The objective of this study was to assess the universality of gluconate as a hydrogen donor for the reductive dechlorination of chloroethenes in groundwater. For this, we conducted trichloroethene (TCE) degradation experiments using five groundwater samples collected from different chloroethenes-contaminated sites as the microbial seed and gluconate as the hydrogen donor. Although the TCE dechlorination rate was different in each groundwater, the number of genes involved in reductive dechlorination increased and chloroethenes were completely dechlorinated in all groundwater samples. In addition, the groundwater sample whose complete reductive dechlorination of TCE took a long time could also be treated by repeated gluconate supplementation, which resulted in rapid complete TCE dechlorination without the accumulation of chloroethene, a harmful metabolite. These results indicate that gluconate is a universal hydrogen donor that enables the complete reductive dechlorination of chloroethenes.

The environmental DNA (eDNA) derived from fish in marine sediments is preserved for long periods and could be used as successive proxy data for fish assemblages. However, metabarcoding analysis for fish eDNA has never been applied to marine sediments. In this study, metabarcoding analysis for fish eDNA was applied to the Tohoku Earthquake sediment samples collected from Otsuchi Bay after the tsunami induced by the 2011 Earthquake off the Pacific Coast of Tohoku to track the past fish species composition. We successfully detected 17 fish eDNA from sediment samples throughout the study period. The number of sequence reads of migratory fish species was relatively high in the samples of the first two years, whereas that of demersal fish species increased in the samples of the latter two years. Temporal changes in fish species identified by eDNA metabarcoding are consistent with those in fish species identified by visual censuses in the Pacific coast of northeastern Japan. Thus, eDNA in marine sediments could be used to track the past fish species composition.

In this research, the performance characteristics of the multilayered filtration bed (MLF) and non-multilayered filtration bed (n-MLF) in a pilot-scale multistage constructed wetland for treating sewage were compared, and the effect of the multilayered structure on the water purification performance was elucidated. It was confirmed that the effect of the multilayered structure on the aerated treatment performance of, for example, BOD and NH₄⁺-N removal was negligible under the vertical flow condition, but not under the hybrid condition comprising both vertical and horizontal flows. MLF was easier to become anaerated than n-MLF, resulting in a lower aerated treatment performance under the hybrid condition. Furthermore, the effect of a lack of vegetation on MLF manifested as a lower nitrogen removal performance. Although the specific removal unit for BOD and phosphorus under the vertical flow condition in MLF increased 1.5fold compared with that in n-MLF, the removal performance of nitrogen could not be improved. The specific energy consumption for sewage treatment by the constructed wetland in this work was low at 0.32 kWh m^-3, demonstrating the effectiveness of the constructed wetland in accomplishing the decarbonization of sewage works.

The accuracy of the AIST-SHANEL model for estimating chemical concentrations in river water and sediment was evaluated for bisphenol A in the Tama River from 2017 to 2019 to promote the risk assessment of chemicals in river basins. The estimated river water and sediment concentrations of bisphenol A using the PRTR data were more than one order of magnitude lower than the measured values for both. After confirming the validity of the flow rate, the estimated chemical concentrations in river water and sediment were recalculated by adding the emissions of bisphenol A other than the PRTR data. As a result, the estimated river water concentrations were almost the same as the measured values. Although the concentration in river sediment tended to be underestimated, at about 1/3 of the measurement sites, the estimated concentrations were of the same level as the measured values. To enable further use of the AIST-SHANEL model, it is necessary to accumulate the accuracy evaluation data for more rivers and chemical substances and to examine the validity of the model.

The effluents from wastewater treatment plants in Kyoto City are disinfected with chlorine or ozone before they are discharged. We measured the concentrations of disinfection by-products with chlorine or ozone and their formation potentials with chlorine in the effluents. Each effluent had its own characteristics on the disinfection by-product formation potential, which was considered to depend on the water quality of each sewage influent. The chloroform formation potential decreased after the disinfection of effluents with ozone. Conversely, the concentration of formaldehyde and its formation potential increased. However, the difference between formaldehyde formation potential and formaldehyde concentration decreased. We considered that the concentration of formaldehyde precursors decreased after the disinfection with ozone because the precursors were oxidized and converted to formaldehyde. Additionally, the concentration of formaldehyde in the effluent decreased downstream of the discharging point. Therefore, we concluded that the disinfection of effluents with ozone reduced the loads of formaldehyde, its precursors, and the formation potentials of some disinfection by-products on the downstream area.

We investigated longitudinal variations in metal concentrations and in benthic macroinvertebrate and periphyton communities at 13 sites in the tributaries of the upstream Hida River to assess the ecological impacts of mine drainage. At the sites immediately downstream of the inflow of mine drainage, the concentrations of trace metals such as zinc increased (e.g., the maximum zinc concentration of 0.94 mg L^-1 was observed ) , large reductions in the taxon richness and abundance of macroinvertebrates and in the taxon richness of periphyton were observed, and tolerant taxa (e.g., chironomids and baetid mayflies, and Achnanthidium diatoms) , which are known to be present in metal-contaminated rivers, dominated their respective communities. Metal concentrations decreased at the downstream sites, and the macroinvertebrate community composition observed at the most downstream site was similar to those at reference sites. Although the longitudinal variations in the taxon richness and community composition of macroinvertebrates and periphyton were similar in the studied river, we observed some differences such as the markedly increased abundance of periphyton at the sites downstream of the inflow of mine discharge. Thus, the investigaton of multiple biological groups is required for a comprehensive understanding of the ecological impacts of mine drainage on aquatic communities.