Experimental investigation of the complex deflagration phenomena of hybrid mixtures of activated carbon dust/hydrogen/air

This paper aims to develop quantitative insights based on measured deflagration parameters of hybrid mixtures of activated carbon (AC) dust and hydrogen (H₂) gas in air. The generated experimental evidence is used to reject the claim of the null hypothesis (H₀) that severity of deflagrations of H₂/air mixtures always bound the severity of deflagrations of heterogenous combustible mixtures of AC dust/H₂/air containing the same H₂ concentrations as in the H₂/air binaries. The core insights of this investigation show that the maximum deflagration pressure rise (ΔP_MAX) and maximum rate of pressure rise ((dP/dt)_MAX) of this hybrid mixture are greater than those corresponding to deflagrations of H₂/air mixtures for all the dust and H₂ concentrations being examined. The deflagration severity indices (K_St and ES) of the hybrid mixture containing 29 mol% H₂ are found to be greater than those of the H₂/air mixture containing 29 mol% H₂. Also, the minimum explosible concentration (MEC) of the hybrid mixture is lower than that of the AC dust in air only. The insights gained should lead to better realization of the severity of a postulated safety-significant accident scenario associated with on-board cryoadsorption H₂ storage systems for fuel-cell (FC) powered light-duty vehicles. The identified insights could also be relevant to other industrial processes where combustible dusts are generated in the vicinity of solvent vapors. Moreover, these insights should be useful for supporting quantitative risk assessment (QRA) of on-board H₂ storage systems, designing improved safety measures for cryoadsorption H₂ storage tanks, and guiding H₂ safety standards and transportation regulations.     

Assessment of airborne environmental bacteria and related factors in 25 underground railway stations in Seoul,Korea

This study assessed bacterial concentrations in indoor air at 25 underground railway stations in Seoul, Korea, and investigated various related factors including the presence of platform screen doors (PSD), depth of the station, year of construction, temperature, relative humidity, and number of passengers. A total of 72 aerosol samples were collected from all the stations. Concentrations of total airborne bacteria (TAB) ranged from not detected (ND) to 4997 CFU m^?3, with an overall geometric mean (GM) of 191 CFU m^?3. Airborne bacteria were detected at 23 stations (92%) and Gram-negative bacteria (GNB) were detected at two stations (8%). TAB concentrations of four stations (16%) exceeded 800 CFU m^?3, the Korea indoor bio-aerosol guideline. The results of the study showed that TAB concentrations at the stations without PSD showed higher TAB concentrations than those with PSD, though not at statistically significant levels. TAB concentrations of deeper stations revealed significantly higher levels than those of shallower stations. Based on this study, it is recommended that mitigation measures be applied to improve the indoor air quality (IAQ) of underground railway stations in Seoul, with focused attention on deeper stations.     

Sorption of imidacloprid and its metabolites on tropical soils

Abstract

The sorption of imidacloprid (l‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐N‐nitro‐2‐imidazolid‐inimine) (IMI) and its metabolites imidacloprid‐urea (l‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐2‐imidazol‐idinone) (IU), imidacloprid‐guanidine (l‐[(6‐chloro‐3‐pyridinyl)‐methyl]‐4,5‐dihydro‐lH‐imidazol‐2‐amine) (IG), and imida‐cloprid‐guanidine‐olefin ( 1 ‐[(6‐chloro‐3‐pyridinyl)methyl]‐lH‐imidazol‐2‐amine) (IGO) was determined on six typical Brazilian soils. Sorption of the chemicals on the soil was characterized using the batch equilibration method. The range and order of sorption (Kd) on the six soils was IG (4.75–134) > IGO (2.87–72.3) > IMI (0.55 ‐16.9) > IU (0.31–9.50). For IMI and IU, Kd was correlated with soil organic carbon (OC) content and CEC, the latter due to the high correlation between OC and cation exchange capacity (CEC) (R²=0.98). For IG and IGO, there was no correlation of sorption to clay, pH, OC or CEC due to the high sorption on all soils. Average Koc values were IU = 170, IMI = 362, IGO = 2433, and IG = 3500. Although Kd and Koc values found were consistently lower than those found in soils developed in non‐tropical climates, imidacloprid and its metabolites were still considered to be slightly mobile to immobile in Brazilian soils.     

Rethinking the management of transboundary freshwater resources: a critical examination of modern international law and practice

Available freshwater stocks are being depleted and impaired on a widespread basis, with acute shortages an increasingly frequent condition in arid climates. In transboundary basins, water scarcity and pollution compound interstate tension and contribute to human suffering and ecological damage. This article provides theoretical perspectives on shared freshwater disputes and on the evolution of the international law of shared water resources. It argues that the UN Convention on the Non-Navigational Uses of International Watercourses (ratified by some countries, but not yet in force) is inadequate as a framework convention in terms of providing general obligations on the future parties or an institutional framework for future action. The paper suggests that three critical concepts be considered in future management of shared water resources: (1) the unitary character of watersheds (where the absence of extra-basin diversions allows); (2) joint or "communitarian" watershed management; and (3) the relevance of international trade to alleviating regional food stress, resulting from local water scarcity. Finally, it proposes the establishment of an international advisory body on shared water disputes, modelled after the Intergovernmental Panel on Climate Change (IPCC), whose role is codified in the Kyoto Protocol to the United Nations Framework Convention on Climate Change.     

Debriefing with teachers after the Marmara earthquake: an evaluation study1

The aim of this study was to evaluate the effectiveness of the debriefing meetings conducted after the 1999 earthquakes in Marmara, Turkey. The sample consisted of 265 teachers, 223 of whom attended the debriefing meetings. The personal satisfaction ratings of the teachers who attended the meetings revealed that they found the sessions satisfactory. The results of the comparison between those who reported that they benefited from the meetings and those who felt they did not indicated that the first group had lower scores on all of the psychopathology measures. A comparison between 42 teachers who did not attend the meetings and a randomly chosen group of 45 teachers who did attend revealed that the two groups differed significantly in terms of their post‐traumatic stress symptom scores. The findings of the study suggest that, in general, the teachers' debriefing sessions were satisfactory.     

Formation of submicron sulfate and organic aerosols in the outflow from the urban region of the Pearl River Delta in China

Size-resolved chemical compositions of non-refractory submicron aerosols were measured using a quadrupole Aerodyne aerosol mass spectrometer at a rural site near Guangzhou in the Pearl River Delta (PRD) of China in the summer of 2006. Two cases characterized as the outflows from the PRD urban region with plumes of high SO₂ concentration were investigated. The evolution of sulfate size distributions was observed on a timescale of several hours. Namely mass concentrations of sulfate in the condensation mode (with vacuum aerodynamic diameters (D_va) < 300 nm) increased at a rate of about 0.17–0.37 ppbv h^?1 during the daytime. This finding was consistent with the sulfuric acid production rates of about 0.17–0.3 ppbv h^?1, as calculated from the observed gas-phase concentrations of OH (～3.3 × 10⁶–1.7 × 10⁷ cm^?3) and SO₂ (～3–21.2 ppbv). This implies that the growth of sulfate in the condensation mode was mainly due to gas-phase oxidation of SO₂. The observed rapid increase was caused mainly by the concurrent high concentrations of OH and SO₂ in the air mass. The evolution of the mass size distributions of m/z 44, a tracer for oxygenated organic aerosol (OOA), was very similar to that of sulfate. The mass loadings of m/z 44 were strongly correlated with those of sulfate (r² = 0.99) in the condensation mode, indicating that OOA might also be formed by the gas-phase oxidation of volatile organic compound (VOC) precursors. It is likely that sulfate and OOA were internally mixed throughout the whole size range in the air mass.     

The Reuse of Urban and Industrial Waste in Tai-Lin-Pu Reclamation Project,Taiwan

Abstract

This study introduces the principles of KMG's (Kaoshiung Municipal Government) dealing with the non-poisonous urban and industrial waste through reclamation of shore land in reinforcing a sense of coastal protection and land development in Tai-Lin-Pu coastal area, southern Taiwan.

Through a series of experimental studies, we found that substitutes of coarse aggregate with a broad spectrum of integrating slag powder, fly ash, and cementitious material can be obtained with a benefit up to 80% saving of cement. the integrated aggregates from the non-poisonous industrial wastes were subsequently made into armour units and used in the field tests at Tai-Lin-Pu coastal area, where the shorelines are seriously eroded. After being subjected to several severe typhoon advents, the results showed that the waste-made units used as the protection breakwater, together with construction wastes and excavated soil as the filling material, prove to be an effective practice in utilizing recycled urban waste to reclaim erosive shore lands. Moreover, this study also demonstrates that through detailed analysis of the waste characteristics, scrap material could be turned into valuable construction aggregates, and highlights the value of non-poisonous urban and industrial waste as a alternative resource for the shore protection engineering.