Basic limnological study in an alpine Lake Puma Yumco, the pre-Himalayas, China

Lake Puma Yumco is a typical alpine lake (altitude; 5,030m) located in the pre-Himalayas of Tibet, China. This study was the first limnologicak investigation. Puma Yumco (28°34'N,90°24'E) has the following morphometric properties: maximum length of 31 km; maximum width of 14 km; mean width of 9 km; shoreline of 90 km; surface area of 280 km²; shoreline development of 1.5. Transparency was approximately 10 m. Dissolved oxygen was l7 mg O₂ L⁻¹ and showed saturated values. Saljnity was 360 mg L⁻¹. The chemical type of the lake water was Mg-Ca-HCO₃-SO₄. Total nitrogenous nutrients and phosphate were extremely low at 1μM and 0.02 μM, respetively. Chlorophyll-a concentration was 0.2 mg chl.a m⁻³. Phytoplankton and zooplankton were dominated by Aphanocapsa. and Diaptomidae. The grain size of lake sediment was that of silt in most cases.Article信州大学山地水環境教育研究センター研究報告 2: 83-90(2004)departmental bulletin pape

Dynamics of dissolved and bubbled methane in Lake Youngrang and HwaJlnPO, Korea

Article信州大学山地水環境教育研究センター研究報告 6: 69-72(2010)departmental bulletin pape

Highly efficient silica sink in monomictic Lake Biwa in Japan

In order to clarify the mechanisms underlying high efficiency of the silica sink in monomictic Lake Biwa in Japan, vertical flux of biogenic silica (BSi) was measured using sediment traps over a period of 15 months. The sediment traps were deployed at depths of 30 and 70 m. On a global scale, BSi fluxes in Lake Biwa were very high, ranging from 20 to 1087 mg Si.m−2.d−1 at the 30 m trap and 12–999 mg Si.m−2.d−1 at the 70 m trap throughout the observation period. The BSi fluxes at both traps increased significantly during the winter period and the ratio of BSi fluxes in the winter period to annual BSi fluxes ranged from 27 to 62%. In the winter period, when nutrients are supplied from the hypolimnion to the epilimnion, the distribution of photosynthetically active diatoms was almost homogeneous in all layers, including the aphotic layer. At this time, the diatoms assimilated dissolved silica (DSi) in a wider layer containing a part of aphotic layer in order to produce rigid frustules, which accumulated rapidly in bottom sediments as DSi concentration in the water column decreased. Thus, size of the silica sink in Lake Biwa is enhanced during the winter holomictic mixing period through interaction between physical (thermocline disruption: transfer of diatoms to deep layers by vertical convection), chemical (nutrient supply from deep layers) and biological (dominance of active diatoms in all layers) processes

Insoluble Fe-Humic Acid Complex as a Solid-Phase Electron Mediator for Microbial Reductive Dechlorination

We report that the insoluble Fe-HA complex, which was synthesized with both commercial Aldrich humic acid (HA) and natural HA, functions as a solid-phase electron mediator (EM) for the anaerobic microbial dechlorination of pentachlorophenol. Spectroscopic characterizations and sequential Fe extraction demonstrated that the Fe-HA complex was predominated with Na₄P₂O₇-labile Fe (represented as the organically bound Fe fraction) and poorly ordered Fe fraction (the fraction left in the residue after the sequential extraction), which were associated with different possible binding processes with carboxylate and phenolic groups. The change in the electron-mediating activity caused by Fe extraction indicated that the electron-mediating function of the Fe-HA complex is attributable to the Na₄P₂O₇-labile Fe fraction. The Fe-HA complex also accelerated the microbial reduction of Fe­(III) oxide, which suggested the presence of multiple electron-mediating functions in the complex. The electron shuttle assay showed that the Fe-HA complex had an electron-accepting capacity of 0.82 mequiv g^–1 dry Fe-HA complex. The presence of redox-active moieties in the Fe-HA complex was verified by cyclic voltammetry analysis of the sample after electrical reduction, with a redox potential estimated at 0.02 V (vs a standard hydrogen electrode)