Language：English   Publishing type：Research paper (scientific journal)  

Gran's plot is an ingenious tool to find endpoints in potentiometric neutralization titrations. It can also be utilized for determining the formal potential of the electrodes, which is required in the case of obtaining the hydrogen ion concentration with pH sensor electrodes involving glass electrodes. Furthermore, autoprotolysis constants can be determined through Gran's plots with high accuracy, even those containing impurities. Gran's plot is thus a fundamental technique for investigating the properties of novel solvents such as protic ionic liquids as acid-base media. However, there are limitations in the autoprotolysis constants of the solvents and the ionization constants of the impurities, and so on, where Gran's plots work well. Hence, we have clarified the reliable range of these constants to be determined through Gran's plot by calculating the titration curves under various conditions and simulating these determination processes.

DOI： 10.1016/j.molliq.2023.122180

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Language：English   Publishing type：Research paper (scientific journal)  

To determine the long-term dynamics of mercury discharged from Chisso chemical plant between 1932 and 1968, the vertical variation in mercury concentrations in Yatsushiro Sea sediments was studied from 2013 to 2020 at 31 locations and compared to the mercury concentration distribution obtained in 1996. The results suggest that new sedimentation occurred after 1996, but the mercury concentrations at the surface ranged from 0.2 to 1.9 mg kg-1, which did not decrease significantly over a 20-year period. It was estimated that approximately 17 t of mercury remained in the southern Yatsushiro Sea sediment, which is equivalent to 10-20% of the total mercury discharged between 1932 and 1968. From results of WD-XRF and TOC measurement, it was suggested that mercury in sediment had been transported with suspended particles derived from sludges from the chemical plant and further suggests that the suspended particles derived from the sediment surface layer are still slowly diffusing.

DOI： 10.1007/s11356-023-27505-0

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PubMed

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Sensitive detection methods for nitrite (NO2-) and nitrate (NO3-) ions are essential to understand the nitrogen cycle and for environmental protection and public health. Herein, we report a detection method that combines ion-chromatographic separation of NO2- and NO3-, on-line photochemical conversion of these ions to peroxynitrite (ONOO-) by irradiation with a 222 nm excimer lamp, and chemiluminescence from the reaction between luminol and ONOO-. The detection limits for NO2- and NO3- were 0.01 and 0.03 μM, respectively, with linear ranges of 0.010-2.0 and 0.10-3.0 μM, respectively, at an injection volume of 1 μL. The results obtained by the proposed method for seawater analysis corresponded with those of a reference method (AutoAnalyzer based on the Griess reaction). As luminol chemiluminescence can measure ONOO- at picomolar concentrations, our method is expected to be able to detect NO2- and NO3- at picomolar concentrations owing to the high conversion ratio to ONOO- (>60%), assuming that contamination and background chemiluminescence issues can be resolved. This method has the potential to emerge as an innovative technology for NO2- and NO3- detection in various samples.

DOI： 10.1021/acs.est.3c00273

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PubMed

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

N-Nitrosodimethylamine (NDMA) is a carcinogenic constituent commonly found in recycled water and pharmaceuticals. Developing an analytical method to continuously monitor changes in NDMA concentrations during water recycling and pharmaceutical manufacturing can mitigate accidents caused by NDMA formation. However, NDMA analysis in high-matrix water samples, such as beverages, wastewater, and pharmaceutical ingredients, is difficult. In this study, we adapted reverse osmosis (RO) membrane treatment as a pretreatment for NDMA analysis by isolating NDMA from interfering substances in high-matrix water samples. Subsequently, high-performance liquid chromatography-chemiluminescence detection was used for NDMA analysis. In a pure water matrix, 95% of NDMA can pass through at a low permeate flux of 1 L m−2 h−1. The method was then validated using beer, which is known to contain high concentrations of NDMA, as a representative high-matrix water sample. We found that RO pretreatment leads to clean chromatograms in which NDMA peaks are clearly visible while other peaks are mostly absent. Analysis of six different beer samples showed a maximum NDMA concentration of 315 ng L−1, and an average NDMA concentration of 138 ± 83 ng L−1 (n = 6), which fall within the regulation limits for NDMA in beer in the United States of America. The proposed pretreatment method has the potential to provide a platform for developing technologies for continuous monitoring of NDMA in aqueous solutions.

DOI： 10.1039/d3ew00222e

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1007/s11356-022-23497-5

Language：English   Publishing type：Research paper (scientific journal)  

Wakamiko Proto-Caldera, a submarine volcano, is located at the bottom of the sea in the bay head area of Kagoshima Bay. In Kagoshima Bay, several species of fish with total mercury exceeding the provisional regulation value of 0.40 mg kg−1 were found in the 1970s. The effects of mercury released from submarine volcanoes are suspected. However, the path from volcanic mercury to the broader ecosystem has not yet been clarified. In this study, as the first step to elucidate the impact of volcanic activity on the ecosystems of Kagoshima Bay, seasonal changes in the concentrations of dissolved gaseous mercury (DGM), Hg(II), filtered total mercury (FT-Hg), particulate mercury (P-Hg), and mercury in suspended particulate matter (Hg in SPM) in seawater of Kagoshima Bay were tracked every two months from Feb. 2014 to Dec. 2017. The dissolved total mercury (DT-Hg) concentration was calculated by summing the DGM and FT-Hg concentrations. The DT-Hg at the location in the caldera ranged from 0.09 to 6.83 ng L−1 showing higher values in summer compared to winter, that is, in the stratified period. The P-Hg showed similar periodic variation as DT-Hg, and the highest Hg in SPM was 2.15 mg kg−1, which is one order of magnitude higher than that observed at the reference site. The high mercury concentration in SPM suggests the accumulation of dissolved mercury discharged from volcanic activity on SPM. Since mercury loaded on SPM can be taken up by suspension feeders and enter the food chain, the Hg in SPM may be a key factor affecting Hg in fishes in Kagoshima Bay.

DOI： 10.1016/j.marchem.2022.104133

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to investigate the behavior of previously discharged mercury (Hg) released from the Itomuka Hg mine into the surrounding environment, especially into soil. Total-Hg (T-Hg), methylmercury (MeHg), and ethylmercury (EtHg) concentrations in the surface soil at eight sample sites around the mine were 3.8-64.2 mg/kg, 6.0-54.7 μg/kg, and undetected to 4.5 μg/kg, respectively. Core samples collected from seven of the eight sample sites showed that the vertical distribution of T-Hg was the highest in the surface soil layer and decreased rapidly in the lower layers. A strong positive correlation was observed between T-Hg and MeHg concentrations in the core samples; however, the slope of the regression line varied considerably for each core. This suggests that Hg and MeHg were not supplied from the atmosphere simultaneously, but rather that MeHg was produced on-site. Further, the formation of MeHg and EtHg in soil was considered in terms of the total organic carbon/total nitrogen ratio, which is a decomposition index of soil organic matter. The strong positive correlation between T-Hg and MeHg can be attributed to the migration of organic matter containing Hg species to the lower layers. There was no relationship between T-Hg and MeHg at the riverbed sample site because of the high T-Hg in the lower soil layers, suggesting that Hg was supplied by ore at this sample site. These assumptions of the formation change and migration of Hg in soil were supported by the results of the fractionation experiment and the elution test. To understand the current conditions in this area, measurements of Hg in the water, sediment, atmosphere, and plants were also conducted.

DOI： 10.1016/j.scitotenv.2021.152492

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Maghemite nanoparticles coated with polyacrylic acid (pAA) were dispersed in the protic ionic liquid, diethylethanolammonium trifluoromethanesulfonate (DEEAH+⋅TfO−), and the thermodynamics of particle dispersion was studied by means of potentiometric and calorimetric titrations over the entire accessible pH range. As previously reported, the domain of colloidal stability is divided into two pH regions, mildly acidic and basic, separated by a flocculation domain at an intermediate pH. In this study, solvent DEEAH+⋅TfO− was first characterized in terms of the thermodynamic parameters of two reference reactions: autoprotolysis and ionization of acetic acid. A negative autoprotolysis entropy is obtained due to hydrogen-bond formation between the neutralized solvent cation, DEEA, and the neighboring cation DEEAH+. This suggests that the solvent structure is reinforced by the formation of neutral species, being an opposite trend to both ethylammonium nitrate and water. Second, the ionization and flocculation of pAA-coated nanoparticles (CNps) in the ionic liquid were examined. The potentiometric results could be modeled using a simple pAA ionization, independent of the aggregation state over the entire pH range. However, the calorimetric titration detected extra heat generation in an acidic condition prior to flocculation, in addition to an ionization enthalpy of pAA of 30 kJ/mol. This exothermic contribution is attributed to a change in the solvation process of CNps in the ionic liquid. Herein, we propose a model in which different types of solvation in the acidic and basic domains are sufficient to ensure colloidal stability, while aggregation unfolds between the switching pH.

DOI： 10.1016/j.molliq.2021.118146

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Achieving high water recovery using reverse osmosis membranes is challenging during water recycling because the increased concentrations of organics and inorganics in wastewater can cause rapid membrane fouling, necessitating frequent cleaning using chemical agents. This study evaluated the potential of membrane distillation to purify reverse osmosis-concentrated wastewater and achieve 98% overall water recovery for potable water reuse. The results indicate that membrane fouling during membrane distillation treatment was low (4% reduction in permeability) until 98% water recovery. In contrast, membrane fouling during reverse osmosis treatments was high (73% reduction in permeability) before reaching 90% water recovery. Furthermore, membrane distillation showed superior performance in removing dissolved ions (99.9%) from wastewater as compared with reverse osmosis (98.9%). However, although membrane distillation removed most trace organic chemicals tested in this study, a negligible rejection (11%) was observed for N-nitrosodimethylamine, a disinfection byproduct regulated in potable water reuse. In contrast, RO treatment exhibited a high removal of N-nitrosodimethylamine (70%). Post-treatment (e.g., advanced oxidation) after reverse osmosis and membrane distillation may be needed to comply with the N-nitrosodimethylamine regulations. Overall, the membrane distillation process had the capacity to purify reverse osmosis concentrate with insignificant membrane fouling.

DOI： 10.1016/j.chemosphere.2021.132610

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Language：Japanese   Publishing type：Research paper (scientific journal)  

The ultraviolet (UV)-based advanced oxidation process (AOP) is a powerful technology for removing pathogenic microorganisms and contaminants of emerging concern (CECs) from water. AOP in potable water reuse has been predominantly based on traditional low-pressure mercury (LP-Hg) lamps at 254 nm wavelength, supplemented by hydrogen peroxide addition. In this review, we assessed the potential of unconventional UV wavelengths (UV-B, 280-315 nm and UV-C, 100-280 nm) compared to conventional one (254 nm) in achieving the attenuation of pathogens and CECs. At the same UV doses, conventional 254 nm LP-Hg lamps and other sources such as, 222 nm KrCl lamps and 265 nm UV-LEDs, showed similar disinfection capability for viruses, protozoa, and bacteria, and the effect of hydrogen peroxide (H2O2) addition on disinfection remained unclear. The attenuation levels of key CECs in potable water reuse (N-nitrosodimethylamine and 1,4-dioxane) by 185 + 254 nm LP-Hg or 222 nm KrCl lamps were generally greater than those by conventional 254 nm LP-Hg and other UV lamps. CEC degradation was generally enhanced by H2O2 addition. Overall, our review suggests that 222 nm KrCl or 185 + 254 nm LP-Hg lamps with the addition of H2O2 would be the best alternative to conventional 254 nm LP-Hg lamps for achieving target removal levels of both pathogens and CECs in potable water reuse.

DOI： 10.1016/j.chemosphere.2021.131682

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Language：Japanese   Publishing type：Research paper (scientific journal)  

To elucidate the dynamics of mercury emitted and released by artisanal and small-scale gold mining (ASGM) activity and to estimate its impact on the ecosystems of the bay, the distribution of mercury in the atmosphere, soil, water, and sediment around Mambulao Bay, Camarines Norte, Philippines, was investigated. The ASGM operations use mercury to extract gold from ore and are located on the east shore side of the bay. Samplings were conducted in August 2017 and September 2018. The samples were used for determination of total mercury (T-Hg) and organic mercury (org-Hg) concentrations, total organic carbon (TOC) content, and chemical composition. The atmospheric mercury concentration on the east shore side, 6.1-25.8 ng m-3, was significantly higher than the value of 1.4-9.9 ng m-3 observed on the west shore side. The average concentrations of T-Hg in the forest soils of the west shore side and those of the east shore side were 0.081 ± 0.028 mg kg-1 and 0.496 ± 0.439 mg kg-1, respectively. In the vertical distribution of T-Hg in the soil of the east shore side, a higher concentration was observed near the surface. For the vertical variations in T-Hg in the marine sediment, higher values were observed near the estuary, and the vertical variations in core samples showed an increase in mercury concentration toward the surface. The highest concentration of T-Hg in sediment, 9.5 mg kg-1, which was 2 orders of magnitude higher than the background levels of this area, was found near the river mouth. The T-Hg, org-Hg, and TOC levels showed a positive correlation, suggesting that the rivers are the main sources of T-Hg and org-Hg in the bay. Although the fish sample containing a mercury content higher than the regulatory level for fish and shellfish of 0.4 mg kg-1 in Japan was only one of 42 samples, the percentage of org-Hg in fish samples was 91 ± 18%. Mercury released into the surroundings by the ASGM activities can be converted into methylmercury and affect the bay's ecosystem.

DOI： 10.1007/s11356-022-23497-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Advanced oxidation processes (AOPs) play a vital role in attenuating contaminants of emerging concern (CECs) during potable water reuse. AOPs are conventionally performed by irradiating with a 254-nm low-pressure (LP) mercury-vapor (Hg) ultraviolet (UV) lamp along with chemical treatment. Compared with UV-C light treatment (200-280 nm), vacuum-UV (V-UV) light treatment (100-200 nm) is advantageous in terms of hydroxyl radical generation without the requirement for chemical treatment. This study assessed the potential of V-UV (172-nm Xe-2 excimer or 185 + 254-nm LP-Hg) lamps on the destruction of two major CECs in potable water reuse, namely N-nitrosodimethylamine (NDMA) and 1,4-dioxane. Direct irradiation using UV254 (nm) or UV185+254 nm lamps achieved >= 94% removal of N-nitrosamines, including NDMA, at a UV dose of 900 mJ/cm(2). In contrast, the Xe-2 excimer lamp (UV172 nm) was less effective for N-nitrosamine removal, achieving up to 82% removal of NDMA. The removal of 1,4-dioxane by V-UV lamps at a UV dose of 900 mJ/cm(2) reached 51% (UV172 nm) and 28% (UV185+254 nm), both of which results were superior to that obtained using a conventional UV254 nm lamp (10%). The addition of hydrogen peroxide during UV254 nm or UV185+254 nm irradiation was found to enhance the removal of 1,4-dioxane, while UV172 nm irradiation without hydrogen peroxide addition still exhibited greater efficiencies than those UV254 nm lamps-based AOPs. Overall, this study demonstrated that the removal of both NDMA and 1,4-dioxane can be successfully achieved using either a UV254+185 nm lamp with hydrogen peroxide or a UV172 (nm) Xe-2 excimer lamp without hydrogen peroxide. (C) 2021 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chemosphere.2021.130326

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.talo.2021.100035

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

N-nitrosamines are contaminants of emerging concern, and controlling these chemicals in potable water and recycled water for potable reuse has become important for protecting public health. This study aimed to evaluate the influence of the alkyl chain lengths of N-nitrosamine precursors (secondary and tertiary amines) on the formation of N-nitrosamines via chloramination. The molar conversion efficiency from dimethylamine, an N-nitrosodimethylamine (NDMA) precursor, to NDMA (0.67%) was greater than that from diethylamine, an N-nitrosodiethylamine (NDEA) precursor, to NDEA (0.38%). Similarly, the molar conversion efficiency from trimethylamine to NDMA (0.92%) was greater than from triethylamine to NDEA (0.33%). Interestingly, a considerable difference in molar conversion efficiencies were observed for tertiary amines with the N,N-dialkyla-arylamine structure: the molar conversion efficiencies from N,N-dimethylbenzylamine and N,N-diethylbenzylamine to NDMA and NDEA were 50.2% and 1.7%, respectively. These results indicate that amines with ethyl groups have lower potentials for producing the corresponding N-nitrosamines than those with methyl groups. These differences in yields between amines with methyl and ethyl groups can be explained by the difference in electron density in the nitrogen atom of the amine, which influences the protonation of the amine and stabilization of intermediate species. These findings could be useful for enhancing source control of water and wastewater by regulating runoff or industrial wastewater containing high concentrations of specific N-nitrosamine precursors. (C) 2021 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.eti.2021.101520

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Volcanic activity is one of the primary sources of arsenic in nature, and chemical forms of arsenic discharged by volcanic activity are inorganic. Kagoshima Bay has active submarine volcano located in the 200 m deep basin of its northern part. Since dissolved inorganic arsenic is more toxic than organic arsenic it is important to understand the dispersion of discharged arsenic in seawater. To estimate the influence of arsenic emitted from the bottom vents seasonal changes in As(III) and As(V) concentrations in seawater were studied. There are few studies on the impact of arsenic discharged by submarine volcanos in the inner bay. The total concentrations of As(III) and As(V) (T-As) in seawater at the background site in Kagoshima Bay was 1.71 +/- 0.35 mu g L-1 (av. +/- s.d.), similar to the world average value of 1.7 mu g L-1. The highest T-As value at the nearest point to the submarine volcano, 3.48 mu g L-1, was observed in summer. Since the vertical mixing of seawater cannot occur in summer due to the formation of the thermocline, the deep water is strongly affected by volcanic activity. The increase in T-As was caused by the increase in As(III) concentration suggesting the discharge of As(III) from the vents.

DOI： 10.1007/s12665-021-09619-1

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electrical Engineers of Japan  

<p>To reduce the environmental risks posed by mercury (Hg), a simple and rapid detection system for Hg in the environment is needed. We developed a simple Hg measurement method for detecting of Hg in liquid phase using quartz crystal microbalance (QCM-Hg). Mercury is reduced into Hg⁰ by adding the reducing solution (SnCl₂) to the divalent Hg²⁺ in the sample solution. Then, Hg is turned into vapor in reactor bottle by flowing air. It (QCM-Hg) utilizes the direct reaction of Hg and the Au electrode of the quartz crystal element via the phenomenon of Au-Hg amalgamation. In the case of 0.0005 mg/L in liquid phase, a frequency shift of about 13 Hz is obtained using a 20 MHz quartz crystal element. This new detection system allows easy measurement of very low concentrations of Hg in liquid phase.</p>

DOI： 10.1541/ieejsmas.141.50

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2021.0_310

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

© 2020 Elsevier B.V. Removing N-nitrosodimethylamine (NDMA), a regulated carcinogenic chemical, with a reverse osmosis (RO) membrane is a key challenge for enhancing the safety of reused potable water. This study aimed to achieve high rejection of NDMA and salts by plugging the nanopores in an RO membrane with linear-chain amines, amides, and epoxides. Plugging with amines or epoxides generally led to a reduction in water permeance and an increase in conductivity rejection. NDMA rejection increased linearly with the size of amines. The RO membrane plugged with dodecylamine exhibited an NDMA rejection of 80% when treating the effluent from a membrane bioreactor, and this performance was maintained for 8 d. In contrast, amide or epoxide plugs resulted in only minor improvements in NDMA rejection. We speculate that the amine plugs remain in the nanopores through electrostatic attractions, whereas amides and epoxides become readily detached from the nanopores because they are only bound through weaker hydrogen-bonding interactions. This study provides an understanding of the plugging mechanism that enhances NDMA rejection and demonstrated high NDMA rejection using treated wastewater.

DOI： 10.1016/j.seppur.2020.117490

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Language：English   Publishing type：Research paper (scientific journal)  

Natural attenuation of N-nitrosodimethylamine (NDMA) and NDMA precursors was evaluated in infiltration basins, a riverbed filtration system, and constructed wetlands operated as part of a managed aquifer recharge system. Initial NDMA concentrations up to 9.0 ng/L in infiltration basins (advanced purified, recycled water) before sunrise declined to non-detect (<1.5 ng/L) by 10:00 A.M due to natural photolysis (half-life of 33 to 86 min dependent on solar irradiance). NDMA fortified controls adjacent to the infiltration basin showed similar results, while concentrations in dark controls did not change over the basin's hydraulic retention time. NDMA precursor concentrations did not change significantly in the basin containing advanced-treated water from a potable reuse treatment plant, indicating that photolysis did not remove NDMA precursors nor did photolysis produce a significant amount of precursors. For the other environmental buffers evaluated, NDMA removal was variable through laboratory scale soil columns (22 cm height), in full-scale riverbed filtration system that pre-filters water prior to infiltration basin recharge, and in the constructed wetland. Variability in NDMA removal through the wetlands is attributed to high turbidity. In the case of the riverbed filtration system, variability is likely due to short exposure times to sunlight. For the soil columns, limited NDMA removal is attributed to inefficacy of soil aquifer treatment in removing NDMA over short travel times/distances. NDMA precursors were also ineffectively removed in these systems, with effluent concentrations occasionally exceeding influent concentrations. Overall, the removal of NDMA in environmental buffers utilized for planned or de facto indirect potable reuse is dependent on the system's capacity for photolysis, while NDMA precursors are more recalcitrant and unlikely to be removed in such systems without enhancement or sufficient hydraulic residence times.

DOI： 10.1016/j.scitotenv.2020.144287

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

© 2020 Elsevier B.V. The advanced oxidation process (AOP), using conventional low-pressure mercury (LP Hg)-vapor UV lamps, forms a critical barrier for pathogens and contaminants of emerging concern (CECs) in potable water reuse. In recent years, UV-light-emitting diode (UV-LED) has attracted considerable attention as an alternative UV source because it has a long lifetime and is mercury-free. This study assesses the effectiveness of 265-nm UV-LED in removal of characteristic CECs, 1,4-dioxane (100 μg/L) and N-nitrosamines (500 ng/L), including N-nitrosodimethylamine (NDMA), in recycled potable water. Direct photolysis using a UV-LED lamp, at the maximum UV dose of 900 mJ/cm2, achieved a maximum of 31% NDMA reduction, as opposed to a 93% reduction by a conventional LP Hg UV lamp. We attributed this to the longer emission wavelength of the UV-LED (265 nm) than that for the LP Hg UV lamp (254 nm). Both UV lamps failed to photolyze 1,4-dioxane. Using hydrogen peroxide or monochloramine remarkably enhanced the effectiveness of the LP Hg UV-based AOP in removing 1,4-dioxane, and the percentage of NDMA removed also increased slightly; however, it did not improve the effectiveness of the UV-LED-based AOP. We conclude from this study that despite the advantages of the UV-LED over the conventional LP Hg UV lamp, the former performs ineffectively at attenuating major CECs in recycled water.

DOI： 10.1016/j.eti.2020.101147

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Language：English   Publishing type：Research paper (scientific journal)  

© 2020 Elsevier B.V. Advanced wastewater treatment using a reverse osmosis (RO) membrane is a key separation process for ensuring the removal of chemical hazards so that treated wastewater can be used for potable purposes. This study systematically assesses the effects of heat modification conditions of three commercial RO membranes on the removal of a challenging chemical of emerging concern–N-nitrosodimethylamine (NDMA). The RO membranes were modified in pure water at the heat treatment temperature between 70 and 100 °C; 90–100 °C achieved the highest NDMA rejection during separation tests. A lower pH during heat treatment generally resulted in higher NDMA rejection, however a solution pH lower than four can reduce NDMA rejection depending on the presence of a protective layer on the RO membrane surface. Overall, a linear tradeoff between NDMA rejection and water permeance was commonly observed among the heat-treated RO membranes. The stability of a heat-modified membrane in water permeance and NDMA rejection was demonstrated over a week-long test using treated wastewater. The enhanced removal of NDMA by heat-treated RO membranes was speculated to occur due to the shrinking of the passage of solutes–free-volume holes. This study demonstrates the importance of heat modification conditions on RO membranes to achieve a high NDMA rejection.

DOI： 10.1016/j.seppur.2020.116921

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

An ultra-sensitive analytical system that can determine the concentration of N-nitrosamines at the ng/L level without preconcentration was used to investigate the contamination, decomposition, and formation of N-nitrosodimethylamine (NDMA) and other N-nitrosamines in water samples during general analytical procedures. A preliminary experiment was performed to estimate the NDMA concentrations in ambient air. Since the air samples contained NDMA at concentrations in the range of 2.0 - 10.7 ng/m(3), ambient air was identified as the source of NDMA contamination in water samples. We directly confirmed that the concentration of aqueous 10-ng/L NDMA samples stored in clear glass bottles decreased upon exposure to sunlight. Thus, to maintain the N-nitrosamine concentration, such samples must always be protected from sunlight during sampling. The existence of N-nitrosamines in experimental reagents, such as ranitidine and sodium hypochlorite solutions, was also confirmed, as was the formation of NDMA on an activated carbon solid-phase extraction cartridge.

DOI： 10.2116/analsci.20P162

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

© 2020 Elsevier Ltd Total-Hg (T-Hg) and methylmercury (MeHg) concentrations in rice grains were measured to understand the MeHg accumulation process. Rice plants were cultivated in Hg2+-spiked non-contaminated soils in experimental pots at three different places. Although soil MeHg concentrations in the pots changed significantly and individually during the rice-growing season, T-Hg concentration of brown rice grain was high at high soil MeHg concentration. In addition, there was no significant variation in T-Hg concentration in brown rice grains from individual panicles or among panicles obtained from the same pot, although the period of growth for each panicle was different. The highest T-Hg concentration of brown rice grains recorded for a panicle was 1.4 ± 0.1 mg kg−1 (n = 8), and the corresponding MeHg ratio was 76%. In addition, the T-Hg and MeHg concentrations in various parts of the brown rice grain—white rice (endosperm), bran, and embryo—were measured. Among the parts of the brown rice grain, the embryo had the highest Hg concentration. Furthermore, Hg concentration in the grain was constant during grain filling. These findings suggest that MeHg formed in soil accumulates in the rice plant during growth and is supplied to the rice grains continuously for the entire duration of the grain development period.

DOI： 10.1016/j.chemosphere.2020.125827

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

A certified reference material, NIMD-01, was developed for the analysis of mercury speciation in human hair. We collected the hair of Vietnamese males from a barbershop in Hanoi in 2016 and prepared 1200 bottles containing 3 g of sieved and blended hair powder. The certified value was given on a dry-mass basis, with the moisture content obtained by drying at 85 degrees C for 4 h. Certified values with the expanded uncertainties (coverage factor, k = 2) were as follows: methylmercury, 0.634 +/- 0.071 mg kg(-1) as mercury; total mercury, 0.794 +/- 0.050 mg kg(-1); copper, 12.8 +/- 1.4 mg kg(-1); zinc, 234 +/- 29 mg kg(-1); selenium, 1.52 +/- 0.29 mg kg(-1). An indicative arsenic concentration of 0.17 +/- 0.03 mg kg(-1) was measured. Extended uncertainties were estimated by sample homogeneity, long- and short-term stabilities, and a characterization from measurements made by collaborating laboratories.

DOI： 10.2116/analsci.19SBP07

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Language：English   Publisher：(公社)日本分析化学会  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/C9EW00943D

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Language：English   Publishing type：Research paper (scientific journal)  

© 2020, Korean Society of Environmental Risk Assessment and Health Science. Objective: To estimate the impact of mercury released from an artisanal small-scale gold mining (ASGM) activities on the ecosystem. Methods: Total and organic mercury concentrations in paddy field soil and freshwater snails around an artisanal small-scale gold mining area were investigated. Paddy field soil samples and freshwater snails were collected from ten sites along the Cikaniki River. A site located in a national park, which was approximately 12 km upstream from the ASGM site, was considered the reference site for this study. Results: The organic mercury concentration in soil samples collected at the ASGM site was n.d.–0.018 mg kg−1 and that at the reference site was 0.005–0.008 mg kg−1. The organic mercury concentrations in the freshwater snails collected at the ASGM and reference sites were 0.38 ± 0.21 mg kg−1 (31.0 ± 26.6% of total mercury, n = 38) and 0.056 ± 0.032 mg kg−1 (40.5 ± 11.5% of total mercury, n = 16), respectively. Conclusion: Although the original form of mercury in the mining waste was elemental mercury and/or Hg2+, the mercury form changed to organic mercury in environment and the organic mercury was concentrated two orders of magnitude, even in low-order organisms.

DOI： 10.1007/s13530-020-00045-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

This study was conducted to understand the environmental behavior of mercury released by artisanal and small-scale gold mining (ASGM) activities. For this purpose, we attempted to assess the effect of diffused mercury on mercury concentrations in soil, demonstrate the presence of methylmercury in soil affected by the deposited mercury and determine the reactions associated with methylmercury production. The vertical profiles of mercury were obtained from two sites in the forest of the ASGM village in Pongkor (West Java, Indonesia) and from two sites in Mount Halimun-Salak National Park, which is approximately 12 km from the ASGM village. The highest total mercury concentration, 8.9 mg kg(-1), was observed for soil samples collected at the ASGM village. The mercury was concentrated at the surface or in the subsurface layers, and the concentrations were several times to more than ten times higher than the lowest values observed in the deeper layers at each site. Even in the national park, the highest concentration of 1.9 mg kg(-1) was observed in the upper soil layer. These results suggest that the primary source of mercury in the forest soil is atmospheric deposition; fallen plant leaves also deliver accumulated mercury to the soil surface. The organic mercury percentages of the total mercury were 0.2 +/- 0.1% for the national park and 0.3 +/- 0.2% for ASGM sites. The vertical variation in organic mercury concentration did not always match that in total mercury concentration, which suggested that the formation of methylmercury in soil was closely related to the decomposition of organic matter near the surface. The soil surface is an important reaction field for methylmercury production in forested areas.

DOI： 10.1007/s42452-020-3008-5

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. The safety of recycled water for potable water reuse can be enhanced by improving the reliability of reverse osmosis (RO) treatment for the removal of trace organic chemicals. This study assessed the mechanisms underlying the variable rejection of a carcinogenic N-nitrosamine, namely N-nitrosodimethylamine (NDMA), caused by RO membrane fouling. Foulants that cause the variable rejection were evaluated through rejection tests and foulant characterization. The RO treatment of wastewaters with and without pre-treatment using an ultrafiltration or nanofiltration membrane showed that NDMA rejection commonly increased with increasing membrane fouling. The characterization of organics in the treated wastewater samples revealed that increased NDMA rejection can be caused by foulants composed of low-molecular-weight organics (<300 Da), including tryptophan (or tryptophan-like substances). It is speculated that small organics such as tryptophan form a densely packed cake layer on the membrane surface, which may function as an additional barrier for the membrane transport of NDMA. The results of this study indicate that RO membrane fouling that occurs during long-term wastewater treatment can increase NDMA rejection. The enhanced separation performance can yield positive consequences for the credibility of RO treatment in potable water reuse.

DOI： 10.1016/j.eti.2019.100576

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Language：English   Publishing type：Research paper (scientific journal)  

Attenuation of trace organic chemicals (TOrCs), including pesticides, by reverse osmosis (RO) membrane treatment is critical for ensuring public health protection in potable water reuse. This study aimed to elucidate the mechanisms underlying the poor rejection of small pesticides by polyamide-based RO membranes. Rejection of the selected TOrCs (four N-nitrosamines and 158 pesticides) was primarily governed by size exclusion, charge interactions, and dipolar interactions when evaluated at high water temperatures. Further investigation indicated that small and uncharged secondary amide pesticides showed low and highly variable rejections, compared to similarly sized counterparts with no amide functional groups. Remarkably, three secondary amide pesticides that have no other atoms holding a high partial negative charge showed very low rejections (34–65%), likely due to the cooperativity of hydrogen bonding which occurs between amide functional groups of the pesticides and RO membranes. In contrast, secondary amide pesticides that have an atom holding a high partial negative charge showed higher rejections (72–98%), likely due to the inducted electrostatic repulsion. This study proposed that secondary amide pesticides that have no other atoms holding a high partial negative charge can be poorly rejected. The findings are useful to predict the rejection level of unregulated TOrCs.

DOI： 10.1016/j.memsci.2019.117577

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI} {AG  

DOI： 10.3390/w11102019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.chemosphere.2019.124939

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/chem.201903485

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.scitotenv.2019.134002

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DOI： 10.1016/j.envres.2019.108668

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

To estimate the impact of mercury discharged from artisanal and small-scale gold mining (ASGM) activity, variations in the concentrations of elemental mercury (Hg0), mercury ion (Hg2+), particulate mercury (P-Hg), and total mercury in filtered river water (FT-Hg) were investigated from sampling locations extending from 10 km upstream to 30 km downstream of ASGM operations in West Java, Indonesia. The average of the annual concentrations at the ASGM site from 2013 to 2017 were 0.14-0.85 mu g L-1, 0.27-12.9 mu g L-1, 4.3-49.5 mu g L-1, and 1.2-12.5 mu g L-1 for Hg0, Hg2+, P-Hg, and FT-Hg, respectively. The concentration of mercury species decreased as the distance from the ASGM site increased, while the ratio of P-Hg increased towards the lower reaches of the river system, with the percentage of P-Hg estimated at 90% of Hg at the sample location furthest downstream. A high mercury concentration of 600 mg kg(-1) was observed for suspended particulate matter (SPM) at the ASGM site. The SPM maintained a high concentration of mercury, even in the downstream area. In the annual variations of the mercury species from 2013 to 2017, FT-Hg and P-Hg concentrations tended to decrease from 2016, which suggested a decline of ASGM activity in this area. However, SPM and river sediment showed no apparent changes in their mercury concentrations over this period, indicating that the contamination in the river system is persistent and does not recover quickly.

DOI： 10.1007/s11356-019-05718-6

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Language：Japanese   Publisher：GEOCHEMICAL SOCIETY OF JAPAN  

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DOI： 10.14862/geochemproc.66.0_259

Language：Japanese   Publisher：GEOCHEMICAL SOCIETY OF JAPAN  

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DOI： 10.14862/geochemproc.66.0_126

Language：English   Publishing type：Research paper (scientific journal)  

© 2018 American Chemical Society. Reliable and adequate removal of small and uncharged trace organic chemicals, particularly N-nitrosodimethylamine (NDMA) that is carcinogenic and known to occur in treated effluent, is essential for implementing direct potable water use. This study provides new insights to explain the low rejection of NDMA and other N-nitrosamines by reverse osmosis (RO) membranes by examining the role of molecular size and polarity in their molecular structure. The results show that molecular weight is not a suitable molecular property for evaluating the rejection of small uncharged chemicals. In this study, NDMA and two other uncharged chemicals have similar molecular weights (i.e., 72-74 g/mol), but their rejection by the ESPA2 RO membrane varied considerably from 30 to 88%. Instead, a minimum projection area was identified as a more suitable molecular property, indicating that size exclusion plays a primary role in their rejection. It was also determined that chemicals with more nitrogen atoms in their chemical structure consistently showed rejections lower than those of their similarly sized counterparts. The results suggest that chemicals bearing more nitrogen atoms (e.g., NDMA) have higher affinity to amide or amine functional group of a polyamide RO membrane possibly through hydrogen bonding interactions.

DOI： 10.1021/acs.estlett.8b00624

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DOI： 10.1021/acs.jpcb.8b08870

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DOI： 10.1039/C8EW00271A

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DOI： 10.1007/s12665-018-7616-y

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

A newly developed, ion exchange-based inline pretreatment system was used to mitigate the effect of background constituents in natural water and treated wastewater to achieve rapid, reliable, and sensitive analysis of N-nitrosamines. The pretreatment system (anion exchange module, AEM) was incorporated into a high-performance liquid chromatograph (HPLC) coupled with a photochemical reactor (PR) and chemiluminescence (CL) detector (HPLC-PR-CL), which can analyze four hydrophilic N-nitrosamines at ng/L levels. This system requires no pre-concentration of the water sample nor the use of deuterated surrogates, unlike other conventional N-nitrosamine analytical techniques. The AEM converted anions in the eluent to hydroxide ions after HPLC separation and increased eluent pH, allowing for the subsequent photochemical reactions, which are otherwise achieved by pH conditioning with an additional dosing pump of basic chemical. The AEM also removed anionic interfering compounds (e.g. nitrate) from the samples, allowing for improved N-nitrosamine analysis in treated wastewater. The operating conditions of the AEM and PR were optimized to obtain sensitive and stable analytical performance. As a result, the lowest-concentration minimum reporting levels of N-nitrosodimethylamine, N-nitrosomorpholine, N-nitrosomethylethylamine, and N- nitrosopyrrolidine using the optimized system were 0.42, 0.54, 0.58, and 1.4 ng/L, respectively. The improved analytical method was validated by comparing the results with a conventional method based on gas chromatography coupled with a mass spectrometric ion trap detector. These results indicated that HPLC-PR-CL equipped with an inline AEM can be competitively applied as a rapid analytical technique for the determination of N-nitrosamines in various water matrices.

DOI： 10.1016/j.chroma.2018.04.030

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© 2017 Elsevier Ltd Direct potable reuse is becoming a feasible option to cope with water shortages. It requires more stringent water quality assurance than indirect potable reuse. Thus, the development of a high-rejection reverse osmosis (RO) membrane for the removal of one of the most challenging chemicals in potable reuse – N-nitrosodimethylamine (NDMA) – ensures further system confidence in reclaimed water quality. This study aimed to achieve over 90% removal of NDMA by modifying three commercial and one prototype RO membrane using heat treatment. Application of heat treatment to a prototype membrane resulted in a record high removal of 92% (1.1-log) of NDMA. Heat treatment reduced conductivity rejection and permeability, while secondary amines, selected as N-nitrosamine precursors, were still well rejected (>98%) regardless of RO membrane type. This study also demonstrated the highly stable separation performance of the heat-treated prototype membrane under conditions of varying feed temperature and permeate flux. Fouling propensity of the prototype membrane was lower than a commercial RO membrane. This study identified a need to develop highly selective RO membranes with high permeability to ensure the feasibility of using these membranes at full scale.

DOI： 10.1016/j.watres.2017.12.025

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Language：English   Publishing type：Research paper (scientific journal)  

© 2018 Elsevier B.V. The polyamide skin layer of reverse osmosis (RO) membranes was characterised using advanced and complementary analytical techniques to investigate the mechanisms underlying the permeation of contaminants of emerging concern in potable water reuse – N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA). This study used five RO membrane samples with similar membrane properties. The five RO membrane samples spanned over a large range of water permeance (0.9–5.8 L/m2 h bar) as well as permeation of NDMA (9–66%) and NMEA (3–29%). Despite these differences among the five RO membranes, characterisations of the skin layer using positron annihilation lifetime spectroscopy, atomic force microscopy and field emission scanning electron microscopy revealed almost no variation in their free-volume hole-radius (0.270–0.275 nm), effective surface area (198–212%) and thickness (30–35 nm) of the skin layer. The results suggest that there could be other RO skin layer properties, such as the interconnectivity of the protuberances within the polyamide skin layer additional to the free-volume hole-size and thickness of the skin layer, which can also govern water and solute permeation.

DOI： 10.1016/j.memsci.2018.02.069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

The security of recycled water quality in potable reuse can be enhanced by improving the credibility of reverse osmosis (RO) treatment for the removal of trace organic chemicals (TOrCs). This study evaluated the potential of online monitoring of N-nitrosodimethylamine (NDMA) before and after RO treatment as a surrogate indicator for TOrC removal by RO. This pilot-scale study monitored NDMA concentrations in RO feedwater (ultrafiltration-treated wastewater) and RO permeate every 22 min using novel online NDMA analyzers—high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection. NDMA rejection by RO varied considerably in response to changes in operating conditions (permeate flux and feedwater temperature). A high linear correlation between NDMA rejection and the rejection of six other TOrCs was observed. The linear correlation was also identified for an RO membrane damaged with chlorine. The correlation between another potential surrogate indicator (conductivity rejection) and TOrC rejection was relatively low. NDMA, which is the smallest compound among regulated TOrCs, revealed rejections lower than the other TOrCs, indicating that NDMA rejection can be a conservative surrogate indicator capable of predicting changes in TOrC removal.

DOI： 10.1016/j.chemosphere.2018.02.098

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Direct potable reuse requires stringent water quality assurance to protect public health. This study developed an online analytical technique-high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection (HPLCPR-CL)-for determination of the concentration of N-nitrosodimethylamine (NDMA) and three other N-nitrosamines. Its feasibility for near real-time analysis was evaluated by analyzing an ultrafiltration (UF)-treated wastewater before and after a pilotscale reverse osmosis (RO) treatment system. The online instrument with a method detection limit of 0.3-2.7 ng L-1 requires a direct injection (i.e., no sample pre-concentration) of only 20-200 mu L sample volume for the determination of N-nitrosamine concentrations every 20 min. NDMA concentrations in UF-treated wastewater were successfully monitored in a range of 50-200 ng L-1 over the course of 24 h. Likewise, NDMA concentrations in RO permeate ranged from 26-81 ng L-1 over the course of 48 h. The online monitor was capable of recording variations in N-nitrosamine concentration in RO permeate that occurred following changes in feedwater concentration and temperature. This study demonstrates the potential for online water quality assurance via direct measurement of trace levels of organic contaminants, which is highly relevant to the implementation of potable reuse.

DOI： 10.1039/C7EW00296C

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Metal ions in ionic liquids are laid under an unprecedented reaction field. In order to assess the reaction thermodynamics of metal ions in such a situation, Cu2+-chloro complex formation was examined with spectroscopic and calorimetric titrations in an ionic liquid, 1-buthy1-3-methylimidazolium trifluoromethanesulfonate (C(4)mimTfO). In addition, the effect of the structure of the solvated complexes on the complexation mechanism was investigated with the aid of DFT calculations. Chloro complexation successively proceeded and finally provided a [CuCl4](2-) species, which is also the final product in conventional molecular solvents. Their stability constants were comparable to those in molecular solvents. Interestingly, in spite of the charged solvent in the ionic liquid, the entropy profile of the complexation resembled that in the conventional molecular liquids. This indicates that the entropy gain of the released solvent species from the complexes is the main driving force of the chloro complexation in the ionic liquid. In contrast, unlike the major molecular solvents, the total coordination number of Cu2+ is saturated to 4 in the ionic liquid, and the Cl- complexation tends to be accompanied by a 1:1 exchange of the solvent TfO- from the complex. In addition, this ligand exchange was almost athermal. This possibly indicates that the coordination number is dominated by the electrostatic hindrance among the ligands including the solvent ions in the primary coordination sphere.

DOI： 10.1021/acs.jpcb.7b06287

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The effectiveness of hypochlorite cleaning for fouling mitigation of a prototype chlorine-resistant nanofiltration (NF) membrane was assessed for direct filtration of a secondary treated effluent. The chlorine resistance and separation performance of the prototype NF membrane were also compared to commercial NF and reverse osmosis membranes. The prototype chlorine resistant NF membrane did not show any changes in permeability and conductivity rejection after exposing a NaOCl solution for up to 5 x 10(4) ppm-h. By contrast, a considerable deterioration in rejection was observed for the other two commercial membranes. Direct filtration of a secondary treated effluent by the prototype NF membrane resulted in a progressive permeability reduction by up to 25% after 10 h of filtration. The membrane permeability was fully restored by hypochlorite cleaning with a 2000 ppm NaOCl solution for 1 h. Effective permeability recovery by hypochlorite cleaning was demonstrated with multiple hypochlorite cleaning cycles. Membrane fouling and hypochlorite cleaning were also simulated using solutions containing a model foulant (sodium alginate, humic acids or bovine serum albumin). Among them, an insufficient permeability recovery was observed for membrane fouling caused by humic acids. Further research is recommended to develop an improved hypochlorite cleaning protocol to control various membrane fouling.

DOI： 10.1016/j.seppur.2017.07.080

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese  

DOI： 10.1007/s40726-017-0052-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The distributions of the total mercury (T-Hg), methylmercury (MeHg), and ethylmercury (EtHg) concentrations in soil and their relationship to chemical composition of the soil and total organic carbon content (TOC, %) were investigated. Core samples were collected from hill slope on the right and left riverbanks of the Idrija River. Former smelting plant is located on the right bank. The T-Hg average in each of the core samples ranged from 0.25 to 1650 mg kg(-1) .The vertical T-Hg variations in the samples from the left bank showed no significant change with depth. Conversely, the T-Hg varied with depth, with the surface, or layers several centimeters from the surface, tending to show the highest values in the samples from the right bank. Since the right and left bank soils have different chemical compositions, different pathways of mercury delivery into soils were suggested. The MeHg and EtHg concentrations ranged from n.d. (not detected) to 444 mu g kg(-1) and n.d. to 17.4 mu g kg(-1), respectively. The vertical variations of MeHg and EtHg were similar to those of TOC, except for the near-surface layers containing TOC greater than 20%. These results suggest that the decomposition of organic matter is closely related to organic mercury formation. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chemosphere.2017.05.123

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The impact of fouling substances on the rejection of four N-nitrosamines by a reverse osmosis (RO) membrane was evaluated by characterizing individual organic fractions in a secondary wastewater effluent and deploying a novel high-performance liquid chromatography-photochemical reaction-chemiluminescence (HPLC-PR-CL) analytical technique. The HPLC-PR-CL analytical technique allowed for a systematic examination of the correlation between the fouling level and the permeation of N-nitro. samines in the secondary wastewater effluent and synthetic wastewaters through an RO membrane. Membrane fouling caused by the secondary wastewater effluent led to a notable decrease in the permeation of N-nitrosodimethylamine (NDMA) while a smaller but nevertheless discernible decrease in the permeation of N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPYR) and N-nitrosomorpholine (NMOR) was also observed. Fluorescence spectrometry analysis revealed that major foulants in the secondary wastewater effluent were humic and fulvic acid-like substances. Analysis using the size exclusion chromatography technique also identified polysaccharides and proteins as additional fouling substances. Thus, further examination was conducted using solutions containing model foulants (i.e., sodium alginate, bovine serum albumin, humic acid and two fulvic acids). Similar to the secondary wastewater effluent, membrane fouling with fulvic acid solutions resulted in a decrease in N-nitrosamine permeation. In contrast, membrane fouling with the other model foulants resulted in a negligible impact on N-nitrosamine permeation. Overall, these results suggest that the impact of fouling on the permeation of N-nitrosamines by RO is governed by specific small organic fractions (e.g. fulvic acid-like organics) in the secondary wastewater effluent. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.watres.2017.03.057

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The separate influences of drying and storage conditions on methylmercury (MeHg) concentrations in soil and sediment samples were investigated. Concentrations of MeHg and total Hg were determined in various soil and sediment samples that had been stored or dried under differing conditions. The influence of drying conditions (oven-drying (40 degrees C) versus freeze-drying) on MeHg concentrations in marine sediments, river sediments, soils, and paddy field soils was investigated (n = 43). The ratio of the MeHg concentration in oven-dried sub-samples divided by the concentration in freeze-dried sub-samples ranged from 0 to 336%. In order to confirm the production of MeHg during storage in some samples, Hg2+ was added at 15 mg kg(-1) to a paddy soil, and the sample was then stored at 30 degrees C. The concentrations of MeHg at 1-h, 1-day, 4-days and 7-days after Hg2+ spiking were 2.0 +/- 0.1, 13.8 +/- 1.0, 36.0 +/- 5.0, and 24.9 +/- 1.6 mu g kg(-1) (n = 3), respectively. The concentration of MeHg at 4-days after Hg spiking and sterilizing (121 degrees C, 30 min) was 1.8 mu g kg(-1), similar to the original value. These results indicate that bacterial Hg methylation and MeHg demethylation occurred within days in the soil. In addition, tests of the stability of MeHg in wet and dry samples during storage were also performed. Overall, our results indicate that the best way to preserve MeHg in soil and sediment samples is to freeze the samples immediately after collection, followed subsequently by freeze-drying, grinding, homogenization, and storage of the dry material in cool, dark conditions until analysis.

DOI： 10.1016/j.chemosphere.2017.01.053

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

An inter-laboratory study was conducted to compare results from different analytical methods for monomethylmercury (MeHg) concentrations in 17 soil and sediment samples. The samples were collected from mercury-contaminated areas, including Minamata Bay and Kagoshima Bay in Japan, the Idrija mercury mine in Slovenia, and an artisanal small-scale gold mining area in Indonesia. The Hg in these samples comes from several different sources: industrial waste from an acetaldehyde production facility, volcanic activity, Hg mining activity, and artisanal and small-scale gold mining activity (ASGM). MeHg concentrations in all the samples were measured in four separate laboratories, using three different determination methods: Kagoshima University (Japan), using high-performance liquid chromatography chemiluminescence detection (HPLC-CL); National Institute for Minamata Disease (Japan), using gas chromatography electron capture detection; and Metropolitan Council Environmental Services (USA) and Jozef Stefan Institute (Slovenia), both using alkylation-gas chromatography atomic fluorescence spectrometry detection. The methods gave comparable MeHg results for most of the samples tested, but for some samples, the results exhibited significant variability depending on the method used. The HPLC-CL method performed poorly when applied to samples with elevated sulfur concentrations, producing MeHg concentrations that were much lower than those from the other methods. Additional analytical work demonstrated the elimination of this sulfur interference when the method was modified to bind sulfur prior to the analytical step by using Hg2+ as a masking agent. These results demonstrate the value of laboratory intercomparison exercises in contributing to the improvement of analytical methods. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chemosphere.2016.10.129

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

This study investigates the distribution of total mercury (T-Hg) and methylmercury (MeHg) in the soil and water around the artisanal and small-scale gold mining (ASGM) area along the Cikaniki River, West Java, Indonesia. The concentration of T-Hg and MeHg in the forest soil ranged from 0.07 to 16.7 mg kg(-1) and from &lt; 0.07 to 2.0 mu g kg(-1), respectively, whereas it ranged from 0.40 to 24.9 mg kg(-1) and from &lt; 0.07 to 56.3 mu g kg(-1), respectively, in the paddy field soil. In the vertical variation of the T-Hg of forest soil, the highest values were observed at the soil surface, and these values were found to decrease with increasing depth. A similar variation was observed for MeHg and total organic carbon content (TOC), and a linear relationship was observed between them. Mercury deposited on the soil surface can be trapped and retained by organic matter and subjected to methylation. The slope of the line obtained for the T-Hg vs. TOC plot became larger near the ASGM villages, implying a higher rate of mercury deposition in these areas. In contrast, the plots of MeHg vs. TOC fell along the same trend line regardless of the distance from the ASGM village. Organic carbon content may be a predominant factor in controlling MeHg formation in forest soils. The T-Hg concentration in the river water ranged from 0.40 to 9.6 mu g L-1. River water used for irrigation can prove to be a source of mercury for the paddy fields. The concentrations of Hg-0 and Hg2+ in river water showed similar variations as that observed for the T-Hg concentration. The highest Hg-0 concentration of 3.2 mu g L-1 can be attributed to the waste inflow from work sites. The presence of Hg-0 in river water can become a source of mercury present in the atmosphere along the river. MeHg concentration in the river water was found to be 0.004-0.14% of T-Hg concentration, which was considerably lower than the concentrations of other Hg species. However, MeHg comprised approximately 0.2% of the T-Hg in paddy field soil. Mercury deposited from the atmosphere and the river water can be subjected to methylation. Paddy fields are very important ecosystems; therefore, the effect of MeHg on these ecosystems and human beings should be further investigated.

DOI： 10.1007/s11356-016-7998-x

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A novel method for the determination of secondary amines at the nanomolar level was developed. The method is based on the nitrosation reaction of secondary amines, with the generated N-nitrosamines being measured using an HPLC separation, photochemical reaction, and chemiluminescence detection system. The efficient nitrosation of secondary amines was performed using sodium nitrite (200 mM) and acetic acid (0.8 M) at 80 degrees C over 60 min. Although compounds bearing OH and SH functional groups also underwent the nitrosation reaction, the sensitivity of these compounds was 1000 times lower than that of the secondary amines. Our method was applied to the determination of low molecular weight secondary amines, including dimethylamine, morpholine, pyrrolidine, diethylamine, and piperidine, giving method detection limits of 0.7 nM, 0.2 nM, 0.4 nM, 0.7 nM, and 1.5 nM, respectively. The calibration curves were linear in the range of 5-100 nM. We then applied this method for the detection and quantification of these secondary amines in samples of tap water, river water, treated wastewater, and sea water. Dimethylamine was detected at concentrations up to 15.4 nM, &lt;0.7 nM, and 48.5 nM in tap water, river water, and treated wastewater samples, respectively, with recoveries ranging from 94 to 103%. Other amines were also detected at nanomolar levels. These results indicate that our proposed method can be applied to the analysis of secondary amines in various environmental water samples. To the best of our knowledge, the proposed method is one of the most sensitive and selective methods for the determination of secondary amines without pre-concentration steps. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2016.11.045

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DOI： 10.1016/j.chroma.2016.07.014

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chemosphere.2016.06.094

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DOI： 10.1002/anie.201511328

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DOI： 10.2343/geochemj.2.0368

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DOI： 10.1016/j.marchem.2015.10.009

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DOI： 10.1016/j.marchem.2013.12.002

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/bio.2466

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/bunsekikagaku.62.891

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.envres.2013.03.015

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DOI： 10.1016/j.chroma.2013.02.004

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.28.959

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s12665-011-1379-z

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/bunsekikagaku.61.21

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chemosphere.2012.04.027

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/00032719.2011.565442

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.27.187

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/bunsekikagaku.59.665

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/bunsekikagaku.58.539

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chroma.2009.01.096

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.talanta.2008.11.001

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chroma.2008.11.025

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.aca.2008.05.050

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.2008.80

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5182/jaie.18.434

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.23.407

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chroma.2006.11.059

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chroma.2005.10.059

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.chroma.2005.09.006

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.21.497

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1081/AL-200045155

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/analsci.20.1065

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2116/bunsekikagaku.52.763

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5182/jaie.14.Supplement_229

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

Event date： 2019.9

Language：English   Presentation type：Poster presentation  

Venue：Krakow, Poland  

国際会議

Event date： 2019.9

Language：English   Presentation type：Poster presentation  

Venue：Krakow, Poland  

国際学会

Event date： 2019.9

Language：English   Presentation type：Poster presentation  

Venue：Krakow, Poland  

国際学会

Event date： 2019.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡  

国内会議

Event date： 2019.5

Language：Japanese   Presentation type：Poster presentation  

Venue：福岡  

国内会議

Event date： 2018.9

Language：Japanese   Presentation type：Poster presentation  

Venue：宮城  

国内学会

Event date： 2018.9

Language：Japanese   Presentation type：Poster presentation  

Venue：宮城  

国内学会

Event date： 2018.9

Language：Japanese   Presentation type：Poster presentation  

Venue：宮城  

国内学会

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：千葉  

国内学会

Event date： 2018.6

Language：Japanese   Presentation type：Poster presentation  

Venue：福岡  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Poster presentation  

Venue：山口  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Poster presentation  

Venue：山口  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Poster presentation  

Venue：山口  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Poster presentation  

Venue：山口  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：千葉  

国内学会

Event date： 2018.5

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：千葉  

国内学会

Event date： 2017.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京  

国内学会

Event date： 2017.10 - 2017.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌  

Event date： 2017.9

Language：English   Presentation type：Poster presentation  

Venue：Bratislava, Slovak  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京  

Event date： 2017.9

Language：Japanese   Presentation type：Poster presentation  

Venue：東京  

Event date： 2017.9

Language：Japanese   Presentation type：Poster presentation  

Venue：東京  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京  

Event date： 2017.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京  

Event date： 2017.7

Language：English   Presentation type：Poster presentation  

Venue：Providence, RI, USA  

Event date： 2017.7

Language：English   Presentation type：Poster presentation  

Venue：Providence, RI, USA  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Venue：京都  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Venue：京都  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Venue：京都  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Venue：京都  

Event date： 2017.5

Language：Japanese   Presentation type：Poster presentation  

Venue：京都  

Event date： 2017.4

Language：English   Presentation type：Oral presentation (general)  

Venue：San Francisco, CA, USA  

Event date： 2016.9

Language：Japanese   Presentation type：Poster presentation  

Venue：大阪  

Event date： 2016.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌  

Event date： 2016.9

Language：Japanese   Presentation type：Poster presentation  

Venue：札幌  

Event date： 2016.6

Language：Japanese   Presentation type：Poster presentation  

Venue：甲府  

Event date： 2016.6

Language：Japanese   Presentation type：Poster presentation  

Venue：新潟  

Event date： 2015.12

Language：English   Presentation type：Poster presentation  

Venue：米国  

Event date： 2015.9

Language：Japanese   Presentation type：Poster presentation  

Venue：福岡  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (keynote)  

Venue：福岡  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡  

Event date： 2015.9

Language：Japanese   Presentation type：Oral presentation (keynote)  

Venue：福岡  

Event date： 2015.9

Language：Japanese   Presentation type：Poster presentation  

Venue：福岡  

Event date： 2015.9

Language：Japanese   Presentation type：Poster presentation  

Venue：福岡  

Event date： 2015.9

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：福岡  

Event date： 2015.6

Language：English   Presentation type：Poster presentation  

Venue：韓国  

Event date： 2015.6

Language：English   Presentation type：Poster presentation  

Venue：韓国  

Event date： 2015.6

Language：English   Presentation type：Poster presentation  

Venue：韓国  

Event date： 2015.6

Language：English   Presentation type：Poster presentation  

Venue：韓国  

Event date： 2015.5

Language：Japanese   Presentation type：Poster presentation  

Venue：甲府  

Event date： 2015.5

Language：Japanese   Presentation type：Poster presentation  

Venue：甲府  

Event date： 2015.5

Language：Japanese   Presentation type：Poster presentation  

Venue：甲府  

Event date： 2014.12

Language：Japanese  

Venue：神戸  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：広島  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：広島  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：広島  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：富山  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：富山  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：富山  

国内学会

Event date： 2014.9

Language：Japanese  

Venue：富山  

国内学会

Event date： 2014.9

Language：English  

Venue：中国  

国際学会

Event date： 2014.9

Language：English  

Venue：中国  

国際学会

Event date： 2014.5

Language：Japanese  

Venue：福島  

国内学会

Event date： 2014.5

Language：Japanese  

Venue：福島  

国内学会

Event date： 2014.4

Language：Japanese  

Venue：神奈川  

国内学会

Event date： 2014.4

Language：Japanese  

Venue：神奈川  

国内学会

Event date： 2014.2

Language：Japanese  

Venue：東京  

国内学会

Event date： 2013.11

Language：Japanese  

Venue：熊本  

国内学会

Event date： 2013.8

Language：English  

Venue：スコットランド  

国際学会

Event date： 2013.8

Language：English  

Venue：スコットランド  

国際学会

Event date： 2013.8

Language：English  

Venue：スコットランド  

国際学会

Event date： 2013.5

Language：English  

Venue：北海道  

国際学会

Event date： 2013.5

Language：Japanese  

Venue：北海道  

国内学会

Event date： 2013.5

Language：Japanese  

Venue：北海道  

国内学会

Event date： 2013.5

Language：Japanese  

Venue：北海道  

国内学会

Event date： 2013.5

Language：Japanese  

Venue：北海道  

国内学会

Event date： 2013.3

Language：Japanese  

Venue：東京海洋大学  

国内学会

Event date： 2012.9

Language：Japanese  

Venue：石川  

国内学会

Event date： 2012.9

Language：Japanese  

Venue：石川  

国内学会

Event date： 2012.9

Language：Japanese  

Venue：石川  

国内学会

Event date： 2012.9

Language：Japanese  

Venue：石川  

国内学会

Event date： 2012.9

Language：Japanese  

Venue：石川  

国内学会

Event date： 2012.6

Language：Japanese  

Venue：東京  

国内学会

Event date： 2012.3

Language：Japanese  

Venue：静岡  

国内学会

Event date： 2012.3

Language：Japanese  

Venue：東京  

国内学会

Event date： 2012.2

Language：Japanese  

Venue：東京  

国内学会

Event date： 2012.2

Language：Japanese  

Venue：東京  

国内学会

Event date： 2011.11

Language：Japanese  

Venue：宮崎  

国内学会

Event date： 2011.9

Language：Japanese  

Venue：名古屋  

国内学会

Event date： 2011.9

Language：Japanese  

Venue：名古屋  

国内学会

Event date： 2011.9

Language：Japanese  

Venue：名古屋  

国内学会

Event date： 2011.9

Language：Japanese  

Venue：名古屋  

国内学会

Event date： 2011.7

Language：English  

Venue：Canada  

国際学会

Event date： 2011.7

Language：English  

Venue：Canada  

国際学会

Event date： 2011.7

Language：English  

Venue：Canada  

国際学会

Event date： 2011.3

Language：Japanese  

Venue：石川  

研究会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：仙台  

国内学会

Event date： 2010.9

Language：Japanese  

Venue：Slovenia  

研究会

Event date： 2010.5

Language：Japanese  

Venue：島根  

国内学会

Event date： 2010.5

Language：Japanese  

Venue：島根  

国内学会

Event date： 2010.5

Language：Japanese  

Venue：島根  

国内学会

Event date： 2010.5

Language：Japanese  

Venue：島根  

国内学会

Event date： 2010.5

Language：Japanese  

Venue：島根  

国内学会

Language：Japanese  

Language：Japanese  

Venue：鹿児島  

Language：Japanese  

Venue：岡山  

Language：Japanese  

Venue：岡山  

Language：Japanese  

Venue：岡山  

Language：Japanese  

Venue：岡山  

Language：Japanese  

Venue：水戸  

Language：Japanese  

Venue：水戸  

Language：Japanese  

Venue：Web  

Language：Japanese  

Venue：神戸（オンライン）  

Language：Japanese  

Venue：名古屋  

Language：Japanese  

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DOI： 10.14862/geochemproc.69.0_113