Comparative study of microbial dechlorination of chlorinated ethenes in an aquifer and a clayey aquitard

In order to determine whether natural attenuation of chlorinated ethenes by microbial activity occurs in aquitards, sediments at a site contaminated with tetrachloroethene were vertically studied by drilling. The distribution of microbes (Dehalococcoides group and anaerobic hydrogen producers) and the ability of the sediments to sustain microbial dechlorination were determined in an aquitard as well as in an aquifer. Close-spaced sampling revealed the existence of large populations of Dehalococcoides and H(2)-producing bacteria, especially in the organic-rich clayey aquitard rather than in the aquifer. The vinyl chloride reductase gene was also detected in the clay layer. Furthermore, incubation experiments indicated that the clay sediment could sustain transformations of tetrachloroethene at least to vinyl chloride. In contrast, no significant transformation was observed in the aquifer sand. Our results indicate that dechlorination of tetrachloroethene by bacteria can take place in an organic-rich clayey aquitard, and that organic-rich clay may also be important in the natural attenuation in an adjacent aquifer, possibly supplying a carbon source or an electron donor.     

Compound-specific isotopic and congener-specific analyses of polychlorinated biphenyl in the heat medium and rice oil of the Yusho incident

Compound-specific isotope analysis (CSIA) can be used to examine the source and transformation processes of organic pollutants in the environment. We performed a carbon stable isotope analysis of polychlorinated biphenyl (PCB) congeners in the PCB heat-transfer medium (heat medium) and the original Kanechlor-400 (KC-400, a commercial brand of PCBs) involved in the Yusho incident. The main purpose is to investigate whether isotope fractionation occurred in the rice oil deodorization process that caused the incident. The carbon isotope ratios (δ¹³C values) of the targeted PCB congeners ranged from ? 29.39 to ? 27.00‰ in the heat medium and from ? 28.77 to ? 27.05‰ in the original KC-400. No significant differences were found in the δ¹³C values, suggesting carbon isotope fractionation did not occur for the targeted PCB congeners in the heat medium when deodorization of rice oil occurred at temperatures above 200 °C. Furthermore, we also conducted a congener-specific analysis of 64 PCB congeners found in the heat medium and rice oil contaminated by it. The total PCB congener concentrations were 503 mg/g in the heat medium and 81 μg/g in the rice oil. The concentrations of the highly chlorinated congeners were significantly lower in the heat medium than in the original KC-400, and the compositional ratios of the lowly chlorinated congeners were relatively lower in the rice oil than in the heat medium. These results suggest that the PCB congener patterns gradually changed from that of the original KC-400 in the deodorization process and subsequent contamination into the rice oil. Thus, a combination of CSIA and congener-specific analysis is a new approach for investigating the changing PCB congener profiles in samples from the Yusho incident.     

Prediction of individual Freundlich isotherms from binary and ternary phenolic compounds mixtures

Method for simultaneous determination of individual component's adsorption equilibrium parameters for binary and ternary phenolic compounds mixtures was investigated in this research. The Freundlich equilibrium parameters of binary and ternary component of phenolic compounds were determined from one fixed composition of phenolic wastewater. The simulation results obtained from both binary and ternary systems on the basis of ideal adsorbed solution theory were consistent with single component equilibrium data.     

Material cycle, waste disposal, and recycling in a Leontief–Sraffa–von Neumann economy

The purpose of this paper is to analyze problems concerning household waste disposal and material flow by means of a Leontief–Sraffa–von Neumann framework. We treat household residuals as if they were traded and valued in a daily market transaction. Thus, we can calculate the shadow price of waste, making a value system compatible with a quantity system. We show the theoretical existence of an equilibrium solution between a value system and a quantity system. This means that if there is a well-organized market for waste treatment, the flow of waste is smoothly regulated by a price adjustment mechanism. Household residuals are shown to be negatively valued if a certain constraint is satisfied. Thus, those residuals are bads instead of goods. Interestingly enough, household waste treatment in the market does not affect the price formation of normal commodities, since waste treatment services or recycling services are nonbasics in Sraffa's sense. Partly due to this character, the Hawkins–Simon condition is required only for normal production sectors, and not for recycling sectors. In the final section, we have dropped the assumption that household residuals are always treated as waste, since some residuals may be traded as normal commodities. Applying the Gale–Nikaido–Debreu lemma to a newly defined excess demand function, we have proved that our model can accommodate such a situation. By this analysis, we have shown that the goods/bads (waste) relationship is a relative matter, being dependent upon economic conditions. The changes in demand for, or supply of, residuals may turn some goods into bads, and vice versa. Received: October 5, 1999 / Accepted: October 18, 1999     

Concentrations of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls in blood and breast milk collected from pregnant women in Sapporo City, Japan

We measured the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (PCBs), and non-dioxin-like PCBs in paired samples of blood and breast milk collected from 67 secundiparas in Sapporo City, Japan, and combined this data with those of the 30 secundiparas previously measured. The arithmetic mean total toxic equivalents (TEQ-WHO) concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs in blood and breast milk of the 97 secundiparous subjects were 3.0-23 (mean: 13, median: 14) and 2.7-20 (mean: 8.6, median: 8.5) pg TEQ g⁻¹ lipid, respectively. The sums of the concentrations of 56 non-dioxin-like PCB congeners that were measured in the subjects’ blood and breast milk were 16-326 (mean: 107, median: 100) and 12-252 (mean: 73, median: 67) ng g⁻¹ lipid, respectively. The partitioning ratios of individual congeners of PCDDs, PCDFs, dioxin-like PCBs, and non-dioxin-like PCBs from blood to breast milk in secundiparas were almost the same as those of primiparas that have been recently reported, suggesting that the partitioning ratios of these compounds from maternal blood to breast milk in women is little affected by delivery. Furthermore, the partition of PCB congeners with chlorine at the 2-, 3-, 4′-, and 5-positions or the 2-, 4-, 4′-, and 5-positions of the biphenyl ring from the blood to the breast milk tended to occur at a higher level than that of other congeners. In particular, the levels of tetraCB-74 and hexaCB-146 in the breast milk for both primiparous and secundiparous mothers were slightly higher than those in the blood.     

Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy

We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.     

Position-Controlled III–V Compound Semiconductor Nanowire Solar Cells by Selective-Area Metal–Organic Vapor Phase Epitaxy

We demonstrate position-controlled III–V semiconductor nanowires (NWs) by using selective-area metal–organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core–shell NW solar cells. We form a ‘flexible NW array’ without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.     

Differences in the lethality of occupational accidents in OECD countries

International comparisons of the frequency of occupational accidents are rare because figures reported by each country are influenced by factors other than differences in the occurrence of actual accidents. In this study, we performed an international comparison of occupational accidents which distinguishes between fatal cases and all reported accidents, in order to control for the effects of other factors in accident reporting. Annual data on the numbers of fatal and non-fatal occupational accidents in member countries of the Organisation for Economic Co-operation and Development (OECD) between 1993 and 1998 were obtained from the Labour Statistics Database, which is operated by the International Labour Organization (ILO). The average incidence of all accidents across OECD countries ranged from 17 to 4608 per 100,000 persons in the labor force, whereas the incidence of fatal accidents across OECD countries ranged from 1 to 12 per 100,000 persons in the labor force. Lethality rates per 10,000 total accident cases ranged from 9 (Germany) to 3252 (Turkey). When comparing countries using the same statistical definition of accidents, three or more absence days, the difference in lethality of reported accidents within the same industrial sector is reduced to a sixfold difference (49 for the United Kingdom versus 333 for Ireland). Furthermore, the difference in lethality decreased to about twofold (18 for Spain versus 35 for Czech Republic) in the group using definitions with a criteria of one absent day. The results suggest that reported differences in lethality can reflect artificial administrative factors rather than the harmful factors that cause actual occupational accidents. To make more valid comparison of occupational accident between countries, harmonization of accident statistics is required.     

Improving sustainable recovery of metals from waste printed circuit boards by the primary copper smelter process

In this paper, utilizing the existing primary copper smelter process for the recovery of metals from waste printed circuit boards (PCBs) is proposed as an alternative to the current backyard operations in developing countries. The Model for Evaluating Metal Recycling Efficiency from Complex Scraps (MEMRECS) concept is introduced as a tool for the evaluation of the eco-efficiency of metals recovery from waste PCBs. Based on the MEMRECS approach, the relative contribution of every metal fraction to the recyclability of the whole product is estimated. Thereby, gold content is identified as a key factor strongly influencing the efficiency of metals recovery from waste PCBs. Furthermore, it could be used as an indicator for the categorization of waste PCBs before feeding them into the recycling process. Finally, an integrated process is proposed to optimize the eco-efficiency of metals recovery from waste PCBs in developing countries.     

Evaluating the Impact of Distance Measures on Deforestation Simulations in the Fluvial Landscapes of Amazonia

Land use and land cover change (LUCC) models frequently employ different accessibility measures as a proxy for human influence on land change processes. Here, we simulate deforestation in Peruvian Amazonia and evaluate different accessibility measures as LUCC model inputs. We demonstrate how the selection, and different combinations, of accessibility measures impact simulation results. Out of the individual measures, time distance to market center catches the essential aspects of accessibility in our study area. The most accurate simulation is achieved when time distance to market center is used in association with distance to transport network and additional landscape variables. Although traditional Euclidean measures result in clearly lower simulation accuracy when used separately, the combination of two complementary Euclidean measures enhances simulation accuracy significantly. Our results highlight the need for site and context sensitive selection of accessibility variables. More sophisticated accessibility measures can potentially improve LUCC models’ spatial accuracy, which often remains low.