Transformation products and reaction kinetics of fragrances in advanced wastewater treatment with ozone

The reaction of the fragrance compounds 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta[g]isochromene (HHCB), 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone (AHTN), 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (musk xylene/MX), 1-(4-tert-butyl-2,6-dimethyl-3,5-dinitrophenyl)ethanone (musk ketone/MK), and 1-(2,3,8,8-tetramethyl-1,3,4,5,6,7-hexahydronaphthalen-2-yl)ethanone (OTNE) with ozone in tap water as well as waste water treatment plant (WWTP) effluents is described. Several transformation products are characterized by means of gas chromatography coupled to mass spectrometry. One transformation product (HHCB-Lactone) was confirmed by means of a true standard. Musk xylene and musk ketone do not react with ozone under the conditions used in this study. AHTN and HHCB reacted slowly to a multitude of transformation products, while OTNE reacted quickly to several stable transformation products. The reaction constants and half lives are used to predict removal efficiencies for full scale reactors.     

Three views of two degrees

Limiting global warming to 2°C above pre-industrial global mean temperature has become a widely endorsed goal for climate policy. It has also been severely criticized. We show how the limit emerged out of a marginal remark in an early paper about climate policy and distinguish three possible views of it. The catastrophe view sees it as the threshold separating a domain of safety from a domain of catastrophe. The cost-benefit view sees it as a strategy to optimize the relation between the costs and benefits of climate policy. The focal point view sees it as a solution to a complex coordination problem. We argue that the focal point view is the most appropriate. It leads to an emphasis on implementing effective steps toward a near-zero emissions economy, without panicking in the face of a possible temporary overshooting. After several decades of practical experiences, the focal point may or may not be redefined on the basis of knowledge gathered thanks to these experiences.     

Improving the aeration of critical fine-grained landfill top cover material by vegetation to increase the microbial methane oxidation efficiency

The natural methane oxidation potential of methanotrophic bacteria in landfill top covers is a sustainable and inexpensive method to reduce methane emissions to the atmosphere. Basically, the activity of methanotrophic bacteria is limited by the availability of oxygen in the soil. A column study was carried out to determine whether and to what extent vegetation can improve soil aeration and maintain the methane oxidation process. Tested soils were clayey silt and mature compost. The first soil is critical in light of surface crusting due to vertical erosion of an integral part of fine-grained material, blocking pores required for the gas exchange. The second soil, mature compost, is known for its good methane oxidation characteristics, due to high air-filled porosity, favorable water retention capacity and high nutrient supply. The assortment of plants consisted of a grass mixture, Canadian goldenrod and a mixture of leguminous plants. The compost offered an excellent methane oxidation potential of 100% up to a CH₄-input of 5.6 l CH₄ m⁻² h⁻¹. Whereas the oxidation potential was strongly diminished in the bare control column filled with clayey silt even at low CH₄-loads. By contrast the planted clayey silt showed an increased methane oxidation potential compared to the bare column. The spreading root system forms secondary macro-pores, and hence amplifies the air diffusivity and sustain the oxygen supply to the methanotrophic bacteria. Water is produced during methane oxidation, causing leachate. Vegetation reduces the leachate by evapotranspiration. Furthermore, leguminous plants support the enrichment of soil with nitrogen compounds and thus improving the methane oxidation process. In conclusion, vegetation is relevant for the increase of oxygen diffusion into the soil and subsequently enhances effective methane oxidation in landfill cover soils.     

Evaluating the economic effects of climate change on the European sardine fishery

This study evaluates the economic effects of climate change on one of the most relevant fisheries of the Iberian Peninsula, the European sardine fishery; a fishing ground that is particularly sensitive to environmental impacts. For this, the sea surface temperature is introduced into the problem as an additional variable. This variable allows for the gathering of climate change evidence and its repercussions on the oceans and, consequently, on the marine life and ecosystems. Various plausible scenarios are posed with respect to the trends involving the sea surface temperature. The results show that if the trend of rising surface temperatures continues in the Iberian-Atlantic fishing grounds, both the sardine biomass and the expected profits will noticeably decrease. The biomass and profits will further decrease with greater intensity if the immediate effects of global warming on sea surface temperature become more significant. On the other hand, in a palliation of global warming scenario, both variables decrease to a lesser degree.     

Impact of silver nanoparticles on natural marine biofilm bacteria

There has been a recent increase in the use of silver nanoparticles (Ag NPs) in a wide range of consumer products due to their highly effective antimicrobial properties. However, Ag NPs give cause for concern since their wide use makes them likely to be released into aquatic ecosystems and potentially affect natural bacterial communities. In this study marine biofilms were grown in situ in a coastal site (Singapore Harbour) and exposed in the laboratory for a further 24 h to 0-2000 μg L⁻¹ of well characterised Ag NPs. Increasing concentrations of Ag NPs caused a significant decrease in biofilm volume and biomass, and Ag uptake by biofilms per unit of volume was also dependent on concentration. Terminal fragment length polymorphisms and subsequent cluster and phylogenetic analysis showed the presence of major bacterial groups in biofilms irrespective of treatment with Ag NPs. This implies that even at the highest concentrations studied these taxonomic groups were not displaced. Nevertheless, biofilm succession was impeded on Ag NP treated biofilms, affecting the relative abundance of major bacterial groups in the biofilm community, with potential longer term effects on biofilm development and function.     

A first approximation kinetic model to predict methane generation from an oil sands tailings settling basin

A small fraction of the naphtha diluent used for oil sands processing escapes with tailings and supports methane (CH(4)) biogenesis in large anaerobic settling basins such as Mildred Lake Settling Basin (MLSB) in northern Alberta, Canada. Based on the rate of naphtha metabolism in tailings incubated in laboratory microcosms, a kinetic model comprising lag phase, rate of hydrocarbon metabolism and conversion to CH(4) was developed to predict CH(4) biogenesis and flux from MLSB. Zero- and first-order kinetic models, respectively predicted generation of 5.4 and 5.1 mmol CH(4) in naphtha-amended microcosms compared to 5.3 (+/-0.2) mmol CH(4) measured in microcosms during 46 weeks of incubation. These kinetic models also predicted well the CH(4) produced by tailings amended with either naphtha-range n-alkanes or BTEX compounds at concentrations similar to those expected in MLSB. Considering 25% of MLSB's 200 million m(3) tailings volume to be methanogenic, the zero- and first-order kinetic models applied over a wide range of naphtha concentrations (0.01-1.0 wt%) predicted production of 8.9-400 million l CH(4) day(-1) from MLSB, which exceeds the estimated production of 3-43 million l CH(4) day(-1). This discrepancy may result from heterogeneity and density of the tailings, presence of nutrients in the microcosms, and/or overestimation of the readily biodegradable fraction of the naphtha in MLSB tailings.