Viruses are by far the most abundant entities in marine environments, and are mainly phages that infect bacteria and archaea, which also are a significant component of marine ecosystem and a major force behind marine biogeochemical cycles. As a major source of mortality, viral lysis can release highly labile cellular components, both organic matters and inorganic nutrients, regulating the metabolism of its hosts and influencing the biogeochemical cycles. During infection, viruses could hijack the metabolic system of hosts for its own propagation, thereby changing the metabolism and metabolites of host cells. This paper summarized the effects of viruses on the metabolism of marine bacterioplankton at both the cellular and community level, and its influence on the cycling of ocean elements. Then, the potential impact of environmental factors was assessed on the influence of viruses upon bacterial metabolism. This paper will contribute to a comprehensive understanding of the role of microbes within marine biogeochemical cycles. 相似文献
The use of biopolymer to improve the performance of microbially induced carbonate precipitation (MICP)-treated sands is a novel and eco-friendly concept. This work found an anionic biopolymer, γ-polyglutamate (γ-PGA), could significantly improve the performance of MICP-treated sands. Comparing the control with absence of γ-PGA, the concentration of 0.1–9 g/L γ-PGA increased the compressive strength of MICP-treated sands by 1.54–3.96 times and significantly reduced the brittleness. The MICP process analysis and microstructural detection demonstrated that γ-PGA in the specimens provided many nucleation sites and templates for calcite generation, partially kept the bacterial urease activity by replacement of the bacteria as nucleation sites, thereby improving the calcite generation. The γ-PGA also cemented sand grains with calcite through the hydrogen bond-type intermolecular interactions. Both the calcite generation and the hydrogen bond-type intermolecular interactions by γ-PGA played vital roles in enhancing MICP for soil improvement. Additionally, γ-PGA, as a viscoelastic admixture between the crystals and sand grains, effectively dissipated the energy of stress and thus reduced the brittleness of MICP-treated sands. This is the first report on the application of anionic biopolymer to MICP technology. It provides a novel concept in promoting the efficiency and sustainability of MICP.
Lacustrine dolomite nucleation commonly occurs in modern and Neogene evaporitic alkaline lakes. As a result, ancient lacustrine microcrystalline dolomite has been conventionally interpreted to be formed in evaporitic environments. This study, however, suggests a non-evaporitic origin of dolomite precipitated in a volcanic–hydrothermal lake, where hydrothermal and volcanic processes interacted. The dolomite occurs in lacustrine fine-grained sedimentary rocks in the middle Permian Lucaogou Formation in the Santanghu intracontinental rift basin, north-west China. Dolostones are composed mainly of nano-sized to micron-sized dolomite with a euhedral to subhedral shape and a low degree of cation ordering, and are interlaminated and intercalated with tuffaceous shale. Non-dolomite minerals, including quartz, alkaline feldspars, smectite and magnesite mix with the dolomite in various proportions. The 87Sr/86Sr ratios (0.704528 to 0.705372, average = 0.705004) and δ26Mg values (−0.89 to −0.24‰, average = −0.55‰) of dolostones are similar to those of mantle rocks, indicating that the precipitates mainly originated from fluids that migrated upward from the mantle and were subject to water–rock reactions at a great depth. The δ18O values (−3.1 to −22.7‰, average = −14.0‰) of the dolostones indicate hydrothermal influence. The trace and rare earth element concentrations suggest a saline, anoxic and volcanic–hydrothermally-influenced subaqueous environment. In this subaqueous environment of Lucaogou lake, locally high temperatures and a supply of abundant Mg2+ from a deep source induced by volcanic–hydrothermal activity formed favourable chemical conditions for direct precipitation of primary dolomite. This study's findings deepen the understanding of the origin and processes of lacustrine primary dolomite formation and provide an alternative possibility for environmental interpretations of ancient dolostones. 相似文献
Artificial recharge is an effective remediation measure for controlling groundwater level and subsidence in many coastal cities in China. Hydraulic parameters estimated by pumping tests are often used in the design of both pumping and recharge systems. However, the hydraulic parameters in the recharge process have been found to differ from those in the pumping process and should be studied in greater detail. Eight single-well pumping and recharge tests were conducted within a confined aquifer in a soft soil area in the city of Tianjin, and the differences in wellbore storage influences and well losses between the recharge and pumping processes were examined. Furthermore, based on the Hantush and Jacob model, an algorithm combining the Levenberg–Marquardt algorithm (LMA) and genetic algorithm (GA) was employed for estimation of the hydraulic parameters. The results illustrated that the combined algorithm eliminating wellbore storage influences could provide hydraulic parameters from which the groundwater level variation could be accurately simulated. The hydraulic conductivity and specific storage values obtained in the pumping tests were higher than those obtained in the recharge tests. In addition to slight plugging of the recharge well, the specific storage differences could be explained by the compression and rebound deformation characteristics of sand in the confined aquifer. The specific storage estimated by pumping tests should be adjusted when applied in groundwater recharge calculation.
Izvestiya, Physics of the Solid Earth - Abstract—We studied historical and paleoseismic deformations in the southern Issyk-Kul depression—on the territory of adyrs (piedmonts) of the... 相似文献