[Water Chemistry and Characteristics of Dissolved Organic Carbon During the Wet Season in Wulixia Reservoir, SW China].

In recent years, scientists have focused on the karst carbon cycle. To better understand the hydrochemical characteristics and the physical-chemical properties of DOC in the wet season in karst areas, the water chemistry and DOC distribution characteristics in Wulixia reservoir were analyzed. The molecular weight of the water organic matter was analyzed based on the UV absorption spectrum. The results showed that the water chemistry of Wulixia reservoir was HCO3-Ca ·Mg, the nutrient status of the water body was of the medium nutrient type, and the water maintained a good quality. The DOC mass concentration was lower in the wet season than in the dry season, and DOC was the main component of TOC. The DOC mass concentration tended to decrease from the surface to the bottom in a vertical direction. Chl-a and DIC were the main factors affecting the DOC vertical distribution. The organic matter in the reservoir area related to the absorption spectrum parameters of S275~295, M, SUVA254, and E253/E203 showed that the water was dominated by constituents with small molecular weight, a high proportion of fulvic acid, low proportion of humic acid, and weak aroma. The results showed that the organic matter in the reservoir area was readily consumed by microbial bioactivity and that it played an active role in the carbon cycle of the reservoir. It also showed that the DOC endogenous characteristics of the reservoir were strong and provided a sufficient carbon source for heterotrophic microbes.

[Carbon Metabolism Characteristics of the Karst Soil Microbial Community for Pb-Zn Mine Tailings].

BIOLOG and 18S rRNA PCR-DGGE methods were used to estimate the characteristics of carbon source metabolism of the soil microbial community as well as the relationship between soil fungi and soil organic carbon in different karst land use types (corn field, citrus field, and paddy field) contaminated by Pb-Zn tailings at Sidi Village, Yangshuo, Guangxi Zhuang Autonomous Region, SW China. It was found that the concentrations of Pb, Zn, Cu, and Cd were highest in the paddy field, followed by the corn field, citrus field, and control group (dry field). In addition, the geo-accumulation index indicated that the heavy metal pollution at this area was caused by Pb and Cd and that Cd was the key environmental risk factor. With the Pb-Zn tailings, there was low microbial biomass carbon, biological entropy, and microbial carbon source metabolism in the soil samples. The highest soil organic carbon and heavy metal concentrations were found in the paddy field, followed by the corn field and citrus field. According to the DDGE results, it was found that Pycnoporus sp. ZW02.30 was found in control group soils, Fusarium solani and Fusarium oxysporum were found in the corn field and citrus field, and Penicillium decumbens was found in citrus field. These were involved in the degradation of sugars, such as starch, cellulose, hemicellulose, and lignin. However, the fungi were not found in the paddy field. Based on the low functional diversity of the soil microbial community and biological entropy as well as the high soil organic carbon concentration in the paddy field, it was concluded that soil microbial carbohydrate metabolism and the mineralization rate of the soil organic carbon was controlled by soil microorganisms, especially fungi, in different land use soils in the karst area contaminated by Pb-Zn tailings.

[Distinguishing the Properties and Sources of the Dissolved Organic Matter in Karst Reservoir Water During Winter Using Three-Dimensional Fluorescence Spectrum Technology:A Case Study in Wulixia Reservoir of Guangxi Province].

In recent years, the fluorescence spectrum technology has been widely applied to study the physical and chemical properties of dissolved organic matter (DOM) in natural water. In order to reveal the properties of the dissolved organic matter in reservoir water, the three-dimensional fluorescence spectrum and the parallel factor analysis were used to determine the properties of DOM and its sources in the Wulixia reservoir during the winter of 2016. Moreover, the chemical characteristics of water and the relative proportion of DOM fluorescent components were estimated. Results show that:① Ca2+ and HCO3- are the main cations and anions in the Wulixia reservoir during winter. The water is mainly controlled by the carbonate balance system and dissolved organic carbon (DOC) accounted for about 91% of total organic carbon (TOC). ③ DOM from the Wulixia reservoir can be divided into three components:fulvic acid, humic acid, and tryptophan. ③ The parameters, fluorescence index, humification index, biological index, and freshness index show the existence of DOM in the Wulixia reservoir. Microorganisms have a significant effect on DOM composition.

Fast screening target sites for RNA interference using a cell-free system.

A fast and simple procedure to screen target sites for RNA interference by using RNA in a cell-free system of Hela cells, and then evaluating the efficiency by Northern blotting, is described. This procedure produces results with an identical reliability compared to those described previously but which are more time-consuming than this present method.