Seasonal changes and the vertical distributions of the water quality in Kawahara Lake were observed during Feb.-Oct. 2000. With progressing of thermal stratification in the lake, DO decreased gradually in lower layer and the nutritive salts (NH₄-N, PO₄-P) released from bottom sediment.
On the other hand, in the middle layer of 4-5m depth, phytoplankton biomass grew and aggregated densely in the state of thin layer about 1m thick. The dominant species of the phytoplankton in that layer is Gonyostomum semen. It was concluded that the limiting factor for the biomass growth was NO₃-N, because the bloom occurred after inflowing of NO₃-N with heavy rainfall.

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The runoff characteristics of heavy metals in the R. Yodo and its tributary streams, R. Amano and R. Funahashi, were established by observation every third day during 1999-2000. The changes in heavy metal concentrations were frequently fluctuating, especially, in the rivers with small catchment and were ruled mainly by fluctuation of flow. As the observation with high frequency often met with the condition of storm runoff in the rivers, the determined values of heavy metals exceeded sometimes the environmental standard values or the quasi ones. Applying the regression equation, L=a·Qⁿ, to heavy metals, the n values exceeded 1.0, and their correlation coefficients of almost heavy metals were larger than 0.65. During downflow process in the R. Yodo and its three large tributaries, the concentrations of many heavy metals in the R. Katsura at Miyamae Bridge were the highest values. Recently, many new kinds of heavy metal elements became to be determined sometimes over their quantitative limits. As the runoff concentrations and loadings of heavy metals become larger quantities during storm events, it is apprehended that the risks for aquatic lives, drinking water and the Osaka Bay area flowed into by the R. Yodo should rise up.

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Not only application of fertilizer but seawater intrusion seems to affect the groundwater quality in a coastal farming area. In this study, field surveys were conducted to examine the characteristics of groundwater quality over a wide coastal area with farming greenhouses. Principal component analysis revealed that the information contained in the original data set was explained up to 75.8% by only four principal components, and that groundwater quality in the area was affected mainly by soil characteristics, application of fertilizer and seawater intrusion. The observation field was divided into three categories corresponding to the geographical information through the cluster analysis: (1)In the eastern, central and western part of Higashimorogi district, neither application of fertilizer nor seawater intrusion affected groundwater quality except three wells where the influence of fertilizer was large. (2)Characteristics of the soils were supposed to be different in northeastern part of Higashimorogi from other districts. (3)In Kodono district, not only seawater intrusion but application of fertilizer affected the water quality. It was also demonstrated that the effect of seawater intrusion on groundwater quality appeared more remarkably in a well nearer the coast and in a deeper well having the almost same distance from the coast.

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Groundwater pollution by nitrogen is a common environmental problem in the islands covered with coral limestone. Total annual emission of nitrogen from fertilizers, livestock wastes, and domestic wastes at Miyako Island, Okinawa was examined from 1977 to 1998, and compared with the concentration of nitrogen in groundwater. The trend of nitrogen emission was reflected on the groundwater concentration with the delay of seven years. This suggests that the velocity of nitrogen permeating down to the groundwater is 3 m per year. The amount of nitrogen leaching into the groundwater was 39% of the total nitrogen emission on the ground. These results emphasize the importance of data collection on nitrogen emission in order to predict the future nitrogen concentration of groundwater in coral islands.

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Organic and inorganic substances in 36 well water samples in Kuwana area, northern part of Mie prefecture in Japan, were quantified.
Arsenic above 0.005mg·l^-1 was detected by Hydride Generation Atomic Absorption Spectrometry (HG-AAS) method in 12 wells of 25-260m depth. 7 out of the 12 well water samples contained arsenic above the maximum permissible limit in drinking water in Japan although the wells were not used for drinking. Qualification by liquid chromatography with inductively coupled plasma mass spectrometry (LC-ICP⁄MS) showed that some of the samples contained arsenite (As^(III)) above the limit. Deeper underground than 100m, arsenic was found only in the east side of Yoro Fault, which suggests that arsenic in groundwater is associated with some specific strata. Arsenic was slightly correlated with pH and iron. The concentrations of iron in arsenic-rich well waters were high.
The concentrations of iron and magnesium in the groundwater in this area were very high. Specific chemical compositions of the waters from the wells close to the sea suggest that the well waters were affected by seawater, and some of the samples contained arsenic.

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The aim of the investigation is to show how the Ayu (Plecoglossus altivelis), a fish living in clean streams, can return to an urban river that believed to be polluted in the past. It was found that the ammonia nitrogen concentration had decreased remarkably, by monitoring of the water quality at the river. Due to the qualitative improvement of the sewage treatment water that is the river's main discharge source, the ammonia nitrogen concentration was decreased. Ammonia is an important substance for the survival of the creature; and a safe level, which makes the Ayu's survival possible, was estimated.

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Various wastewater treatment plants located in Japan were evaluated for investigating behavior of estrogenic substances using in vitro recombinant yeast assay, enzyme immunoassay (EIA) and chemical analysis. Expressed in 17β-estradiol (E2) equivalent, total estrogen-like activities in influents were found 0.099μg·l^-1 in sewage, 4.0μg·l^-1 in treating animal wastewater and 0.25μg·l^-1 in landfill leachate. The results indicated that 17β-estradiol (E2) (analyzed by EIA) contributed to estrogen-like activity (analyzed by yeast assay) in influents and treated effluents of sewage and treating animal wastewater. On the other hand, bisphenol A significantly contributed to estrogen-like activity in landfill leachate. The activities by yeast assay in some influents of sewage exceeded E2 concentration considerably, suggesting the presence of an unknown estrogenic substance. In these cases, it was found that sewage sample have the overestimation effect on the estrogen-like activity of E2. According these results, it is necessary to evaluate of estrogen-like activity in wastewater to consider effects of some contaminants in it.

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To estimate the application amount of pesticides for paddies, the sales amounts sold by ten agricultural cooperatives (agr-coops) in Ibaraki and Hokkaido were investigated.
The amounts sold from these agr-coops in Ibaraki and Hokkaido and the amounts shown in “Noyaku Yoran”, the Japanese Pesticides Handbook, were compared. The share of the amount of pesticides sold by each agr-coop was investigated by dividing the standard application area for herbicides sold by the agr-coop by the rice planted area to find the herbicide-application-area ratio (R).
The standard application amounts of herbicides for rice plantings were sold by five of agr-coops. Three coops in Ibaraki, however, sold fifty percents or less of the standard application amounts. The amounts sold by three agr-coops cannot be evaluated application amounts of pesticides. The amounts of pesticides used as obtained from the Handbook were quite different from the amounts sold by the agr-coops. Accordingly, the exact amount of pesticides used in the areas evaluated cannot be determined from the Handbook. In order to learn the exact amount of pesticides in the area to be evaluated, it is necessary, therefore, to investigate the amounts sold by agr-coops having a large share of the pesticides market.

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Fluctuations of alkaline phosphatase activities in two streams and in reservoirs receiving the stream waters located in two adjacent but not connected watersheds were investigated from January to December in 2000. Alkaline phosphatase activities (APA) remained nearly constant in both streams, whereas in reservoirs they increased during the summer season. No relation was found between APA and soluble reactive phosphorus concentration. At one sampling station located in the stream, phosphorus concentration extraordinarily increased later in the study, but there were no related change observed in APA. An examination of size-fractionated samples suggested that most the APA in stream could be attributed to dissolved enzymes, whereas in reservoir most APA was related to bacterial particles. It assumed that APA is not indicative of phosphorus status of aquatic microorganisms.

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Geochemical characteristics of surface (0-10cm) sediments (110 samples) collected from the Fujimae tidal flat, Aichi Prefecture, Japan are studied. Tidal flat sediments (<180μm size fraction) in the northwestern region are enriched in Al₂O₃, Na₂O and CaO, but depleted in Zn and Cr, compared with those in the central and eastern regions. These differences are not attributed to the variation in grain size, but rather to that in compositions of detrital materials. The tidal flat sediments at the central and eastern regions are also characterized by the presence of yellowish-brown surface layers less than 3cm thick, which overlie black inner layers. In general, these surface layers are enriched in P₂O₅ compared with the inner layers. This may be attributed partly to redistribution of phosphorus from the inner layer to the surface layer and its adsorption on Fe-hydroxide. Calculations of enrichment factors for minor elements show that some heavy metals such as Zn, Cu and Pb are markedly enriched in the sediments.

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The objective of this study is to evaluate the role of tidal action and benthic animals such as seaworm in denitrification activities of the tidal flat in Tamagawa river through the field investigation. It was regularly observed that only NO₃-N concentrations in interstitial water in surface layers of the tidal flat sediment changed with a high-low tidal action. The 24-hour survey showed that the changes in NO₃-N concentrations in interstitial water were observed regularly through the tidal action cycle. Based on the tidal action-dependent decrease of NO₃-N concentrations, denitrification rates were calculated. The apparent denitrification rates show that (i) water temperature, (ii) NO₃-N concentrations in surface water, (iii) tidal level difference between high- and low-tides, and (iv) existence of benthic animal's burrow affect denitrification activity of the tidal flat sediment.

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We examined the behavior of nonionic surfactants and their degradation products in two municipal sewage treatment plants with anaerobic-aerobic activated sludge treatment system and seven sampling points in Tone River including tributaries in Gunma prefecture, by LC-MS.
In the sewage treatment plants, Nonylphenol ethoxylates (NPE) and alcohol ethoxylates (AE) were removed more than 80% and 90%, respectively, after primary sedimentation tank and anaerobic treatment process. NPE, AE, and nonylphenol (NP) were reduced by 99%, 99.9% and 90-95%, respectively, throughout the treatment. In contrast, nonylphenoxy carboxylic acids (NPEC) rather increased in aeration tank, and were not reduced throughout the treatment. The lengths of ethoxylates of NPE were found shortened after aerobic activated sludge treatment. From these results, NPEC was supposed to generate during degradation of NPE. Since NPE (1), NP and NPEC were detected in the extract of activated sludge, certain portion was found adsorbed into the activated sludge.
NPE, AE, NP and NPEC were detected at 0.1-16.4μg·l^-1, 0.3-12.8μg·l^-1, <0.08-0.2μg·l^-1 and <0.008-3.2μg·l^-1, respectively, in river waters. OP was detected <0.08μg·l^-1 in all points. Concentrations of NPE and AE were comparably higher in downstream, in tributaries and in winter.

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The Database, namely “the Second Sediment Survey Database” in this paper is constructed as a continuation database of the sediment survey by the Japan Environment Agency, and the monitoring/surveying original data published by research centers and administrative organs in Japan are summarized in this database. Its period is eleven years from 1984 to 1994. It is able to refer to the data, which is in the first period for 14 years from 1970 to 1983, from the Second Database. The monitoring items are more than 225, and numbers of sediment samples in the second database are 9,594 in rivers, 713 in lakes and reservoirs, 7,199 in sea areas, respectively.
Monitoring condition, actual distribution, and trends of sediment pollution that data are modified in each prefecture and in time series for 25 years from 1970 to 1994, are discussed with the statistical analysis. Results are as follows: The mean concentrations of sediment for 25 years are 15.7mg·g^-1 as COD, 2.4μg·g^-1 as Cd, 41.9μg·g^-1 as Pb, 10.8μg·g^-1 as As, 1.82μg·g^-1 as total-Hg and 0.74μg·g^-1 as PCB. The mean values in 1994 are 15.3mg·g^-1 as COD, 0.59μg·g^-1 as Cd, 33.3μg·g^-1 as Pb, 7.1μg·g^-1 as As, 0.44μg·g^-1 as total-Hg and 0.056μg·g^-1 as PCB. Thus it is able to consider that the sediment concentration of COD is almost unchanged during in recent 25 years, and other items are gradually decreasing. In addition, the COD contaminant in sediment is noticed the dispersion phenomena of pollution as the remaining concentration in urban area, and as the increasing concentration in local area.

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