Ibaraki Kasumigaura Environmental Science Center

Tsuchiura, Japan

Ibaraki Kasumigaura Environmental Science Center

Tsuchiura, Japan
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Lee Y.P.,Tokyo Institute of Technology | Fujii M.,Tokyo Institute of Technology | Kikuchi T.,Tokyo Institute of Technology | Kikuchi T.,Ibaraki Kasumigaura Environmental Science Center | And 4 more authors.
Chemosphere | Year: 2017

Ferrous iron (Fe[II]) oxidation by dissolved oxygen was investigated in the Shizugawa Bay watershed with particular attention given to the effect of dissolved organic matter (DOM) properties on Fe(II) oxidation. To cover a wide spectrum of DOM composition, water samples were collected from various water sources including freshwater (e.g., river water and wastewater effluent) and coastal seawater. Measurement of nanomolar Fe(II) oxidation by using luminol chemiluminescence under dark, air-saturated conditions at 25 °C indicated that spatio-temporal variation of the second-order rate constant (6.7–74.5 M−1 s−1) was partially explained by the variation of the sample pH (7.5–8.6). However, at comparable pH values, the oxidation rates for freshwater were generally greater than those for coastal seawater. The substantial decline in oxidation rate constant after the removal of humic-type (allochthonous) DOM suggested that this hydrophobic DOM is a key factor that accelerates the Fe(II) oxidation in the freshwater samples. Observed lower oxidation rates for coastal seawater compared with freshwater and organic ligand-free seawater were likely associated with microbially derived autochthonous DOM, and the variation of Fe(II) oxidation at a fixed pH was best described by fluorescence index that represents the proportion of autochthonous and allochthonous DOM in natural waters. Consistently, Fe(II) oxidation was found to be slower in the presence of cellular exudates from phytoplankton. The present study highlighted the significant effect of DOM composition on the Fe(II) oxidation in inland and coastal waters. © 2017 Elsevier Ltd

Lee Y.P.,Tokyo Institute of Technology | Fujii M.,Tokyo Institute of Technology | Kikuchi T.,Tokyo Institute of Technology | Kikuchi T.,Ibaraki Kasumigaura Environmental Science Center | And 2 more authors.
PLoS ONE | Year: 2017

Oxidation and reduction kinetics of iron (Fe) and proportion of steady-state Fe(II) concentration relative to total dissolved Fe (steady-state Fe(II) fraction) were investigated in the presence of various types of standard humic substances (HS) with particular emphasis on the photochemical and thermal reduction of Fe(III) and oxidation of Fe(II) by dissolved oxygen (O2 ) and hydrogen peroxide (H2 O2) at circumneutral pH (pH 7-8). Rates of Fe(III) reduction were spectrophotometrically determined by a ferrozine method under the simulated sunlight and dark conditions, whereas rates of Fe(II) oxidation were examined in air-saturated solution using luminol chemiluminescence technique. The reduction and oxidation rate constants were determined to substantially vary depending on the type of HS. For example, the first-order rate constants varied by up to 10-fold for photochemical reduction and 7-fold for thermal reduction. The degree of variation in Fe(II) oxidation was larger for the H2 O2 -mediated reaction compared to the O2 -mediated reaction (e.g., 15- and 3-fold changes for the former and latter reactions, respectively, at pH 8). The steady-state Fe(II) fraction under the simulated sunlight indicated that the Fe(II) fraction varies by up to 12-fold. The correlation analysis indicated that variation of Fe(II) oxidation is significantly associated with aliphatic content of HS, suggesting that Fe(II) complexation by aliphatic components accelerates Fe (II) oxidation. The reduction rate constant and steady-state Fe(II) fractions in the presence of sunlight had relatively strong positive relations with free radical content of HS, possibly due to the reductive property of radical semiquinone in HS. Overall, the findings in this study indicated that the Fe reduction and oxidation kinetics and resultant Fe(II) formation are substantially influenced by chemical properties of HS. © 2017 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Kamiya K.,University of Tsukuba | Kamiya K.,Ibaraki Kasumigaura Environmental Science Center | Fukushima T.,University of Tsukuba | Ouchi T.,Ibaraki Kasumigaura Environmental Science Center | Aizaki M.,Ibaraki Kasumigaura Environmental Science Center
Limnology | Year: 2016

To investigate the effective depth from the surface sediment, and phosphorus fractions related to phosphorus release under short-term anoxic conditions, varying lengths of sediment cores taken from Lake Kasumigaura, a large shallow polymictic lake in Japan, were incubated for a few weeks and then analyzed. Results showed few differences in total phosphorus (TP) amount per unit area in overlying waters irrespective of the core thickness, and sums of TP in both overlying water and 0- to 2-cm sediment layers were nearly equal before and after the experiment, indicating that phosphorus was released mainly from the 0- to 2-cm layer by dissolution. In contrast, phosphorus was decreased in pore water below a 2-cm depth, probably through sorption to sediment solids. The citrate-dithionite-bicarbonate total phosphorus (CBD-TP) and non-reactive phosphorus extracted by NaOH (NaOH-NRP) in sediment solids in the 0- to 2-cm layer decreased during the experiment. The decreases of CBD-TP were 10 times higher than those of NaOH-NRP, suggesting that the released phosphorus came mainly from the fraction bound to iron in Lake Kasumigaura. © 2016 The Japanese Society of Limnology

Fujita M.,Ibaraki University | Ishiwatari Y.,Ibaraki University | Ishiwatari Y.,Industrial Technology Institute of Ibaraki Prefecture | Mishima I.,Center for Environmental Science in Saitama | And 2 more authors.
Water Resources Management | Year: 2014

Water samples collected from a drinking water supply system were assessed for elemental composition (Al, Si, Ca, Mn, Fe and Zn) of suspended particles. Particulate Fe, Mn and Al concentrations were significantly correlated even though their origins are considered to be different. The results of Principal Component Analysis (PCA) and cluster analysis revealed that elemental compositions can vary according to pipe and lining materials and service ages. Differences in concentrations of the particulate elements were calculated between upstream and downstream sites and then subjected to further PCA. In PC1, Fe, Mn and Al exhibited high factor loadings, whereas only Ca was a high contributor for PC2. This implies that ageing-related corrosion and degradation of mortar lining can affect the elemental composition of suspended particles in water distribution systems. We concluded that the elemental composition of suspended particulates can be used to detect ageing pipes in water distribution systems. © 2014 Springer Science+Business Media Dordrecht.

Watanabe K.,Japan National Institute of Environmental Studies | Komatsu N.,Ibaraki Kasumigaura Environmental Science Center | Kitamura T.,Ibaraki Kasumigaura Environmental Science Center | Ishii Y.,Tokyo Metropolitan Research Institute for Environmental Protection | And 9 more authors.
Environmental Microbiology | Year: 2012

The free-living, cosmopolitan, freshwater betaproteobacterial bacterioplankton genus Polynucleobacter was detected in different years in 11 lakes of varying types and a river using the size-exclusion assay method (SEAM). Of the 350 strains isolated, 228 (65.1%) were affiliated with the Polynucleobacter subclusters PnecC (30.0%) and PnecD (35.1%). Significant positive correlations between fluorescence in situ hybridization and SEAM data were observed in the relative abundance of PnecC and PnecD bacteria to Polynucleobacter communities (PnecC+PnecD). Isolates were mainly PnecC bacteria in the samples with a high specific UV absorbance at 254nm (SUVA254), and a low total hydrolysable neutral carbohydrate and amino acid (THneutralCH+THAA) content of the dissolved organic matter (DOM) fraction, which is known to be correlated with a high humic content. In contrast, the PnecD bacteria were abundant in samples with high chlorophyll a and/or THneutralCH+THAA concentrations, indicative of primary productivity. With few exceptions, differences in the relative abundance of PnecC and PnecD in each sample, determined using a high-sensitivity cultivation-based approach, were due to DOM quality. These results suggest that the major DOM component in the field, which is allochthonously or autochthonously derived, is a key factor for ecological niche separation between PnecC and PnecD subclusters. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

Sugaya K.,Ibaraki Kasumigaura Environmental Science Center
Bunseki Kagaku | Year: 2010

Coumarin in sulfuric acid-pitch/alkali-sludge was determined by GC/MS after an acidified liquid-liquid extraction of alkaline sample extracts. Shading at alkali extraction brought about a good result, and this was probably due to the prevention of UV-rays, which isomerize coumarin in an alkaline solution to trans-o-hydroxycinnamate anion. Outdoor samples of alkali-sludge and sulfuric acid-pitch contained 0.16~0.43 mg/kg and 51~72 mg/kg of coumarin, respectively; and these samples were thought to be derived from production of illegal gas oil. © 2010 The Japan Society for Analytical Chemistry.

Ishiwatari Y.,Industrial Technology Institute of Ibaraki Prefecture | Ishiwatari Y.,Ibaraki University | Mishima I.,Center for Environmental Science in Saitama | Utsuno N.,Ibaraki Kasumigaura Environmental Science Center | Fujita M.,Ibaraki University
Water Science and Technology: Water Supply | Year: 2013

To develop a method for screening ageing of water supply systems by analysing the supplied water's quality, water samples were collected from a water treatment plant, a delivery pump station, two distribution reservoirs and two feed pipes along a water pipe system. Principal component analysis of the water was conducted. In the first principal component, many elements exhibited high factor loadings, whereas the major contributor for the second principal component was iron (Fe). The unlined steel pipe, which was beyond its working lifetime, had a significantly high Fe content in suspended solids. X-ray absorption fine structure (XAFS) analysis showed differences in the abundance ratios of Fe3O4 and α-FeOOH among the sampling points. It was concluded that the concentration and speciation of Fe in supplied water can be a useful index for detecting the ageing of pipes. Copyright © IWA Publishing 2013.

Nagahama Y.,Ibaraki Kasumigaura Environmental Science Center | Nishimura K.,Saga University | Yamanishi H.,Saga University
Lowland Technology International | Year: 2015

Trenches were constructed to control the growth of Phragmites australis on a riverbank in the Ushizu River in Saga, Japan. However, the effect of these trenches on the habitat of aquatic organisms is unclear. The purpose of this study is to clarify the effect that trenches have on aquatic organisms in the tidal river. The burrow density of a type of sand crab (llyoplax deschampsi) and the abundance of aquatic organisms (such as fish and shrimp) in our trenches were measured. The number of I. deschampsi burrows around trench D was similar to that observed before trench construction. However, mud sedimentation was accelerated in shallow trench D', which created a suitable habitat for this species. Additionally, we found shrimp and gobies in all our trenches. This indicates that artificial trenches do provide habitat for shrimp and gobies in riverside marshes. Moreover, an endangered species and many aquatic insects were collected. Our results suggest that trenches provide important habitats for rare fishes and aquatic insects, similar to that of a lagoon.

Futatsugi N.,Shinshu University | Saito R.,Shinshu University | Nakamura K.,Ibaraki Kasumigaura Environmental Science Center | Miyabara Y.,Shinshu University | And 3 more authors.
Japanese Journal of Limnology | Year: 2016

In Lake Suwa, various eutrophication control measures have been taken to reduce external loads of phosphorus and nitrogen. As a result, the composition of the phytoplankton in the lake has also changed. Since 1999, blue-green algae have decreased, and Mougeotia have appeared August–December in 2011. DNA analysis of the 18S rRNA region of Mougeotia revealed that Mougeotia in Lake Suwa come from two phylogenetic clades. A genetic distance(p-distance) of 4% indicated they are strongly differentiated and should be recognized as different species. This work has shown that there are two phylogenetic clades of Mougeotia in Lake Suwa, both of which are different from M. scalaris clades, and that many strains isolated from Lake Suwa and Lake Biwa are the same phylogenetic clades. The longer cell length of Mougeotia in January 2012 than in November 2011 and the form of zygospores in January 2012 suggest it should be classified as M. elegantula. Mougeotia generally occurs in oligotrophic to mesotrophic lakes, and was first found in Lake Suwa in the 1960s. The reappearance of Mougeotia in Lake Suwa in 2011 suggests that, as a result of water quality improvement, the lake is transitioning from a blue-green algae dominated eutrophic lake to a mesotrophic lake. © 2016, Japanese Society of Limnology. All rights reserved.

An analytical method for the determination of Brilliant Blue FCF in water by liquid chromatography mass spectrometry (LC/MS) has been developed. A hundred milliliter of water sample portion of passed through an anion exchange solid phase extraction cartridge at a flow rate of 3 mL min-1. The cartridge eluted with 5 mL of 5 %-NH4OH/methanol. The eluate was concentrated to ca. 0.5 mL, and Fast Green FCF was added as an internal standard and adjusted to 1 mL with purified water. This solution was determined by LC/MS (ESI negative ion mode). The averages of recoveries of Brilliant Blue FCF from purified water and pond water were 97.4 % and 94.8 %, respectively. For the 32 rivers in Ibaraki Prefecture investigated by this method, Brilliant Blue FCF was detected from 26 rivers. A detected mean concentration was 0.13 μg L-1, and the maximum concentration was 1.2 μg L-1. This result shows that Brilliant Blue FCF exists in the environment widely. © 2012 The Japan Society for Analytical Chemistry.

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