Landfill gas as a source of anthropogenic antimony and arsenic release

Comparative analysis of metal oxide nanoparticle accumulation in landfill gas engine combustion chambers: Insights from three sites

Combustion chamber deposits adversely affect the operating performance of gas engines. In this study, the elemental composition of deposit samples collected from the inner surface of combustion chambers in gas engines across three different facilities was examined using various methods. The proportional changes in metal oxides along the internal cross-sectional surfaces of the deposits were examined to depict the deposit formation process from beginning to end. Additionally, the study investigated the identification of metals accumulated in the engine oil, their contribution to deposit formation, and the accumulation mechanisms of metal oxide nanoparticles on the engine's interior metal surfaces. The main elements identified in the deposits from the Odayeri and Kömürcüoda facilities were Si, S, and Ca, whereas deposits from the Dilovası facility contained Si and Sb. These major elements, identified by SEM-EDS, were confirmed through XRF analysis. XRD analysis further confirmed the presence of Ca and S as CaSO4 crystals in the deposits. Ca originates from additives used to increase the total base number of engine oil and control the corrosive effects of landfill gas. It has been determined that silicon accumulates in engine oil over time. An important finding is that metal oxides in the combustion chamber primarily accumulate through impaction, sticking, and thermophoresis mechanisms.

Ecotoxicological impacts of landfill sites: Towards risk assessment, mitigation policies and the role of artificial intelligence

Waste disposal in landfills remains a global concern. Despite technological developments, landfill leachate poses a hazard to ecosystems and human health since it acts as a secondary reservoir for legacy and emerging pollutants. This study provides a systematic and scientometric review of the nature and toxicity of pollutants generated by landfills and means of assessing their potential risks. Regarding human health, unregulated waste disposal and pathogens in leachate are the leading causes of diseases reported in local populations. Both in vitro and in vivo approaches have been employed in the ecotoxicological risk assessment of landfill leachate, with model organisms ranging from bacteria to birds. These studies demonstrate a wide range of toxic effects that reflect the complex composition of leachate and geographical variations in climate, resource availability and management practices. Based on bioassay (and other) evidence, categories of persistent chemicals of most concern include brominated flame retardants, per- and polyfluorinated chemicals, pharmaceuticals and alkyl phenol ethoxylates. However, the emerging and more general literature on microplastic toxicity suggests that these particles might also be problematic in leachate. Various mitigation strategies have been identified, with most focussing on improving landfill design or leachate treatment, developing alternative disposal methods and reducing waste volume through recycling or using more sustainable materials. The success of these efforts will rely on policies and practices and their enforcement, which is seen as a particular challenge in developing nations and at the international (and transboundary) level. Artificial intelligence and machine learning afford a wide range of options for evaluating and reducing the risks associated with leachates and gaseous emissions from landfills, and various approaches tested or having potential are discussed. However, addressing the limitations in data collection, model accuracy, real-time monitoring and our understanding of environmental impacts will be critical for realising this potential.

Didactical approaches and insights into environmental processes and cardiovascular hazards of arsenic contaminants

Arsenic, as a metalloid, has the ability to move and transform in different environmental media. Its widespread contamination has become a significant environmental problem and public concern. Arsenic can jeopardize multiple organs through various pathways, influenced by environmental bioprocesses. This article provides a comprehensive overview of current research on the cardiovascular hazards of arsenic. A bibliometric analysis revealed that there are 376 papers published in 145 journals, involving 40 countries, 631 institutions, and 2093 authors, all focused on arsenic-related concerns regarding cardiovascular health. China and the U.S. have emerged as the central hubs of collaborative relationships and have the highest number of publications. Hypertension and atherosclerosis are the most extensively studied topics, with redox imbalance, apoptosis, and methylation being the primary mechanistic clues. Cardiovascular damage caused by arsenic includes arrhythmia, cardiac remodeling, vascular leakage, and abnormal angiogenesis. However, the current understanding is still inadequate over cardiovascular impairments, underlying mechanisms, and precautionary methods of arsenic, thus calling an urgent need for further studies to bridge the gap between environmental processes and arsenic hazards.

Effect of waste-derived soil amendments on mitigating leaching impacts from municipal solid waste incineration (MSWI) ash

This study explores modifying a sandy soil with a low solid to liquid partitioning coefficient (Kd) by adding amendments including iron-rich industrial slag byproducts and biochars, which contain sorption sites for trace metals present in MSWI ash leachate (notably Sb, cited as a concern for reuse applications). Kd values for Sb were determined for the sandy soil to be as low as 1.6 ± 0.1 L/kg. With amendments, Kd values varied from 1.4 ± 0.2 L/kg for combined ash leachate exposed to a blend of sandy soil and 20% iron slag, to 990 L/kg for combined ash leachate exposed to a blend of sandy soil and 20% magnetic solids. A blend of 20% magnetic solids showed orders of magnitude increase beyond 100% sandy soil. The biochars showed limited capacity to reduce leached Sb in the ash-derived leachate, which is likely due to negative surface charges of the biochars and Sb at basic pH. A risk assessment (US EPA IWEM) performed using experimental Kd for each blend suggests that using soil amendments could reduce leached concentrations at points of concern, which could open additional avenues for ash reuse.

Per- and polyfluoroalkyl substances (PFAS) distribution in landfill gas collection systems: leachate and gas condensate partitioning

While per- and polyfluoroalkyl substances (PFAS) have been reported extensively in municipal solid waste (MSW) landfill leachate,they have rarely been quantified in landfill gas or in discrete landfill liquids such as landfill gas condensate (LGC), and the potential for PFAS to partition to the condensate has not been reported. LGC and leachate collected from within gas wells known as gas well pump-out (GWP) from three MSW landfills underwent physical-chemical characterization and PFAS analysis to improve understanding of the conditions under which these liquids form and to illuminate PFAS behavior within landfills. LGC was observed to be clear liquid containing ammonia and alkalinity while GWP strongly resembled leachate - dark in color, high in chloride and ammonia. Notably, arsenic and antimony were found in concentrations exceeding regulatory thresholds by over two orders of magnitude in many LGC samples. LGC contained a lower average concentration of ΣPFAS (19,000 ng L) compared to GWP (56,000 ng L); however, LGC contained more diversity of PFAS, with 53 quantified compared to 44 in GWP. LGC contained proportionally more precursor PFAS than GWP, including more semi-volatile PFAS which are rarely measured in water matrices, such as fluorotelomer alcohols and perfluoroalkane sulfonamido ethanols. This study provides the first detailed comparison of these matrices to inform timely leachate management decisions.