The habitat distribution of iron-oxidizing bacteria in the lower reaches of Tamagawa hot spring was investigated as a preliminary study to develop an advanced neutralization technique for acidic river water in the region. First, the 16S rRNA nucleotide sequences of the bacteria isolated from river water in this stream area were analyzed. It was confirmed that the inclusion of acidophilic iron-oxidizing bacteria showed 100% homology with Acidithiobacillus ferrooxidans. Water samples were collected from 8 spots selected in the region relatively close to the neutralization plant. The number of bacteria was determined by the most probable number (MPN) method. From a correlation analysis between pH and the number of bacteria, the 8 spots were classified into four groups. In the spots, classified as the Yukawa-Shibukuro region, it was found that the water is quite acidic at a pH=2-3 and that the number of bacteria was relatively large at 10⁴-10⁵ [MPN · 100 ml^-1].

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The control of phosphorus release from eutropHicated coastal sediment by a carbonated steelmaking slag was examined. Batch experiments showed the following. Without slag addition, the pH, DO and ORP of seawater easily decreased with the progress of coastal sediment corruption. Moreover, phosphorus release from coastal sediment occurred rapidly. On the other hand, with steelmaking slag addition, the decreases in pH and DO were inhibited and the high ORP values of seawater were maintained. Phosphorus release from coastal sediment was clearly inhibited by slag addition. Even when the carbonated steelmaking slag was compared with sand, phosphorus release from coastal sediment was further improved. In the mechanism of phosphorus release control through steelmaking slag addition, it was considered that a carbonated steelmaking slag promotes calcium hydroxyapatite (HAP) generation induced by the high Ca²⁺ concentration of seawater. Furthermore, continuous experiments for more than 300 days showed that pH control and phosphorus release control from coastal sediment by carbonated steelmaking slag addition were maintained for a long term.

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The habitat of Aphyocypris chinensis in Jeollabuk-do, Korea was surveyed in March and July 2007 to obtain basic information on its habitat preference. The data obtained are expected to contribute to the conservation of the endangered Japanese population of the present species. Twenty species including A. chinensis, belonging to nine fish families, were caught at four stations using a wide hand net. Among these, Carassius spp., Macropodus ocellatus and Monopterus albus were found in habitats similar to that of A. chinensis. The habitats in Korea were similar to a nearly traditional irrigation canal, which are identical to those in Japan. From this survey, we confirm that a traditional style of farming provides the most suitable habitat for A. chinensis.

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Field surveys were conducted in rivers/canals in peri-urban areas of Dhaka and Bangkok in October and December, 2006. The distributions of turbidity and chlorophyll-a (Chl-a) concentrations on a graph could distinguish the measurement results of four water bodies, the Shitalakhya River, Bangladesh, and the Chao Phraya River, Tha Chin River and Tamru Canal, Thailand. Chl-a concentrations were 2∼4 μg l^-1 in the Shitalakhya River, 4∼6 μg l^-1 in the Chao Phraya River, 5∼13 μg l^-1 in the Tha Chin River, and 12∼35 μg l^-1 in the Tamru Canal. Moderate mixing was observed near the river mouth, and the turbidity maximum and Chl-a maximum were observed in the Tha Chin River estuary. Salt water intrusion was not observed in the Tamru Canal, the reason for which should be the water depth being smaller than the critical minimum water depth of salt water intrusion. In the Tamru Canal, the turbidity maximum and Chl-a maximum were observed both in the upper canal and at the canal mouth, which should be typical of eutrophicated and shallow coastal rivers/canals. Vertical water quality profile monitoring including nutrients and Chl-a concentrations is necessary to quantify land-based pollutant contributions to pollutant loads in the estuarine zone.

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