Weidong Zhao

Prolonged and intensive mining operations in the Huainan Coal Mining Area (HCMA), have damaged its environment, jeopardizing the Huainan city’s sustainability. However, there is a lack of studies on the primary influence factors and evolutionary patterns of the ecological environment vulnerability (EEV) in the HCMA. Therefore, this study employed 12 indices such as elevation, slope, and soil type to establish the evaluation index system, used the sensitivity-resilience-pressure (SRP) model and analytic hierarchy process (AHP) to study the evolutionary patterns and primary influencing factors of the EEV in the HCMA from 2010 to 2020. The results showed that (1) in terms of time, EEV was generally moderate and gradually weakening. In terms of spatial distribution, EEV was generally high in the northwest, low in the central, and highest in the southeast, decreasing then increasing from northwest to southeast. (2) The ecological conditions in the northern new coal mining area and the southern old coal mining area were generally improving. Coal mining and vegetation cover primarily affected the north, and coal mining and ecological restoration projects primarily affected the south. The southeastern built-up area’s ecological environment showed minimal change and it was primarily impacted by urban construction activities. (3) Coal mining and the implementation of ecological environment management and restoration projects are the primary factors influencing the EEV of the HCMA. The ecological environment management and restoration projects such as filling mining, comprehensive recycling and utilization of coal gangue, backfilling of subsidence areas, in CMSWA can reduce the ecological vulnerability of local areas and improve their ecological environment.

Previous studies show aquifer heterogeneity has an important influence on removal of Cr(VI) in groundwater, but little research has revealed the role of aquifer heterogeneity in Cr(VI) migration and how effective using emulsified vegetable oil is for Cr(VI) removal in groundwater. We simulated a laboratory sand-packed box over a 50-day period to research the effects of aquifer heterogeneity on Cr(VI) diffusion and also injected emulsified vegetable oil (EVO) into the permeable reactive barrier (PRB) filled with compost to investigate the influences of aquifer heterogeneity on Cr(VI) removal from groundwater, with fixed conditions of simulated true water temperature of shallow groundwater (19±0.5 ℃), hydraulic gradient (3‰), the Suzhou coal mining area (Anhui, China). The results show that aquifer heterogeneity had the significant impact on Cr(VI) diffusion with an overall diffusion direction of Cr(VI) that was from the upper left corner to the lower right corner along the direction of the groundwater; permeable reactive barrier would effectively remove Cr(VI) from groundwater in heterogeneous aquifer due to the vertical movement of microorganisms between different aqueous media; coarse sand and medium sand showed high performance in Cr(VI) diffusion, with a slight superiority to fine sand; following a one-time EVO injection, a considerably stable and uniform effective remove zone similar to the shape of ∑ was formed in the heterogeneous aquifer, and its Cr(VI) removal efficiency was over 95%.

Solute transport in a single vertical fracture (SVF) cannot be reliably described by the classical advection-dispersion equation (ADE) model, due to the heterogeneity nature of fracture. This study conducted a group of experiments to investigate chloride ion transport in the SVFs under different rough-walled conditions, and then applied a time fractional advection-dispersion equation (F-ADE) model to offer an accurate description. A comparison between F-ADE model and a classical ADE model in describing experimental data, was also carried out. Results show that the FADE model is better than the ADE model in describing the breakthrough curve and heavy-tail phenomenon of solute transport in the fracture. Especially in the experiments with lower flow rate and higher roughness fracture, the FADE model can offer an accurate description, indicating that it is a promising tool for characterizing solute transport heterogeneous vertical fracture.