidation rate on: (i) substrate concentration; (ii) catalyst amount; and (iii) initial pH was investigated. The influence of the presence of strong oxidant species (H₂O₂, S₂O₈²⁻) and some ions (Cl⁻, SO₄²⁻) on the process was also studied.     

Sublethal detergent concentrations increase metabolization of recalcitrant polyphosphonates by the cyanobacterium Spirulina platensis

As a consequence of increasing industrial applications, thousand tons of polyphosphonates are introduced every year into the environment. The inherent stability of the C–P bond results in a prolonged half-life. Moreover, low uptake rates limit further their microbial metabolization. To assess whether low detergent concentrations were able to increase polyphosphonate utilization by the cyanobacterium Spirulina platensis, tolerance limits to the exposure to various detergents were determined by measuring the growth rate in the presence of graded levels below the critical micellar concentration. Then, the amount of hexamethylenediamine-N,N,N′,N′-tetrakis(methylphosphonic acid) that is metabolized in the absence or in the presence of sublethal detergent concentrations was quantified by ³¹P NMR analysis on either P-starved or P-fed cyanobacterial cultures. The strain tolerated the presence of detergents in the order: nonionic > anionic > cationic. When added to the culture medium at the highest concentrations showing no detrimental effects upon cell viability, detergents either improved or decreased polyphosphonate utilization, the anionic sodium dodecyl sulfate being the most beneficial. Metabolization was not lower in P-fed cells—a result that strengthens the possibility of using, in the future, this strain for bioremediation purposes.     

Risk management of terrorist attacks in the transport of hazardous materials using dynamic geoevents

This paper focuses attention on emergency management associated with a terrorist attack in the transport of hazardous materials in urban areas. The case study is in an urban area, a potential target for terrorist attacks due to its high vulnerability. Since it is not possible to predict where and when an attack will occur, the risk associated with terrorism is complex. It is only possible to identify the critical points for potential actions where counter measure must be applied. In the case of incidents which evolve relatively slowly, mitigation actions can be applied. The use of dynamic geoevents permits the immediate location of the event on a georeferenced map and the possibility of having a dynamic evolution of the scenario and of the number of people involved. The dynamic scenario has been created using the output of a consequence simulation code and a GIS software. Some assumptions were necessary but, since the aim of the paper is to define the procedure for the construction of the dynamic geoevent, these can be considered acceptable. The method will be further implemented in future.     

Sensing the intruder: a quantitative threshold for recognition cues perception in honeybees

The ability to discriminate among nestmates and non-nestmate is essential to defend social insect colonies from intruders. Over the years, nestmate recognition has been extensively studied in the honeybee Apis mellifera; nevertheless, the quantitative perceptual aspects at the basis of the recognition system represent an unexplored subject in this species. To test the existence of a cuticular hydrocarbons’ quantitative perception threshold for nestmate recognition cues, we conducted behavioural assays by presenting different amounts of a foreign forager’s chemical profile to honeybees at the entrance of their colonies. We found an increase in the explorative and aggressive responses as the amount of cues increased based on a threshold mechanism, highlighting the importance of the quantitative perceptual features for the recognition processes in A. mellifera.     

Emotions,habits and rational choices in ecological behaviours: The case of recycling and use of public transportation

Two field studies examined the role of attitudes, subjective norms, perceived control, anticipated emotions, past behaviour and desire in the prediction of pro-environmental behavioural intention. The model of goal-directed behaviour (MGB) was applied to predict intentions to use public transportation instead of the private car for going to work (Study 1, N=180), and to recycle household waste (Study 2, N=154). Multiple regression and structural equation modeling were used to test the hypotheses in studies 1 and 2, respectively. As expected, results of the two studies indicate that negative anticipated emotions and past behaviour are significant predictors of desire to engage in pro-environmental action. Desire, in turn, positively predicts pro-environmental behavioural intentions. A direct link between past behaviour and intentions was also detected. Implications of the results for the promotion of pro-environmental behaviour are discussed.     

Teil II: Analytik von Toxaphenrückständen (UWSF 2/1998)

Residue analysis of toxaphene has been difficult because of the complexicity of the technical mixture consisting of a high number of compounds with very similar structure and differing chloro content. Furthermore, the composition of toxaphene in environmental samples varies widely and is normally not like that of the technical mixture. Therefore, quantification of single components in environmental samples was impossible. After the isolation and identification of a great number of components during the last decade, enough standards are available for reliable quantification of toxaphene in all environmental compartments. Recently, most research has been done on the separation of chiral components of toxaphene with a view to identify degradation mechanisms and distribution pathways.