New insights into identifying sediment phosphorus sources in river-lake coupled system: A framework for optimizing microbial community fingerprints.

Identifying sediment phosphorus sources in river-lake coupled system is a question in developing preferential control strategies for phosphorus. As sediments adsorbed phosphorus and microbes would be transported with changing hydrodynamic, the phosphorus source-specific microbial community fingerprints shed light on determining the major sediment phosphorus sources. However, the identification of microbial community fingerprints is a challenge because both microbial succession and hydrological characteristics of river-lake systems would affect the stability of fingerprints. Therefore, this study provided a framework for optimizing phosphorus source-specific microbial community fingerprints, and attempted to identify the major sources of sediment phosphorus in river-lake coupled ecosystem. Meiliang Lake is one of the highly eutrophic area in Taihu Lake, where the sediments, bacterial communities, and phosphorus had a close relationship. Through analyzing the connectivity of microbes along water continuum, a microbial fingerprints candidate database was constructed. The phosphorus-related bacterial communities were screened and optimized by comparing the difference of predicted results between upstream and downstream, forming the stable microbial community fingerprints which consisted of Bacteroidia, Bacilli, Clostridia, and other species at the class level. SourceTracker results that based on the optimized phosphorus source-specific microbial community fingerprints indicated that the major sediment phosphorus sources to Meiliang Lake were Liangxi River, Wujingang River, and Donghuandi River, with the relative standard deviations ranging from 2.59% to 27.56%. The accuracy of phosphorus source apportionments was further confirmed based on the composite pollution index and hydrodynamic condition. This study put forward suggestions on how to improve the stability of microbial community fingerprints, and would help to improve the understanding of applying microbial source tracking method to identify the sources of abiotic pollution like sediment phosphorus.

Adsorption behavior of azo dye C. I. acid red 14 in aqueous solution on surface soils.

Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior of azo dyes in aqueous solution on DG06, GSE17200, and GSE17201 soils using C. I. Acid Red 14 (AR14) as example. The experimental results indicate that the Freundlich model expresses the adsorption isotherm better than the Langmuir model and the pseudo-second-order model achieves adsorption of AR14 on the three soils well. Based on the pseudo-second-order model, the adsorption thermodynamic of AR14 on DG06 soil have been studied and the thermodynamics parameter of deltaG0 is determined and deltaG0 value shows the adsorption process of AR14 on DG06 is mainly physical in nature. Furthermore, the effects of temperature, pH and salinity (NaCl) on adsorption have been investigated. The decrease in pH or the increase in salinity enhances the adsorption of AR14 by DG06, GSE17200, and GSE17201.

[Preliminary study on the relationship between the water quality and the aquatic biological health status of Taihu Lake].

Nemerow index method and benthic index of biological integrity method have been used to evaluate the water quality and the health status of aquatic organisms in Taihu Lake during 2008-2012, respectively. The results showed that the water in the whole Taihu Lake was polluted, and the aquatic organisms were basically kept in sub-health state. The results of the water quality and aquatic biological assessment exhibited generally the same trend at a large scale. In the view of the whole lake, the water quality and aquatic health status in East Taihu Lake were better than those of the other parts. In the view of time, the water quality and aquatic health status during 2008-2010 were worse than those of the lake in the 1960s. The results observed from the two assessment methods were not the same during short periods of time and in some special sample points, which were attributed to the following reasons: (1) the two assessment methods focused on different time scales and (2) the aquatic biological health status was related to the water quality as well as the environmental habitat. Since organic pollutants and excessive nutrients were the main factors influencing the water quality and aquatic health status, reducing the concentrations of the organic pollutants and inorganic nutrients should be a feasible method to improve the water quality and the ecological function of Taihu Lake.