The quality of roof runoff water from an inclined tiled roof was investigated during two rain events. The runoff characteristics of polycyclic aromatic hydrocarbons (PAHs) with two to five rings were elucidated. The following results were obtained: (1) The runoff of roof sediments depended on their state and rain conditions. (2) The concentration of particulate PAHs increased with an increase in SS concentration, whereas the concentration of soluble PAHs decreased with time, which is due probably to a gradual decrease in both PAH concentration in the rain and the amount of PAHs remaining in the roof sediments over time. (3) When the molecular weight of PAH was higher, the ratio of soluble PAH to total PAH became smaller because of the lower water solubility. (4) PAH partition to particulate phase was 10 to 1000 times greater compared to the experimental equilibrium equation. (5) The major components of the particulate PAHs were four- to five-ring PAHs, while those of soluble PAHs were two- to three-ring PAHs.

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The microbial activities in aquatic environments significantly influence arsenic cycles such as turnover between inorganic arsenic and organoarsenic compounds. In Lake Kahokugata, the inorganic arsenic was detected through all season, while the dimethylarsinic acid (DMAA) produced by microorganisms such as phytoplankton detected only at winter. Consequently, the changes in the methylarsenic species concentration did not correlate with the changes in phytoplankton abundance (chlorophyll a contents). The lake water spiked with 1 μmol/l of DMAA indicated the DMAA-diminish and the increase of inorganic arsenic under dark and anaerobic condition. Contrary, the lake water under aerobic or light condition did not show the DMAA-diminish. The lake water that bacterial activities were eliminated by filtration, NaN₃ addition and autoclave-sterilization also did not show the DMAA-diminish, indicating that anaerobic bacteria would degrade DMAA in the lake water. Moreover, the incubation at 30 °C, the water samples collected in summer rapidly degraded 1 μmol/l of DMAA within 7days. In the lake water collected in winter incubated at 4 °C, DMAA-degradation did not observed. Presumably, the DMAA-biodegradation activities in the natural lake water of Kahokugata seasonally change depending on water temperatures and several degrees of DMAA-degradation activities influence the seasonal changes of concentrations of arsenic compounds.

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In this study, we identified the best tree species for the afforestation of salt-affected land. Although some planting trials have been carried out in the wheat belt of Western Australia, minimal detailed data on the mortality and growth rates of trees under salinity stress have been reported. Such data would facilitate the selection of species with sufficient salinity tolerance and high growth rates. In the present study, a cultivation experiment was conducted to clarify the salinity tolerance and growth rates of three Eucalyptus species widely planted in Western Australia. The experimental results were analyzed in terms of height growth, maximum photosynthetic rate, water use efficiency, and total biomass. The results suggest that the most suitable species for afforestation depends on the site environment because of the different salinity tolerance levels and growth rates of trees.

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Vertical changes in sandy bottom level, wave height, and current velocity were measured inside and outside a dense eelgrass (Zostera marina) bed. Waves of 0.9m eroded the sandy bottom by up to 0.12 m outside the dense eelgrass bed but did not cause erosion inside the bed. Rough waves caused rapid erosion but gentle waves restored the original sandy bottom levels. Shield's number, an indicator of the instability of sea bottom sediment, was larger inside the dense eelgrass bed than outside. These results showed that the dense large scale eelgrass bed functioned to stabilize the bottom sediment and prevent the sandy bottom from eroding. In addition, it appeared that this function was made possible by the density of eelgrasses and a sheet of subterranean stems.

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This study was conducted to investigate the environmental factors affecting the phytoplankton (chlorophyll-a content) dynamics in Inohana Lake, Japan. Inohana Lake is a stratified estuary during summer, and eutrophication and the bottom hypoxia have occurred. A field survey was carried out in Inohana Lake during summer in 2007, and includes the water temperature, salinity, water density, the phosphate phosphorus, the total phosphorus, and chlorophyll-a concentrations. The meteorological factors include the wind, rainfall and solar radiation. Based on the water quality and meteorological data, the simple correlation and multiple linear regression analyses were used. The phosphorus flows into Inohana Lake through the river discharge. The PO₄-P in the lake was sufficiently to use for phytoplankton growth and other factors rather than the phosphorus were proposed as limiting factors for phytoplankton growth. It was proposed that rain controls the phytoplankton (chl-a) dynamics bio-chemically by causing the phosphorus loadings through the river discharge and physically by changing the estuarine circulation and residence time. Wind also affects physically the movement of chl-a content by contributing to the mixing and exchange of water.

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Speciation analysis of Cr in some environmental waters in Niigata Prefecture was performed by applying size fractionation and ion-exchange methods. Moreover, the concentration of humic substances was also determined for investigating the relationship between the concentration of humic substances and the speciation of Cr in environmental waters. The experiments yielded the following results: (1) Roughly 50-80 % of total Cr is present in the “dissolved” in normal weather condition. (2) In case of lagoon water samples, the distribution percentage of Cr in the “suspended” (the fraction left on 0.45μm filter when filtrating sample water) or “colloidal” (the fraction left on 0.1μm filter, although passing through 0.45μm filter) is generally large compared to that of river water samples. (3) For all of the investigated water samples, the concentration of Cr (III) species is higher than that of Cr (VI) species. (4) The concentration of total Cr and the distribution percentage of “suspended” remarkably increases after rainfall event. (5) The order of the amount of humic substances in Sakata is LS1 (downstream point of Lower Lagoon (Shitakata)) › LS2 (conflux point of Lower Lagoon (Shitakata) and Upper Lagoon (Uwakata)) ›LS3 (spring water at shore of south area in Lower Lagoon (Shitakata)); and the average concentration of humic substances is about 10ppm.

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In this study, we discuss the effects of biodegradable chelators on the bioavailability of iron and the growth of radish sprouts. In alkaline soils, iron exists as hardly soluble states of hydrated oxide. In experiments at pH 10, iron moved into the upper layer (without iron) from the bottom layer (with iron) of the medium, and the mobility depended on the chelators. The content of iron in the upper layer of the medium was 7.0 % of the total iron in the medium without chelators, and 17.3 % in the medium with HIDS. These results suggest that chelators can dissolve the hardly soluble iron hydroxide species in alkaline conditions, increase the mobility of iron, and increase plant growth.

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In this study, we assessed the influence of eutrophication on arsenic speciation in lake waters. By combining hydride generation atomic absorption spectrometry with ultraviolet irradiation, inorganic, methyl and ultraviolet-labile fractions of arsenic were determined. Organoarsenicals, which are methyl and ultraviolet-labile arsenic, composed 30-60% of the total arsenic in most lakes in the summer of 2007. On the other hand, the percentage of ultraviolet-labile fractions was higher in eutrophic lakes. For the seasonal changes, the percentage of DMAA was higher in the winter of 2008. The observed results suggest that the conversion of inorganoarsenicals to the more complicated organoarsenicals was higher in the eutrophic lake.

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The microbial communities transported by Asian desert dust (KOSA) events have attracted much attention as bioaerosols because the transported microorganisms are thought to influence the downwind ecosystems in Korea and Japan. Bioaerosol samples were collected at 10 and 600 m above the ground within the KOSA arrival area, Suzu City, Japan, during KOSA coming season. The microorganisms in bioaerosol samples grew in media containing up to 15 % NaCl, suggesting that bacteria tolerant to high salinities remain viable in the atmosphere. Denaturing gradient gel electrophoresis using 16S rDNA sequences revealed that the viable halobacterial communities in the bioaerosol samples were composed of members of the genus Bacillus. Moreover, the relative bacteria of B. subtilis was found to dominate in the atmosphere at 600 m and detected from a culture amended with 10% NaCl of aerosol sample at 10 m. Presumably, active mixing processes of the boundary layer transport viable halotolerant bacteria from the atmosphere to the ground surface in Suzu City, where the long-range KOSA particle transport from China is frequently observed.

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