Dispersion of Pollutants in Street Canyon under Traffic Induced Flow and Turbulence

A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic induced flow rate and turbulence. The method is applied to pollutants dispersion in a street canyon. The approach is based on CFD calculations using Eulerian approach to the continuous phase and Lagrangian approach to the "discrete phase" of moving objects - vehicles. A commercial CFD code StarCD was used into which the Lagrangian model was integrated. As an example a street canyon is taken into consideration. It has the length of 50 m and the aspect ratio of 1.27. The speed of wind was assigned values of 4, 7 and 12 m/s at the altitude of 300 m. The total height of the domain is 115 m. In the study different traffic situations are considered, namely one-way and two-way traffic with different traffic rates per lane. The predictions show that different traffic situations affect pollutants dispersion in the street canyon and that there are also differences in the pollutants dispersion in case of one- and two-way traffic.     

Effect of drying on leaching testing of treated municipal solid waste incineration APC-residues

Air-pollution-control (APC) residues from waste incinerators are hazardous waste according to European legislation and must be treated prior to landfilling. Batch and column leaching data determine which type of landfill can receive the treated APC-residues. CEN standards are prescribed for the batch and column leaching test; however, these standards do not specify whether or not the residue samples should be dried prior to the leaching testing. Laboratory tests were performed in parallel (dried/non-dried) on treated APC-residue samples and evaluated with respect to Cr, Cd, Cu, Pb and Zn leaching. The effect of drying of the wet APC-residue samples was particularly dramatic regarding the leaching of Cr. Drying resulted in 10-100 times more Cr leaching in both batch and columns test. Drying also affected the leaching of Cd, Cu and Pb. Initial Cd leaching was up to 100 times higher in column tests with dried APC-residue than in tests with wet residues. The effect of drying appeared to be a combination of decreasing the reduction capacity of the sample (Cr), decreasing pH (Cd, Cu) and in column tests also a wash-out of salts (probably affecting Cd and Pb). If the leaching tests are intended to mimic landfill conditions, the results of this paper suggest that the tests should be done on wet, non-dried residue samples, although this may be less practical than testing dried samples.     

A roadmap for ladybird conservation and recovery

Ladybirds (Coleoptera: Coccinellidae) provide services that are critical to food production, and they fulfill an ecological role as a food source for predators. The richness, abundance, and distribution of ladybirds, however, are compromised by many anthropogenic threats. Meanwhile, a lack of knowledge of the conservation status of most species and the factors driving their population dynamics hinders the development and implementation of conservation strategies for ladybirds. We conducted a review of the literature on the ecology, diversity, and conservation of ladybirds to identify their key ecological threats. Ladybird populations are most affected by climate factors, landscape composition, and biological invasions. We suggest mitigating actions for ladybird conservation and recovery. Short-term actions include citizen science programs and education, protective measures for habitat recovery and threatened species, prevention of the introduction of non-native species, and the maintenance and restoration of natural areas and landscape heterogeneity. Mid-term actions involve the analysis of data from monitoring programs and insect collections to disentangle the effect of different threats to ladybird populations, understand habitat use by taxa on which there is limited knowledge, and quantify temporal trends of abundance, diversity, and biomass along a management-intensity gradient. Long-term actions include the development of a worldwide monitoring program based on standardized sampling to fill data gaps, increase explanatory power, streamline analyses, and facilitate global collaborations.     

Combined biocidal action of silver nanoparticles and ions against Chlorococcales (S<Emphasis Type="Italic">cenedesmus quadricauda</Emphasis>, <Emphasis Type="Italic">Chlorella vulgaris)</Emphasis> and filamentous algae (<Emphasis Type="Italic">Klebsormidium sp.</Emphasis>)

Despite the extensive research, the mechanism of the antimicrobial and biocidal performance of silver nanoparticles has not been unequivocally elucidated yet. Our study was aimed at the investigation of the ability of silver nanoparticles to suppress the growth of three types of algae colonizing the wetted surfaces or submerged objects and the mechanism of their action. Silver nanoparticles exhibited a substantial toxicity towards Chlorococcales Scenedesmus quadricauda, Chlorella vulgaris, and filamentous algae Klebsormidium sp., which correlated with their particle size. The particles had very good stability against agglomeration even in the presence of multivalent cations. The concentration of silver ions in equilibrium with nanoparticles markedly depended on the particle size, achieving about 6 % and as low as about 0.1 % or even less for the particles 5 nm in size and for larger ones (40–70 nm), respectively. Even very limited proportion of small particles together with larger ones could substantially increase concentration of Ag ions in solution. The highest toxicity was found for the 5-nm-sized particles, being the smallest ones in this study. Their toxicity was even higher than that of silver ions at the same silver concentration. When compared as a function of the Ag⁺ concentration in equilibrium with 5-nm particles, the toxicity of ions was at least 17 times higher than that obtained by dissolving silver nitrite (if not taking into account the effect of nanoparticles themselves). The mechanism of the toxicity of silver nanoparticles was found complex with an important role played by the adsorption of silver nanoparticles and the ions released from the particles on the cell surface. This mechanism could be described as some sort of synergy between nanoparticles and ions. While our study clearly showed the presence of this synergy, its detailed explanation is experimentally highly demanding, requiring a close cooperation between materials scientists, physical chemists, and biologists.     

Leaching from MSWI bottom ash: evaluation of non-equilibrium in column percolation experiments

Impacts of non-equilibrium on results of percolation experiments on municipal solid waste incineration (MSWI) bottom ash were investigated. Three parallel column experiments were performed: two columns with undisturbed percolation and one column with two sets of 1-month-long flow interruptions applied at liquid-to-solid (L/S) ratios of L/S 2L/kg and 12L/kg, respectively. Concentrations of Na, K, Cl(-), Ca, Si, SO(4)(2-), Al, Cu, Ni, Mo, Ba, Pb, Zn, and dissolved organic carbon (DOC) were monitored throughout the entire leaching period; geochemical modeling was used to identify non-equilibrium-induced changes in the solubility control. Despite both physical and chemical non-equilibrium, the columns were found to provide adequate information for readily soluble compounds (i.e., Na, Cl(-), and K) and solubility-controlled elements (i.e., Ca, SO(4)(2-), Ba, Si, Al, Zn, and Pb). The leaching of Cu and Ni was shown to depend strongly on DOC leaching, which was likely affected by physical non-equilibrium during flow interruptions. Consequently, the leaching of Cu and Ni in the undisturbed columns was shown to be by about one order of magnitude lower compared with the interrupted column. The results indicate that the leaching of DOC-related metals in laboratory column experiments may be considerably underestimated compared with full-scale scenarios in which the impacts from non-equilibrium may be significantly lower. The leaching of Mo (or MoO(4)(2-)) may be controlled solely by its availability in the mobile zone, which in turn appeared to be controlled by diffusion from the stagnant zone; no Mo controlling minerals were predicted by the geochemical modeling.     

Stabilization/Solidification of Salt from a Waste Incinerator

ABSTRACT

A laboratory procedure was developed and verified for stabilizing salt produced by an industrial waste incinerator. This procedure is based on salt stabilization by means of an asphalt binder. Conductivity values and relevant anion contents in leachates of stabilized waste with an asphalt coating were near zero. The pH value of these leachates equaled the pH value of the water used, so that the stabilized waste salt represented inert material, posing no environmental hazard. An unusually significant reduction in the volume of processed salt occurred during stabilization. After compacting under 10.4 MPa pressure, the volume of test specimens was almost 55% smaller than the initial salt volume. In practice, this would mean more than a doubling of landfill waste capacity. Volume reduction was successfully explained by means of a mathematical model.     

A model of natural degradation of 17-α-ethinylestradiol in surface water and identification of degradation products by GC-MS

Over the past decade, the environment has been polluted by a wide spectrum of exogenous chemicals and environmental analysis has become one of the most progressive parts of analytical research. The aim of this work was to determine the kinetics of natural degradation, and to identify the degradation products of the massively used estrogenic drug, 17-α-ethinylestradiol. The photodegradation, oxidation and thermostability conditions were selected according to ICH requirements for pharmaceutical stability testing. A simple 72-h photodegradation study in purified water exhibited significant first-order kinetics with the kinetic constant k = 0.0303 h^?1, and degradation halftime 22.8 h. The basic halftime could be reduced to 17.1 h by the addition of sea salt, and increase in temperature. Monohydroxy, dihydroxy and dehydrogenated derivatives of ethinylestradiol with intact steroidal structure were identified as major degradation products resulting from simple photodegradation. The addition of an oxidative agent significantly accelerated the degradation rate; combined with higher temperature, the degradation halftime was reduced to 1.1 h with the first-order kinetic constant k = 0.632 h^?1. TOC analysis showed a notable decrease of organic mass (18% in 3 days) during oxidation experiments, and confirmed the degradation of steroidal structure.