Abstract
At landfill sites, uncontrolled leachate is a serious cause of groundwater and soil contamination at landfills and can occur extensively when there are looploopholesin the vertical HDPE ...(High-density polyethylene) membrane. For this reason, detecting HDPE membranes is necessary. The conventional electrode running poles approach is limited, it reflects the distribution of resistivity in 2D subsurface profiles, which is difficult to deploy electrodes above vertical HDPE membrane. According to the structural characteristics and field conditions of vertical HDPE membranes, the two-row current and potential (CP) electrode array is proposed to be applied to the testing of vertical HDPE membranes. The forward geoelectric model of the vulnerability was built using pyGimli, and data on 1519 apparent resistivity were acquired. The previous knowledge without the vulnerability was taken into consideration as the constraint condition, and the regional control was added to conduct the inversion, all using the least square approach. The model was used to analyze data on the detection of vertical HDPE membranes in a landfill In Yancheng, and potential flaws were discovered. Results show that the CP electrical measuring device can be efficient, quick, and accurate in the positioning of vertical HDPE membrane hole detection, and it is a cost-effective method. To verify the results, in the vertical HDPE membrane, through the Wenner device, the inversion of the 2D profile, and low resistivity anomalies are detected. This is thought to be through the leachate of leakage of HDPE membrane resistance rate is about 1.8 ohm. The findings demonstrate that the vertical HDPE membrane susceptibility may be located and detected using a CP electrical measuring instrument, which is a practical and efficient approach.
•A method to investigate leachate’ long-term leakage and its impact on groundwater was constructed.•Production and leakage of leachate increase due to performance degradation of landfill.•The ...currently safe landfill may pollute the groundwater around it due to performance degradation.•The decline in landfill performance magnifies the uncertainty of its environment risk.
The long-term dynamics of leachate leakage from hazardous waste landfills (HWLs) and its influence on the surrounding groundwater and human health urgently requires decision-making processes for long-term HWL management and risk control. This study, based on the DMFU model, which is described in the literature as simulating the performance degradation of a landfill's main functional units, constructs a comprehensive model by coupling the HELP, EPACMTP, and Dose-Effect modules to investigate the long-term emissions of leachate from HWLs and their potential influence on groundwater quality and human health. Our results showed that the leakage rate over a long time period (50–1000 years) is 10 times higher than that of either a short (0–10 years) or medium (10–50 years) period. Due to the substantial increase in leakage rate, the negative influence on regional groundwater quality and human health changes from “insignificant” in the short term to “slight but acceptable” in the medium term, and finally to “substantial and unacceptable” in the long term. Studies also reveal that the uncertainty of risk increases over time. The information gained from this research provides useful insights into the long-term dynamics of leachate leakage, its risk consequences, and associated uncertainty, which can help landfill owners or risk managers make better decisions regarding the after-closure management of landfills.
Storage sites are the main sites for solid waste storage and also involve environmental pollution risks, but the aging of geomembrane materials and the evolution of defects in hazardous waste storage ...yards in service environment, which may lead to long-term increase in leakage and sudden increase in pollution risks, have received less attention from scholars. Taking a hazardous waste storage site in northern China (the main solid waste is cadmium-containing slag) as an example, the geomembrane damage characteristics (vulnerability density) and aging characteristics (aging onset time and half-life) were obtained through on-site dipole testing and laboratory geomembrane performance assessment. On the basis of this, we used a hydrological process assessment model (HELP) to simulate the rainfall-evaporation-runoff-infiltration and leachate generation processes under regional scale conditions, and a landfill groundwater contamination risk simulation model (Landsim) to simulate the lateral discharge-leakage processes inside the storage site and the migration-diffusion behavior in the saturated-unsaturated zone after leakage under the aging and defect evolution of geomembrane materials.
Landfilling is one of the important methods in hazardous waste treatment. In order to prevent the landfill leachate from connecting with external groundwater and prevent leachate from flowing into ...external polluted water bodies and soil, vertical anti-seepage membranes will be installed along the perimeter of the reservoir area. Given the structural characteristics of vertical HDPE membranes and site conditions, this study proposes the application of three-dimensional high-density electrical resistivity (3D-HDER) tomography for the detection of these membranes. Compared with the traditional resistivity method, the high-density resistivity method can realize automatic switching of electrode device type, electrode spacing and measuring points during the measurement process, thereby improving detection accuracy and work efficiency. By employing 3D-HDER for data collection on vertical HDPE membranes and inverting the subsurface resistivity distribution, the presence of leaks can be inferred based on the distribution of low-resistivity anomalies in the target underground area, thereby facilitating the integrity assessment of the vertical HDPE membranes. This research was applied in a practical investigation at a municipal landfill site in Hunan Province, where field tests were conducted, and the effectiveness of 3D-HDER in detecting vertical HDPE membranes was validated through excavation. The experimental results indicate that: (1) 3DHDER is capable of effectively and accurately locating shallow leaks, and (2) low resistivity anomalies were observed in the vicinity of the leaks.
Different pollutants affect electrical characteristics of soil, e.g., electric resistivity and capacity. The most extensively used non-intrusive methods in mapping these physical characteristics are ...electrical method. To better understand the effect of different hydrogeological and environmental process on resistivity and phase of complex resistivity under water-saturated soil, we carried out a controlled laboratory experiment where the host material was simulated by sand soil and the hydrogeological and environmental processes by groundwater table rise, seawater intrusion and heavy metal contamination. The experiment measured the resistivity and phase of soil saturated and unsaturated, with different pollutants added, together with their time-lapse change in a well-controlled column. With the involvement of more measurement parameters, complex resistivity method can provide more information than resistivity method, thereby having better performance in the detection and monitoring of changes in electrical properties of complex contaminated sites. For example, it is capable of discriminating the different contamination process, in this case, e.g., seawater intrusion and heavy metal contamination. In addition, it is still sensitive to the change of pollutant concentration even in site with high added concentration. Furthermore, simulating the saltwater-intruded site contaminated by manganese, it was found that the change of resistivity (ρ) can hardly be observed, while the responses of phase (φ) are so obvious that can be clearly observed.
The leakage of leachate is a crucial but often overlooked hydrological process in the landfill water cycle. The concealed leakage of leachate not only leads to soil and groundwater pollution in ...surrounding areas but also affects the distribution of water and the metabolism of organic matter within the landfill. To accurately quantify this concealed hydrological process, we propose a method for detecting leachate leakage based on joint inversion of multi-source geophysical exploration data. By integrating multiple geophysical exploration data (resistivity and self-potential information), we reconcile the spatial differences in different exploration data to improve the accuracy of leachate and its pollution plume imaging. Additionally, we introduce an efficient alternating iteration technique within the joint inversion framework to ensure convergence of separately inverted models toward similar spatial structures. Simulation results indicate that: (1) for the early detection of small-scale high-concentration leachate pollution, the proposed confidence-induced joint inversion framework (CI-JIF) improves precision by 15.6 % compared to separate inversions. (2) for the detection of leachate long-term diffusion, CI-JIF accurately delineates the distribution of widespread high-concentration leachate, improving precision by 17.4 % compared to separate inversions. Further on-site experiments demonstrate that CI-JIF can more accurately reconstruct the distribution of leachate.
•Joint inversion framework for complex subsurface geophysical imaging.•Dynamic regularization with confidence Spearman correlation coefficients.•Efficient iterative strategy for faster model parameter convergence.•The proposed algorithm compensates the deficiencies of separate inversion.
Micro-hotplates (MHPs) have become widely used basic structures in many micro sensors and actuators. Based on the analysis of the general heat transfer model, we propose a new MHP design based on a ...transversal composite dielectric layer, consisting of different heat transfer materials. Two general proven materials with different thermal conductivity, Si3N4 and SiO2, are chosen to form the composite dielectric layer. An annular heater is designed with a plurality of concentric rings connected with each other. The relationship between MHP performance and its geometrical parameters, including temperature distribution and uniformity, thermal deformation, and power dissipation, has been fully investigated using COMSOL simulation. The results demonstrate that the new planar MHP of 2 μm thick with a Si3N4-SiO2 composite dielectric layer and annular heater can reach 300 °C at a power of 35.2 mW with a mechanical deformation of 0.132 μm, at a large heating area of about 0.5 mm2. The introduction of the composite dielectric layer effectively reduces the lateral heat conduction loss and alleviates the mechanical deformation of the planar MHP compared with a single SiO2 dielectric layer or Si3N4 dielectric layer.
The rapid pace of urbanization has increased the development and land reuse value of China’s closed industrial solid waste landfill (CISWL) sites. In-situ development of land without waste excavation ...has both economic and environmental benefits. Therefore, the present study systematically evaluates the on-site risks of a CISWL site under in-situ development conditions by sampling analysis and process model simulation to predict its long-term evolution. The results demonstrated that 93% of the waste leaching concentration was harmful and 66% of the waste was not suitable for soil directly used for urbanized land after nearly 20 years of leaching and degradation. The groundwater quality had changed from “no possibility of exceeding the standard (short term)” to “only a few harmful substances (Pb) have a very small possibility of exceeding the standard (medium term),” to “both Pb and total cyanide (T-CN) have a high probability of exceeding the standard (later stage).” At the same time, the health risks of the site use process have gradually increased over time. The carcinogenic risk posed by As and the non-carcinogenic risk from T-CN exceeded the acceptable level by 139–267 times and 4.9–17.2 times, respectively. The above results suggest that risk assessment and management strategies of CISWL site development and reuse should focus on long-term risks. For sites with unacceptable long-term risks, acceptable long-term risks can be lowered appropriately by reducing the concentration of toxic substances in leached waste. The present study proposes a calculation framework and method for the corresponding leaching concentration limits.
•Harmful pollutants degrade slowly in closed landfill environment.•Long-term health risks exceed 4.9–267 times the acceptable level for this site.•Long-term risks should be considered when reusing industrial solid waste sites.
The stability of hazardous waste (HW) landfill is a major security risk to the landfill environmental safety. The mechanical behavior of waste controls many aspects of landfill design and operation, ...including stability and settlement issues and the integrity of geosynthetic and liner components. This study presents the results of a laboratory experiment to learn the mechanical properties of HW collected from the Hangzhou HW landfill. Measured mechanical behavior was compared with results for municipal solid waste (MSW) to assess their discrepancies. The particle size of HW was analyzed by the sieving and hydrometer methods. Because HW comes primarily from industrial plants in the form of sludge or slag, their particle sizes are generally smaller than those of MSW. This study indicates that the shear strength parameters of HW are more sensitive to the methods of testing and calculation than those of MSW. Numerical simulations demonstrate that the safety factor of a landfill is affected by the mechanical properties of HW, especially cohesion and friction angle. Because of the lower particle size and wider compression ratio, compared to MSW, an HW landfill should be taken more care in its operational procedures so as to increase its stability.
Fly ash from waste incineration is growing rapidly and has become a global problem. Landfill is the main treatment method, but the release behavior of ultra-alkaline fly ash needs further study. In ...this study, the release pattern of heavy metals from fly ash, the long-term risk after seepage, and the main control mechanisms were explored by indoor simulation experiments and process simulation modeling. The results show that carbonation is the main control mechanism for the release rate of heavy metals from super-alkaline fly ash, and the release rate is slow at the initial stage, but the release concentration of Zn and Pb may increase tens of times with the continuous reaction between the acidic substances in the leachate and the alkaline substances in the fly ash. The heavy metals released into the leachate can cause the concentration of Zn, Cd and Pb in the groundwater to exceed the standard by 39.50, 6.70 and 5.99 times due to seepage. Furnace type is the key controlling factor for background concentrations of heavy metals in ultra-alkaline fly ash, and the exposure concentrations of Cu, Cd, Zn, and Pb in ultra-alkaline fly ash from grate furnaces as well as the GT1 facility are 4.19, 4.19, 4.14, and 37.5 times greater than those of fluidized beds, respectively, with a higher risk of long-term landfill. Regionally, the regional occupancy rate of heavy metal concentrations indicated that the risk of adequate rainfall was high in the southeastern coastal region, which was five times higher than that in the inland northwest. Therefore, the long-term dynamics and risk evolution of Zn, Cd, and Pb in the groundwater around MSWLs in the coastal area should be paid attention to after the landfilling of ultra-alkaline fly ash in order to ensure the safety of the shallow groundwater environment after landfilling.
Fly ash from waste incineration is growing rapidly and has become a global problem. Landfill is the main treatment method, but the release behavior of ultra-alkaline fly ash needs further study. In this study, the release pattern of heavy metals from fly ash, the long-term risk after seepage, and the main control mechanisms were explored by indoor simulation experiments and process simulation modeling. The results show that carbonation is the main control mechanism for the release rate of heavy metals from super-alkaline fly ash, and the release rate is slow at the initial stage, but the release concentration of Zn and Pb may increase tens of times with the continuous reaction between the acidic substances in the leachate and the alkaline substances in the fly ash. The heavy metals released into the leachate can cause the concentration of Zn, Cd and Pb in the groundwater to exceed the standard by 39.50, 6.70 and 5.99 times due to seepage. Furnace type is the key controlling factor for background concentrations of heavy metals in ultra-alkaline fly ash, and the exposure concentrations of Cu, Cd, Zn, and Pb in ultra-alkaline fly ash from grate furnaces as well as the GT1 facility are 4.19, 4.19, 4.14, and 37.5 times greater than those of fluidized beds, respectively, with a higher risk of long-term landfill. Regionally, the regional occupancy rate of heavy metal concentrations indicated that the risk of adequate rainfall was high in the southeastern coastal region, which was five times higher than that in the inland northwest. Therefore, the long-term dynamics and risk evolution of Zn, Cd, and Pb in the groundwater around MSWLs in the coastal area should be paid attention to after the landfilling of ultra-alkaline fly ash in order to ensure the safety of the shallow groundwater environment after landfilling. Display omitted
•The long-term landfill risk of SAFA was assessed experimentally and by modeling.•The long-term risk of SAFA was found to be much higher than that of ordinary fly ash.•Furnace type was the main influencing factor for heavy metal concentrations in SAFA.
PDF
