Tao Li,Yuhua Li,Xike Zhang,Jiawei Yuan,Junkang Guo,Pan Wang,Gehong Wei,Chun Chen
The widespread application of metal-based nanoparticle (MNPs)/reduced graphene oxide (rGO) composites inevitably leads to their release into soils. However, we lack a detailed understanding of the bacterial community response to MNPs-rGO exposure in farmland soils. Here, we conducted a soil microcosm experiment to analyze the potential impact of MNPs-rGO on bacterial communities in two field soils via high-throughput sequencing. The change in alpha diversity of bacterial communities was more susceptible to Ag-rGO and ZnO-rGO treatments than CuO-rGO. In both soils, MNPs-rGO significantly changed the bacterial community structure even at a low dose (1 mg kg −1 ). The bacterial community structure was most strongly affected by Ag-rGO at 30 days, but the greatest changes occurred in ZnO-rGO at 60 days. The differences in soil properties could shape bacterial communities to MNPs-rGO exposure. Distance-based redundancy analysis and functional annotation of prokaryotic taxa showed that some bacterial species associated with nitrogen cycling were greatly influenced by Ag-rGO and ZnO-rGO exposure. In sum, Ag-rGO and ZnO-rGO may potentially affect bacterial communities and nitrogen turnover under long-term realistic field exposure. These findings present a perspective on the response of bacterial communities to MNPs-rGO and provide a fundamental basis for estimating the ecological behavior of MNPs-rGO.
Adsorption desorption is an important behavior affecting the migration of phenanthrene in soil. In this study, three typical soils of loess, silts and silty sand in Guanzhong Basin, Shaanxi Province, China were used as adsorbents. Batch equilibrium experiments were carried out to study the adsorption desorption kinetics and isotherm of phenanthrene in different soils. Response surface method (RSM) was used to study the effects of temperature, pH, phenanthrene concentration and organic matter content on soil adsorption of phenanthrene. The results showed that after adsorption, the outline of soil particles became more blurred and the degree of cementation increased. The kinetic adsorption of phenanthrene by soil conforms to the quasi second-order kinetic model, and the adsorption desorption isotherm is nonlinear and conforms to the Freundlich model. Due to the difference of soil properties, the adsorption amount of phenanthrene by soil is loess > silty sand > silts. The thermodynamic results show that the adsorption of phenanthrene by soil is spontaneous and endothermic, and the desorption is spontaneous and exothermic. Through RSM, the interaction between phenanthrene concentration and soil organic matter in Loess and silts is significant, and the interaction between temperature and soil organic matter in silty sand is significant. Among the four factors affecting the adsorption rate of loess, silts and silty sand, soil organic matter is the most significant. The theoretical optimum adsorption rates of loess, silts and silty sand are 98.89%, 96.59% and 93.37% respectively.
Xing Xing Wang,Guan Cheng Jiang,Guo Shuai Wang,Li Li Yang,Yin Bo He,Xiao Ya Wu
In South China Sea, the natural gas hydrates are usually reserved in argillaceous siltstones. These argillaceous siltstones are weakly cemented and incorporated with the solid hydrates. During the drilling process, the natural gas hydrates may decompose unexpectedly, resulting in the wellbore collapse. To improve the stability of the wellbore, this study develops a wellbore strengthener for water-based drilling fluids used in argillaceous siltstones. Tannic acid/polyvinyl (TA/PVA) alcohol has been adopted for preparing the wellbore stabilizer. A series of experiments have been conducted to investigate the effects of newly developed wellbore strengthener on the mechanical properties of the argillaceous siltstones as well as its mechanisms on the wellbore stability. The experimental results show that the wellbore strengthener developed in this study can significantly improve the compressive strengths of the argillaceous siltstone cores. The AFM characterizations indicate that the adhesion force between the silica (the major compound in argillaceous siltstones) microspheres and the wellbore strengthener can reach up to 2138 nN. Moreover, the SEM images visually show good cementation of the argillaceous siltstones after being treated by the wellbore strengthener. In addition, the wellbore strengthener can also assist in reducing the fluid losses of water-based drilling fluids. It is hopeful that the wellbore strengthener provided in this study help the development of underwater natural gas hydrates.
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