The vertical profiles of the physical properties, and nutrient and radio-isotope concentrations of the sediments in Lakes Kasumigaura and Suwa were determined in 2003 and then compared with previous results. Sedimentation rates estimated from the profiles of radio isotopes showed decreasing tendencies in both lakes, which possibly resulted in the difference between the long-term trends of water and sediment concentrations. As regards to phosphorus, it sedimentation rate was in good agreement with those calculated as the difference between the input and output loads divided by its concentration in the surface sediments; on the other hand, a large difference was found in the case of nitrogen, suggesting denitrification. Then, we compare the difference between the nutrient amount accumulated in sediments and the sum of residuals of nutrient budgets in Lake Kasumigaura for 1981 – 2003; the residual nutrient budgets were approximately twofold the former for phosphorus and approximately tenfold for nitrogen. This discrepancy for phosphorus was probably due to the inaccuracy of the calculated parameters for calculation and/or the assumption that the residual nutrient budget is uniformly distributed in the lake.

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Fly ash polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) added to the fish feed were given to carp for 5 days. After 7, 30, 90, 180 and 360 days from feeding, their concentrations in the muscle, gills and the internal organs, such as intestines, reproductive organ and liver of carp were determined. Co-PCBs labeled ¹³C were given to carp for 4 days, and then after 7 and 187 days from feeding, their concentrations in such organs of carp were determined. The following results were obtained.
(1) The PCDDs/PCDFs with greater TEF values accumulated more than those with smaller TEF values in the gills, muscle and reproductive organ of carp, and the PCDDs/ PCDFs with greater TEF values had similar half-life patterns in the organs of carp considered, except the reproductive organ.
(2) Relative accumulation ratios (RARs) of T4CBs (#77, #81) were smaller than those of other Co-PCBs in all the parts of carp considered, and RARs of Co-PCBs, except T4CBs, were almost the same. Co-PCBs with many chlorine had longer half-lives in the organs, except the gills and ovaries or testies.

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In this study, the material properties and adsorption characteristics of the adsorption material which consists of volcanic ash soil heated with ferrous sulfate (VASHF) are examined. VASHF simultaneously has cation exchange capacity and anion exchange capacity. Moreover, even though its hardness is less than that of sand, its durability to beating and water reverse washing is high, and it has sufficient physical strength to act as a filtration material. The adsorption rate of VASHF is very high. VASHF shows a high amount of phosphorus adsorption from the low-concentration stage to the high-concentration stage, and the amount of phosphorus adsorption is 8.1-22.3mgP·g^-1(168h). Additionally, it can efficiently reduce the amount of phosphate, tripolyphosphate and phosphite ions, however, it can hardly reduce the amount of phosphinate monohydrate ions. The lower the pH is, the higher the removal rate of those forms of phosphorus that can be achieved with pH5.0-9.0, Coexisting with AsO₄^3- 5.0mgAs·l^-1, F^- 20.0mg·l^-1, Cl^- and SO₄^2- 200.0mg·l^-1 and SiO₄^2- 50.0mgSi·l^-1, it is found out that VASHF did not influence phosphorus removal. Finally, highly effective phosphorus removal is verified by the phosphorus removal experiment of the column and the secondary effluent.

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The EC50 value of several alkylphenols (APs) on the swimming velocity of unicellular green algae Chlamydomonas reinhardtii was measured and its relationship with the octanol⁄water partition coefficient (Pow) of APs was investigated. To clarify the sensitivity of C. reinhardtii to APs, the EC50 value was compared with that for crustacea Daphnia magna, a standard species for motility toxicology tests. As a result, there is a strong correlation (r=0.96) between the log Pow of APs and the log EC50 value for C. reinhardtii. The log EC50 value for C. reinhardtii strongly correlated (r=0.98) with that for D. magna and the sensitivities of C. reinhardtii and D. magna were almost equivalent when the log Pow of APs were large. These results confirm the reliability of the toxic evaluation of APs from the endpoint of the swimming velocity reduction test using C. reinhardtii. This method requires only 1 hour for evaluation, enabling a rapid and convenient bioassay for testing the acute toxicity of environmental pollutants in waters.

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Recently, the frequency of red tide occurrence has been increasing with the advancement of Nori laver (Porphyara) cultivation, while the production of bivalves has been decreasing particularly at fisheries in Ariake Bay. That is, a great number of planktons causing red tide consume large amounts of nutrients such as dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP), which are essential for the growth of Nori laver, even under a condition of decreasing nutrient supplies. Moreover, the decrease in the production of bivalves might accelerate photosynthesis because the rate of plankton feeding by bivalves decreased. This competition for nutrient uptake among Nori laver and phytoplanktons such as Dinoflagellates, Diatoms and Raphidophyceae is considered to be the cause of the recent deterioration of Nori cultivation qualities in Ariake Bay. After examining the process of competition for nutrient uptake with a box-model simulation, we found that phytoplanktons can grow at water temperatures higher than before. Moreover, it was considered that DIN is taken up for the primary production of phytoplanktons, and is reduced by the increase in particulate organic nitrogen (PON) by the decrease in bivalves, as evidenced by the increasing ΔCOD.

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We developed a method of effectively purifying untreated graywater by the self-purification of surface soil. In this method, polluted water is purified by infiltrating and running it in a carrier of a thin container. The top of the container is open, and the base is sloped. We called this method “Keisya-Dosou-Hou”, meaning sloped layers of soil. We performed an experiment to purify kitchen wastewater using this method. The experiment was carried out for two years and six months without changing or supplying in the carrier. The average volume of treated water was 90l·d^-1, and 70l·m^-2·d^-1 per soil area. The average removal rates in percentage were as follows : SS: 86%, BOD: 82%, COD: 85%, T-N: 78% and T-P: 86%. The average removed weight per soil area were as follows : SS: 8.6g·m^-2·d^-1, BOD: 45.9g·m^-2·d^-1, COD: 24.6g·m^-2·d^-1, T-N: 1.72g·m^-2·d^-1, T-P: 0.338g·m^-2·d^-1. The results show that it is possible to purify organic pollution and nutrients concomitantly. It was considered that T-N was removed concurrently due to progress of nitrification and denitrification in both layers of the structure. When wastewater containing much organic pollution was treated with a thin layer of soil, the upper part of the container became aerobic by bordering with atmosphere, and the bottom part became anaerobic by decomposing organic pollution. The results of this experiment show that “Keisya-Dosou-Hou” is an economical and compact technique of purifying graywater. Also the result made clear the accuracy of the self-purification of surface soil, and it was considered that the results had paved ways for the construction of new water purification system.

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