Huan Shen

The parameter variations in the aquitard have an important influence on the migration laws of contaminants in the aquitard. In order to study the influence of dynamic changes in parameters during pumping on the migration laws of Light Non-aqueous Phase Liquid (LNAPL) in the aquitard, the one-dimensional consolidation and groundwater flow equations for the aquitard were employed to derive the governing equations for the migration of LNAPL in the aquitard. A self-designed experimental platform was developed to investigate the effects of the pore water pressure, consolidation deformation, and pumping rate on LNAPL migration during pumping. The laboratory experimental results indicated that during pumping, the migration behavior of LNAPL in the aquitard typically exhibited a trend toward the pumping well and the overlying aquifer. The closer to the pumping well, the greater the change in the pore water pressure, the greater the amount of consolidation deformation, the earlier the state of densification, and the slower the migration rate of LNAPL in the aquitard. The nearer to the bottom of the aquitard, the larger the amount of consolidation deformation in the aquitard and the slower the migration rate of LNAPL in the aquitard. Also, the pumping rate had an important influence on groundwater flow movement and contaminant migration. The characteristics of parameter variations in the aquitard and laws of LNAPL migration during pumping were systematically studied and analyzed; these research results can provide a reference for the prediction and remediation of LNAPL in contaminated sites.

Research on the migration behaviors of contaminants in the aquitard has been deficient for an extended period. Clay is commonly employed as an impermeable layer or barrier to stop the migration of contaminants. However, under certain conditions, the clay layer may exhibit permeability to water, thereby allowing contaminants to infiltrate and potentially contaminate adjacent aquifers. Consequently, it holds immense importance to scrutinize and investigate the migration characteristics of light non-aqueous phase liquid (LNAPL) within the aquitard for the purposes of groundwater pollution control and remediation. To evaluate the environmental risk posed by organic contaminants in the aquitard, an experimental model was formulated and devised to monitor the LNAPL concentration in the aquitard under pumping conditions. The correlation between pumping rate and LNAPL concentration was investigated. A self-developed plexiglass sandbox model was used to simulate the migration characteristics of LNAPL in the aquitard under pumping conditions. Four experimental scenarios were designed, varying pumping rates, aquitard thicknesses, and groundwater level changes. The LNAPL concentration curve was derived by systematically tracking and analyzing LNAPL levels at various locations within the aquitard. The results indicated that higher pumping rates corresponded to increased migration of LNAPL, resulting in greater LNAPL ingress into the pumping well during extraction. A thicker aquitard demonstrated a more pronounced inhibitory effect on LNAPL, leading to an extended penetration time of LNAPL within the aquitard. The drawdown within the aquitard exerted a discernible influence on LNAPL migration, with the LNAPL concentration continuing to decrease in tandem with declining water levels during pumping. These research findings can establish a scientific foundation for the control and remediation of contaminants within aquitards.

As a technology for in situ treatment and remediation of groundwater contamination, permeable reaction barriers (PRBs) have the advantages of operational efficiency and low infrastructure footprint. In order to clarify previous research results and provide references for future research on remediation of contamination by dissolved oil contaminants in groundwater, the focus of this article is to review and compare the application of PRBs for the removal of dissolved oil contaminants and highlights the research gaps. We concentrate on the relationship between structure design, media types and service life of PRBs, along with groundwater flow velocity, temperature, pH and other hydrochemical conditions. These influencing factors are used to make a detailed explanation and analysis of remediation of oil contamination in groundwater. The current application of PRBs is mainly limited to heavy metals and inorganics, rather than persistent organics such as components in oil. The application of new PRB materials and combination of multiple remediation technologies in oil‐contaminated sites will be the focus of future research.

A coupled model has been developed to simulate groundwater flow in fractured karst systems according to the complex geological and karst hydrogeological conditions of the dam site, where a 3D mathematical model based on Boussinesq equation was used to describe the movement of groundwater flow in fractured medium, and a 1D conduit model for karst medium. The model was solved with the continuous hydraulic heads at the common boundaries. The hydraulic conductivities of karst medium were determined by geometrical parameters and flux of pipes. Furthermore, the permeability parameters for fractured medium were calibrated by the measured and calculated groundwater levels. The calibrated model was employed to predict the variation of groundwater flow field and leakage from the karst pipes and underground powerhouse during the reservoir operation. The simulated results showed that the groundwater level of the powerhouse had decreased by about 2–5 m. The water level of conveyance pipeline had risen by 10–20 m, and the water level on both banks had risen by 15–25 m. The leakage of karst conduits for impervious failure was larger than that for normal seepage control. In addition, the leakage of the powerhouse was estimated to be about 1000–3000 m³/d, and the seepage control of karst pipes had little influence on the leakage of underground powerhouse.

Based on the geological and hydrogeological conditions, and in situ hydrogeological tests of the emergency groundwater source in Nantong City, China, a 3D numerical model of the heterogeneous anisotropy in the study area was established and calibrated using data from pumping and recovery tests. The calibrated model was used to simulate and predict the water level of the depression cone during the emergency pumping and water level recovery. The results showed that after seven days of pumping, the water level in the center of the depression cone ranged from −51 m to −55 m, and compared with the initial water level, the water level dropped by 29 m to 32 m. The calculated water level has a small deviation compared with that of the analytical solution, which indicates the reliability and rationality of the numerical solution. Furthermore, during water level recovery, the water level of pumping wells and its surroundings rose rapidly, which was a difference of about 0.28 m from the initial water level after 30 days, indicating that the groundwater level had recovered to the state before pumping. Due to the emergency pumping time is not long, the water levels of Tonglu Canal, surrounding residential wells, and other aquifers will not be affected. After stopping pumping, the water level recovers quickly, so the change of water level in a short time will not lead to large land subsidence and has little impact on the surrounding environment.

In this paper, we propose an improved lane determination algorithm to increase the accuracy and stability of the driving assistance system in an automatic driving system when determining the position of a lane in a complex driving environment. Based on the proposed single-scale Retinex enhancement and Gamma correction fusion image enhancement algorithm, we introduce a Hidden Markov Model improvement road segmentation algorithm to extract lane feature points by separating the region of interest and at the same time, we design a vanishing line detection technology based on improved V-disparity map. Experimental data show that the proposed algorithm has excellent detection capabilities and can detect main lanes in complex road environments such as shadows, traffic congestion, and uneven lighting.

With the rapid growth of the global demand for low-carbon energy, the development of hydropower has ushered in new development, but the ecological and environmental problems caused by this cannot be ignored. Taking the safe and efficient operation of water conservancy projects as the goal, this paper took the Maling Water Conservancy Project (MWCP) as an example to predict and evaluate the ecological environment risks of water conservancy projects. Based on the on-site geological surveys and experiments, the big well method and the long narrow horizontal tunnel method were used to estimate the water inflow from the underground caverns. The contaminant migration model was used to predict and analyze the groundwater quality. The impact of the MWCP on the surrounding environment was systematically analyzed and evaluated. The results showed that the estimated water inflow from the underground powerhouse and the water conveyance pipeline was about 7403.6 m³/d during the construction period. The groundwater level in the reservoir area could recover after a short drop, which had little effect on the surrounding vegetation. The groundwater quality was affected obviously because the migration speed of contaminants was very fast under abnormal conditions. During the operation period, it had little effect on groundwater level and had certain influence on groundwater flow field in local area. The source of sewage was mainly a small amount of domestic sewage, which could be ignored after taking anti-seepage measures. After storing water in the reservoir area, there was a possibility of small-scale immersion on the right bank. Most of the reservoirs had good stability conditions but the stability of the upper fault valley was poor; however, the possibility of leakage was very small. Overall, the project had little impact on the surrounding environment. The research results could also provide some references for other hydroelectric projects within the basin.