To enhance the phosphorus adsorption by soils, we examined several distinct characteristics of different soils by subjected to heating treatment. Then, the relationship between the amount of phosphorus adsorbed and the various nature characteristics of soils, and the mechanism of the increase in phosphorus adsorption were examined. The results are outlined below. With three soil types (volcanic ash soil, brown forest soil, red soil), the increase in phosphorus adsorption caused by heating, was maximum at 500°C. Phosphorus adsorption differed depending on soil types, and the amount of phosphorus adsorbed was in the order of volcanic ash soil> brown forest soil > red soil at 500°C. Volcanic ash soil, brown forest soil, red soil needs 300°C, 200°C and 300°C, respectively, of heat temperature in order to achieve the maximum specific surface area. The amount of silicon from oxalate extraction dissolution was maximum at 300°C in the volcanic ash soil, and was maximum at 500°C in both the brown forest soil and the red soil. Furthermore, each of the three types soil achieved the maximum amounts of both active aluminum and free aluminum at 500°C, and the maximum amounts of both active iron and free iron at 300°C. One of the factors affecting phosphorus adsorption by heated soils is soil type. We confirmed that the amount of phosphorus adsorbed onto these three soil types commensurate with the amount of active aluminum, free aluminum and silicon from oxalate extraction dissolution.

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Concrete blocks with phosphorous adsorption ability have been developed to remove non-point source phosphorous from rivers and canals. The concrete blocks were prepared by mixing cement with a hydrotalcite compound (HT) that has high selectivity and large phosphorous adsorption capacity. The concrete blocks (test pieces) with various the filling ratios of 85, 90 and 95% were prepared using fresh concrete, and the result of the slump test was 0 cm. Also, the compressive strength and phosphorous removal capacity were investigated fundamentally. The results showed that the compressive strength of all the test pieces was above 18N·mm^-2 and they were sufficiently strong for use as laying blocks. For a test piece with a low filling ratio, phosphorous was removed by Ca²⁺ and for a test piece with a high filling ratio, phosphorous was not removed by ion exchange. However, these results suggest that high strength and high phosphorous adsorption ability are compatible with each other, which can be controlled by regulating the mix proportion. Furthermore, field tests were conducted using large concrete blocks containing HT (HT specimens). The results showed that phosphorous was adsorbed at the uppermost layer of the HT specimens. In the tests, the break-through of phosphorous adsorption occurred three months later and the average removal rate for such break-through was 3.69mg P·m^-2·d^-1.

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It is well known that oxygen transfer in an irrigation and drainage system occurs on the flow surface by reaeration as agricultural water flows down the waterway, and that water management structures, such as drops or weirs, largely improve this oxygen transfer. We focus on a labyrinth weir, where an improvement of the aeration function is expected because the crest length per unit channel width is longer than that of a full-width rectangular weir. The oxygen transfer at a labyrinth weir was clarified from reaeration experiments in a circular channel. The aeration function of a labyrinth weir improves as the crest becomes longer, and the maximum value of the function is reached at approximately 1.6 times the channel width. Furthermore, the predicted formula of reaeration with the upstream energy of the weir, the tail water depth, the function which expresses the influence of the crest length of the labyrinth weir, and the high degree of conformity were obtained. The labyrinth weirs do not require a large fall to produce the same aeration effect, as compared with conventional drops or weirs. The labyrinth weir is effective for the efficient uptake of oxygen into agricultural water.

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Myriophyllum spicatum is known to cause allelopathic growth inhibition of a cyanobacterium Microcystis aeruginosa. This study was carried out to identify unknown allelochemicals released from M. spicatum and to investigate their anti-cyanobacterial effects.
A fraction containing unknown allelochemicals was obtained by the fractionation of a culture solution of M. spicatum using high performance liquid chromatography. A series of analyses of its culture solution and methanol extract using gas chromatography mass spectrometry revealed that fatty acids, i. e. nonanoic, tetradecanoic, hexadecanoic, octadecanoic, and octadecenoic acids were released by M. spicatum. Nonanoic, 6-cis-octadecenoic, and 9-cis-octadecenoic acid significantly inhibited the growth of M. aeruginosa, while tetradecanoic, hexadecanoic, octadecanoic acids did not show any effect. Comparing the inhibitory effect of nonanoic acid with those of the four polyphenols and eugeniin which were previously reported as M. spicatum-released anti-cyanobacterial compounds, nonanoic acid was found to be most inhibitory to M. aeruginosa. In addition, nonanoic acid and pyrogallic acid, one of the M. spicatum-released anti-cyanobacterial polyphenols, caused synergistic growth inhibition of M. aeruginosa. These results indicate that not only polyphenols and tannins but also fatty acids such as nonanoic acid must be studied to reveal how M. spicatum causes its allelopathic effect on M. aeruginosa.

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Groundwater contamination often occurs because of discharge, leakage or spillage of industrial chemicals. This type of contamination must be prevented because high-tech industries should be able to procure the required amounts of high-quality groundwater for their manufacturing processes. It is now recognized that the reduction of negative external effects of manufacturing is not only necessary for ecological sustainability, but also for economic sustainability. The objective of the Advanced Environmental Monitoring System (AEMS) is to develop effective systems for the fast and continuous monitoring of groundwater contamination around industrial facilities. The AEMS will identify the contaminants and locate their sources, thus enabling users to take appropriate measures to prevent the contamination from spreading. It can also be used as a tool capable of assessing environmental hazards caused by contaminated groundwater by rapidly and efficiently identifying the toxic contaminants. In this paper, we present the state of soil and groundwater contamination in Japan, the necessity of groundwater monitoring, the state of monitoring apparatus, and the outline of the AEMS project. The AEMS can be used not only for the leakage monitoring of industrial chemicals but also for risk management in such fields as waste disposal landfill or in bioremediation sites that require long and real-time monitoring.

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Seasonal changes in the vertical profile of chlorophyll-a, COD_Mn and nutrient concentrations in an agricultural irrigation reservoir were investigated for two years. The reservoir had a maximum depth of 9 m, a surface area of 1.2 × 10⁵ m² and a maximum storage volume of 5.6 × 10⁵ m³. The hydraulic retention time was about 3 days from April to August, and was 7 days from September to March. In July, Volvox sp. were dominant when the retention time was less and nutrient supply rates were high. On the other hand, Microcystis sp. were dominant when the retention time was more and nutrient supply rates were low in September. These results coincided partly with the occurrence of cyanobacteria blooms in nutrient-rich and slow-flowing waters.

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