Evaluation of greenhouse gas emission and reduction potential of high-food-waste-content municipal solid waste landfills: A case study of a landfill in the east of China.

This study proposes a comprehensive evaluation method based on a two-stage model to assess greenhouse gas (GHG) emissions and reductions in high-food-waste-content (HFWC) municipal solid waste (MSW) landfills. The proposed method considers typical processes such as fugitive landfill gas (LFG), LFG collection, flaring, power generation, and leachate treatment. A case study of an HFWC MSW landfill in eastern China is considered to illustrate the evaluation. The findings revealed that the GHG emissions equivalent of the case landfill amounted to 21.23 million tons from 2007 to 2022, averaging 1.03 tons CO2-eq per ton of MSW. There was a potential underestimation of LFG generation at the landfill site during the initial stages, which led to delayed LFG collection and substantial fugitive LFG emissions. Additionally, the time distribution of GHG emissions from HFWC MSW was significantly different from that of low-food-waste-content (LFWC) MSW landfills, with peak emissions occurring much earlier. Owing to the rapid degradation characteristics of HFWC MSW, the cumulative LFG production of the landfill by 2022 (2 years after the final cover) was projected to reach 77 % of the total LFG potential. In contrast, it would take until 2030 for LFWC MSW landfills to reach this level. Furthermore, various scenarios were analyzed, in which if the rapid LFG generation characteristics of HFWC MSW are known in advance, and relevant facilities are constructed ahead of time, the collection efficiency can be improved from 31 % to over 78 %, resulting in less GHG emissions.

Carbapenemase and extended-spectrum beta-lactamase-producing bacteria in waters originating from a single landfill in Slovenia.

Groundwater, rainwater, and leachate associated with a single landfill were analysed to detect extended-spectrum beta-lactamase (ESBL)-producing and carbapenemase (CP)-producing bacteria. After cultivation on three commercial selective-differential media, 240 bacterial isolates were obtained and identified by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Isolates from clinically relevant species were further genotyped by enterobacterial repetitive intergenic consensus polymerase chain reaction, and tested for antibiotic susceptibility and presence of CPs and ESBL enzymes. Two ESBL-producing isolates and two isolates producing CPs were detected in rainwater, groundwater, and leachate: Klebsiella oxytoca complex with the gene for the ESBL enzyme CTX-M-1 and the gene for the CP OXA-48, Serratia fonticola with the gene for the ESBL enzyme FONA-2, and Pseudomonas aeruginosa with the gene coding Verona integron-encoded Metallo-beta-lactamases (VIM) metallo-beta-lactamase. Our study indicates that bacteria with ESBL and CP genes can be present in landfill-associated waters.

Intermittent aeration mitigating carbon emission from landfills with gas-water joint regulation.

Landfill is a significant source of atmospheric CH4 and CO2 emissions. In this study, four landfill reactor systems were constructed to investigate the effects of different ventilation methods, including continuous aeration (20 h d-1) and intermittent aeration (continuous aeration for 4 h d-1 and 2 h of aeration every 12 h, twice a day), on properties of landfilled waste and emissions of CH4 and CO2, in comparison to a traditional landfill. Compared with continuous aeration, intermittent aeration could reduce the potential global warming effect of the CH4 and CO2 emissions, especially multiple intermittent aeration. The CH4 and CO2 emissions could be predicted by the multiple linear regression model based on the contents of carbon, sulfur and/or pH during landfill stabilization. Both intermittent and continuous aeration could enhance the methane oxidation activity of landfilled waste. The aerobic methane oxidation activity of landfilled waste reached the maximums of 50.77-73.78 µg g-1 h-1 after aeration for 5 or 15 d, which was higher than the anaerobic methane oxidation activity (0.45-1.27 µg g-1 h-1). CO2 was the predominant form of organic carbon loss in the bioreactor landfills. Candidatus Methylomirabilis, Methylobacter, Methylomonas and Crenothrix were the main methane-oxidating microorganisms (MOM) in the landfills. Total, NO2--N, pH and Fe3+ were the main environmental variables influencing the MOM community, among which NO2--N and pH had the significant impact on the MOM community. Partial least squares path modelling indicated that aeration modes mainly influenced the emissions of CH4 and CO2 by affecting the degradation of landfilled waste, environmental variables and microbial activities. The results would be helpful for designing aeration systems to reduce the emissions of CH4 and CO2, and the cost during landfill stabilization.

Study of LFG bubble accumulation and discontinuous flow in the highly saturated region of landfill below the leachate level.

Landfills in developing countries are typically characterized by high waste water content and elevated leachate levels. Despite the ongoing biodegradation of waste in the highly saturated regions of these landfills, which leads to gas accumulation and bubble formation, the associated gas pressure that poses a risk to landfill stability is often overlooked. This paper introduces a landfill gas (LFG) bubble generation model and a two-fluid model that considers bubble buoyancy and porous medium resistance. The entire process can be divided into two stages based on the force balance and velocity of bubbles: Bubble Development Stage and the Two-Fluid Flow Stage. The models were validated using a one-dimensional analytical solution of hydraulic distribution that considers bubble generation, as well as an experiment involving air injection into a saturated medium. The mechanisms of LFG accumulation and ascent, leachate level rise, and discontinuous leachate-gas flow were then investigated in conjunction with continuous flow in the unsaturated region. The results indicate that the generation of LFG bubbles below the leachate level can cause a rise in the level height of more than 20%. During the Bubble Development Stage, there is a critical height for bubble ascent, above which the buoyancy exceeds the combined forces of gravity and resistance, resulting in less than 10% of bubbles continuously flowing into the unsaturated zone for recovery. The developed model effectively captures the accumulation and flow of LFG bubbles below the leachate level and could be further utilized to study leachate-gas pumping in the future.

Biodegradation of low-density polyethylene by mixed fungi composed of Alternaria sp. and Trametes sp. isolated from landfill sites.

With the development of industry and modern manufacturing, nondegradable low-density polyethylene (LDPE) has been widely used, posing a rising environmental hazard to natural ecosystems and public health. In this study, we isolated a series of LDPE-degrading fungi from landfill sites and carried out LDPE degradation experiments by combining highly efficient degrading fungi in pairs. The results showed that the mixed microorganisms composed of Alternaria sp. CPEF-1 and Trametes sp. PE2F-4 (H-3 group) had a greater degradation effect on heat-treated LDPE (T-LDPE). After 30 days of inoculation with combination strain H-3, the weight loss rate of the T-LDPE film was approximately 154% higher than that of the untreated LDPE (U-LDPE) film, and the weight loss rate reached 0.66 ± 0.06%. Environmental scanning electron microscopy (ESEM) and Fourier transform infrared spectroscopy (FTIR) were used to further investigate the biodegradation impacts of T-LDPE, including the changes on the surface and depolymerization of the LDPE films during the fungal degradation process. Our findings revealed that the combined fungal treatment is more effective at degrading T-LDPE than the single strain treatment, and it is expected that properly altering the composition of the microbial community can help lessen the detrimental impact of plastics on the environment.

A new approach for the assessment of the environmental risk of a soil-like fraction in landfills due to PTE contamination.

In the context of the shift toward a closed-loop economy, soil-like fractions from landfills are increasingly seen as a potential raw material. Pollution, including potentially toxic elements (PTEs), limits the use of soil-like fractions. The study objective was to assess the level of contamination with PTEs and the ecological risk of the soil-like fraction from a landfill using an interval method on the basis of a quantile analysis. Quantile analysis allows visualization and interpretation of data based on statistical principles using a cumulative distribution function for the data. Quantiles divide the entire dataset into equal parts by probability, and they indicate the proportion of observations that have a value less than or equal to a given quantile. A study was conducted at a landfill in Volgograd. The contents of Cd, Ni, Pb, Hg, Cu, and Zn were studied in a soil-like fraction. The contents of Hg, Pb, and Zn were low and did not pose any risks to the environment. Cd, Ni, and Cu were the main reasons for the contamination of the soil-like fraction. Quantile analysis has shown that the soil-like fraction is polluted unevenly and is described by several contamination levels. The pollution level with PTEs in the soil-like fraction is low, with a probability of 27-31%. The other part of the soil-like fraction has a pollution level ranging from moderate to very high. The environmental risk of a soil-like fraction is associated with Cd and Ni. With a probability of 23.5%, a soil-like fraction is a high environmental risk and requires a responsible attitude and measures to ensure environmental safety. With probabilities of 29.4% and 47.1%, the complex potential environmental risks of a soil-like fraction are low and moderate, respectively. The soil-like fraction located at a depth of more than 2.5 m has a low level of pollution and a low environmental risk. Potentially, this part of a soil-like fraction can be isolated and, after detoxification, used. The significance of this research lies in providing a novel approach to evaluate the ecological risk of soil-like fractions from landfills, which can inform more effective sustainable waste utilization practices in landfill mining.

Megacity solid waste disposal suitability mapping in Dhaka, Bangladesh: an integrated approach using remote sensing, GIS and statistics.

Selecting suitable Megacity Solid Waste Disposal (MSWD) sites is a challenging task in densely populated deltas of developing countries, exacerbated by limited public awareness about waste management. One of the major environmental concerns in Dhaka City, the world's densest megacity, is the presence of dumps close to surface water bodies resources. This study employed the Geographic Information System (GIS)-Analytic Hierarchy Process (AHP) framework to integrate geomorphological (slope and flow accumulation), geological (lithological and lineament), hydrogeological (depth to groundwater table and surface waterbody), socioeconomic (Land use land cover, distance to settlement, road, and airport), and climatological (wind direction) determinants, coupled by land-use and hydro-environmental analyses, to map optimal dumps (MSWDO) sites. The resulting preliminary (MSWDP) map revealed 15 potential landfill areas, covering approximately 5237 hectares (ha). Combining statistical analysis of restricted areas (settlements, water bodies, land use) with AHP-based ratings, the MSWDO map revealed two optimal locations (2285 ha). Additionally, the hydro-environmental analysis confirmed the unsuitability of northern sites due to shallow groundwater (< 5.43 m) and thin clay, leaving 11 options excluded. Sites 12 (Zone A, 2255 ha) and 15 (Zone B, 30 ha), with deeper groundwater tables and thicker clay layers, emerged as optimal choices for minimizing environmental risks and ensuring effective long-term waste disposal. This study successfully integrates remote sensing, geospatial data, and GIS-AHP modeling to facilitate the development of sustainable landfill strategies in similar South Asian delta megacities. Such an approach provides valuable insights for policymakers to implement cost-effective and sustainable waste management plans, potentially minimizing the environmental risks to achieve Sustainable Development Goals (SDGs) 6, 11, 13, and 15.

Of the first five US states with food waste bans, Massachusetts alone has reduced landfill waste.

Diverting food waste from landfills is crucial to reduce emissions and meet Paris Agreement targets. Between 2014 and 2024, nine US states banned commercial waste generators-such as grocery chains-from landfilling food waste, expecting a 10 to 15% waste reduction. However, no evaluation of these bans exists. We compile a comprehensive waste dataset covering 36 US states between 1996 and 2019 to evaluate the first five implemented state-level bans. Contrary to policy-makers' expectations, we can reject aggregate waste reductions higher than 3.2%, and we cannot reject a zero-null aggregate effect. Moreover, we cannot reject a zero-null effect for any other state except Massachusetts, which gradually achieved a 13.2% reduction. Our findings reveal the need to reassess food waste bans using Massachusetts as a benchmark for success.

Development of a floating constructed wetland for landfill leachate treatment and its potential to remove recalcitrant organic matter.

The development of simple and economical treatment technologies for the removal of recalcitrant organic matter is required to achieve long-term and sustainable treatment of landfill leachates in tropical regions. In this study, we evaluated the fundamental properties required to develop the floating constructed wetland (FCW), which consists of a buoyant planting unit made of foamed glass and cattails. The results showed that foamed glass alone can be used as a planting substrate for cattails. Treatment of a synthetic landfill leachate by a lab-scale FCW demonstrated that the test system effectively and continuously removed recalcitrant organic matter, whereas the control system did not. This removal by FCW was shown to proceed through nearly equal contributions from adsorption and potential biological processes. Furthermore, the effect of introducing an FCW in an actual waste landfill site in Thailand was simulated using the parameters obtained from this study. The simulation indicated that the introduction of the FCW into the stabilisation pond was effective in reducing both leachate volume and recalcitrant organic matter. It is important to determine how much of the stabilisation pond should be covered with the FCW for cost-effectiveness. The FCW is expected to contribute to improving long-term, sustainable, and appropriate management of landfill leachate in tropical developing countries.

Biogas recovery from a state-of-the-art Italian landfill.

The Fossetto landfill has operated in the municipality of Monsummano Terme (Tuscany, Italy) since 1988, being considered a state-of-the-art landfill for 35 years. Initially, Fossetto acted as a conventional sanitary landfill for mixed municipal solid waste. With changes in regulations and technology, the Fossetto landfill was gradually equipped with a biogas recovery and valorisation system, a mechanical-biological treatment (MBT) plant in 2003 and a reverse osmosis leachate treatment plant, so the concentrated leachate has been recirculated back into the landfill body since 2006. Long-term biogas monitoring, enables the calculation of the efficiency of biogas recovery using a rather simplified methodology, which was assessed as being approximately 40% over the prior ten-years period. This value was lower than expected, confirming the results of previous studies and indicating the need of attributes. Applying the USEPA LandGEM model showed that the adoption of MBT substantially reduced biogas generation yields and rates by up to approximately 90% which was facilitated by the adoption of landfill leachate recirculation transforming the conventional landfill into a bioreactor. Detailed fugitive emission monitoring has allowed the evaluation of the impact of the cover type (final or temporary) and the emissions hotspots. From these results, possible remedial actions have been suggested including the more frequent monitoring of the fugitive emissions using simple and cost-effective methods (e.g., UAVs). Approximately 50% of fugitive emissions can be attributed to emissions hotspots, which reduce biogas recovery and the efficiency of temporary covers.

Leachate reduction and pollution control strategies for landfills in hilly areas based on site condition analysis and numerical simulation.

Landfill is an important means of municipal solid waste treatment. Previous studies have shown that the combination of "cut-off wall and pumping well" technology is an effective measure to deal with the leachate emission reduction and pollution control of landfill, and has been widely used in plain areas. However, for landfills in hilly areas with complex terrain and geological conditions, there is still a lack of clear and referable ideas and operational strategies for leachate emission reduction and pollution control. In this study, we proposed strategies for determining the position and depth of cut-off walls and pumping wells and reasonable combinations of the cut-off wall depth and pumping quantity for leachate reduction and pollution prevention of landfills in hilly areas. The determination of leachate reduction and pollution control strategy need to be achieved in two stages, qualitative and quantitative: (1) In the qualitative stage, the natural conditions (Weathering degree, groundwater flow characteristics, topography condition, hydrometeor condition, and aquifer thickness) and engineering conditions (Operation status, landfill location, and excavation status) of the study area are analysed in detail, and then the depth range and location of the cut-off wall and pumping well are determined. (2) In the quantitative stage, we need to quantify the combination of the cut-off wall depth and pumping quantity by using profile particle tracing and pollutant transport modelling. A reasonable cut-off wall depth needs to control the leakage of pollutants inside the wall, and a reasonable pumping quantity needs to ensure that the depth of the pollutant distribution is equivalent to the depth of the separation line, which separates the water flow towards the pumping well and the water flow downstream. (3) The effectiveness of the leachate reduction and prevention strategies proposed in this study was verified through an example of a landfill in Northeast China. This study provides a reference and operation method for leachate emission reduction and pollution control of landfills in hilly areas.

Improving landfill liner performance with bentonite-slag blend permeated with ammonia for a Municipal solid waste landfill.

Leachate emanating from landfills contains ammonia which may cause serious health effects on living things. An effectively designed clay barrier should not allow the contaminant to infiltrate the soil and groundwater systems. The utilization of certain industrial by-products in engineered landfill barriers, not only reduces the need for conventional liner materials but also helps in sustainable waste management. This study investigated the hydraulic conductivity, unconfined compressive strength, compaction, and adsorption characteristics of lithomargic clay blended with an optimum percentage of bentonite (10%) and granulated blast furnace slag (15%) permeated with ammonia. The results revealed that increasing the content of granulated blast furnace slag decreased the maximum dry density while increasing the optimum moisture content. In comparison to lithomargic clay, the hydraulic conductivity of the amended soil liner permeated with ammonia decreased from a value of 3 × 10-8 m/s to 5 × 10-10 m/s. The unconfined compressive strength of the amended soil specimens showed an increasing trend with curing times (i.e., 0, 14, 28, and 56 days). The batch adsorption results revealed that Freundlich and Langmuir's isotherm fits the equilibrium adsorption data and the adsorption of ammonia on clay liner follows non-linear behaviour. Overall, the experimental results implied that lithomargic clay blended with 10% bentonite and 15% granulated blast furnace slag can be used as an impermeable soil reactive barrier in engineered landfills.

Risk of hydrogen sulfide pollution from pressure release resulting from landfill mining.

Landfill mining (LFM) has gained widespread recognition due to its benefits in terms of resource utilization of landfill waste and reuse of landfill sites. However, it is important to thoroughly assess the associated environmental risks. This study simulated the pressure release induced from LFM in small-scale batch anaerobic reactors subject to different initial pressures (0.2-0.6 MPa). The potential risk of hydrogen sulfide (H2S) pollution resulting from pressure release caused by LFM was investigated. The results demonstrated that the concentration of H2S significantly increased following the simulated pressure treatments. At the low (25 °C) and high (50 °C) temperatures tested, the peak H2S concentration reached 19366 and 24794 mg·m-3, respectively. Both of these concentrations were observed under highest initial pressure condition (0.6 MPa). However, the duration of H2S release was remarkably longer (>90 days) at the low temperature tested. Microbial diversity analysis results revealed that, at tested low temperature, the sulfate-reducing bacteria (SRB) communities of various pressure-bearing environments became phylogenetically similar following the pressure releases. In contrast, at the high temperature tested, specific SRB genera (Desulfitibacter and Candidatus Desulforudis) showed further enrichment. Moreover, the intensified sulfate reduction activity following pressure release was attributed to the enrichment of specific SRBs, including Desulfovibrio (ASV585 and ASV1417), Desulfofarcimen (ASV343), Candidatus Desulforudis (ASV24), and Desulfohalotomaculum (ASV506 and ASV2530). These results indicate that the pressure release associated with LFM significantly increases the amount of H2S released from landfills, and the SRB communities have different response mechanisms to pressure release at different temperature conditions. This study highlights the importance of considering the potential secondary environmental risks associated with LFM.

A global metagenomics-based analysis of BPA degradation and its coupling with nitrogen, sulfur, and methane metabolism in landfill leachates.

Microbial metabolism in landfill leachate systems is critically important in driving the degradation reactions of organic pollutants, including the emerging pollutant bisphenol A (BPA). However, little research has addressed the microbial degradation of BPA in landfill leachate and its interactions with nitrogen (N), sulfur (S), and methane (CH4) metabolism on a global scale. To this end, in this study on a global scale, an extremely high concentration of BPA was detected throughout the global landfill leachates. Subsequent reconstructive analyses of metagenomic datasets from 113 sites worldwide revealed that the predominant BPA-degrading microflora included Proteobacteria, Firmicutes, and Bacteroidota. Further metabolic analyses revealed that all four biochemical pathways involved in the degradation of BPA were achieved through biochemical cooperation between different bacterial members of the community. In addition, BPA degraders have also been found to actively collaborate synergistically with non-BPA degraders in the N and S removal as well as CH4 catabolism in landfill leachates. Collectively, this study not only provides insights into the dominant microbial communities and specific types of BPA-degrading microbial members in the community of landfill leachates worldwide, but also reveals the synergistic interactions between BPA mineralization and N, S, and CH4 metabolism. These findings offer valuable and important insights for future comprehensive and in-depth investigations into BPA metabolism in different environments.

Evaluating the efficacy of biogeochemical cover system in mitigating landfill gas emissions: A large-scale laboratory simulation.

Municipal solid waste (MSW) landfills are a significant source of methane (CH4) emissions in the United States, contributing to global warming. Current landfill gas (LFG) management methods, like the landfill cover system and LFG collection system, do not entirely prevent LFG release. Biocovers have the potential to reduce CH4 emissions through microbial oxidation. However, LFG also contains carbon dioxide (CO2) and trace hydrogen sulfide (H2S) depending on waste composition, temperature, moisture content, and age of waste. An innovative biogeochemical cover (BGCC) was developed to tackle these concerns. This cover comprises a biochar-based biocover layer overlaid with a basic oxygen furnace (BOF) steel slag layer. The biochar-based biocover layer oxidizes CH4 emissions, while the BOF slag layer reduces CO2 and H2S through carbonation and sulfidation reaction mechanisms. The BGCC system's field performance remains unexamined. Therefore, a large-scale tank setup simulating near-field conditions was developed to evaluate the BGCC system's ability to mitigate CH4, CO2, and H2S from LFG simultaneously. Synthetic LFG was passed through the BGCC in five distinct phases, each designed to simulate the varying gas compositions and flux rates typical of MSW landfill. Gas profiles along the depth were monitored during each phase, and gas removal efficiency was measured. After testing, biocover and BOF slag samples were extracted to analyze physico-chemical properties. Batch tests were also conducted on samples extracted from the biocover and BOF slag layers to determine potential CH4 oxidation rates and residual CO2 sequestration capacity. The results showed that the BGCC system's CH4 removal efficiency decreased with higher CH4 flux rates, achieving its highest removal (74.7-79.7%) at moderate influx rates (23.9-25.5 g CH4/m2-day) and reducing to its lowest removal (27.4%) at the highest influx rate (57.5 g CH4/m2-day). Complete H2S removal occurred during Phase 3 in the biocover layer of BGCC system. CH4 oxidation rates were highest near the upper (277.9 µg CH4/g-day) and lowest in the deeper region of the biocover layer. In the tank experiment, CO2 breakthrough occurred after 156 days due to drying of the BOF slag layer, with an average residual carbonation capacity of 46 gCO2/kg slag after moisture adjustment. Overall, the BGCC system effectively mitigated LFG emissions, including CH4, CO2, and H2S, at moderate flux rates, showing promise as a comprehensive solution for LFG management.

Radionuclide Solid:liquid partitioning in an aged, reducing-grout wasteform recovered from a disposal facility.

The Saltstone Disposal Facility on the Savannah River Site in South Carolina disposes of Low-Level Waste in a reducing-grout waste form. Reducing grout is presently being evaluated as a subsurface disposal waste form at several other locations in the United States, as well as in Europe and Asia. The objective of this study was to collect core samples directly from the Saltstone Disposal Facility and measure desorption distribution coefficients (Kd; radionuclide concentration ratio of saltstone:liquid; (Bq/kg)/Bq/L)) and desorption apparent solubility values (ksp; radionuclide aqueous concentration (moles/L)). An important attribute of this study was that these tests were conducted with actual aged, grout waste form materials, not small-volume simulants prepared in a laboratory. The reducing grout is comprised of blast furnace slag, Class F fly ash, ordinary portland cement, and a radioactive salt waste solution generated during nuclear processing. The grout sample used in this study underwent hydrolyzation in the disposal facility for 30 months prior to measuring radionuclide leaching. Leaching experiments were conducted either in an inert (no oxygen) atmosphere to simulate conditions within the saltstone monolith prior to aging (becoming oxidized) or they were exposed to atmosphere conditions to simulate conditions of an aged saltstone. Importantly, these experiments were designed not to be diffusion limited, that is, the saltstone was ground finely and the suspensions were under constant agitation during the equilibration period. Under oxidized conditions, measured Tc Kd values were 10 mL/g, which was appreciably greater than the historical best-estimate value of 0.8 mL/g. This difference is likely the result of a fraction of the Tc remaining in the less soluble Tc(IV) form, even after extensive oxidation during the experiment. Under oxidized and reducing conditions, the measured Ba and Sr (both divalent alkaline earth metals) Kd value were more than an order of magnitude greater than historical best-estimate values of 100 mL/g. The unexpectedly high Ba and Sr Kd values were attributed to these radionuclides having sufficient time to age (form strong bonds) in the sulfur-rich saltstone sample. Apparent ksp values under reducing conditions were 10-9 mol/L Tc and 10-13 mol/L Pu, consistent with values measured with surrogate materials. Measured apparent Ba, Sr, and Th ksp values were significantly greater than historical best-estimates. The implications of the generally greater Kd values and lower ksp values in these measurements is that these cementitious waste forms have greater radionuclide retention than was previously estimated based on laboratory studies using surrogate materials. This work represents the first leaching study performed with an actual aged, reducing-grout sample and as such provides an important comparison to studies conducted with surrogate materials, and provides high pedigree data for other programs around the world evaluating reducing grouts as a wasteform for subsurface nuclear waste disposal.

Multifaceted anomaly detection framework for leachate monitoring in landfills.

The imperative to preserve environmental resources has transcended traditional conservation efforts, becoming a crucial element for sustaining life. Our deep interconnectedness with the natural environment, which directly impacts our well-being, emphasizes this urgency. Contaminants such as leachate from landfills are increasingly threatening groundwater, a vital resource that provides drinking water for nearly half of the global population. This critical environmental threat requires advanced detection and monitoring solutions to effectively safeguard our groundwater resources. To address this pressing need, we introduce the Multifaceted Anomaly Detection Framework (MADF), which integrates Electrical Resistivity Tomography (ERT) with advanced machine learning models-Isolation Forest (IF), One-Class Support Vector Machines (OC-SVM), and Local Outlier Factor (LOF). MADF processes and analyzes ERT data, employing these hybrid machine learning models to identify and quantify anomaly signals accurately via the majority vote strategy. Applied to the Chaling landfill site in Zhuzhou, China, MADF demonstrated significant improvements in detection capability. The framework enhanced the precision of anomaly detection, evidenced by higher Youden Index values (≈ 6.216%), with a 30% increase in sensitivity and a 25% reduction in false positives compared to traditional ERT inversion methods. Indeed, these enhancements are crucial for effective environmental monitoring, where the cost of missing a leak could be catastrophic, and for reducing unnecessary interventions that can be resource-intensive. These results underscore MADF's potential as a robust tool for proactive environmental management, offering a scalable and adaptable solution for comprehensive landfill monitoring and pollution prevention across varied environmental settings.

Assessing the complexation of dissolved organic matter with heavy metals (Cu2+, Pb2+) in leachate from an old Japanese landfill site using fluorescence quenching.

Dissolved organic matter (DOM) in landfill leachate impacts the toxicity, bioavailability, and migration of heavy metals. The present study investigated the complexation of heavy metals (Cu2+ and Pb2+) with DOM from two landfill leachate samples, representing an old landfill site containing incineration residues and incombustible waste. The logarithms of the stability constant (log KM) and percentage of complexed fluorophores were calculated using both the Ryan-Weber non-linear model and the modified Stern-Volmer model, yielding good agreement. The log KM values (at pH = 6.0 ± 0.1) calculated using both methods for the two sampling points were 5.02-5.13 and 4.85-5.11 for Cu2+-DOM complexation, and 5.01-5.13 and 4.46-4.87 for Pb2+-DOM complexation, respectively. Log KM was slightly higher for binding of DOM with Cu2+ than Pb2+, and the quenching degree was stronger for complexation with Cu2+ (28.5-30.6% and 38.0-45.9%) than Pb2+ (6.5-7.1% and 10.0-15.4%) in both leachate samples. While log KM values were similar, differences in the contributions of functional groups and molecular composition led to varying degrees of quenching. This study reveals the potential for heavy metal binding by DOM in landfill leachate with a unique solid waste composition and emphasizes variations in fluorescence quenching between Cu2+ and Pb2+ despite similar log KM levels. These findings may be useful for assessing heavy metal behavior in landfill leachate and its impacts on the surrounding environment.

Solid waste detection, monitoring and mapping in remote sensing images: A survey.

The detection and characterization of illegal solid waste disposal sites are essential for environmental protection, particularly for mitigating pollution and health hazards. Improperly managed landfills contaminate soil and groundwater via rainwater infiltration, posing threats to both animals and humans. Traditional landfill identification approaches, such as on-site inspections, are time-consuming and expensive. Remote sensing is a cost-effective solution for the identification and monitoring of solid waste disposal sites that enables broad coverage and repeated acquisitions over time. Earth Observation (EO) satellites, equipped with an array of sensors and imaging capabilities, have been providing high-resolution data for several decades. Researchers proposed specialized techniques that leverage remote sensing imagery to perform a range of tasks such as waste site detection, dumping site monitoring, and assessment of suitable locations for new landfills. This review aims to provide a detailed illustration of the most relevant proposals for the detection and monitoring of solid waste sites by describing and comparing the approaches, the implemented techniques, and the employed data. Furthermore, since the data sources are of the utmost importance for developing an effective solid waste detection model, a comprehensive overview of the satellites and publicly available data sets is presented. Finally, this paper identifies the open issues in the state-of-the-art and discusses the relevant research directions for reducing the costs and improving the effectiveness of novel solid waste detection methods.

Reduced sulfur compound formation from a leachate-saturated zone under changing temperature conditions.

In the leachate-saturation zone of landfills, sulfate reduction is influenced by temperature and electron donors. This study assessed sulfate reduction behaviors under varied electron donor conditions by establishing multiple temperature variation scenarios based on stable temperature fields within the leachate-saturation zone. The results showed that temperature variations altered the microbial community structure and significantly influenced the sulfate reduction process. A more pronounced effect was observed with a temperature difference of 30 °C compared to one of 10 °C. In addition, sulfate reduction was influenced by the presence of electron donors and acceptors. In the middle and low-temperature regions (35 °C and 25 °C), sulfate reduction reaction of acidic organic matter was more significant, while alcohol and saccharide organic substances were more effective in promoting sulfate reduction at high-temperature regions (55 °C). Notably, a 30 °C temperature difference within the leachate-saturation zone significantly altered the microbial community structure, which influenced the sulfate reduction behavior. In particular, Firmicutes and Synergistota played essential roles in mediating the variance in sulfate reduction efficiency with a 30 °C decrease and 30 °C increase, respectively. The results also revealed that temperature changes within landfills were influenced by leachate migration, therefore, controlling leachate recharge can help prevent secondary risks associated with sulfate reduction processes.