Green Synthesis of Silver Nanoparticles and Study of Their Antimicrobial Properties

One of the major disadvantages of polymers when used in food-contact applications is that they are very susceptible to microbial attack. On the other hand, silver nanoparticles have received increased attention as novel antimicrobial agents. Therefore, the introduction of silver nanoparticles into conventional polymers results in new materials with improved properties. In this investigation, colloidal silver nanoparticles using an environmentally friendly procedure were synthesized. An aqueous solution of AgNO₃ was used as a silver precursor with ‘green’ reducing agents either different types of honey, or β-d-glucose. In the first case, different pH values, as well as the addition of poly(ethylene glycol), PEG were studied, while in the latter, the effect of reduction time in the presence of PEG with various average molecular weights was examined. Properties of the nanoparticles were measured using X-Ray diffraction, UV–Vis and FTIR spectroscopy. Using honey it seems that spherical particles are produced with the smaller average particle size obtained at pH 8.5. Use of honey has the advantage of being a natural product, although its main drawback is that its composition varies and it cannot be predefined to result in reproducible results. Use of β-d-glucose results in stable silver nanoparticles with small average particle size after 24 h reduction. The addition of low molecular weight PEG seems to be beneficial in the production of stable nanoparticles. Finally, the antimicrobial activity of the nanoparticles produced was investigated at different concentrations on both Gram positive and negative bacteria, such as Bacillus cereus, Bacillus subtilis, Escherichia coli and Staphylococcus aureus.     

Evaluating the Environmental Performance of Urban Parks in Mediterranean Cities: An Example from the Barcelona Metropolitan Region

In a context of increasing urban sprawl and water scarcity common to other Mediterranean cities, this article focuses on the urban parks in the Region of Barcelona (Catalonia, Spain) to examine how these parks are distributed in this region and to assess whether their design and management follow criteria adapted to Mediterranean environmental conditions, especially in what concerns water use. In order to evaluate the environmental performance of these parks, we selected four factors possibly influencing the adoption of park management practices at the local scale: urban density, population size of the municipality, municipal income per capita, and political orientation of the city council. After determining the location and area of urban parks in the region, we correlated these four explanatory factors with several management tasks extracted from two different samples of parks (one of 315 parks and another of 125 parks) and a survey of 86 city councils. Results show that, in general, urban parks were more frequent in large, dense, and left/green municipalities but that environmentally sound practices were more common in small and low-density municipalities. We conclude that changes in certain practices (especially the substitution of high water demanding species) could improve significantly the environmental performance of public spaces in large urban areas with Mediterranean climates. Our observations may be pertinent for other cities interested in the provision of environmental public goods such as parks that necessitate water for irrigation.     

Quantification of greenhouse gas emissions from waste management processes for municipalities--a comparative review focusing on Africa

The amount of greenhouse gases (GHG) emitted due to waste management in the cities of developing countries is predicted to rise considerably in the near future; however, these countries have a series of problems in accounting and reporting these gases. Some of these problems are related to the status quo of waste management in the developing world and some to the lack of a coherent framework for accounting and reporting of greenhouse gases from waste at municipal level. This review summarizes and compares GHG emissions from individual waste management processes which make up a municipal waste management system, with an emphasis on developing countries and, in particular, Africa. It should be seen as a first step towards developing a more holistic GHG accounting model for municipalities. The comparison between these emissions from developed and developing countries at process level, reveals that there is agreement on the magnitude of the emissions expected from each process (generation of waste, collection and transport, disposal and recycling). The highest GHG savings are achieved through recycling, and these savings would be even higher in developing countries which rely on coal for energy production (e.g. South Africa, India and China) and where non-motorized collection and transport is used. The highest emissions are due to the methane released by dumpsites and landfills, and these emissions are predicted to increase significantly, unless more of the methane is captured and either flared or used for energy generation. The clean development mechanism (CDM) projects implemented in the developing world have made some progress in this field; however, African countries lag behind.     

Chemical, dimensional and morphological ultrafine particle characterization from a waste-to-energy plant

Waste combustion processes are responsible of particles and gaseous emissions. Referring to the particle emission, in the last years specific attention was paid to ultrafine particles (UFPs, diameter less than 0.1 μm), mainly emitted by combustion processes. In fact, recent findings of toxicological and epidemiological studies indicate that fine and ultrafine particles could represent a risk for health and environment. Therefore, it is necessary to quantify particle emissions from incinerators also to perform an exposure assessment for the human populations living in their surrounding areas.To these purposes, in the present work an experimental campaign aimed to monitor UFPs was carried out at the incineration plant in San Vittore del Lazio (Italy). Particle size distributions and total concentrations were measured both at the stack and before the fabric filter inlet in order to evaluate the removal efficiency of the filter in terms of UFPs. A chemical characterization of UFPs in terms of heavy metal concentration was performed through a nuclear method, i.e. Instrumental Neutron Activation Analysis (INAA), as well as a mineralogical investigation was carried out through a Transmission Electron Microscope (TEM) equipped with an Energy Dispersive Spectrometer (EDS) in order to evaluate shape, crystalline state and mineral compound of sampled particles.Maximum values of 2.7 × 10⁷ part. cm⁻³ and 2.0 × 10³ part. cm⁻³ were found, respectively, for number concentration before and after the fabric filter showing a very high efficiency in particle removing by the fabric filter. With regard to heavy metal concentrations, the elements with higher boiling temperature present higher concentrations at lower diameters showing a not complete evaporation in the combustion section and the consequent condensation of semi-volatile compounds on solid nuclei. In terms of mineralogical and morphological analysis, the most abundant compounds found in samples collected before the fabric filter are Na–K–Pb oxides followed by phyllosilicates, otherwise, different oxides of comparable abundance were detected in the samples collected at the stack.     

Environmental assessment of biodegradable multilayer film derived from carbohydrate polymers

Multilayer films exhibit excellent properties for food packaging. However, existing products are not biodegradable. Conventional plastics, manufactured from fossil fuels, not only consume non-renewable and finite resources, but also impact heavily on waste disposal. For this reason, a new multilayer film has been developed in the Multibio Project for the production of food packaging. In this paper, the environmental impacts of the new biodegradable multilayer film—based on modified starch and polylactic acid (PLA)—and those of the conventional multilayer film—based on PP and PA6—are quantified in the categories of climate change, fossil fuel depletion, acidification and eutrophication. Conventional multilayer film has a 90% higher impact than the Multibio multilayer film. The main difference between the LCA presented and the cited literature is the inventory data obtained in the phase of polymer processing to obtain multilayer film, and the assessment of the disposal phase of the multilayer film wastes.     

All that glitters is not gold: the effect of top-down participation on conservation knowledge,attitudes and institutional trust in a Central Indian tiger reserve

Researchers and policymakers emphasize that people’s involvement in forest management can secure their support of conservation initiatives. However, the evidence on the effectiveness of top-down participation is weak. This study uses cross-sectional household data from 16 villages in the buffer zone of Pench Tiger Reserve (Madhya Pradesh) in India to contribute to the evidence base of such assumption. Using a propensity score matching to control for observable bias, we evaluate the effects of two state-driven incentive-based participatory projects, i.e. the Joint Forest Management and Ecodevelopment, on selected social outcomes. Specifically, we measured local people conservation knowledge, biodiversity attitudes as well as trust in and satisfaction with the tiger reserve management authorities. We found that the effects of participatory management on conservation knowledge were positive, but negligible. We found no significant effects on local people’s biodiversity attitudes, trust and satisfaction with the tiger reserve management authorities. Top-down and externally induced participation may explain our results. Our findings clearly indicate that the effectiveness of participatory conservation interventions is conditional on the level and nature of local participation. Top-down participatory projects may not be sufficient to generate local support of conservation and in some cases, they may even exacerbate local conflicts.     

Individual and collective foraging decisions: a field study of worker recruitment in the gypsy ant <Emphasis Type="Italic">Aphaenogaster senilis</Emphasis>

In social insects, the decision to exploit a food source is made both at the individual (e.g., a worker collecting a food item) and colony level (e.g., several workers communicating the existence of a food patch). In group recruitment, the recruiter lays a temporary chemical trail while returning from the food source to the nest and returns to the food guiding a small group of nestmates. We studied how food characteristics influence the decision-making process of workers changing from individual retrieving to group recruitment in the gypsy ant Aphaenogaster senilis. We offered field colonies three types of prey: crickets (cooperatively transportable), shrimps (non-transportable), and different quantities of sesame seeds (individually transportable). Colonies used group recruitment to collect crickets and shrimps, as well as seeds when they were available in large piles, while small seed piles rarely led to recruitment. Foragers were able to “measure” food characteristics (quality, quantity, transportability), deciding whether or not to recruit, accordingly. Social integration of individual information about food emerged as a colony decision to initiate or to continue recruitment when the food patch was rich. In addition, group recruitment allowed a fast colony response over a wide thermal range (up to 45°C ground temperature). Therefore, by combining both advantages of social foraging (group recruitment) and thermal tolerance, A. senilis accurately exploited different types of food sources which procured an advantage against mass-recruiting and behaviorally dominant species such as Tapinoma nigerrimum and Lasius niger.     

Sterols in sediment samples from Venice Lagoon, Italy

Sterols of different origin were analysed in sediment samples collected in the Venice Lagoon. The purpose of the study was to investigate the degree of sewage contamination within the Lagoon using fecal sterols (coprostanol, epicoprostanol and coprostanone) and to analyse the pattern of the sterols to plot the origin of the organic matter.

Sedimentary coprostanol at Canal Grande within the city of Venice was more than one order of magnitude higher than other stations in the Lagoon and two orders higher than in a sediment sample collected in the open sea. The cholesterol/coprostanol ratio, like the percentage of coprostanol in total sterols at this sample site was very similar to values in sewage sludge. The different pattern of sterols at station 2 which had the largest amount of total sterol indicates a difference in the origin of the organic material. Nevertheless the sterols used as tracer of terrestrial vascular plants did not show any particular trend at this station, receiving fresh water inputs. (3-Sitosterol and cholestanol reached the highest levels at the station within the Chioggia basin.