No abstract

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).

Lake Puma Yumco is a typical alpine lake (altitude 5030 m) located in the pre-Himalayas of Tibet, China, and this study was the first limnological investigation ever conducted on it. Lake Puma Yumco (28°34ЈN, 90°24ЈE) has the following morphometric properties: maximum length 31 km, maximum width 14 km, mean width 9 km, shoreline 90 km, surface area 280 km 2 , and shoreline development 1.5. Transparency was approximately 10 m, even in the thawing season. The extinction coefficient of the lake water was calculated as 0.15 m Ϫ1 . Annual maximum transparency was estimated from the depth of the Chara zone to be 30 m. Dissolved oxygen was 7 mg O 2 l Ϫ1 and showed saturated values, and salinity was 360 mg l Ϫ1 . The chemical type of the lake water was Mg-Ca-HCO 3 -SO 4 , and it was slightly alkaline in character. Total nitrogenous nutrients (sum of ammonia, nitrite, nitrate, and urea nitrogen), phosphate, and silicate were extremely low at 1, 0.02, and 9 µM, respectively. Dissolved organic carbon, nitrogen, and phosphorus concentrations were 160, 11, and 0.08 µM and the molar ratio was calculated as 2100 : 140 : 1. Chlorophyll a concentration was 0.2 mg m Ϫ3 . Phytoplankton and zooplankton were dominated by Aphanocapsa sp. and Diaptomidae. Both nitrogen and phosphorus appear to be the limiting parameters for phytoplankton growth. Organic carbon and nitrogen contents in lake sediments were low and the sediments contained a large amount of CaCO 3 . The grain size of sediment was that of silt-sand in most cases. The present results indicate that the pre-Himalayan alpine freshwater Lake Puma Yumco is an ultraoligotrophic lake.

Temporal changes of biomass and dominant species in benthic algal communities were investigated in a littoral sand-beach zone in the north basin of Lake Biwa

No abstract