To characterize stream water nutrient concentrations during snowmelt period (Jan-Apr) in a forested headwater catchment in the central Chugoku Mountains, hydrological observations and weekly stream water sampling were conducted for one year. Even in the coldest period (Jan-Feb), snow melting progressed temporally and generated a relatively large streamflow in the catchment. Compared with those during the no-snow period (May-Aug and Sep-Dec), the dissolved nitrogen (DN) and phosphorus (DP) concentrations during snowmelt period were high, whereas the particulate nitrogen (PN) and phosphorus (PP) concentrations were the same or slightly low. The DN and DP concentrations during the snowmelt period might have been strongly influenced by melting water from accumulated snow rather than by leaching water from the soil layer. On the other hand, the PN and PP concentrations during the snowmelt period seemed to reflect the decrease in the extent of accumulation of mobile sediments within the stream channel. In conclusion, in areas of the Chugoku Mountains around the catchment studied, 1) the use of DN, DP and TN concentrations measured during no-snow periods as substitutes for those measured during snowmelt period can underestimate the annual export load of the nutrients, and 2) stream water sampling at shorter intervals, i.e., every 1~3 days, is necessary for accurate nutrient load evaluation based on field investigation during snowmelt periods.

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Degradation and mineralization of sulfamethoxazole by the photo-Fenton reaction (Fe²⁺/H₂O₂/UV) were investigated. It was found that 176 mg•L^-1 sulfamethoxazole was completely degraded by the photo-Fenton reaction in 5 min with an initial total iron ion concentration of 15 mg•L^-1 and an initial hydrogen peroxide concentration of 500 mg•L^-1 under ultraviolet light irradiation. About 65% mineralization of the initial total organic carbon concentration of 83 mg•L^-1 was achieved in 40 min. Under the initial total iron ion concentration of 5 mg•L^-1, the degradation rate constant of sulfamethoxazole (SMX) increased with the initial total iron ion concentration. However, over the initial total iron ion concentration of 5 mg•L^-1, the degradation rate constant of SMX did not increase with the initial total iron ion concentration owing to scavenger effects. From the results of the measurement of the organic acid concentration during the sulfamethoxazole degradation and mineralization by the photo-Fenton reaction, organic acids were found to accumulate in the solution. The comparison between the reaction rate constants of SMX and coexisting substances in real sewage revealed that degradation of micropollutants such as pharmaceuticals could be significantly affected by matrix effects.

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The objective of this study is to clarify the genetic diversity and seed sources of the Zostera marina population colonizing the habitat constructed in a depression on the coast of Iwakuni in Hiroshima Bay. We investigated Zostera beds in Hiroshima Bay and conducted genetic analysis of 30 samples collected at each of the six beds, using five microsatellite markers. Our results are as follows. The major seed production areas were considered to be Nomijima, Obatake-Kojiro and Miyajima. The mean numbers of alleles per locus and heterozygosities were almost the same between the constructed and natural habitats. The pairwise Fst ranged from 0.000 to 0.037, suggesting a high gene flow among populations in Hiroshima Bay. Assignment test showed the maximum likelihood values between the samples of the constructed habitat and distant populations (more than 15-20 km away) as well as of neighboring populations. These results suggested that the Z. marina population colonizing the constructed habitat had almost the same genetic diversity as the natural population, and that distant populations as well as neighboring populations in Hiroshima Bay can serve a seed supply source.

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The Slanted-Soil-Chamber-Method (SSCM) is an energy-saving aerobic purification method. We performed an experiment to elucidate this purification mechanism using a SSC reactor filled with a sponge carrier. This experiment demonstrated concurrent purification of organic pollutants, total nitrogen (T-N) and total phosphorus (T-P) for a hydraulic retention time of 20-50 min. Water and organic pollutants are separated as the gravity-fed wastewater passes through the reactor chamber. Treatment of the dissolved organic pollutants relies upon biological adsorption, which takes approximately 20-50 min. Since biological purification activity within the SSC reactor is high except the winter season, the organic matter that is trapped in the chamber is efficiently decomposed by organisms that are typically found in soil. The SSC reactor weight increased in the winter season and decreased in spring. The extent of T-N and T-P purification was dependent upon heterotrophic microbial utilization. Furthermore, T-N is purified by nitrification/denitrification, and T-P is purified by trapping the phosphorus-containing soil in the SSC reactor. The advantages of the SSC reactor are that it separates pollutants from water, degrades organic matter, reduces sludge, and simultaneously removes T-N and T-P in the same reactor chamber.

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To clarify the regional difference in mercury pollution the Lake Biwa watershed in central Japan, we monitored the mercury concentration in rainwater at four sites in the Lake Biwa watershed in Shiga prefecture. These observation sites were as follows Surumi as the northern site, Kutsuki as the western site, Aburahi as the southern site and Hikone as the eastern site. The total mercury average concentrations in Surumi, Kutsuki, Aburahi, and Hikone were 6.67±1.74 ng•L^-1, 5.98±1.66 ng•L^-1, 8.76±3.29 ng•L^-1, and 7.45±2.08 ng•L^-1, respectively. We estimated the annual mercury deposition in 2012 in Surumi, Kutsuki, Aburahi, and Hikone, and found into range from 10.4 to 17.5 μg•m^-2. The Lake Biwa watershed is wide to the north and south, and the environmental conditions are different between sites. The mercury deposition markedly fluctuates throughout the north and south of the Lake Biwa watershed. Therefore, it is necessary to evaluate the direct mercury load to Lake Biwa through rainwater at many sites.

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Air-cathode single-chamber microbial fuel cells (MFCs) were operated with different organic substrate concentrations or different external resistances. Phosphate, magnesium and ammonium were added to form struvite deposit on the cathode. As the substrate concentration increased, current production increased, and more deposits were observed. With the lower external resistance, current production increased, and more deposits were observed. Moreover, the larger drop of current density after struvite deposition was observed in the MFC with higher current production at the beginning of the deposition test. A possible reason for this is that mass transfer for oxygen reduction reaction was inhibited by the deposit on the cathode.

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