The Omuta City North Sewage Treatment Plant (STP) conducts seasonal operations to release nutrients into the Ariake Sea. However, it is unclear how much of the nutrient load from STP is supplied to the Ariake Sea via the Domen River. Therefore, in this study, we calculated the nutrient load from the STP and the nutrient load upstream of the Domen River, and investigated the effect of seasonal operation on the nutrient load supplied from the Domen River to the Ariake Sea. As a result, the ratio of the T-N load from the STP to the T-N load supplied from the Domen River to the Ariake Sea accounts for 82 to 98% in the nitrification control period and 61 to 94% in the nitrification accelerated period. The average annual T-N load from the STP, which increased due to seasonal operation, was 23 tons.

Analytical method for the determination of major-to-ultratrace elements in environmental water samples around sewage treatment plant by ICP-MS was examined in detail. In the present work, solid phase extraction using chelating-resin was adopted as the preconcentration method for the determination of ultratrace elements. Prior to solid phase extraction, environmental water samples were heated with nitric acid and hydrogen peroxide at 200 °C for 4h to decompose chelating agents contained in sewage effluent such as EDTA, which cause low recovery values for several elements. As a result, 53 elements in the concentration range from sub-ng/L to several 10 mg/L could be determined with good reproducibility. The reliability of the whole analytical procedure was confirmed by analyzing river water certified reference materials (JSAC 0301-4a and JSAC 0302-4a). From the analytical results for environmental water (river water) samples around sewage treatment plant (upstream, just below outlet, downstream 1 and downstream 2), it was found that various elements such as Fe, Co, Ni, Cu, Zn, Cd, and Pb were emitted from sewage effluent into environmental water (river water) as dissolved forms, while the element existed mainly in particulate matters (Al, Ti, and rare earth elements) showed low concentrations in sewage effluent. Distribution patterns of rare earth element for sewage effluent and downstream samples showed characteristic large Gd anomalies and increase from light REE to heavy REE, which were the same as other environmental water samples affected by the influx of sewage effluent.

Trimethyl (octadecyl) ammonium and it's salts is widely used as a cationic surfactant. In this study, an analytical method for trimethyl (octadecyl) ammonium and it's salts in sediment by liquid chromatography tandem-mass spectrometry (LC-MS/MS) was developed. In this method, trimethyl (octadecyl) ammonium and it's salts in sediment is measured as trimethyl (octadecyl) ammonium chloride. The method detection limit (MDL) and method quantification limit (MQL) were 0.00026 μg/g-dry and 0.00069 μg/g-dry, respectively. This method was able to measure the trimethyl (octadecyl) ammonium and it's salts in organic or inorganic-rich sediments, which had been difficult with conventional methods. In addition to the hydrophobic adsorption of trimethyl (octadecyl) ammonium and it's salts on organic matter, electrostatic adsorption on inorganic matter was also observed. It was also detected in the sediments at Yamagata Prefecture, which is considered to be relatively less polluted by chemical substances. The substances were detected in both rivers and sea areas in sediments at Nagoya City, and was found to be at higher concentrations than that detected in sediments at Yamagata Prefecture. Trimethyl (octadecyl) ammonium and it's salts was detected in all sediments at Nagoya City after 2003, which means its continuous pollution in sediments at Nagoya City.

In order to adopt "screening analysis" in drinking water quality testing, which performs qualitative and quantitative analysis based on information registered in a database without measuring standard materials at the time of each testing, a validation test was conducted to evaluate the difference on the chromatogram data analysis by analysts. In the validation test, chromatograms of 6 water samples were analyzed using the same database and software by 16 analysts in 13 laboratories. Peak identification was performed based on Retention time (RT), (qualifier and target ion) QT ratio, and degree of matching of mass spectra, and if necessary, peak shapes in water samples were compared with those in calibration curve samples. Large differences were observed in the detection of pesticides among the analysts. There were two main reasons for the disagreement. The first is that the judgement of peak detection at low concentrations near the quantification limit of each pesticide, particularly below the concentration at three times of quantification limit, differed depending on the analyst. The other reason was that some analysts made clear misidentifications and identified wrong peaks close to the predicted retention time, despite the QT ratio and mass spectrum didn't match that in the database. In addition, there were some cases where the quantified values were reported by misidentifying the peaks of degradation products and metabolites, even when the peak detection was correctly judged. In order to use screening analysis practically by drinking water quality testing laboratories, it is important to conduct a validation test like this study in advance to use screening analysis and to coordinate criteria for peak identification and quantification among data analysts.

We investigated the side of parking lots, garbage collection points and house wall to understand the source of plastic pieces. The survey was conducted approximately monthly from Apr. 2020 to Feb. 2021 with the aim of clarifying detailed rainfall variation in the density of plastic pieces on the shoulder. The discharge coefficient of gravel is 0.30 to 0.70, lower than that of asphalt, 0.70 to 0.95. As the plastic pieces on the gravel surface could be hard to be washed away and easy to be accumulated, the mass of plastic pieces flowing into the side was larger than that flowing out. PE, PP, PS, PET and PVC were predominant among the found polymer materials (43-66%by mass). The size corresponding to the cumulative ratio of 50% the plastic pieces on the side of house wall was smaller than that on the others. On the sides of house wall that was not near the plastic source, the plastic pieces could be weathered to fragment into smaller pieces than on the others. The number density of plastic pieces scattered on the side of garbage collection point was affected by the structure. It was found that the behavior of plastic load was complicatedly influenced by land properties, uses and rainfall.

A Nankai Trough mega-earthquake with a magnitude of 8 to 9 on the Richter scale is predicted to occur with a probability of 70 to 80% within the next 30 years. Therefore, there are concerns about the risk to the health of residents due to the leakage of hazardous chemical substances from factories and business establishments associated with the earthquake. In this study, we attempted to estimate the stock amount of chemical substances subject to the PRTR Law at factories and business establishments in the area expected to be inundated by the tsunami caused by the earthquake.

It was found that the chemical substance stock in the tsunami inundation area nationwide was 19.5 million tons, accounting for 87.1% of the total stock of the 23 prefectures concerned. In addition, it was found that this amount is equivalent to the amount of chemical substances released for about 93 years in the 23 prefectures concerned.

We developed a novel mass spectrometric method using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC/MS/MS) with nitrogen as the carrier gas to quantify simazine and thiobencarb under the regulatory environmental quality standards for water pollution. We modified the previous official method and optimized the sample preparation procedure using solid-phase extraction (SPE) cartridges. Our study demonstrated good recoveries for simazine and thiobencarb in all SPE cartridges, with the percentage recoveries ranging from 70% to 120%. Of the examined SPE cartridge, a marked measurement precision with the least variation was achieved on Smart-SPE PLS3-20 (PLS3) cartridge, which is packed with nitrogen-containing divinylbenzene methacrylate. Consequently, we selected the PLS3 SPE cartridge for the sample preparation in this method. Moreover, The method's detection and quantification limit values for simazine and thiobencarb in river and seawater samples were one order of magnitude lower than those of the environmental quality standard values. Furthermore, simazine and thiobencarb were identified and quantified with excellent separation, minimizing potential interferences.

Using available PRTR and environmental monitoring data, the visualization of human health risks due to hazardous air pollutants in Saitama was examined. A simple regression analysis was conducted to verify the relationship between PRTR release amounts and measured concentrations of the eight target chemical substances. The agreement between ambient air concentrations estimated from the releases of target chemical substances into the air and measured concentrations was verified, and hazard quotients (HQs) indicating hazardous properties were calculated from each dataset. HQs were plotted on a map of Saitama, creating an environmental risk map to visualize the toxicity status of the eight chemical substances. As a result, a correlation was found between the amounts of reported releases and measured concentrations for five chemical substances, and there were no areas where HQs exceeded one for those substances. The distribution of HQ was different for each compound, and areas with high HQ were observed for ethylene oxide and formaldehyde. As the environmental risk map presented in this study effectively visualizes air quality status, and is simple and inexpensive to create, we propose a environmental risk mapping method that can be used to promote the management of chemical substances in factories and business establishments.

Concentrations of an insecticide fipronil in paddy water and paddy soil were investigated as well as water and sediment form the Kaname River. The partition coefficient (Kd) of fipronil obtained from the elution test using the sampled paddy soil was compared to the rate of fipronil concentration in paddy soil to that of paddy water. When the paddy field was dammed, the rate decreased due to elution of fipronil from the paddy soil, and when water was circulated through the paddy, the fipronil concentration in paddy water decreased and the rate increased. Risk assessment for aquatic environment which was based on environmental concentration and registration standards of fipronil regarding prevention of damage to flora and fauna indicated that adverse effects were anticipated by fipronil up to one month after rice planting. Risk assessment for human health which was based on environmental concentration and registration standards of fipronil regarding water pollution indicated the need for alternative pesticides that are less toxic than fipronil.