Hypoxia develops in bottom water in enclosed water bodies with limited water exchange and long water retention times, especially near the river mouth. The inner part of Tokyo Bay is an example. This study is focused on the development and decline of hypoxia around the Haneda Airport D-runway, which was constructed nearby the river mouth of the Tama River, and a comparison was made between monitoring data at a monitoring post at the Haneda Airport and those far off the river mouth nearby Kawasaki artificial island. Multiple sets of data have been incorporated, including water quality data collected every hour in monitoring posts by MLIT, and meteorological data of JMA. The hypoxia period and the average thickness of hypoxia were calculated, and the sudden recovery of DO was analyzed. The analysis revealed general characteristics of hypoxia development and its decline. Especially, three mechanisms of the DO recovery process were found to be dominated nearby the river mouth: strong and continued southerly wind, the intrusion of dense oceanic water, and extreme freshwater discharge of the Tama River associated with the typhoon. Year-to-year variations of hypoxia periods or volume at Haneda Airport showed no increasing tendency of hypoxia after the construction of the D-runway.

This study aimed to investigate how degradation of organic matters in surface water by ultraviolet-activated persulfate (UV/PS) contributed to mitigation of formation of haloacetonitriles (HANs) comparing with conventional UV-activated hydrogen peroxide (UV/H₂O₂). A surface water sample containing 10 mM of PS or H₂O₂ was irradiated up to 3,000 mJ/cm² of 254 nm UV lump. Consequently, 3,000 mJ/cm² of UV/PS reduced formation potentials (FP) of dichloroacetonitrile (DCAN) and bromochloroacetnitrile (BCAN) from 3.8 to 0.2 µg/L and 2.8 to 0.6 µg/L, respectively. UV/H₂O₂ also showed similar tendencies but reductions of DCAN and BCAN were less significant. However, both UV/PS and UV/H₂O₂ were likely to increase FP of dibromoacetonitrile (DBAN). Additionally, correlation coefficient tests indicated that degradation of chromophore aromatic compounds and fulvic acid-like substances by both UV/PS and UV/H₂O₂ showed significant correlations with reduction of DCAN-FP. Degradation of some fluorophore aromatic proteins by UV/PS correlated to reduction of BCAN-FP, while increase of other portions of fluorophore aromatic proteins by UV/H₂O₂ correlated to increase of DBAN-FP. Precursors of DCAN were easily decomposed by both treatments, whereas precursors of brominated HANs (BCAN and DBAN) were not preferentially attacked by them. However, strong oxidation potential of UV/PS achieved decomposition of these organic moieties.

The effect of anionic surfactants on organic matter degradation during enhanced in-sewer purification by porous media was evaluated in this study. Surfactants, wherein the anionic subgroup comprises a significant portion of surfactant load in domestic wastewater, are anticipated to affect biofilm activity during enhanced in-sewer purification negatively. To evaluate this, synthetic feed containing a fixed concentration of readily biodegradable organic matter and different anionic surfactant concentrations was supplied intermittently to an airtight channel intended for enhanced in-sewer purification for 32 days. Dodecylbenzene sulfonate, as sodium dodecylbenzene sulfonate, was used as a model anionic surfactant. Results showed that increased anionic surfactant concentration up to 160 mg L⁻¹ decreased aerobic organic matter degradation rate by up to 36% of the initial rate. It was inferred from the compositional analysis of effluent surfactants by liquid chromatography tandem mass spectrometry that the accumulation of possible inhibitory intermediate products may have caused decline in rates over time. Recovery of aerobic activity related to organic matter degradation was observed with continued operation under decreasing influent anionic surfactant concentration. Findings highlight that although increased surfactants concentrations negatively affected aerobic activity, aerobic organic matter was still continuously degraded aerobically.

Porous coordination polymers (PCPs) are porous materials with large specific surface area and pore ume, and are expected to be used as separation materials for environmental pollutants. The aim of this study was to evaluate the applicability of MIL-53(Al), a type of PCP, for the separation of geosmin and 2-MIB. The adsorption performance of MIL-53 (Al) for methylene blue and iodine was determined to be lower than that of activated carbon. The time required for the adsorption of musty odorants by MIL-53(Al) was longer than that by activated carbon, and the final adsorption amount was lower than that by activated carbon. Furthermore, adsorption isotherms for the adsorption of musty odorants by each adsorbent were prepared and their adsorption performance was evaluated. The amount of odorant adsorbed by MIL-53(Al) in pure water was extremely low compared to that of activated carbon. On the other hand, the amount of odorants adsorbed by MIL-53(Al) in raw water for water supply was not much lower than that of activated carbon. This study suggests that adsorbents with uniform pore size, such as MIL-53(Al), are less susceptible to interference by other coexisting substances. This finding may be important for future development of adsorbents for musty odorants.

The environmental presence and drinking water contamination of per- and polyfluoroalkyl substances (PFAS) have been reported since the early 2000s. This study seeks to develop a liquid chromatography/tandem mass spectrometry analytical method for the simultaneous determination of 21 perfluoroalkyl acids (PFAAs) in drinking water to support future regulations in Japan. Inter-laboratory tests were conducted in 16 laboratories using different instrument to verify the applicability of the developed method for a wide range of drinking water samples in Japan. Recovery tests of PFAA-fortified tap water samples obtained in each laboratory were conducted at set points of 1 and 10 ng/L. Calibration curve linearity, trueness (recovery), repeatability (RSD_r), and reproducibility (RSD_R) at these analyte concentrations were calculated using data obtained from the recovery tests. The trueness, RSD_r, and RSD_R of most PFAA analytes were satisfactory when the recoveries were corrected by ¹³C-PFAA extraction standards with similar recovery to the corresponding PFAS analytes. The developed analytical method is valid for the quantification of the target PFAAs in drinking water. However, satisfactory PFAA quantification requires recovery adjustment using surrogates with similar recovery characteristics to the PFAA analytes.

To analyze physiological and biochemical marker responses of brackish water clam Corbicula japonica under global warming conditions, different water temperatures (20°C and 25°C), salinity (5 and 20 psu), and food availability (0.5 and 2.0 mg SS ind⁻¹ d⁻¹) levels were tested. Appropriate biomarkers were selected based on the sensitivity of biomarker responses, condition index (CI), energy reserves, superoxide dismutase (SOD), catalase, oxyradical-absorbance capacity, and lipid peroxidation (LPO) (p < 0.05), and five methods of integrated biomarker response index (IBR) were calculated. CI, SOD, and LPO were employed for IBR_I, although four biochemical biomarkers were generally employed for IBR. At high water temperature (HT), all biomarkers were deleteriously affected. HT significantly affected all the IBR methods (p < 0.05), and the highest correlation was discovered in IBR_I (r = 0.92, p < 0.01). The lowest and highest IBRs were observed at natural (control = 1.14) and global warming (HT = 2.43) conditions, respectively. The contribution of LPO scores was higher under HT, demonstrating poor organism health. Based on our estimates, three sensitive biomarkers could detect stress in C. japonica under global warming conditions. We conclude that the IBR method based on sensitive biomarkers should be used to quantify anthropogenic impacts on aquatic organisms, especially C. japonica.

Seventy borehole data were used to appraise the groundwater resources of the sedimentary and Basement Complex rock terrains of Ogun State, Nigeria. Borehole depth, static water level, discharge and drawdown were evaluated to determine the hydrogeological and hydraulic properties of the aquifers. Specific capacity of the boreholes was estimated at one hour using discharge and drawdown values. Most boreholes in the sedimentary terrain explored shallower aquifers of < 100 m, while most boreholes in the Basement Complex rock terrain explored deeper aquifers > 100 m. The sedimentary rock aquifers had thinner groundwater storage of 65.28 m and average borehole yield of 43.51 m³ hr⁻¹, while the Basement Complex rock aquifers had thicker groundwater storage of 95.02 m and average borehole yield of 5.53 m³ hr⁻¹. The average efficiency of boreholes in the sedimentary and Basement Complex rock terrains were 0.66 and 7.14 m² hr⁻¹, respectively. Boreholes within Basement Complex rocks had higher efficiency than those within sedimentary rocks. Adequate groundwater occurs in the sedimentary and Basement Complex rock terrains for domestic, industrial and agricultural purposes. The groundwater is weakly acidic with small amount of TDS, hence falls within the fresh water category. The groundwater is not potable but could serve domestic and general purposes.

Cyanotoxins produced by blue-green algae in lakes are among the most serious threats to water quality worldwide. As global warming rapidly extends the locations and timing of blue-green algae blooms, a simple and accessible method for the detection and quantification of cyanotoxins in fresh water is increasingly necessary. Here, a quick, simple and accessible simultaneous analytical method for five cyanotoxins (cylindrospermopsin, anatoxin-a, microcystin-RR, YR and LR) is reported. This method has three advantages. First, it does not require complicated operations, such as a concentration operation. Second, it employs an HPLC column without high pressure. Third, the use of stable isotope-labeled surrogates enables correct identification and precise quantification of cyanotoxins. The method was applied to the lakes of Fukuoka Prefecture in Japan, and four of the five above-named cyanotoxins (i.e., all but cylindrospermopsin) were detected. The limits of quantification were 20–43 ng/L, which were considerably lower than the WHO guideline values. The recovery levels were 97–104%. Microbial flora analysis revealed that the sources of anatoxin-a were Pseudanabaena limnetica and Cuspidothrix issatschenkoi, and the source of microcystins was the group A1 of Microcystis aeruginosa. This study provides a quick, easy and accessible method for the worldwide monitoring of cyanotoxin levels.