Nitrate dynamics during impoundment and flood periods in a subtropical karst reservoir: Hongfeng Lake, Southwestern China.

Nitrogenous species, particularly nitrate, are some of the most significant contaminants in freshwater rivers and lakes in China, posing a significant threat to human and ecosystem health. To identify the major nitrate sources and transformation processes in a subtropical karst lake (Hongfeng, HF) in Southwest China, two sampling campaigns involving three lake profiles were conducted during the impoundment period (April) and flood period (August). Hydro-chemistry parameters, concentration of nitrogenous species, and dual isotopes of nitrate were analyzed.

Lentzea pudingi sp. nov., isolated from a weathered limestone sample in a karst area.

A novel Gram-stain-positive, aerobic bacterium, designated strain DHS C021, was isolated from a limestone sample collected from the Puding Karst Ecosystem Research Station of Guizhou Province, southwest China. This strain developed branched vegetative mycelia, and its aerial mycelia fragmented into rod-shaped spores. The cell-wall peptidoglycan contained meso-diaminopimelic acid and the whole-cell sugars comprised galactose, ribose and mannose.

Impacts of hydrologic variations on chemical weathering and solute sources in the Min River basin, Himalayan-Tibetan region.

Feedback between hydrologic variations and chemical weathering is thought to play a crucial role in modulating global carbon cycling. The mechanisms associated with the impacts of hydrologic variations on solute sources and chemical weathering were evaluated by examining the relationships between river discharge and hydrochemistry based on high-frequency sampling of the Min River, which originates in the Himalayan-Tibetan region. Fluid transit times and flow pathways vary with changes in discharge, thereby affecting various biogeochemical processes.

Sensitivity of chemical weathering and dissolved carbon dynamics to hydrological conditions in a typical karst river.

To better understand the mechanisms that hydrological conditions control chemical weathering and carbon dynamics in the large rivers, we investigated hydrochemistry and carbon isotopic compositions of dissolved inorganic carbon (DIC) based on high-frequency sampling in the Wujiang River draining the carbonate area in southwestern China. Concentrations of major dissolved solute do not strictly follow the dilution process with increasing discharge, and biogeochemical processes lead to variability in the concentration-discharge relationships. Temporal variations of dissolved solutes are closely related to weathering characteristics and hydrological conditions in the rainy seasons.

Carbonate Mineral Formation under the Influence of Limestone-Colonizing Actinobacteria: Morphology and Polymorphism.

Microorganisms and their biomineralization processes are widespread in almost every environment on earth. In this work, Streptomyces luteogriseus DHS C014, a dominant lithophilous actinobacteria isolated from microbial mats on limestone rocks, was used to investigate its potential biomineralization to allow a better understanding of bacterial contributions to carbonate mineralization in nature. The ammonium carbonate free-drift method was used with mycelium pellets, culture supernatant, and spent culture of the strain.

Lentzea guizhouensis sp. nov., a novel lithophilous actinobacterium isolated from limestone from the Karst area, Guizhou, China.

A novel filamentous actinobacterium, designated strain DHS C013(T), was isolated from limestone collected in Guizhou Province, South-west China. Morphological and chemotaxonomic characteristics of the strain support its assignment to the genus Lentzea. Phylogenetic analyses showed that strain DHS C013(T) is closely related to Lentzea jiangxiensis FXJ1.

[Chemical characterization of rainwater in a karst rural site: a case study of Puding, China].

Rainwater samples of a karst rural site in Puding County, Guizhou Province, China over a period of one year (2008) were collected and the major ion concentrations were measured. The pH of samples varied from 4.6 to 7.

Short-term field observations of nitrous oxide saturations in Lake Taihu, China: the need for high temporal resolution studies.

The incomplete understanding of the processes which control aquatic nitrous oxide (N2O) production is partially due to a lack of onsite data with which to describe the temporal resolution of N2O production. To help resolve this, we directly measured the N2O saturation (relative to atmospheric partial pressure) on an hourly basis over two survey periods (July and September 2003) in Lake Taihu, a large eutrophic lake in eastern China. July N2O saturations displayed a distinct diurnal pattern, opposite to those observed by others in subtropical streams, but similar to N2O emissions observed from incubated estuarine sediments.

The spatial distribution and emission of nitrous oxide (N2O) in a large eutrophic lake in eastern China: anthropogenic effects.

The emission of N(2)O from China is globally significant, but relatively few direct observations have been made in many of the fresh water environments most likely to be important sites of N(2)O production. In this paper, N(2)O saturations were examined in the ecologically heterogeneous, eutrophied, Lake Taihu, as well as in surrounding rivers in eastern China. The emissions of N(2)O were estimated and compared with those from other landscapes within the Lake Taihu drainage basin.

Carbon biogeochemistry of ground water, Guiyang, southwest China.

Variations in the concentrations and isotopic compositions (delta13C(DIC)) of dissolved inorganic carbon (DIC) reflect contamination and biogeochemical cycling of the carbon in ground water. In order to understand contamination and biogeochemical cycling of DIC, we carried out research on the geochemistry of ground water of Guiyang, the capital city of Guizhou Province, China. Results show that ground water is mainly characterized by SO4.