Mutagenicity and identification of products formed by aqueous ozonation of humic acids of different origins

Ozonated soil-humic acid induced direct mutagenicity on TA98, TA100 and TA104, while not the ozonated reagent- and wastewater-humic acids. Oxygen radicals generated from mutagens such as glyoxal and hydrogen peroxide identified as the ozonation products might, in part, contribute to the mutagenicity of ozonated soil-humic acid.     

The phytal animals on the thalli of Sargassum serratifolium in the Sargassum region,with reference to their seasonal fluctuations

In the Sargassum region on the coast of Mukaishima, in the Inland Sea of Japan, the phytal animals living on Sargassum serratifolium, and the alga itself as a habitat for phytal animals, were studied from August, 1966 to August, 1968. The standing crop of Sargassum/m² bottom was 4.93 kg/m² (March, 1967) and 3.53 kg/m² (February, 1968) in the most luxuriant season, and 0.4 to 0.5 kg/m² (July, 1967 and 1968) in the off-season. The individual number of phytal animals per mean plant, without sessile fauna, reached a maximum in late winter and early spring (about 130,000 in 1967, 266,000 in 1968) when Sargassum was luxuriant, and a minimum in summer (about 15,000 in both years) when Sargassum was declining. Among the phytal animals, benthonic copepods (Harpacticoida) were very abundant in most seasons. Their dominance decreased in spring, whilst nematode dominance increased. It appears that such seasonal changes are closely related to the standing crop of S. serratifolium. Fluctuations in numbers of most groups of the meiofauna of phytal animals, such as foraminiferans, ostracods, isopods, amphipods, copepods, tanaids and nematodes, are connected with changes in the standing Sargassum crop. Seasonal fluctuations of some groups, such as echinoderms, actinians, mysids and decapod crustaceans (macrofauna), were, however, independent of Sargassum crop variations. The individual number of phytal animals/m² bottom in the Sargassum region were compared with findings of previous studies in other habitats, such as naked sandy and mud bottoms.Contribution No. 100 from the Mukaishima Marine Biological Station.     

Deposition of 137Cs in Rokkasho, Japan and its relation to Asian dust

Biweekly atmospheric depositions of (137)Cs were measured in Rokkasho, Aomori, Japan from March 2000 to March 2006 to study recent (137)Cs deposition. Although the deposition level was generally lower than the detectable limit, deposition samples collected in spring occasionally had measurable levels of (137)Cs. The annual (137)Cs deposition from 2001 to 2005 was 0.04-0.69 Bq m(-2) with a mean value of 0.27 Bq m(-2). Depositions of insoluble Al, Fe and Ti were strongly correlated with the (137)Cs deposition, suggesting that suspension of soil particles was the main source of the recent (137)Cs deposition. Asian dust events were coincident with some of the significant (137)Cs depositions in spring. It was found that the ratios of (137)Cs/Al and Fe/Al could be used as indices for discriminating Asian dust from suspension of the local surface soil. Backward trajectory analysis suggested southern Mongolian and northeastern China regions as sources of the significant (137)Cs depositions.     

Recombinant human AhR-mediated GUS reporter gene assays for PCB congeners in transgenic tobacco plants in comparison with recombinant mouse and guinea pig AhRs

Four expression plasmids for recombinant human aryl hydrocarbon receptor (hAhR) consisting of a ligand binding domain of hAhR, a DNA-binding domain of LexA and a transactivation domain of VP16 as well as β-glucuronidase (GUS) reporter genes were constructed. All the expression plasmids were transformed into tobacco plants. The selected transgenic tobacco plants were used to assay. PCB congeners showed GUS activity in a TEF-dependent manner. The selected transgenic tobacco plant XhD4V17 was compared with the transgenic tobacco plants XmD4V26 and XgD2V23 containing recombinant mouse (m) AhR-mediated GUS reporter gene expression cassette and recombinant guinea pig (g) AhR-mediated GUS reporter gene expression cassette for PCB congener-inducible GUS activity. The data revealed that the tobacco plant XgD2V23 was the most active in PCB congener-inducible GUS activity. In a 1:1 mixture of PCB126 and PCB80 a reduced PCB126-induced GUS activity was observed in plant XgD2V23, which could possibly be due to interaction between PCB126 and PCB80.     

Numerical investigation concerning the impact of CO2 geologic storage on regional groundwater flow

Large-scale storage of carbon dioxide in saline aquifers may cause considerable pressure perturbation and brine migration in deep rock formations, which may have a significant influence on the regional groundwater system. With the help of parallel computing techniques, we conducted a comprehensive, large-scale numerical simulation of CO₂ geologic storage that predicts not only CO₂ migration, but also its impact on regional groundwater flow. As a case study, a hypothetical industrial-scale CO₂ injection in Tokyo Bay, which is surrounded by the most heavily industrialized area in Japan, was considered, and the impact of CO₂ injection on near-surface aquifers was investigated, assuming relatively high seal-layer permeability (higher than 10 microdarcy). A regional hydrogeological model with an area of about 60 km × 70 km around Tokyo Bay was discretized into about 10 million gridblocks. To solve the high-resolution model efficiently, we used a parallelized multiphase flow simulator TOUGH2-MP/ECO2N on a world-class high performance supercomputer in Japan, the Earth Simulator. In this simulation, CO₂ was injected into a storage aquifer at about 1 km depth under Tokyo Bay from 10 wells, at a total rate of 10 million tons/year for 100 years. Through the model, we can examine regional groundwater pressure buildup and groundwater migration to the land surface. The results suggest that even if containment of CO₂ plume is ensured, pressure buildup on the order of a few bars can occur in the shallow confined aquifers over extensive regions, including urban inlands.     

The dynamics of mercury around an artisanal and small-scale gold mining area,Camarines Norte,Philippines

Environmental Science and Pollution Research - To elucidate the dynamics of mercury emitted and released by artisanal and small-scale gold mining (ASGM) activity and to estimate its impact on the...     

Feasibility investigation on a dual waste-plastics recycling system concept

Fiber-reinforced plastics (FRP) were first used as a material for boats and bath tubs about 40 years ago. Because of their great durability, wastes including FRP products are increasing. In addition, since the FRP resin is synthesized from expensive reactants, material recycling is highly desirable. Recycling using supercritical water is one solution; however, the cost of producing the high pressure and temperature needed to produce supercritical water prevents the concept from being realized. Therefore, we proposed a system concept based on dual waste-plastics recycling. A numerical survey of the results confirmed that our concept was feasible and would contribute to resource recycling as we expected. Received: January 6, 1998 / Accepted: July 23, 1999     

Simulation of pedestrian contra-flow by multi-agent DEM model with self-evasive action model

A pedestrian contra-flow can be seen frequently in urban spaces such as a pedestrian crossing, an open space and a concourse. A pedestrian simulation with taking a pedestrian contra-flow into account will be a rational tool for designing urban pedestrian facilities. The objective of our research is to develop a microscopic model for a pedestrian contra-flow. Although we have been developing a DEM (Distinct Element Method)-based microscopic model of crowd behavior, this conventional crowd behavior model does not necessarily provide satisfactory agreement with an observation in a pedestrian crossing with heavy commute traffic. In this paper, we newly develop a self-evasive action model, which can describe either a collision avoidance or an alignment behavior between adjacent pedestrians. The multi-agent DEM model with the self-evasive action model shows good predictions of the characteristics of pedestrian contra-flow.     

High seagrass diversity and canopy-height increase associated fish diversity and abundance

Seagrass species function as typical foundation species that unifies most ecosystem processes. This ecosystem role depends largely on the morphological characteristics and structural complexity of seagrass beds, including their ecological importance for fish species. This study examined relationships between seagrass bed characteristics and associated fish communities in mixed seagrass beds. Correspondence analysis (CA) and canonical correlation analysis (CCoA) were performed to estimate relationships for individual seagrass bed characteristics. The CCoA results revealed that species richness and three-dimensional structure of seagrass had great effect on the biomass and richness of the associated fish community. The CA results revealed that the relative importance of seagrass bed characteristics differed among fish functional groups including fishes appearing on the surface of, inside, and on the bottom of seagrass beds. The fishes found on the surface of the beds preferred beds with low seagrass biomass and high three-dimensional structure, those inside the beds preferred beds with high seagrass biomass and high three-dimensional structure, and those on the bottom of the beds preferred locations with low seagrass biomass and low three-dimensional structure. The results of this study provide compelling evidence that seagrass beds with high species diversity and high three-dimensional structure, but intermediate biomass, may provide the great benefit to the associated fish community. Such niche complementarity among fishes may be a process facilitated by seagrass diversity for secondary production as an ecosystem functioning.     

Shedding of gametes in the compound ascidian Botryllus primigenus

The shedding of gametes of Botryllus primigenus Oka occurs in the natural environment early in the morning, about 1 h after dawn. The shedding of the sperm from a testis is completed within a few seconds. All the spermatozoa in a testis are released at once. Ovulation begins about 10 min after shedding of sperm and is completed in about 1 min. In general, combinative testes, i.e., testes accompanied by egg follicles, macure first, followed by egg follicles, solitary testes located on the left side of the zooid, and finally those on the right side, in that order. As a result, a population of zooids of the same generation in a colony sheds sperm on 2 or 3 successive days. Illumination preceded by darkness effectively induces shedding of gametes experimentally. The required minimum dark-adaptation period is 40 min; the required minimum illumination period is dependent on light-intensity, 8, 4 and 1 min being required at 70, 200 and 3,000 lux, respectively; the latent period is temperature-dependent, 100 to 130, 70 to 90 and 50 to 60 min being required at 21^o, 26^o and 27.5°C, respectively. An experiment in which only part of the colony was illuminated clearly indicated that each zooid responds to light-stimulus independently.Contribution No. 306 from the Shimoda Marine Research Center, University of Tsukuba, Japan.