Effect of arsenic and mercury speciation on inhibition of respiration rate in activated sludge systems

The inhibition effect of arsenite, As(III), arsenate, As(V), inorganic mercury, Hg(II) and methylmercury, MeHg, on the respiration rate of activated heterotrophic sludge microorganisms was evaluated. As(III) and MeHg were much more toxic to activated sludge than As(V) and Hg(II) respectively. The effect of various experimental parameters on the toxicity, such as sludge age, concentration of suspended solids and exposure time, was investigated. An increase of sludge age or the concentration of suspended solids reduces the observed inhibition. Longer exposure seems to dramatically increase the inhibition of As(III), MeHg and Hg(II) during the first hours of exposure, while the later inhibition increases at a slower rate. On the contrary, in the presence of As(V), 24 hours after exposure, the respiration rate was similar to that of the control biomass.     

Evaluating the Efficiency of a Uniform N-Input Tax under Different Policy Scenarios at Different Scales

Nitrate pollution from agriculture is an important environmental externality, caused by the excessive use of fertilizers. The internalization of this problem, via a tax on mineral nitrogen, could lead to a second best solution, reducing nitrate emissions. Several authors suggest that a reduction in agricultural support could produce similar results. In this paper, we examine the effects of different levels of a uniformly implemented nitrogen tax in France under two policy scenarios, corresponding to post Agenda 2000 and 2003 Luxembourg reforms of European Union’s Common Agricultural Policy, in order to reveal the synergies and conflicts between the tax and the policy scenarios in terms of nitrate emissions abatement. The analysis is performed at different geographical scales, from the national to the regional and is based on a bioeconomic approach that involves the coupling of the economic model AROPAj with the crop model STICS. Results show that the efficiency of the N-tax varies according to the geographical scale of the analysis and the type of farming. Furthermore, we prove that a uniform implementation may lead to perverse effects that should always be taken into account when introducing second-best instruments.     

Radiosynthesis of perfluorooctanesulfonate (PFOS) and perfluorobutanesulfonate (PFBS), including solubility, partition and adhesion studies

Here, we describe for the first time the synthesis of [³⁵S] PFOS and [³⁵S] PFBS with sulfur-35 enriched sulfur dioxide as the radiolabelled reagent, resulting in 2.5 and 2.3 mCi of product, respectively. Basic information concerning the physicochemical properties of perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate (PFBS) and perfluorooctanoic acid (PFOA) are still limited. Hence, we utilized these radiolabelled perfluoroalkanesulfonates (PFSAs), as well as carbon-14 labelled perfluorooctanoic acid ([¹⁴C] PFOA) to determine some basic characteristics of physiological and experimental significance.The solubility of PFOS in buffered aqueous solutions at pH 7.4 was found to be severely reduced in the presence of potassium and sodium ions, which, however, did not reduce the solubility of PFOA or PFBS. PFOS was found to adhere to a small extent to polypropylene and polystyrene, whereas no such adhesion of PFOA or PFBS was detected. The extents of adhesion of PFOS and PFOA to glass were found to be 20% and 10%, respectively. For the first time, the partition coefficients for PFOS, PFBS and PFOA between n-octanol and water were determined experimentally, to be −0.7, −0.3, and 1.4, respectively, reflecting the difference in the amphiphilic natures of these molecules.     

Fate of large-scale vortices in idealized tidal lagoons

Environmental Fluid Mechanics - The generation and evolution of tidally-induced vortices in coastal and estuarine regions can influence water quality and sedimentary processes. These effects must...     

Indoor concentrations of PM2.5 and associated water-soluble and labile heavy metal fractions in workplaces: implications for inhalation health risk assessment

Environmental Science and Pollution Research - PM2.5 (i.e., particles with aerodynamic diameters less than 2.5 μm) and the associated water-soluble, dissolved, and labile fractions of...     

Seeing the Wind (Farm): Applying Q-methodology to Understand the Public’s Reception of the Visuals Around a Wind Farm Development

This research investigates the reception of the visual representations of a wind farm (WF) development by local stakeholders. Using non-verbal Qmethodology, residents of Lesvos’ island, Greece, sort images according to how these images represented their opinion about the proposed Aegean Link WF project. We found three opinion types. The “Risk Averter” type is focused on the various risks of constructing and operating the Aegean Link wind development. The “Green Developer” type believes that the renewable energy project will benefit both their local community and the environment. The “Realist” type defers to expert knowledge to make decisions about project outcomes and is sceptical of media bias. While the former two types seem to form their visual opinions based on whether they are in favour or against (respectively) of the WF development, the Realist opinion is rather guided by carefully considering whether the visual stimuli are representative of the project’s actual characteristics.     

Modeling an air pollution episode in northwestern United States: Identifying the effect of nitrogen oxide and volatile organic compound emission changes on air pollutants formation using direct sensitivity analysis

Air quality impacts of volatile organic compound (VOC) and nitrogen oxide (NO_x) emissions from major sources over the northwestern United States are simulated. The comprehensive nested modeling system comprises three models: Community Multiscale Air Quality (CMAQ), Weather Research and Forecasting (WRF), and Sparse Matrix Operator Kernel Emissions (SMOKE). In addition, the decoupled direct method in three dimensions (DDM-3D) is used to determine the sensitivities of pollutant concentrations to changes in precursor emissions during a severe smog episode in July of 2006. The average simulated 8-hr daily maximum O₃ concentration is 48.9 ppb, with 1-hr O₃ maxima up to 106 ppb (40 km southeast of Seattle). The average simulated PM_2.5 (particulate matter with an aerodynamic diameter <2.5 μm) concentration at the measurement sites is 9.06 μg m^?3, which is in good agreement with the observed concentration (8.06 μg m^?3). In urban areas (i.e., Seattle, Vancouver, etc.), the model predicts that, on average, a reduction of NO_x emissions is simulated to lead to an increase in average 8-hr daily maximum O₃ concentrations, and will be most prominent in Seattle (where the greatest sensitivity is??0.2 ppb per % change of mobile sources). On the other hand, decreasing NO_x emissions is simulated to decrease the 8-hr maximum O₃ concentrations in remote and forested areas. Decreased NO_x emissions are simulated to slightly increase PM_2.5 in major urban areas. In urban areas, a decrease in VOC emissions will result in a decrease of 8-hr maximum O₃ concentrations. The impact of decreased VOC emissions from biogenic, mobile, nonroad, and area sources on average 8-hr daily maximum O₃ concentrations is up to 0.05 ppb decrease per % of emission change, each. Decreased emissions of VOCs decrease average PM_2.5 concentrations in the entire modeling domain. In major cities, PM_2.5 concentrations are more sensitive to emissions of VOCs from biogenic sources than other sources of VOCs. These results can be used to interpret the effectiveness of VOC or NO_x controls over pollutant concentrations, especially for localities that may exceed National Ambient Air Quality Standards (NAAQS).

Implications: The effect of NO_x and VOC controls on ozone and PM_2.5 concentrations in the northwestern United States is examined using the decoupled direct method in three dimensions (DDM-3D) in a state-of-the-art three-dimensional chemical transport model (CMAQ). NO_x controls are predicted to increase PM_2.5 and ozone in major urban areas and decrease ozone in more remote and forested areas. VOC reductions are helpful in reducing ozone and PM_2.5 concentrations in urban areas. Biogenic VOC sources have the largest impact on O₃ and PM_2.5 concentrations.     

Decision support models for solid waste management: Review and game-theoretic approaches

This paper surveys decision support models that are commonly used in the solid waste management area. Most models are mainly developed within three decision support frameworks, which are the life-cycle assessment, the cost–benefit analysis and the multi-criteria decision-making. These frameworks are reviewed and their strengths and weaknesses as well as their critical issues are analyzed, while their possible combinations and extensions are also discussed. Furthermore, the paper presents how cooperative and non-cooperative game-theoretic approaches can be used for the purpose of modeling and analyzing decision-making in situations with multiple stakeholders. Specifically, since a waste management model is sustainable when considering not only environmental and economic but also social aspects, the waste management bargaining game is introduced as a specific decision support framework in which future models can be developed.     

Climate Change Implications on Flood Response of a Mountainous Watershed

The modification of the flood response due to future climate change is presented for the Illecillewaet watershed of British Columbia, Canada. The Canadian Centre for Climate Modeling Analysis General Circulation Model (CGCMa1) was used for the assessment of changes of precipitation and temperature due to climate change. The runoff was simulated using the UBC watershed model and considering, also, changes on the spatial distribution of precipitation with elevation, cloud cover, glaciers, vegetation distribution, vegetation biomass production, and plant physiology. The results show that the future climate would be wetter and warmer than the present climate affecting the type, the magnitude and the temporal distribution of floods as well as the frequency of flood peaks. The above changes in the flood response of the study watershed could be explained by the change of the form of precipitation from snowfall to rainfall, the consequent decrease of the snowpack, and the initiation of the snowmelt earlier in the season, under the altered climate.