Combined steam-dry reforming of toluene in syngas over CaNiRu/Al2O3 catalysts

Cracking, steam reforming, dry reforming, and combined steam and dry reforming of toluene in model syngas were performed using catalysts to simulate tar removal produced during biomass gasification. The catalysts were prepared by adding Ru, Ca, and Mn to Ni-based catalysts, and their properties were measured using BET, pulse CO chemisorption, XRD and TG. In steam and dry reforming of toluene, a high toluene conversion was observed with increasing Ca content in the catalyst and catalysts containing Ca showed a higher activity than those containing Mn. In combined steam-dry reforming with syngas, 1%CaNiRu/Al₂O₃ indicated a conversion of 93.9% at 800°C.     

When and where do we see the proximity effect of a new park? –A case study of the Dream Forest in Seoul,Korea

This study aimed to unpack the dynamic proximity effects of a park on residential values in the urban regeneration context: first by the development phase of the park, and second, by specific characteristics of the residential units. The study site is the Dream Forest in Seoul, South Korea, and the study period is from 2006 to 2015. The two-fold multilevel regression analysis suggests that the Dream Forest began exerting proximity effects from the time of site acquisition by the city, which peaked at a 3.7% price increment per 100-meter distance to the park from a prototypical housing unit, soon after the public announcement of the park procurement plan. During construction, inauguration and stabilization, the effect has remained at around 3.0%. The analysis also suggests that the proximity effect applies unevenly to housing units: apartment type or older housing units are more sensitive to the externality effects than their counterparts – multifamily type or newer housing units.     

Air Pollution in the Republic of Korea

This paper discusses the potential for using commercially available treatment techniques to remove VOCs from hazardous waste streams and addresses some of the issues associated with making waste treatment a viable VOC emission control technique for hazardous waste management facilities. It discusses the waste streams of concern because of their volatile constituents and describes potentially applicable treatment techniques. The use of models for treatment process design is described. Finally, the paper discusses treatment cost, treatment residuals, and considerations of importance in choosing where in the life cycle of a hazardous waste stream to treat it.     

Male's return rate, rather than territory fidelity and breeding dispersal, explains geographic variation in song sharing in two populations of an oscine passerine (Oreothlypis celata)

Males of some oscine passerines learn and share songs of neighboring males. This process can lead to the formation of song pattern neighborhoods or microhabitat song dialects. The degree to which song sharing occurs between populations and the spatial scale over which neighboring males share songs, however, can vary widely, and interpopulation comparisons have suggested that song sharing is more common in residents than in migrants. Here, we examine two populations of the orange-crowned warbler (Oreothlypis celata) to quantify patterns of song sharing at the northern (long-distance migrant) and southern (short-distance migrant) edges of the breeding distribution and to test if return rate, territory fidelity, and breeding dispersal explain the patterns found in the two populations. The southern population (O. celata sordida breeding on Santa Catalina Island, California; 33°N) had a higher annual return rate to their territories and exhibited higher song sharing in neighborhoods than their counterparts (O. celata celata breeding in Fairbanks, Alaska; 64°N). Year-to-year patterns of territory fidelity and breeding dispersal distances were similar between populations. Our results suggest that if migratory distance generally covaries with the proportion of returning males, this could explain different levels of song sharing between the short- and long-distance migrants.     

Kinetic modeling of fenton oxidation of phenol and monochlorophenols

A kinetic model, consisting of 28 reactions, was proposed to understand the key mechanism of the Fenton oxidation of phenol and o-, m-, and p-chlorophenols. Particular attention is paid to the interactions of the organic intermediates with the Fe species. The proposed model reasonably predicts the decomposition kinetics and by-product formation for the different phenols at widely varying levels of Fe2+, H2O2, and the phenols. For the phenols and intermediates, change in concentrations with time was predicted within 20-30% deviation from the measured data. The single model predicts the overall kinetics of Fenton oxidation of all the tested phenols by adjusting the rate constant of hydroxyl radical for each phenol. Sensitivity analysis indicates that the key reactions are those that directly govern the levels of OH radical and Fe2+. Both the model prediction and the experimental results show that the decomposition rate could be complicated particularly by the availability of Fe2+. Understanding the interactions of the organic intermediates with Fe2+ is thus of critical importance to improve the decomposition performance.     

Effect of water content on transient nonequilibrium NAPL-gas mass transfer during soil vapor extraction

The effect of water content on the volatilization of nonaqueous phase liquid (NAPL) in unsaturated soils was characterized by one-dimensional venting experiments conducted to evaluate the lumped mass transfer coefficient. An empirical correlation based upon the modified Sherwood number, Peclet number, and normalized mean grain size was used to estimate initial lumped mass transfer coefficients over a range of water content. The effects of water content on the soil vapor extraction SVE process have been investigated through experimentation and mathematical modeling. The experimental results indicated that a rate-limited NAPL-gas mass transfer occurred in water-wet soils. A severe mass transfer limitation was observed at 61.0% water saturation where the normalized effluent gas concentrations fell below 1.0 almost immediately, declined exponentially from the initiation of venting, and showed long tailing. This result was attributed to the reduction of interfacial area between the NAPL and mobile gas phases due to the increased water content. A transient mathematical model describing the change of the lumped mass transfer coefficient was used. Simulations showed that the nonequilibrium mass transfer process could be characterized by the exponent beta, a parameter which described the reduction of the specific area available for NAPL volatilization. The nonequilibrium mass transfer limitations were controlled by the soil mean grain size and pore gas velocity, were well described by beta values below 1.0 at low water saturation, and were well predicted with beta values greater than 1.0 at high water saturation.     

Molecular markers of heavy metal toxicity--a new paradigm for health risk assessment

Last decade has witnessed increased interest in studies dealing with molecular markers of health and disease expression of genes. Specific toxicant "signatures" have been detected using genome base technologies such as microarrays. Further toxins have been classified on the basis of these signatures. Knowledge on these signatures has helped in the identification of novel drug candidates. This review discusses the gene expression studies recently made on arsenic, cadmium, mercury, chromium, lead, copper, nickel, manganese, and other essential elements. Toxicogenomics standards and their organizations have also been briefly described. Although this information can not be considered as complete, recent reports from different laboratories on bacteria, fish, laboratory animals and humans have been summarized. It is expected that toxicogenomics data presented in this review will be helpful in planning and excretion of human health risk assessment programs.     

Metabolic responses in zebrafish (Danio rerio) exposed to zinc and cadmium by nuclear magnetic resonance -based metabolomics

Heavy metals are common marine and soil pollutants that are mainly the result of industrial activity, and are a threat to the environment and human health. In this study, ¹H nuclear magnetic resonance (NMR)-based metabolomics was applied to adult Danio rerio to monitor the metabolic change as a response to ZnCl₂ and CdCl₂ exposure at different concentrations for 72?h. NMR spectroscopy was used to identify and quantify the metabolites extracted from D. rerio. The metabolite profiles of the control and heavy metal exposed group were classified by partial least squares – discriminant analysis (PLS-DA) analysis, and potential contaminant-specific biomarkers were suggested. For the ZnCl₂-exposed zebrafish, the levels of ATP, aspartate and NAD⁺ were increased, whereas the levels of formate, inosine, hypoxanthine and succinate decreased. In addition, the CdCl₂-exposed zebrafish showed an increase in the levels of ATP and formate and a decrease in the levels of glutamate, inosine and glutathione. Overall, Zn and Cd may lead to neurotoxicity, disturbances in the energy metabolism and oxidative stress. Our finding demonstrated that the application of NMR-based metabolomics might be useful for detecting the toxicity caused by sub-lethal concentrations of heavy metal contaminants in the environment.     

Removal of contaminants in leachate from landfill by waste steel scrap and converter slag

This study may be the first investigation to be performed into the potential benefits of recycling industrial waste in controlling contaminants in leachate. Batch reactors were used to evaluate the efficacy of waste steel scrap and converter slag to treat mixed contaminants using mimic leachate solution. The waste steel scrap was prepared through pre-treatment by an acid-washed step, which retained both zero-valent iron site and iron oxide site. Extensive trichloroethene (TCE) removal (95%) occurred by acid-washed steel scrap within 48 h. In addition, dehalogenation (Cl⁻ production) was observed to be above 7.5% of the added TCE on a molar basis for 48 h. The waste steel scrap also removed tetrachloroethylene (PCE) through the dehalogenation process although to a lesser extent than TCE. Heavy metals (Cr, Mn, Cu, Zn, As, Cd, and Pb) were extensively removed by both acid-washed steel scrap and converter slag through the adsorption process. Among salt ions (NH₄⁺, NO₃⁻, and PO₄³⁻), PO₄³⁻ was removed by both waste steel scrap (100% within 8 h) and converter slag (100% within 20 min), whereas NO₃^- and NH₄⁺ were removed by waste steel scrap (100% within 7 days) and converter slag (up to 50% within 4 days) respectively. This work suggests that permeable reactive barriers (PRBs) with waste steel scrap and converter slag might be an effective approach to intercepting mixed contaminants in leachate from landfill.