Masaki Sagehashi

Gramine-induced growth inhibition, oxidative damage and antioxidant responses in freshwater cyanobacterium Microcystis aeruginosa

In recent years, the exploration and development of the effective methods of treatment and prevention to algal blooms, especially Microcystis aeruginosa blooms has been an important issue in the field of water environment protection. Allelochemicals (natural plant toxins) are considered promising sources of algicides to control algal blooms. The objective of this study is to determine the inhibitory effects and potential mechanisms of a well-known allelochemical gramine (N,N-dimethyl-3-amino-methylindole) on bloom-forming cyanobacterium M. aeruginosa. The results showed that this indole alkaloid effectively inhibited the growth of M. aeruginosa. The effective concentration causing a 50% inhibition at 3 d (EC(50, 3 d)) increased with the initial algal density (IAD) increasing. When IAD increased from 5x10(4) to 5x10(5)cellsmL(-1), the values of EC(50, 3 d) increased from 0.5 to 2.1mgL(-1). In the cells of M. aeruginosa, gramine caused an obvious increase in the level of reactive oxygen species (ROS). The lipid-peroxidation product malondialdehyde (MDA) increased significantly in gramine-treated cells. The effects of gramine on enzymatic and non-enzymatic antioxidants were in different manners. The activity of superoxide dismutase (SOD) was decreased after gramine exposure. The catalase (CAT) activity was increased after 4h but decreased from 60h. Both the contents and the regeneration rates of ascorbic acid (AsA) and reduced glutathione (GSH) were increased after 4h of exposure to gramine. However, only GSH content was still increased after 40h of exposure. These results suggested that the activation of antioxidants in M. aeruginosa played an important role to resist the stress from gramine at initial time, the inactivation of SOD is crucial to the growth inhibition of M. aeruginosa by gramine, and the phytotoxicity of gramine on M. aeruginosa may be due to oxidative damage via oxidation of ROS.

Adsorption and decomposition of water-dissolved ozone on high silica zeolites

The adsorption properties of water-dissolved ozone on high silica zeolites were investigated. Adsorbed ozone was desorbed almost reversibly. The adsorption equilibrium relations were described by a linear expression written as q=betaC, where q is the amount adsorbed, C is the equilibrium concentration and beta is the equilibrium constant. Also, the beta values were strongly dependent on the SiO(2)/Al(2)O(3) ratio (mol/mol) and on the pore structure of the high silica zeolites. The larger the SiO(2)/Al(2)O(3) ratio, the larger the value of beta. ZSM-5 (SiO(2)/Al(2)O(3) ratio: 3000), which gave the highest adsorption capacity of water-dissolved ozone, was able to highly concentrate water-dissolved ozone on the adsorbent. The decomposition behavior of adsorbed ozone was also investigated. Ozone adsorbed on high silica zeolite was observed to be a little more stable than ozone existing in bulk water. The decomposition rate was independent of SiO(2)/Al(2)O(3) ratios in the range of 30-3000 or a solution pH in the range of 4-6.

Decomposition of trichloroethene on ozone-adsorbed high silica zeolites

We developed a novel ozonation process for water treatment using high silica zeolites as an adsorptive concentrator of water-dissolved ozone and organic pollutants, resulting in a significant increase in reaction rate. In experiments involving trichloroethene (TCE) decomposition using a tubular flow reactor, TCE decomposition was much greater in the presence of ZSM-5 (SiO(2)/Al(2)O(3) ratio=3000) than in its absence, possibly due to the high concentrations of ozone and TCE inside the adsorbent. The TCE conversion obtained in our experiments was found to reach its theoretically maximum limit.

A predictive model of long-term stability after biomanipulation of shallow lakes.

Abstract The eutrophication of lakes causes serious problems, such as water-bloom consisting of the harmful blue-green algae. To prevent an unusual degree of growth of phytoplankton, various restoration methods have been tried. “Biomanipulation”, which uses zooplankton to prey on the phytoplankton, is a promising method because it can, in principle, create a desirable ecosystem. However, there are many equivocal points in the long-term stability of a newly developed ecosystem after biomanipulations. The fate prediction of a water ecosystem using a lake mathematical model is thus essential for implementing biomanipulations. There remain, however, many uncertain points in the dynamic parameters of the lake models, especially the parameters concerned with zooplankton and fish. In this study, we established a lake mathematical model based on the carbon, nitrogen and phosphorus flows among the biotic and abiotic substances in a water ecosystem. In this model, two types of phytoplankton (non blue-green algae and blue-green algae), three types of zooplankton (rotatoria, cladocera and copepoda), planktivorous fish (crucian carp), detritus and dissolved matters were considered. The dynamic parameters were estimated with a set membership estimation algorithm using random scanning based on mesocosm experiments, which can provide more rigid data than actual lake observations can. The model calculations showed good agreement with the observation data for both the non-filamentous blue-green algae dominant case and the filamentous blue-green algae dominant case. Using this model, we calculated the long-term stability of the effects of biomanipulations in a hypothetical lake. The calculation results clarified the blue-green algal species specificity in the long-term effects of biomanipulations. In the non-filamentous blue-green algal dominant case, the long-term stable suppression of algal growth was predicted under a certain threshold fish biomass, while in the filamentous blue-green algal dominant case, the suppression was not sustainable even in a no-fish-coexisting series. Model simulation is very important to the design of biomanipulations, and the model proposed in this study is suitable for this purpose.

A mathematical model of a shallow and eutrophic lake (The Keszthely basin. Lake Balaton) and simulation of restorative manipulations

Concern about the overall management of lakes has been growing, and a lake ecological model provides the guidelines necessary for such management. In this study, an ecological model describing the ecosystem of the Keszthely Basin, Lake Balaton, Hungary, one of the typical shallow and eutrophic lakes, was proposed. This model includes three types of zooplankton and two types of fish as well as two types of algae and nutrients. Parameters concerning the algae and fish were estimated based on observations in the basin between 1991 and 1995. The other parameters and the structure of the model were determined by our previous study. The parameters of the model were calibrated with the Monte Carlo technique, and its predictability was confirmed. The effects on the basins ecosystem of three restorative manipulations, namely a biomanipulation, reduction of loading phosphorus, and dredging the sediment, were assessed by simulation studies using the proposed model. The simulation results indicated that a biomanipulation that removed 90% of the bream should suppress the growth of algae temporarily through bottom-up regulation; however, this effect seemed to not be perpetuated in this basin. The reduction of loading phosphorus seemed to be the most effective means to suppress algal growth, while dredging of sediment seemed to be the most desirable restoration method from the standpoint of the overall management of the lake, because it was expected to accelerate the growth of fish population as well as to suppress algal growth. Furthermore, the algal growth suppression mechanism of the dredging was discussed on the basis of the model calculations.

Modelling the structural dynamics of a shallow and eutrophic water ecosystem based on mesocosm observations

A structural dynamic model describing a shallow, eutrophic water ecosystem is proposed in this paper. This type of model is useful for predicting the effects of biomanipulation. Various examples of this kind of model have been suggested in previous reports. The next salient issue demanding attention would be calibrating such models on the basis of more rigid data. In this paper, some of model parameters were calibrated and validated on the basis of observations of a mesocosm. In the mesocosm, almost complete material balances can be measured; these allow for the control of important factors in such systems. Hence, mesocosm observations were used in the calibration of parameters. The calibrated model was strongly supported on the basis of other observations of the mesocosm. The simulation study used in the proposed model indicated that the effects of biomanipulation on algal growth suppression differs depending on their zooplankton composition.

CH4 and N2O emissions from different varieties of forage rice (Oryza sativa L.) treating liquid cattle waste

To evaluate global warming potential (GWP) on livestock waste treatment and biomass production in rice field, methane (CH(4)) and nitrous oxide (N(2)O) fluxes from forage rice fields planted with 4 different cultivars (Oryza sativa L. cv. Hamasari, Leafstar, Kusahonami and Takanari) were measured. Each of the cultivars were subjected either to basal fertilization alone (control plots) (84 kg N ha(-1)), or to basal fertilization plus topdressing with liquid cattle waste or LCW (treatment plots) (567 kg N ha(-1)). Liquid cattle waste application to the rice field resulted in peak CH(4) fluxes ranging from 22.0 to 32.1 mg m(-1)h(-1) during flooded conditions and large N(2)O fluxes ranging from 526 to 8591 μg m(-1)h(-1) after midsummer drainage and final drainage. The GWP of the control plots was between 1358 and 3872 kg CO(2)eq ha(-1), while the treatment plots ranged between 4503 and 8426 kg CO(2)eq ha(-1) and more than 60% of the GWP was from the N(2)O emission in treatment plots. In both the control and treatment plots, the lowest GWPs per ton of above-ground biomass were found to be from the Leafstar cultivar, which had a higher aboveground biomass than other cultivars; 117 kg CO(2)eq t(-1) from the control and 257 kg CO(2)eq t(-1) from the treatment plots. Thus, both forage production and suitable disposal of the LCW may be able to be achieved concomitantly with lower levels of GWP by cultivation of Leafstar in our field.

Human factors and tidal influences on water quality of an urban river in Can Tho, a major city of the Mekong Delta, Vietnam

In this study, we focused on water quality in an urban canal and the Mekong River in the city of Can Tho, a central municipality of the Mekong Delta region, southern Vietnam. Water temperature, pH, electrical conductivity, BOD5, CODCr, Na+, Cl−, NH4+−N, SO42−−S, NO3−−N, and NO2−−N for both canal and river, and tide level of the urban canal, were monitored once per month from May 2010 to April 2012. The urban canal is subject to severe anthropogenic contamination, owing to poor sewage treatment. In general, water quality in the canal exhibited strong tidal variation, poorer at lower tides and better at higher tides. Some anomalies were observed, with degraded water quality under some high-tide conditions. These were associated with flow from the upstream residential area. Therefore, it was concluded that water quality in the urban canal changed with a balance between dilution effects and extent of contaminant supply, both driven by tidal fluctuations in the Mekong River.

A 20–40 SECOND PROCESS FOR SYNTHESIS OF MULTI-WALLED CARBON NANOTUBES

We report on a 20–40 s process for growing aligned, uniformed, high purity multi-walled carbon nanotubes (MWNTs) using an alcohol lamp burner. With an appropriate catalyst precursor concentration, MWNTs can be grown on a Co-coated 304 stainless steel mesh under incomplete combustion conditions at 680–700°C. The process provides a rapid, easy, economic and safe method for the formation of carbon nanotubes. We suggest that the proposed method be considered as an educational kit for college or high school level experiments.

Promoting Environmental Education to Face Energy Issues from Japan

2011年3月の東日本大震災に伴い発生した東京 電力福島第一原発事故は、甚大な環境汚染と様々 な被害を引き起こすとともに、電力供給の不安定 化をもたらし、現代社会に生きる我々に、エネル ギーのあり方を再考する機会を与えた。 この事態に直面した日本の環境教育関係者から は、「これほど大きい環境への被害、長期にわた り続く放射能の問題をもたらした原発について、 問題提起もまたそれを進める日本のエネルギーに ついての教育や研究活動も不十分であった」(岡 島ほか 2012)といった反省が表明された。実際、 事故前の日本において「エネルギー教育」といえ ば、原子力発電の推進を支える国民の合意形成を 目的とした取組が一般的であった(萩原 2009a)。 また、環境教育において、資源やエネルギーは取 り上げるべき課題と認識されても、原発について はセンシティブな問題への発展が恐れられ、避け られることが多かった(萩原 2009a、藤岡 2007)。 こうした反省を踏まえ、事故後、環境教育関連 の様々な集会で原発やエネルギーをテーマとした 情報や意見が交わされ、原発に関する小中高校向 け授業案が作成されるなど(日本環境教育学会 「原発事故のはなし」授業案作成ワーキンググ ループ 2011、2012)、取組が広がりつつある。 今、日本の環境教育は、エネルギー問題に真正 面から向き合わねばならない。原発事故の影響や それへの対応を学ぶのみならず、エネルギー供 給・消費の状況と背景を理解し、あるべき形とそ の実現への道筋を描き、行動する力を育む環境教 育を実践せねばならない。そして、そうした実践 を国内外の人々と共有しながら、事故の経験と反 省を生かした環境教育を日本から推進することに よって、地球社会の一員としての責任を果たして いかねばならない。 大学は、エネルギー問題に向き合う環境教育を 推進すべき重要な主体の一つである。2005年か ら「国連・持続可能な開発のための教育(ESD) の10年」が実施されているが、その発案国であ る日本の大学には特に推進の拠点となる期待が寄 せられ(日本学術会議環境学委員会環境思想・環 境教育分科会 2008)、政府も様々な施策で大学の ESDを支援しようとしている(野村ら 2010)。 持続可能な発展を考える上で、エネルギーは現代 社会の抱える主要な課題であり、今回の原発事故 がまさに非持続的状況を露呈させたことを思え ば、日本の大学による今後のESD展開において 報告 エネルギー問題と向き合う環境教育を日本から推進する