In this study, we monitored the stream temperature of four first class rivers in Chugoku District, Japan, from July to August 2016, and determined the environmental DNA (eDNA) concentration of Plecoglossus altivelis altivelis. We attempted to understand the relationship between the concentration of P. altivelis altivelis and the mean stream temperature. Our results showed that the longitudinal distribution pattern of P. altivelis altivelis differs along the studied rivers, and the concentration of eDNA is high in sites where the mean stream temperature from July to August remains close to 23 °C. These results indicate that P. altivelis altivelis may have a suitable stream temperature in summer.

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 It is important to secure evacuation space for fish during floods to create comfortable environment. Evacuation area includes wando, groyne and vegetation. Wando is a dead water region connecting the main current of a river. However, little is known about the relationship between evacuation behavior of fish and geometric shape of wando. In this study, an investigasion on evacuation behavior of Candidia temminckii was conducted under the condition that the direction of wando opening and also the flow velocity are changed. It was found that the low velocity area increased when wando opening was faced downstream, and this area became evacuation area for Candidia temminckii. Besides, it was shown that Candidia temminckii swim facing mainly the sidewall or downstream directions when the wando opening was faced downstream.

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 Monitoring of Tubuca arcuata in the Sumiyoshi tidal flat of Yoshinogawa Estuary, Tokushima Prefecture, has been conducted for five years through civic cooperation. This cooperative monitoring has clarified temporal change in the population density of Tubuca arcuata and in its distribution by particle size composition of the sediment. However, a questionnaire survey confirmed differences in awareness among citizens. Going forward, it will be necessary to conduct activities to raise satisfaction among participants, and to raise awareness to recruit participants.

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 Fishway is important structure to expedite the migration of fish. It is necessary to grasp the influence that the conditions of the fishway give on swimming characteristics of the fish in designing the fishway. Therefore, it is necessary to examine the fishway of various shapes. However, the examination that changed a spanwise gradient at the bottom of fishway is not yet carried out. In this study, an investigation on swimming characteristics of Candidia temminckii was conducted under the condition that spanwise gradient at the bottom of open-channel and also the flow velocity are changed. It was found that the number of fish that swims at the deepest area in open-channel increases with the increase of the spanwise gradient at the bottom of open-channel. The fish in the case open-channel with the spanwise gradient at bottom is more stagnant than the case open-channel with the flat bottom.

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 In this study, authors carried out some experiments those using Tribolodon hakonensis in the stream type fishway with different rocky ramp arrangement.
 As the results, run-up ratio R_r did not have the change by the difference the rocky ramp arrangement. Moreover, Tribolodon hakonensis performed choice of approximately 2 ~ 8BL(cm/s) and run up without related to flow quantity Q and rocky ramp arrangement. Run up time and distance of Run2 (alignment arrangement) shortened them in comparison with Run1 (zigzag arrangement). In Run1, Tribolodon hakonensis run up zigzag in the channel in all. On the other hand, in Run2, they run up straight in the channel at wall side mainly. Therefore, the run up of Tribolodon hakonensis were more effective Run2 than Run1.

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 Although calcium-based adsorbents are expected as effective arsenic adsorbents, the spent adsorbents which removed arsenic from contaminated water would contain a great amount of arsenic. If they were dumped into environment without an appropriate treatment, arsenic leached from them might cause a secondary environmental pollution. Also, silicic acid leached from soils or cementitious solidification materials may affect the environmental stability of the spent adsorbents.
 In this study, the leaching tests with silicic acid solutions on the spent calcium-based adsorbents (CaO and Ca(OH)₂) were carried out. The arsenic leaching ratios of spent Ca-based adsorbents were found to decrease as silicic acid concentration in liquid is higher. Calcium ions leached from the spent adsorbents can be considered to react with silicic acid components in the liquid to form calcium silicate species. Then, arsenic components leached from the spent adsorbents can be considered to be incorporated into the silicates during the above formation process. In addition, the average chemical compositions of the calcium silicates formed are considered to depend on the initial silicic acid concentration in the test solutions. In the cases of around 25 or 50～100 mg/L as the initial Si concentration, each of the average chemical composition formula was estimated to be Ca₂SiO₄ and CaSiO₃. On the other hand, in the case that initial Si concentration was relatively low (around 5 mg/L), the reaction in which silicic acid components adsorb directly onto the spent adsorbent surface (ion-exchange or chemical adsorption reaction) was inferred to be predominant.

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 Plants use siderophore, high affinity with iron low molecular chelators, produced by microorganisms to get iron. Some reports reveal that siderophores are effective in dissolution of Cs in clay or soil^4),5). This indicates the possibility to dissolve Cs in plant and microbial ecology. In this study, effects on Cs elution behavior of microbial siderophores are focused. It was found that at most 68.2% of spiked Cs was eluted from 920 ppm vermiculite.

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 Nonylphenol in water and digested sludge samples was degraded with potassium ferrate (K₂FeO₄) produced by the wet chemical method. Nonylphenol consisted of benzene ring labeled with ¹⁴C was used as a tracer to clarify the potentials of NP mineralization with ferrate and biodegradability of product from NP degradation with K₂FeO₄. The addition of K₂FeO₄ to the NP solution spiked with the tracer resulted in no remarkable decrease in the concentration of ¹⁴C. The inoculation of activated sludge microorganisms without K₂FeO₄ gradually diminished the concentration of ¹⁴C. The pretreatment with K₂FeO₄ slightly promoted the reduction of ¹⁴C with the microorganisms. These results suggested that NP was transformed to more biodegradable product through the pretreatment with K₂FeO₄.

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 Pollution potential of road dusts which run off from road surfaces into receiving water during rain events are considered to be high. Road dusts contain micro toxic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals, which flow into the receiving water through no treatment facilities. So it is important to obtain knowledge on characteristics of such pollutants contained in the highway dusts. The authors have focused on pollutants originated from car traffics and collected highway dusts to measure content ratios of such pollutants in the dusts. As a result of examinations on the measured data, some significant findings were obtained. The data showed that road dusts in a winter season contained a lot of Na due to inclusion of snow melting agents. They also showed high content ratios of Zn and Cu of heavy metals in the road dusts. The examination showed a positive correlation between ClPAHs and its parent PAHs in small particle size, which implied that PAHs and ClPAHs were generated at the same time. On the other hand, PAHs and Cu were negatively correlated, which meant that Cu might be catalytic during photo decomposition of PAHs.

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 Recently, a new exposure pathway of micropollutants via Microplastics (MPs) to aquatic organisms have been a great concern. Main objective of this study was to understand adsorption characteristics of perfluoroalkyl acids (PFAAs), polycyclic aromatic hydrocarbons (PAHs) and their halogenated compounds (X-PAHs) in water environment by focusing on the diameters of MPs. Adsorption bach experiments with standard substances of MPs were conducted. Field surveys were conducted in Lake Biwa and Osaka bay from Oct. to Nov. 2017 in order to analyze 15 PFAAs, 16 PAHs, 11 X-PAHs on adsorbed MPs in surface water. It was shown that MPs in water environment with smaller diameter tended to adsorb more PFAAs, PAHs, X-PAHs. It was assumed that micropollutants were adsorbed more to MPs than to suspended solids when their diameters were in the range of several tens of μm. In addition, it was suspected that more PFAAs and PAHs were adsorbed to MPs when surface areas of MPs were increased by the effect of physical and/or chemical reactions in the water environment.

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Editor-in-Chief, Shigeo Fujii
Editorial Board of JSCS Journal of Environmental Research
Environmental Engineering Committee, JSCE

The following article has been retracted at the author’s request, because of the problem with the definition of suspended particulate matter (SPM) used in the manuscript.

Yasuhide TAKANO: MEASUREMENT OF VERTICAL PROFILE OF SUSPENDED PARTICULATE MATTER (SPM) NUMBER CONCENTRATION USING SPM SAMPLER HUNG ON MOORING CABLE OF CAPTIVE BALOON, Journal of Japan Society of Civil Engineers, Ser. G, Vol.68, No. 7, pp. III_575-III_583, 2012.

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