Sonochemical degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxins in aqueous solution with Fe(III)/UV system

2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) was rapidly decreased by sonication in aqueous solution. The degradation efficiency was strongly influenced by ultrasonic power and reaction temperature. An initial 2,3,7,8-TeCDD concentration of 20 ng l(-1) was completely degraded within 60 min under sonochemical conditions using a 20 kHz frequency with a 150 W ultrasound power. The activation energy is 21.9 kJ/mol in the temperature range of 10-40 degrees C, suggesting a diffusion-controlled reaction. To increase the efficiency of 2,3,7,8-TeCDD treatment, degradation system combined ultrasound with Fe(III) (2 x 10(-4)mol l(-1)) and UV irradiation. Both UV and Fe(III) induced Fenton, Fenton-like and photo-Fenton reactions, leading to additional OH radicals and rapid 2,3,7,8-TeCDD removal.     

Effects of biosurfactants on assays of PCB congeners in transgenic arabidopsis plants carrying a recombinant guinea pig AhR-mediated GUS reporter gene expression system

The transgenic Arabidopsis plants carrying a recombinant guinea pig (g) aryl hydrocarbon receptor (AhR)-mediated β-glucuronidase (GUS) reporter gene expression system were generated for assays of polychlorinated biphenyl (PCB) congeners. The selected transgenic Arabidopsis plant XgD2V11-6 exhibited a correlation between uptake of PCB126 and PCB126-induced GUS activity. Also, the plants showed induced GUS activity towards the supplemental indole 3-acetic acid (IAA). Thus, the GUS assay may reflect induction by both endogenous and exogenous AhR ligands. When biosurfactants, MEL-B, produced in the culture of yeast isolated from plants were used for assays of PCB congeners in the transgenic Arabidopsis plants, they showed marked PCB126 dose-dependent and toxic equivalency factor (TEF) dependent GUS activities. The effects of biosurfactants were clearer when the plants were cultivated on soils containing PCB congeners for 7 days as compared with on soils for 3 days as well as in the medium for 3 days. Therefore, it was estimated that biosurfactants form micellae with PCB congeners, which are easily uptaken by the plants in a mode of passive diffusion, transport into the aerial parts and then induce GUS activity.     

Diffusion of Policy Discourse into Rural Spheres Through Co-Management of State Forestlands: Two Cases from West Java,Indonesia

In the context of state forestland management in tropical regions, the implementation of a co-management approach has been widely advocated in order to include the voices of local people and accommodate their interests in management decision-making. Most co-management literatures, however, underestimate the significance of statutory authority held by state to control forestlands and resources. By clarifying the implications of state ownership of forestland, this article aims to critically examine co-management processes with reference to Foucault's notion of power and subject. Case studies were conducted at two co-management pilot sites in Gunung Halimun-Salak National Park, West Java, Indonesia. Findings demonstrate that co-management processes actually materialize shared decision-making arrangements between state forest bureaucracy and rural people through the application of equity approaches, such as deliberation, negotiation, and experimentation. At the same time, these processes can also function to diffuse state policy discourse in rural spheres, which makes rural subjects who accept and practice the policy discourse. The research also reveals that the diffusion process is complex and does not necessarily make a durable subject unless they are pertinently organized. The results of this research indicate that co-management of state forestlands is a double-edged process for local people who risk becoming a proxy of state bureaucracy in the implementation of state policy. Proponents of co-management should, therefore, critically examine whether new institutional arrangements, which are developed through co-management, truly reflect values and needs of local people and assist them to develop a pertinent subject to deal with it.     

Reactions of model compounds of phenol resin in sub- and supercritical water under an argon atmosphere

Model compounds of phenol resin were reacted in sub- and supercritical water to clarify the mechanism of the decomposition reaction of plastics in water. Cleavage reaction of methylene bonds was confirmed in the reactions of model compounds of phenol resin such as bis(hydroxyphenyl)methanes in sub- and supercritical water under an Ar atmosphere, although the methylene bond was stable in thermal reactions. It was also confirmed that sub- and supercritical water played important roles not only as a stable solvent thermally, but also as a chemical reagent. Received: July 19, 2000 / Accepted: September 14, 2000     

Use and disposal of large home electronic appliances in Vietnam

In this study, e-waste flows of five large home appliances (color televisions, refrigerators, washing machines, personal computers, and air conditioners) in Vietnam are investigated. A social survey was performed to investigate the situation on using appliances in households as well as on the disposal of appliances by the first users. Future quantities of e-waste were estimated using a model that combines use of the Weibull distribution, the logistic function, and the population balance model. It was forecast that about 3.86 million appliances, or 114 000 tons, will be discarded in 2010, and about 17.2 million appliances, or 567 000 tons, in 2025, showing a rapid increase of e-waste in the near future.     

Scenario study for a regional low-carbon society

Japan should undertake drastic greenhouse gas (GHG) emission reductions by the middle of this century in order to mitigate climate change problems. Municipalities should design and execute scenarios toward a low-carbon society suited to their respective regions. This study describes long-term future visions developed for Shiga Prefecture targeting CO₂ emission reductions of 30–50% by 2030, and presents scenarios to attain these targets, which are achievable with mild economic growth. For targets over a 30% reduction, region-specific measures including land-use reform and citizen behavioral changes are necessary. Compared with other regions in Japan, Shiga should give priority to a modal shift in transport, efficiency improvements in industry, and photovoltaic energy generation.     

Assays of dioxins and dioxin-like compounds in actually contaminated soils using transgenic tobacco plants carrying a recombinant mouse aryl hydrocarbon receptor-mediated β-glucuronidase reporter gene expression system

This article has been retracted.     

Degradation of polychlorinated dibenzo-p-dioxins in aqueous solution by Fe(II)/H2O2/UV system

The photodegradation of polychlorinated dibenzo-p-dioxins (PCDDs), which include tetra- to octa-CDDs (TeCDD, PeCDD, HxCDD, HpCDD and OCDD), was carried out in the presence of Fe(II) and H2O2 mixed reagent. The degradation efficiency was strongly influenced by UV irradiation, and the initial concentrations of H2O2 and Fe(II). An initial TeCDD concentration of 10 ng l(-1) was completely degraded within 20 min under the optimum conditions. All PCDDs tested were successfully degraded by Fe(II)/H2O2/UV treatment and complete degradation of TeCDD, PeCDD and HxCDD was achieved within 120 min. PCDD photodegradation rates decreased with the number of chlorine atoms. The degradation process of TeCDD by this system seems to be initiated by an oxidative reaction (OH* radical attack) because less chlorinated DDs as intermediate products were not detected. From the Frontier electron density calculation, the first OH* radical attack positions on TeCDD were found to be four C atoms neighboring two O atoms. The decomposition of TeCDD gave 4,5-dichlorocatechol as an intermediate product. A TeCDD degradation scheme was proposed based on the identified intermediate and the values of Frontier electron density. Based on these results, Fe(II)/H2O2/UV system could be useful technology for the treatment of wastewater containing persistent pollutants such as dioxins and polychlorinated biphenyls.     

SUSPENDED SEDIMENT DYNAMICS IN SMALL FOREST STREAMS OF THE PACIFIC NORTHWEST1

This paper reviews suspended sediment sources and transport in small forest streams in the Pacific Northwest region of North America, particularly in relation to riparian management. Mass movements, reading and yarding practices, and burning can increase the supply of suspended sediment. Sediment yields recovered to pre‐harvest levels within one to six years in several paired catchment studies. However, delayed mass movements related to roads and harvesting may produce elevated suspended sediment yield one or more decades after logging. There is mixed evidence for the role of streamside tree throw in riparian buffers in supplying sediment to streams. Harvesting within the riparian zone may not increase suspended sediment yield if near stream soils are not disturbed. Key knowledge gaps relate to the relative roles of increased transport capacity versus sediment supply, the dynamics of fine sediment penetration into bed sediments, and the effects of forest harvesting on suspended sediment at different scales. Future research should involve nested catchments to examine suspended sediment response to forest practices at multiple spatial scales, in combination with process‐based field studies.     

Removal of heavy metals in rinsing wastewater from plating factory by adsorption with economical viable materials

The removal of heavy metals from plating factory wastewater with economical materials was investigated by the column method. Montmorillonite, kaolin, tobermorite, magnetite, silica gel and alumina were used as the economical adsorbents to wastewater containing Cd(II), Cr(VI), Cu(II) and Pb(II). This removal method of heavy metals proved highly effective as removal efficiency tended to increase with increasing pH and decrease with increasing metal concentration. The removal percentages by adsorption onto montmorillonite, tobermorite, magnetite, and silica gel showed high values for all metals. From the results for the heat of adsorption, the adsorption process in the present study might be chemisorption. The proposed method was successfully applied to the removal of Cd(II), Cr(VI) and Cu(II) in rinsing wastewater from plating factory in Nagoya City, Aichi Prefecture, Japan. Since the economical adsorbents used can be obtained commercially because they are easily synthesized, the wastewater treatment system developed is rapid, simple and cheap for the removal of heavy metals.