Thermogravimetric pyrolysis of waste polyethylene-terephthalate and polystyrene: A critical assessment of kinetics modelling

Pyrolysis is considered as possible technique to thermally convert waste plastics into chemicals and energy. Literature on experimental findings is extensive, although experiments are mostly performed in a dynamic heating mode, using thermogravimetric analysis (TGA) and at low values of the heating rate (mostly below 30 K/min). The present research differs from literature through the application of far higher heating rates, up to 120 K/min. The use of these dynamic results to define the reaction kinetics necessitates the selection of an appropriate reaction mechanism, and 21 models have been proposed in literature considering the rate limiting step being diffusion, nucleation or the reaction itself.The current research studied the cracking of PET and PS by TGA at different heating rates (temperature ramps). Results were used to check the validity of the proposed mechanisms. Several conclusions are drawn: (i) to obtain fair results, the heating ramp should exceed a minimum value, calculated at 30 K/min for PET and 80 K/min for PS; (ii) application of the majority of the models to experimental findings demonstrated that they do not meet fundamental kinetic considerations and are questionable in their use; and (iii) simple models, with reaction order 1 or 2, provide similar results of the reaction activation energy.A further comparison with literature data for dynamic and isothermal experiments confirms the validity of these selected models. Since TGA results are obtained on a limited amount of sample, with results being a strong function of the applied heating rate, the authors believe that isothermal experiments, preferably on a large scale both towards equipment and/or sample size, are to be preferred.     

Mental representations of animal and plant species in their social contexts: Results from a survey across Europe

Despite a growing body of literature on public views on biodiversity and nature, our understanding of public attitudes towards animal and plant species is still rudimentary. This study investigates mental representations, constituted by beliefs, of three types of species (a large mammal, a spider and a non-native plant), and explores their links with cultural factors such as value orientations and cultural capital, in order to better understand attitudes towards these species.We conducted a survey in eight sites across Europe (n = 2378) and found strong relationships between beliefs about species, in particular with regard to their harmlessness, value and previous population change, and the desirability of an increase in this species. Other beliefs, such as perceived nativeness, were less influential. We discuss how respondents combined beliefs to mental representations of species, and show how representations are related to species-independent factors that tap respondents’ cultural context, such as socially shared value orientations and education.     

Medaka (Oryzias latipes) for use in evaluating developmental effects of endocrine active chemicals with special reference to gonadal intersex (testis-ova).

Japanese medaka (Oryzias latipes) has been widely used for the evaluation of the toxicity of endocrine active chemicals (EACs) and other chemicals as well as for monitoring the adverse effects of effluent discharges in relation to sexual development and function. It is useful for these evaluations for many reasons including the following: 1) it has a short life cycle facilitating studies extending over long phases of development and over multigenerations, 2) it is easy to rear, 3) male and female phenotypes can easily be distinguished on the basis of secondary sex characteristics, and 4) a genetic marker (DMY) is available for identifying the true genotypic sex. Several biomarkers have been found to be useful for identifying the effects of exposure to estrogenic and androgenic chemicals in medaka and they include increased levels of hepatic vitellogenin (VTG) and testis-ova induction in males for exposure to estrogenic chemicals, and decreased levels of hepatic VTG in females and an altered morphology of dorsal and anal fins and formation of papillae for androgenic chemicals. In this paper, we present a critical analysis of the use of medaka as a test species for studies of endocrine disruption and report on the use of sex-related genetic markers and alterations in gonadal development, including the induction of testis-ova formation, for assessing the disruptive effects of EACs. In this paper, we focus on some of the more recent studies and findings.     

Rating the risks of anticoagulant rodenticides in the aquatic environment: a review

Environmental Chemistry Letters - Anticoagulant rodenticides are used worldwide to control commensal rodents for hygienic and public health reasons. As anticoagulants act on all vertebrates, risk...     

Assimilating concentration observations for transport and dispersion modeling in a meandering wind field

Assimilating concentration data into an atmospheric transport and dispersion model can provide information to improve downwind concentration forecasts. The forecast model is typically a one-way coupled set of equations: the meteorological equations impact the concentration, but the concentration does not generally affect the meteorological field. Thus, indirect methods of using concentration data to influence the meteorological variables are required. The problem studied here involves a simple wind field forcing Gaussian dispersion. Two methods of assimilating concentration data to infer the wind direction are demonstrated. The first method is Lagrangian in nature and treats the puff as an entity using feature extraction coupled with nudging. The second method is an Eulerian field approach akin to traditional variational approaches, but minimizes the error by using a genetic algorithm (GA) to directly optimize the match between observations and predictions. Both methods show success at inferring the wind field. The GA-variational method, however, is more accurate but requires more computational time. Dynamic assimilation of a continuous release modeled by a Gaussian plume is also demonstrated using the genetic algorithm approach.     

Does quinone or phenol enrichment of humic substances alter the primary compound from a non-algicidal to an algicidal preparation?

Dissolved organic matter (DOM) has been shown to affect phytoplankton species directly. These interactions largely depend on the origin and molecular size of DOM and are different in prokaryotes and eukaryotes. In a preceding study, however, two humic substance preparations did not adversely affect coccal green algae or cyanobacterial growth even at high concentrations of dissolved organic carbon (DOC). These results contradicted previous findings, showing a clear, negative response of different phototrophs to much lower DOC concentrations. To test whether or not at least defined building blocks of humic substances (HSs) are effective algicidal structures, we enriched two humic preparations with hydroquinone and p-benzoquinone, respectively, and exposed two different green algae, Pseudokirchneriella subcapitata and Monoraphidium braunii, and two cyanobacterial species, Synechocystis sp. and Microcystis aeruginosa, to the unmodified and enriched HSs. As response variables, growth rates in terms of biomass increase, chlorophyll-a content, and photosynthetic yield were measured. The highest concentration (4.17 mM DOC) of the modified HSs clearly inhibited growth; the cyanobacterial species were much more sensitive than the green algal species. However, realistic ecological concentrations did not adversely affect growth. Aerating the exposure solution for 24 h strongly reduced the inhibitory effect of the modified HSs. The algicidal effect was obviously caused by monomers and not by polymerised high molecular weight HSs themselves. Furthermore, the maximum quantum yield (Φ PSII max) was stimulated in the green algal species by low and medium DOC concentrations, but reduced in the cyanobacterial species upon exposure to higher HS concentrations. The quinone- and phenol-enriched HSs only showed algicidal activity at high concentrations of 4.17 mM DOC and lost their effects over time, presumably by oxidation and subsequent polymerisation. This study confirms that the applied humic substances themselves are not effective algicides even if enriched in effective structures.     

Conflicts between biodiversity conservation and human activities in the central and eastern European countries

Conflicts between the conservation of biodiversity and other human activities have been and continue to be of increasing concern in the European Union, often having important political, economic, and environmental repercussions. These conflicts have been addressed in the European Union by using a wide array of top down and bottom up tools, with varying degrees of success. A new challenge is now facing Europe with the integration of 10 new countries in the European Union (EU) and an additional range of biodiversity-rich habitats placed under EU legislation. The rich biodiversity of the central and eastern European countries (CEEC) is likely to be threatened by some aspects of the integration process, and conflicts between the conservation of biodiversity and other human activities are expected. In this paper, we review certain existing conflicts between biodiversity conservation and human activities in the CEEC, expected conflicts associated with integration to the EU, particularly in terms of new policy and legislation implementation, and, finally, explore possible conflict management options.