Korea has a large number of irrigation reservoirs and small streams. Periphyton is one of key factors to affect the self-purification of the local aqua system. This study presents a partial result of the investigation on the growth of periphyton at three particular natural sites; pool (P-1 and P-2), laminar flow zone (L-F) and riffle (R-1).Observation was performed mainly with flow velocity. From the test of site and laboratory, the larger biomass of periphyton was found in the riffle (R-I), where faster current velocity was observed, than in the pools. A threshold velocity distinguishing the current velocity dependency of periphyton attachment was about 0.11 ∼ 0.12 m/s. A high organic ratio of carbon to nitrogen, 9.22, was observed at the pool (P-2), while a lower ratio, 5.4, was observed at the laminar zone (L-F).
A rapid coprecipitation technique using gallium phosphate as a coprecipitant was investigated as a technique for preconcentration of thallium in its atomic absorption spectrometric determination. Gallium phosphate could coprecipitate thallium(III) quantitatively at pH 5. The precipitate which collected thallium(III) was centrifuged and then dissolved in nitric acid. The concentration of thallium(III) in the solution were measured by using electrothermal atomic absorption spectrometry; the concentration of gallium in the solution was also consecutively did by using flame atomic absorption spectrometry. The content of thallium(III) in the initial sample solution could be calculated based on the ratio of the amount of gallium in the final sample solution to that added to the initial sample solution. In the determination, an oxidation process using ammonium peroxodisulfate was required to oxidize thallium(I) to thallium(III) before the coprecipitation because thallium(I) was little coprecipitated with gallium phosphate. Since the rapid coprecipitation technique does not require any filtration and complete collection of the precipitate because the ratio of the recovery of thallium to that of gallium was almost constant regardless of the recovery of the precipitate, the operation for the preconcentration was simple, and the time required for the preconcentration was considerably shortened. The method was applicable to the preconcentration of at least 0.02-0.30 μg of thallium in 100 mL of tap and mineral water samples.
Though TiO2 is one of the most effective photocatalysts, effective use of solar light is limited since TiO2 photocatalyst can only absorb ultraviolet light. It is important to develop photocatalysts which can absorb visible light in order to promote effective use of solar light and light of fluorescent lamp. In this study, the responses of the mixtures of TiO2 and WO3, TiO2 and Fe2O3, TiO2 and Cu2O as well as the fired mixtures of these compounds to visible light were investigated in terms of degradation rates of methyleneblue aqueous solution. Degradation of methyleneblue by visible light was confirmed only when the fired mixtures of TiO2 and WO3 were added as photocatalysts.
Many streams of Kureha Hill, Toyama, Japan, are believed to suffer from nitrogen saturation because of their extremely high concentration of nitrate. The enhanced nitrification by nitrogen saturation would accelerate an emission of N2O to the atmosphere. In addition, the nitrate leached to the stream water was thought previously to be produced in the shallow soil layers with plenty of electron donors, i.e., organic matter. The existence of both nitrate and electron donors could promote the denitrification process by which N2O is produced. We measured the N2O flux to the atmosphere both from a nitrogen-saturated forest floor and from a non-nitrogen-saturated forest floor in order to determine the effect of nitrogen saturation on the emission of N2O. As a representative of a nitrogen-saturated watershed, Hyakumakidani was selected because it is one of the most acidified streams on Kureha Hill with a high concentration of nitrate as 158μmol/l. Sannokuma Stream, adjacent to Kureha Hill, was selected as a non-nitrogen-saturated watershed because it contains less than 10μmol/l of nitrate. Both forested watersheds are covered mainly by hardwood. Their vegetation, soil types, and nitrogen deposition are similar. The average N2O flux from the nitrogen-saturated watershed was 1.81 μg-N/m2/h from October 2004 to January 2005, while it was only 0.17 μg-N/m2/h from the non-nitrogen-saturated watershed. This result clearly shows that nitrogen saturation could promote N2O emission to the atmosphere.
The concentrations of boron gas in the exhaust gas and in the atmosphere were measured after the removal of particles by a teflon filter with a pore size of 0.2μm . The temperature of the filter was kept at 130°C for the sampling of exhaust gas to prevent sublimation of boron compounds, while it was kept at the atmospheric temperature for the sampling of the atmospheric air. The gas-phase boron compounds was absorbed with the 3% hydrogen peroxide solution in the absorption bottle made by polypropylenes. The measurement method by the use of ICP-MS has been established by improving many points to avoid contamination, which lowered the quantitation limit to the level of a 0.5μg/m3.
Many streams of Kureha Hill, Toyama, Japan, have high nitrate concentration throughout the year. This nitrate leaching into the streams is believed to be the result of nitrogen saturation because the nitrogen budget shows excess loss of nitrate to the stream water over the nitrogen deposition on the forested watersheds. We examined variations of nitrate and other components in detail of Hyakumakidani, one of the streams on Kureha Hill, in order to investigate the effects of nitrogen saturation on the water chemistry. Two first tributaries of the Hyakumakidani stream were investigated for their discharges and major ions. Clear relationships were found between the nitrate concentration and the discharge, while the chloride concentration remained constant throughout the year for both the tributaries. A reverse relationship between nitrate and sulfate was also found for both the tributaries, however, the absolute concentrations of these ions were quite different. A denitrification process involved with pyrite was a possible explanation of the reverse relation, however, no conclusive evidences have not been obtained from the laboratory experiments.