Processing and Characterization of Recycled Polypropylene and Acrylonitrile Butadiene Rubber Blends

In this paper investigation on thermoplastic elastomers (TPE) and thermoplastic vulcanizates (TPV) derived from waste polypropylene (WPP) of Municipal Solid Waste (MSW) and acrylonitrile-butadiene rubber (NBR) are reported. The WPP was segregated, cleaned, dried and melt processed with NBR at 180 °C in a Brabender Plasticorder at different blend ratios. TPV was prepared by dynamic vulcanization of the TPE with conventional sulfur accelerator curing system. The mechanical properties measured were found to decrease with increase in NBR proportion in the blend; however the dynamic vulcanization of the nitrile rubber phase enhanced the strength properties of the corresponding TPE. The crystallinity of the WPP reduced with increase in NBR ratio. The dynamic modulus decreased with nitrile rubber content in the TPE. Interestingly, the storage modulus of the TPV at higher rubber content enhanced significantly and damping characteristics increased sharply. The rheology studies reveal that the damping of the blend has been reduced with the addition of high storage modulus rubber at melt processing conditions and hence increased viscosity. The amorphous rubber content with higher storage modulus imparts higher viscosity for the polypropylene (PP) matrix at the processing temperature. The SEM study reveals that the dynamic vulcanization of the rubber phase in the blend caused a smoother and finer surface morphology.     

Body feathers as a potential new biomonitoring tool in raptors: a study on organohalogenated contaminants in different feather types and preen oil of West Greenland white-tailed eagles (Haliaeetus albicilla)

We investigated the variation in concentrations and profiles of various classes of organohalogenated compounds (OHCs) in different feather types, muscle tissue and preen oil from 15 white-tailed eagle (Haliaeetus albicilla) carcasses from Greenland. The influence of moult patterns and potential external contamination onto the feather surface was examined, while the present study is also the first to investigate the use of body feathers for OHC monitoring. Concentrations of sum polychlorinated biphenyls (PCBs) in feathers from white tailed eagles ranged from 2.3 ng/g in a primary wing feather to 4200 ng/g in body feathers. Using 300 mg of body feathers, almost 50 different OHCs could be quantified and median concentrations in body feathers were 10 fold higher than concentrations in tail feathers (rectrices) or primary wing feathers. Body feathers could be very useful for biomonitoring taking into account their easy sampling, short preparation time and high levels of OHCs. In addition, the effects of confounding variables such as feather size, moult and age are also minimised using body feathers. Correlations with concentrations in muscle tissue and preen oil were high and significant for all feather types (r ranging from 0.81 to 0.87 for sum PCBs). Significant differences in concentrations and profiles of OHCs were found between different primary feathers, indicating that the accumulation of OHCs in feathers varies over the moulting period (maximum three years). Washing of feathers with an organic solvent (acetone) resulted in a significant decrease in the measured concentrations of OHCs in feathers. However, our results indicated that preen oil is probably not the only contributor to the external contamination that can be removed by washing with acetone. Possibly dust and other particles may be of importance and may be sticking to the preened feathers. Rectrices washed only with water showed high and significant correlations with concentrations in muscle and preen oil as well. Washing with acetone therefore does not seem to be of great influence when relating to internal tissue concentrations. We recommend washing feathers only with distilled water in order to remove dirt and dust particles before analysis.     

The Transboundary Nature of the Allende–Piedras Negras Aquifer Using a Numerical Model Approach

The Allende–Piedras Negras (APN) aquifer is located between the states of Texas (United States [U.S.]) and Coahuila (Mexico). The Rio Grande crosses the aquifer, acting as a natural and political divide between the countries. However, it remains unclear whether the APN aquifer can be considered a truly transboundary aquifer flow system, which would potentially require joint management by two different administrative jurisdictions. The main purpose of this study was to evaluate the transboundary nature of this aquifer. This was achieved by developing a detailed hydrogeological model to analyze the direction of volumetric fluxes within the APN aquifer using Visual MODFLOW. The model simulated a spatially averaged cumulative drawdown of 0.76 m for the entire aquifer over an 18‐year modeling period (2000–2017). The flow convergence zone, previously located below the Rio Grande, has shifted to the U.S. side in most locations, driven by higher pumping rates of the wells located near the river. This shift of the convergence zone from one country to the other means that groundwater recharge from one side flows underneath the river to the other side. This qualifies the APN aquifer as a “transboundary groundwater flow system.” The procedure followed in this study may be applied to other aquifers that straddle the U.S.–Mexico border and may motivate future modeling studies on other poorly studied transboundary aquifers around the world and thereby enable bi‐national aquifer management.     

Environmental pollution by antibiotics and by antibiotic resistance determinants

Antibiotics are among the most successful drugs used for human therapy. However, since they can challenge microbial populations, they must be considered as important pollutants as well. Besides being used for human therapy, antibiotics are extensively used for animal farming and for agricultural purposes. Residues from human environments and from farms may contain antibiotics and antibiotic resistance genes that can contaminate natural environments. The clearest consequence of antibiotic release in natural environments is the selection of resistant bacteria. The same resistance genes found at clinical settings are currently disseminated among pristine ecosystems without any record of antibiotic contamination. Nevertheless, the effect of antibiotics on the biosphere is wider than this and can impact the structure and activity of environmental microbiota. Along the article, we review the impact that pollution by antibiotics or by antibiotic resistance genes may have for both human health and for the evolution of environmental microbial populations.     

Falls from height during the floor slab formwork of buildings: Current situation in Spain

Problem

One of the phases with the highest risk of falls from a height in the construction of a building is during the floor slab formwork stage. This paper analyzes this particular risk, as well as the most frequently used fall-protection systems.

Method

A survey was carried out to define the current situation in Spain with regard to falls from a height during floor slab formwork and the fall-protection systems used to prevent such a risk.

Results

The results of the survey clarified the current situation in Spain with regard to this risk, and made it clear that there is considerable risk of falling from a height during the floor slab formwork stage.

Discussion

All the safety systems analyzed presented a series of weak points that should be studied in detail before they can be used on building sites.

Impact on industry

The risk of falling associated with floor slab formwork and the most frequently used protection systems are analyzed. As no research had been carried out to date on this type of risk, we consider the research presented in this article to be a pioneer in the field.     

Relationships between pesticides and organic carbon fractions in sediments of the Danshui River estuary and adjacent coastal areas of Taiwan

In order to understand the fate of pesticides in marine environments, concentrations of pesticides and different carbonaceous fractions were determined for surface sediments in the Danshui River and nearby coastal areas of Taiwan. The major compounds detected were tetrachlorobenzene, HCHs, chlordane, aldrin, DDDs, DDEs and DDTs. Total concentrations of pesticides in the sediments ranged from not detectable to 23 ng g(-1), with the maximum value detected near the discharge point of the marine outfall from the Pali sewage treatment plant. These results confirm that pesticides persist in estuarine and nearby coastal environments of the Danshui River well after their ban. Concentrations of total pesticides significantly correlate with concentrations of total organic carbon and black carbon in these sediments, suggesting that total organic carbon and black carbon regulate the distribution of trace organic pollutants in fluvial and coastal marine sediments.     

Feasibility assessment of electrocoagulation towards a new sustainable wastewater treatment

BACKGROUND, AIM AND SCOPE: Electrocoagulation (EC) may be a potential answer to environmental problems dealing with water reuse and rational waste management. The aim of this research was to assess the feasibility of EC-process for industrial contaminated effluents from copper production, taking into consideration technical and economical factors. EC-technology claims to offer efficient removal rates for most types of wastewater impurities at low power consumption and without adding any precipitating agents. MATERIALS AND METHODS: Real wastewater from Saraka stream with high concentrations of heavy metals was provided by RTB-BOR, a Serbian copper mining and smelting complex. Runs were performed on a 10 l EC-reactor using aluminum plates as sacrificial electrodes and powered by a 40 A supply unit. Results concerning key factors like pH, conductivity and power consumption were measured in real time. Analysis of dissolved metal concentrations before and after treatment were carried out via ICP-OES and confirmed by an independent test via AAS. RESULTS: Several aspects were taken into account, including current density, conductivity, interfacial resistivity and reactor settings throughout the runs, in order to analyze all possible factors playing a role in neutralization and metal removal in real industrial wastewater. DISCUSSION: Electrode configurations and their effects on energy demand were discussed and exemplified based on fundamentals of colloidal and physical chemistry. CONCLUSIONS: Based on experimental data and since no precipitating agents were applied, the EC-process proved to be not only feasible and environmentally-friendly, but also a cost-effective technology RECOMMENDATIONS AND PERSPECTIVES: The EC-technology provides strategic guidelines for further research and development of sustainable water management processes. However, additional test series concerning continuous operation must be still performed in order to get this concept ready for future large-scale applications.