The remediation of polycyclic aromatic hydrocarbon contaminated soil by immobilized microorganisms using distiller's grains.

Polycyclic aromatic hydrocarbons are a persistent organic pollutant, and their biodegradation in the soil is often limited due to the limited degradation ability of indigenous bacteria and the low activity of exogenous PAH degrading bacteria. Immobilized microbial technology can protect microorganisms from the impact of harsh environments, and distiller's grains have the potential as carriers for microbial immobilization. This study aims to use distiller's grains as a microbial carrier, investigate the feasibility of immobilized microorganisms using distiller's grains for remediation of PAH contaminated soil; explore the relationship between soil nutrient content, consumption, and PAH degradation rate; and reveal the mechanism of bioremediation from the perspective of soil enzyme activity and microbial community composition. The results showed that after 72 days of remediation, the removal rates of phenanthrene and pyrene in the treatment of immobilized microorganisms in distiller grains reached 91.78% and 58.59%, respectively. Distiller grains can serve as a carrier for microorganisms, providing them with shelter and nutrients to enhance their chance of survival. Additionally, they can regulate the composition of soil particles and improve aeration, thereby increasing the efficiency of PAH degradation in soil.

Driving Factors Influencing Soil Microbial Community Succession of Coal Mining Subsidence Areas during Natural Recovery in Inner Mongolia Grasslands.

Soil microorganisms significantly influence the energy flow and material cycle of soil ecosystems, making them highly susceptible to environmental changes, such as those induced by mining activities. Studying the succession of soil microbial communities after mining subsidence is crucial for comprehending the significance of soil microbes in the natural recovery process following subsidence. Therefore, the soil properties, vegetation communities, and soil microbial communities of the subsidence area, as well as unexploited areas, were analyzed during the natural restoration process (1, 2, 5, 10, and 15 years). The results demonstrate that mining subsidence has a significant impact on the aboveground vegetation community, soil properties, and microbiological community. Following an extended period of natural recovery, a new stable state has emerged, which differs from that observed in non-subsidence areas. The total nitrogen, nitrate nitrogen, and ammonium nitrogen amounts may be key factors driving the natural recovery of bacterial communities, and total potassium and available potassium may be key factors driving the natural recovery of fungal communities. The natural recovery mechanism of soil microorganisms was analyzed along with the changes related to vegetation and soil physicochemical properties. The mechanism was explained from three perspectives, namely, plant-led, soil-led, and soil-microbial-led, which could provide a theoretical basis for the natural restoration of grassland ecosystems and provide guidance for the treatment of coal mining subsidence areas.

Unsteady free-surface waves due to a submerged body moving in a viscous fluid.

Unsteady viscous free-surface waves generated by a three-dimensional submerged body moving in an incompressible fluid of infinite depth are investigated analytically. It is assumed that the body experiences a Heaviside step change in velocity at the initial instant. Two categories of the velocity change, (i) from zero to a constant and (ii) from a constant to zero, will be analyzed. The flow is assumed to be laminar and the submerged body is mathematically represented by an Oseenlet. The Green functions for the unbounded unsteady Oseen flows are derived. The solutions in closed integral form for the wave profiles are given. By employing Lighthill's two-stage scheme, the asymptotic representations of free-surface waves in the far wake for large Reynolds numbers are derived. It is shown that the effects of viscosity and submergence depth on the free-surface wave profiles are respectively expressed by the exponential decay factors. Furthermore, the unsteady wave system due to the suddenly starting body consists of two families of steady-state waves and two families of nonstationary waves, which are confined within a finite region. As time increases, the waves move away from the body and the finite region extends to an infinite V-shaped region. It is found that the nonstationary waves are the transient response to the suddenly started motion of the body. The waves due to a suddenly stopping body consist of a transient component only, which vanish as time approaches infinity.