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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.

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.

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.

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