Time filter

Source Type

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.


Nakamura K.,Ibaraki Kasumigaura Environmental Science Center | Homma T.,Civil Engineering and Ecotechnology Consultants | Miyabara Y.,Shinshu University | Hanazato T.,Shinshu University | Park H.-D.,Shinshu University
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2013

This study examined the influence of hydraulic turnover rate on apparent specific growth rate and maximum biomass of Microcystis in Lake Suwa from 1992 to 2003. The apparent specific growth rate of Microcystis decreased by flushing (>20% day-1 of the hydraulic turnover rate in a day). In addition, the apparent specific growth rate of Microcystis began to be suppressed when the turnover rate reached >2% day-1 in the exponential growth phase. The maximum biomass of Microcystis was affected by the hydraulic turnover rate from June to July. Therefore, we suggest that the short period and long-term changes of hydraulic turnover rate have large impacts on Microcystis bloom in Lake Suwa.


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.


Arayama K.,Ibaraki Prefectural Freshwater Fisheries Research Institute | Sunoh N.,Ibaraki Prefectural Freshwater Fisheries Research Institute | Sunoh N.,Ibaraki Kasumigaura Environmental Science Center | Yamazaki Y.,Ibaraki Prefectural Freshwater Fisheries Research Institute | Yamazaki Y.,Ibaraki Prefectural Fisheries Research Institute
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2010

Seasonal and nocturnal changes in the vertical distribution of ayu, Plecoglossus altivelis altivelis larvae during seaward migration in the lower Kuji River were examined in 2006 and 2007. Sampling was performed at a site, approximately 3 m deep, using 0.3-mm mesh ring nets (45 cm in diameter). Ayu larvae were caught mainly from late October to early November in 2006 and from late October to early December in 2007. In both years, nocturnal vertical larvae distributions were different in late October and from early November onward; the larvae were evenly distributed throughout the water column in late October, but mainly in the middle and bottom layers from early November onward. Body and quantity of yolk sizes of larvae were not different between layers. No marked differences were observed in water velocity within the water column. Seasonal changes in water temperature showed a gradual decrease from 24°C to 6°C from September to December, while in late October and early November, it was 15°C-16°C in both years. These results show that ayu larvae do not always drift at the same depth and that their distribution in the water column changes seasonally as the water temperature decreases.


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.

Loading Ibaraki Kasumigaura Environmental Science Center collaborators
Loading Ibaraki Kasumigaura Environmental Science Center collaborators