Ultrafine Bubble（UFB）water, a technology originating in Japan, is a functional water containing bubbles ＜ 1µm in diameter, that has been attracting attention in recent years. There are reports that UFB water made from CO₂ has a sterilizing effect. However, it is difficult to determine whether CO₂ exists as bubbles because CO₂ is easily soluble in water. In this study, I generated CO₂-UFB water using a pressure dissolution and stirring mixer, and I investigated total dissolved solid（TDS）,CO₂ concentration, pH, nano number density, titration volume by NaOH, and radicals. As a result, TDS, CO₂ concentration, and titration volume by NaOH were increased with greater agitation time when generating CO₂-UFB. Nano number density was increased when the surface area of the second element was reduced against the first element of the mixer. Additionally, the presence of methyl radicals was confirmed in CO₂-UFB water. Moreover, the presence of CO₂-UFB can be presumed by measuring CO₂ concentration and TDS.

　This study was conducted to assess the influence of common reed on the metal removal from acid mine drainage（AMD, Zn 30 ㎎/L, Cd 0.3 ㎎/L, Cu 20 ㎎/L, Pb 2.5 ㎎/L, pH 4.7）in constructed wetlands（CWs）. During 1-year lab-scale treatment in a sequencing batch mode, planted and unplanted CWs neutralized the pH value of the synthetic AMD by substrate limestone and removed Cu and Pb to below the effluent standard. Although Cd was also removed to near the effluent standard, Zn removal was insufficient, especially in the planted CW. The plant increased the soil bacteria population and the ratio of Rhodanobacter and Cellulomonas, but suppressed the pH increase. In conclusion, common reed was found to inhibit Zn and Cd immobilization of Zn and Cd in the CW.

In Lake Biwa, annual vertical mixing of the water column is becoming less likely to occur, and there is concern about a steady state of anoxia in the bottom layer and the associated elution of nutrients and heavy metals. In this study, a 15-day elution test was conducted to estimate the differences in elution fluxes of organic matter, nutrients and heavy metals under aerobic and hypoxic conditions from the undisturbed sediments collected from southern Lake Biwa. Under hypoxic conditions, the elution fluxes of dissolved total phosphorus, total iron and manganese were estimated to be 3.05, 21.3 and 10.5 ㎎/㎡/day, respectively, higher than those under aerobic conditions. The elution flux of sulfate ions was higher under aerobic conditions than under hypoxic conditions. In addition, the dissolved total nitrogen and silica did not differ with the dissolved oxygen concentration. This study provides basic and quantitative data on the organic matter, nutrients and heavy metals that could be eluted from the sediment under hypoxic conditions in Lake Biwa.