Decontamination of water polluted by heavy metals with Taro (Colocasia esculenta) cultured in a hydroponic NFT system

The toxicity and bioaccumulation of two heavy metals—lead (Pb) and cadmium (Cd)—in a semi-aquatic plant, Colocasia esculenta (L. Schott), from a synthetic heavy metal solution were studied. Young plants of equal size were grown hydroponically in shallow raceways containing Hoagland medium amended with 20, 40, and 60 mg l^?1 of Pb and 2, 4, and 6 mg l^?1 of Cd. The medium containing heavy metals was allowed to flow through the raceways with a change in influent heavy metal solution on every 5th day. The experiment was continued for 20 days. A set of control raceways—one comprised of nutrient medium with heavy metal supplements, devoid of plants, and another with the plants and nutrient medium having no metal supplement—was also simultaneously run. Chlorosis in the leaves was the prominent toxicity symptom observed due to Pb and Cd on the test plants. A significant decrease in the relative growth, biomass productivity, and total chlorophyll content were noticed in the plants with an increase in concentration of metal supplement in the solution and exposure time. Both metals accumulated to higher concentrations in the roots than in shoots, suggesting that the metals were bound to the root cells and their translocation to the leaves was limited. The results of the 20-day-long experiments indicate that from a phytoremediation perspective, C. esculenta is a promising plant species for remediation of wastewater polluted with lower concentrations of Pb and Cd.     

A mapping of global warming research based on IPCC AR4

It is easy to get lost in the vast amount of knowledge that is currently produced. In this study, to get a comprehensive picture of current scientific knowledge about global warming issues, we developed a mapping framework for global warming research based on the relationships between nature and human society. The mapping includes seven phases: (1) socioeconomic activity and greenhouse gas emissions, (2) carbon cycle and carbon concentration, (3) climate change and global warming, (4) impacts on ecosystems and human society, (5) adaptation, (6) mitigation, and (7) social systems. We applied the findings of the Intergovernmental Panel on Climate Change Fourth Assessment Report to the mapping. The quantity of research results and their reliability were analyzed on the basis of expert judgment to better understand the extent to which current scientific knowledge provides answers to society’s major concerns. The quantity and reliability of answers have increased in phases 2 and 3 relative to research in the Third Assessment Report. Although a large quantity of results have been produced in phases 4 and 6, they are not always sufficient. More studies are required in phases 1, 5, and 7, and the reliability of existing knowledge needs to be improved in these phases. Mapping global warming issues enabled us to visually comprehend the numerous and varied parts of global warming research as a whole and to discern gaps in knowledge and other research shortfalls. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Comparison of chorionic villus sampling and amniocentesis: Current status of prenatal diagnosis in Japan

Data were tabulated and compared for cases involving prenatal diagnostic procedures performed in the 8 years between January 1985 and December 1992. Of a total of 2781 pregnancies, 2546 cases (91·5 per cent) were diagnosed by amniocentesis, and 235 (8·5 per cent) by chorionic villus sampling (CVS). These findings reflect the fact that amniocentesis has taken deep root as the prenatal diagnostic procedure widely acknowledged by society, whereas even the existence of CVS has yet to be generally recognized. Analysis of our clinical and laboratory results and complication rates, however, suggests that CVS is a safe and accurate alternative to amniocentesis which should and can be positively presented to all patients who are candidates for prenatal diagnosis.     

Ambient and household air pollution on early-life determinants of stunting—a systematic review and meta-analysis

Environmental Science and Pollution Research - Stunting is an important risk factor for early growth and health implications throughout the life course, yet until recently, studies have rarely...     

Development of Mn recovery process from waste dry cell batteries

High-purity Mn is necessary for high strength steel production. However, the availability of metal Mn is limited to a few countries. Therefore, as an alternative to direct purchasing of metal Mn, a process for Mn recovery was investigated. Waste dry cell batteries are considered to be one of the most feasible Mn sources. We have developed a high efficiency chemical separation system. This system consists of a three-phase chemical treatment. In the first phase, the metal components of the waste dry cell batteries were dissolved by acid, along with a reducing agent. Afterward, the undissolved carbon particles were separated by filtration. In the second phase, the dissolved Mn was selectively precipitated as manganese oxide by O₃ oxidation. Then, the precipitated manganese oxide was separated from the other metal components by filtration. Finally, in the third phase, the manganese oxide was reduced to high-purity Mn using an electric furnace.     

On several issues regarding efforts toward a sustainable society

Environmental issues and the future sustainability of society are among the greatest concerns facing society today. How to formulate a pathway toward a sustainable society is a critical question. Several issues associated with this question are presented and discussed. First, a structuring of the issues is presented. The environment can be said to consist of three systems—the natural, social, and human—and their interactions; environmental problems may therefore be defined in terms of perturbations of the interactions among the three systems. A sustainable society can be realized by restoring these interactions. Next, the characteristics of the issues are discussed. Because environmental issues relate to the future, forecasts of the future are essential. Because it is impossible to predict the future with complete accuracy, however, we should develop a method of using information about the future with allowance for error. It should be noted that error characteristics differ according to their time-scale. Third, the relationship between environmental issues and society is discussed. To take collective action on these issues we need society-wide consensus, which requires a reliable and objective platform. Here, more attention must be paid to the distribution of knowledge across society, because scientific knowledge in a modern society tends to be monopolized by research organizations. The role of the media is therefore important. Another important factor is the commitment of the general public; user-friendly ways of galvanizing such commitment should be developed.

Evaluation of material recycling for plastics: environmental aspects

“Zero emissions” is a concept envisaging the creation of a sustainable society with minimal disposal of resources. In order to realize zero emissions for plastics, it is important to establish a method for quantitatively evaluating candidate recycling processes. In this study, the principle of the substitution factor (SF) is introduced. A quantitative evaluation of the recycling process for plastics was then carried out. The production process for monofilament plastics was examined. The recycling of plastics discarded during the production process could be substituted in small amounts for virgin materials, giving reduced CO₂ emissions. Furthermore, production using recycled material mixed with virgin material was more effective in reducing CO₂ emissions than when recycled materials only were used. Received: November 19, 1999 / Accepted: November 28, 2000