Benthic and Intermediate Nepheloid Layers in Lake Biwa

Kumagai, Michio; Shimoda, Chikara; Tsuda, Ryohei; Kodama, Tetsuya

doi:10.3739/rikusui.57.445

Cited by 6 publications

(1 citation statement)

References 21 publications

(9 reference statements)

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“…From July to September, the DSBP concentrations reached their maximum at the thermocline. In Lake Biwa, there are sometimes strong intrusions of highly turbid river water into the thermocline after heavy rain , . The FWAs in the thermocline derived from such subsurface loading of river water can escape photodegradation, thus increasing DSBP concentrations.…”

Section: Resultsmentioning

confidence: 99%

Role of Photodegradation in the Fate of Fluorescent Whitening Agents (FWAs) in Lacustrine Environments

Yamaji

Hayakawa

Takada

2010

Environ. Sci. Technol.

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To understand the behavior of fluorescent whitening agents (FWAs) in a lake environment, we measured the quantities of two FWAs, DSBP, and DAS1, in water samples collected monthly from six depths of the water column, in sediment trap sample, and a sediment core sample from Lake Biwa, the largest lake in Japan, and in sewage, effluent, and river water in the lake's catchment. We conducted a sunlight exposure experiment and developed a method to estimate the degree of photodegradation by using DSBP/DAS1 ratio in environmental samples. The observed seasonal pattern of the vertical distributions of the FWAs in the water column can be explained by stratification of the water, photodegradation in the euphotic zone, the subsurface loading of river water, and their seasonal changes. The DSBP/DAS1 ratio was much lower in the lake water (0.12-0.52) than in sewage (6.4 ± 1.1), indicating intensive photodegradation in rivers and the lake. A mass balance calculation and DSBP/DAS1 ratio demonstrated that ∼95% of DSBP and ∼55% of DAS1 supplied in sewage were photodegraded in inflowing rivers and the lake, and that sedimentation to the lake bottom is insignificant for DSBP and ∼35% for DAS1. More intensive photodegradation of FWAs, especially more photodegradable DSBP, in Lake Biwa than in Greifensee, a lake in Switzerland, was suggested, attributable to the longer residence time of water in and the larger size of Lake Biwa. These results demonstrate that photodegradation is important to the fate of FWAs in lacustrine environments, and that FWAs and the DSBP/DAS1 ratio are useful markers for understanding the role of direct photodegradation in the behavior of water-soluble chemicals in aquatic environments.

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Section: Resultsmentioning

confidence: 99%

Role of Photodegradation in the Fate of Fluorescent Whitening Agents (FWAs) in Lacustrine Environments

Yamaji

Hayakawa

Takada

2010

Environ. Sci. Technol.

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Three‐dimensional eutrophication model for Lake Biwa and its application to the framework design of transferable discharge permits

Yamashiki

Matsumoto

Tezuka

et al. 2003

Hydrological Processes

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Abstract:The main goal of this study is to evaluate the eutrophication status under different management approaches in a basin, by combining the Biwa3D model (three-dimensional eutrophication analysis model) with several nutrient-reduction cases to calculate their effects on the water quality in Lake Biwa, Japan, and by applying the model to evaluate the cost-effectiveness between different scenarios designed to control eutrophication. A non-hydrostatic hydrodynamic model featuring very large eddy simulation (VLES) concepts, combined with ecological components that consider three types of phytoplankton species, one zooplankton, and nutrient cycling in each grid, is developed as the basic component of the research. Nitrogen and phosphorus loads from 111 sub-basins that supply Lake Biwa are set as the boundary condition for the numerical simulation. The chlorophyll a concentration calculated near the water intake, weighted in proportion to the intake discharge, is set as the water quality index. Transferable discharge permits are introduced for estimating the total reduction cost for achieving the objective water quality. Two types of scenario are tested: one considers the difference in location of nutrient reduction in the north and south basins, and the other ignores this difference. Initially, the effect of nutrient loads on the water quality of Lake Biwa was calculated using the Biwa3D model, using estimated nitrogen and phosphorus loads from the basin as the boundary condition. Transferable discharge permits were then designed according to the impact factor on each basin calculated by the model in order to compare the cost-effectiveness of the reduction scenarios. It is concluded that consideration of the characteristics of each basin and the distribution of effluent in designing transferable discharge permits reduces the total costs by around 4-25% of that required for achieving the target concentration of chlorophyll a.

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Spatial distribution and temporal variation of Microcystis species composition and microcystin concentration in Lake Biwa

Ozawa

Fujioka

Muranaka

et al. 2005

Environmental Toxicology

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Spatial and temporal variation in Microcystis species composition and microcystin concentration, quantified by enzyme-linked immunosorbent assay and high-performance liquid chromatography, were investigated during a 3-year period (1998-2000) in the Northern Basin of Lake Biwa. The Northern Basin generally had a concentration of 5 microg L(-1) or less, except at station 1 (Nagahama Bay) from July to October during the study period. The maximum concentration at station 1 was 22.7, 35.9, and 22.0 microg L(-1) in October of 1998, 1999, and 2000, respectively. Eleven species of cyanobacteria were observed: Microcystis aeruginosa, M. ichthyoblabe, M. novacekii, M. wesenbergii, Oscillatoria raciborskii, Anabaena oumiana, A. affinis, A. flos-aquae, A. ucrainica, A. smithii, and A. crassa. Of these, M. aeruginosa and M. wesenbergii were the main components observed. A high concentration of microcystin in the lake water was mostly a result of variation in the relative amount of toxic M. aeruginosa rather than of the total Microcystis cell number. This was supported by the analytical results for isolated strains. Microcystis spp. cell density in the Northern Basin appeared to increase gradually over the course of the study. This is the first study to have surveyed the Northern Basin of Lake Biwa, which supplies drinking water to 14 million people and is the largest lake in Japan.

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Benthic and Intermediate Nepheloid Layers in Lake Biwa

Cited by 6 publications

References 21 publications

Role of Photodegradation in the Fate of Fluorescent Whitening Agents (FWAs) in Lacustrine Environments

Role of Photodegradation in the Fate of Fluorescent Whitening Agents (FWAs) in Lacustrine Environments

Three‐dimensional eutrophication model for Lake Biwa and its application to the framework design of transferable discharge permits

Spatial distribution and temporal variation of Microcystis species composition and microcystin concentration in Lake Biwa

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