Landfill Age Research Articles

Characterisation of Hazardous Waste Landfill Leachate and its Reliance on Landfill Age and Seasonal Variation: A Statistical Approach

Leachate generated due to disposal industrial solid waste into common hazardous waste landfills (HWLs), has high potential to contaminate nearby soil and groundwater and hence its catchment and treatment are crucial for sustainable solid waste management. This research is emphasised on creating an extensive data set generated from analysing three hazardous waste landfills of age 2-year, 11-year and 20-year for a duration of one year to characterise the leachate and to create an in-depth understanding about the effect of landfill age and seasonal variation on leachate characteristics. Results in the form of descriptive statistics showed the simultaneous occurrence of high chemical oxygen demand (COD) (up to 35,000 mg/l) and high concentration of total dissolved solids (TDS) (up to 3,00,000 mg/l), ammoniacal nitrogen (up to 2300 mg/l) and heavy metals. Statistical analysis through ANOVA and Post Hoc analysis indicated that the age of landfill significantly affects the leachate characteristics and for most of the parameters, the concentrations were found to increase till middle age and then subside towards maturity of landfill. In contrast to this, for seasonal variation, less significant influence was observed on the leachate characteristics. Although the concentration of different parameters was found to vary every month, no specific pattern or effect on seasonal variation could be traced from the data.

Antibiotic resistance genes are enriched with prolonged age of refuse in small and medium-sized landfill systems

Landfills are sites for the disposal of waste over decades. The dynamics of contaminants during landfill treatment influence the functions and environmental risks of the landfill systems, but the patterns of these dynamics are not fully characterized, especially for antibiotic resistant genes (ARGs), an emerging contaminant of global concern. Here, seventeen typical ARG subtypes were quantitatively investigated in refuse samples from small and medium-sized landfills with ages of <3 years, ~5 years, and 8–10 years. The abundance of ARGs, including tetM, tetX, blaPER, emrB, sul1 and sul2, increased significantly (p < 0.05), approaching 8- to 304-fold on average, from refuse of < 3years to that of 8–10 years, while there was no obvious change (p > 0.05) in abundance for other ARGs, including tetQ, tetW, ampC, blaCTX-M, blaSHV, emrA, mefA, qnrD, qnrS, and mexF. Accordingly, resistance to tetracyclines, macrolides, and sulfonamides increased with landfill age, while resistance to β-lactams and quinolones remained unchanged. The increase in ARG abundance with increasing refuse age was probably related with the increased horizontal gene transfer (HGT) (indicated by the increased abundance of mobile gene elements) and the enhanced co-selective pressure (suggested by the increased contents of heavy metals). These results indicated a potential risk from ARG enrichment with an increase in refuse age in small and medium-sized landfills, which should be managed to ensure landfill safety.

Influences of geochemical factors and substrate availability on Gram-positive and Gram-negative bacterial distribution and bio-processes in ageing municipal landfills.

Bacteria are primary agents of organic substrate metabolisation and elemental cycling in landfills. Two major bacterial groups, namely, Gram-positive (GP) and Gram-negative (GN), drive independent metabolic functions that contribute to waste stabilisation. There is a lack of explicit exploration of how these different bacterial guilds respond to changing carbon (C) availability and substrate depletion as landfills age and how landfill geochemistry regulates their distribution. This study investigated and compared the abundance and vertical distribution of GP and GN bacteria in 14- and 36-year-old municipal landfills and explored linkages among bacterial groups, nutrient elements, heavy metals and soil texture. We found higher GP bacteria in the 14-year-old landfill, while GN bacteria dominated the 36-year-old landfill. The non-metric multidimensional scaling (nMDS) analysis showed that dissimilarities in the relative abundance of the GP and GN bacteria were linked distinctly to landfill age, and not depth. In support of this inference, we further found that GP and GN bacteria were negatively correlated with heavy metals and essential nutrients in the 14- and 36-year-old landfills, respectively. Notably, the GP/GN ratio, an indicator of relative C available for bacterial mineralisation, was greater in the14-year-old landfill, suggesting greater C availability. Conversely, the C to N ratio was higher in the 36-year-old landfill, indicating lower N mineralisation. Collectively, the results of the study reveal key insights into how landfill ageing and stabilisation influence distinct functional shifts in the abundance of GP and GN bacteria, and these are mainly driven by changes in C and N bioavailability.

In Situ Characterization of Municipal Solid Waste Using Membrane Interface Probe (MIP) and Hydraulic Profiling Tool (HPT) in an Active and Closed Landfill

Municipal solid waste (MSW) landfills near a metropolitan area are renewable energy resources to produce heat and methane that can generate electricity. However, it is difficult to use those sources productively because disposed MSW in landfills are spatially and temporally heterogeneous. Regarding the prediction of the sources, the analysis of in situ MSW properties is an alternative way to reduce the uncertainty and to understand complex processes undergoing in the landfill effectively. A hydraulic profiling tool (HPT) and membrane interface probe (MIP) test measures the continuous profile of MSW properties with depth, including hydraulic pressure, temperature, electrical conductivity (EC), and the relative concentration of methane at the field. In this study, we conducted a series of the tests to investigate the MSW characteristics of active and closed landfills. MIP results showed that the methane existed closer to right below the top cover in the active landfill and several peak concentrations at different layers of the closed landfill. As the depth and age of the waste increased, the hydraulic pressure increased for both landfills. The average EC results showed that the electrical conductivity decreased with the landfill age. The results of hydraulic properties, temperature, and EC obtained from active and closed sites could be used to estimate the waste age and help designing energy recovery systems.

Insights into the stabilization of landfill by assessing the diversity and dynamic succession of bacterial community and its associated bio-metabolic process

The distribution of bacterial community in an actual landfill was analyzed and the bioprocess involved in refuse degradation was clarified. The results showed that the degradation degree of refuse showed great differences with the landfill age, in which the contents of organic matter (OM) and total Kjeldahl nitrogen (TKN) in refuse as well as the chemical oxygen demand (COD) in leachate presented decreasing trends with increasing landfill age. The diversity of bacterial community increased first and then decreased with increasing landfill age. The main bacterial phyla involved in refuse degradation were Proteobacteria, Firmicutes and Bacteroidetes, among which, Proteobacteria had an absolute advantage with a relative abundance ranging of 66–78%. With increasing landfill age, the abundance of Firmicutes decreased gradually, while that of Bacteroidetes increased. Pseudomonas, Thiopseudomonas, Psychrobacter and Desemzia were the main genera. The distribution of bacterial community in samples with landfill ages of 0–1 and 1–3 years were greatly influenced by TKN and pH, respectively. Amino acid and carbohydrate metabolism were the main biological pathways according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and the biodegradation of xenobiotics as well as terpenoids and polyketides also accounted relatively high frequencies in the landfill. These results provide a better understanding of landfill microbiology and bioprocesses for landfill stabilization.

Organic contaminants of emerging concern in leachate of historic municipal landfills.

Many types of contaminants of emerging concern (CECs), including per- and poly-fluoroalkyl substances (PFAS), have been found in leachate of operating municipal landfills. However, there is only limited information on CECs presence in leachate of historic landfills (≥3 decades since closure, often lacking engineered liners or leachate collection systems) at concentrations that may pose a risk to nearby wells and surface water ecosystems. In this study, 48 samples of leachate-impacted groundwater were collected from 20 historic landfills in Ontario, Canada. The CECs measured included artificial sweeteners (ASs), PFAS, organophosphate esters (OPE), pharmaceuticals, bisphenols, sulfamic acid, perchlorate, and substituted phenols. The common presence of the AS saccharin, a known indicator of old landfill leachate, combined with mostly negligible levels of the AS acesulfame, an indicator of modern wastewater, revealed that most samples were strongly influenced by leachate and not cross-contaminated by wastewater (which can contain these same CECs). Several landfills, including ones closed in the 1960s, had total PFAS concentrations similar to those previously measured at modern landfills, with a maximum observed here of 12.7μg/L. Notably elevated concentrations of several OPE, sulfamic acid, cotinine, and bisphenols A and S were found at many 30-60 year-old landfills. There was little indication of declining concentrations with landfill age, suggesting historic landfills can be long-term sources of CECs to groundwater and that certain CECs may be useful tracers for historic landfill leachate. These findings provide guidance on which CECs may require monitoring at historic landfill sites and wastewater treatment plants receiving their effluent.

Microbial community composition and metabolic functions in landfill leachate from different landfills of China

Landfill leachate usually harbors complex microbial communities responsible for the decomposition of municipal solid waste. However, the diversity and metabolic functions of the microbial communities in landfill leachate as well as the factors that influence them are still not well understood. In this study, Illumina MiSeq high-throughput sequencing was used to investigate the microbial community composition and metabolic functions in landfill leachate from 11 cities in China. The microbial diversity and structure of different leachate samples exhibited obvious differences. In general, Bacteroidetes, Firmicutes and Proteobacteria were the three dominant microbial communities among the 26 bacterial phyla identified in landfill leachate, regardless of the geographical locations. Diverse bacterial genera associated with various functions such as cellulolytic bacteria (e.g., Sphaerochaeta and Defluviitoga), acidifying bacteria (e.g., Prevotella and Trichococcus) and sulfate-reducing bacteria (e.g., Desulfuromonas and Desulfobacterium) were detected abundantly in the landfill leachate. Moreover, the archaeal community in all leachate samples was dominated by the orders Methanomicrobiales and Methanosarcinales belonging to the Euryarchaeota phylum. Notably, the archaea-specific primer pair covered more diverse archaeal communities than the universal bacteria-archaea primer pair. Seventeen archaeal genera belonging to acetoclastic, hydrogenotrophic, and methylotrophic methanogens were identified, and the composition of the dominant genera in these samples varied greatly. The canonical correlation analysis indicated that landfill age, electrical conductivity, ammonia nitrogen, and total nitrogen were significantly correlated with the microbial community structure. Based on PICRUSt2, a total of 41 metabolic pathways belonging to six metabolic pathway groups were predicted, and the KEGG pathway Metabolism was the most abundant group across all leachate samples. This study provides an important insight into the composition and functional characteristics of the microbial communities in landfill leachate.

Evaluating the physicochemical properties of refuse with a short-term landfill age and odorous pollutants emission during landfill mining: A case study

A field excavation of refusewitha short-termlandfillage from the Qingdao Xiaojianxi municipal solid waste (MSW) landfill was conducted. The physical composition and chemical properties of refuse with landfill ages of 1–4 years were studied, and the emission characteristics of odorous pollutants during the excavation period were monitored. The refuse aged 1–2 years has a higher proportion of combustible material than that the refuse aged 3–4 years, and the volatile content and calorific value in refuse aged 1–2 years were also higher than those in refuse aged 3–4 years, indicating that the refuse with a short-term landfill age was more suitable for incineration than refuse with a long-term landfill age. The pH and availablephosphorus (AP) gradually increased with increasing landfill age, while the total Kjeldahlnitrogen (TKN) and organic matter (OM) decreased. The contents of the heavy metals Cu, Zn, Ni, Pb and As generally decreased with landfill age, especially in refuse aged 2–4 years, whereas the Cr content showed no significant differences in refuse aged 1–4 years. The main odorous pollutants emitted during the excavation and screening periods were ammonia (NH3) and carbon disulfide (CS2), and the odor intensity of excavated refuse aged 1–3 years was higher than that of refuse aged 4 years. Under the condition of a small excavation area and continuous deodorization, the pollution intensity can meet the discharge standards of the factory boundary.

Antibiotic resistance contamination in four Italian municipal solid waste landfills sites spanning 34 years

Municipal solid waste landfill is now recognized as a significant reservoir of antibiotics and antibiotic resistance genes (ARGs). This study investigates the contamination of antibiotics resistance, in 10 leachate samples collected from four MSW landfills in north Italy spanning 34 years, including ARGs as well as mobile genetic element (MGEs). Antibiotics (0-434740 ng/L) and ARGs (5.56-6.85 × 105copies/μL leachate) were found in leachate. Abundances of the measured ARGs were found to be clustered into two groups with different changing tendencies with landfilling age in different landfills. Even though some antibiotics were banned or limited in Italy, they were found to still occur in landfills and drive the long-term contamination of ARGs indirectly, indicating the persistence of antibiotic resistance. What’s more, the complexity of antibiotic resistance in leachate was found to synthetically relate to antibiotics, metals, microbes and MGEs presenting that Mn, SMX and EFC influence positively (p < 0.01) the contamination of tetW, tetQ, tetM, tetA, ermB, and cat, contributing importantly in new leachate. This study discusses the AR pollution of leachate in Italy where antibiotics are used the most in Europe, less reported in literatures. Our results suggest that a full-scale view for landfill antibiotics resistance should be considered with history of landfills, use of antibiotics and different phase in landfills, with both “relative static” and “dynamic tracking” perspective to focus on the principal antibiotic-resistance pollutants for leachate treatment, and raise the attention for landfill post-closure care and landfill mining.

Municipal solid waste landfill age and refuse-derived fuel

Landfill sites are hard to obtain in Taiwan. Municipal solid waste (MSW) in the closed landfill sites has high combustible content and calorific value (CV). Therefore, activating the closed landfill sites as municipal mine sites to prolong their service life will promote a sustainable environment. This study transforms combustibles from the closed municipal landfill sites of different landfill ages (LAs) into refuse-derived fuel (RDF) through pretreatment and squeeze forming equipment, so to investigate the characteristics of the MSW of different LAs, and the manufacturing conditions and firing behaviour of RDF. The results indicate that the proportion of the combustibles in MSW declines as the LA grows, and therefore the proportions of both incombustible materials and soil and debris correspondingly increased. The LA of the MSW is thus negatively correlated with the CV. The MSW at the LA of 10 years still has high potential as fuel material. The fixed carbon initiation temperatures (i.e. ignition temperatures) of combustibles of the MSW at the LAs of 1 year, 5 years and 10 years are 259°C, 256°C and 245°C, respectively. The CV and flame temperature of the RDF increase slightly with the increasing squeeze temperature (ST) at 100-120°C, but it will decrease when the ST reaches 130°C. Therefore, this study recommends the squeeze pressure of the RDF as 41.65 ± 8.24 kg cm-2, ST 110°C and combustible size 10-20 mm.

Associations between human bacterial pathogens and ARGs are magnified in leachates as landfill ages

Landfills constitute the largest treatment and disposal reservoirs of anthropogenic waste on earth and they are continuously releasing antibiotic resistance genes (ARGs) to the environment for decades via leachates. Little is known about the association between ARGs and human bacterial pathogens as a function of time. Here, we quantified 10 subtypes of ARGs, integrons, and human bacterial pathogens (HBPs). Except for the ARGs encoding resistance to sulfonamides, the subtypes encoding resistance to beta-lactams, macrolides, and aminoglycosides were not related to integrons (Spearman, P > 0.05). Over time presence of ARGs became increasingly more correlated with the presence of human bacterial pathogens (Procrustes test; R = 0.81, P < 0.05), which were primarily identified as the Proteobacteria, Actinobacteria, and Firmicutes. Rather than the prevalence of integrons, dynamics of the bacterial community, including the increased nitrogen metabolism activity of Proteobacteria and decreased bacterial diversity were assumed to lead to a magnified association between HBPs and target ARGs (Varpart; > 13%).

Municipal Solid Waste Landfills: An Underestimated Source of Pharmaceutical and Personal Care Products in the Water Environment.

Pharmaceutical and personal care products (PPCPs) have been the focus of increasing concern in recent decades due to their ubiquity in the environment and potential risks. Out-of-date PPCPs are usually discharged into municipal solid wastes (MSWs), enter the leachates in MSW landfills, and have serious adverse effects on the surrounding water environment. However, the occurrence and removal of PPCPs from landfill leachates have rarely been examined to date. This lack of knowledge makes the landfill an underestimated source of PPCPs in the environment. In this review, we collected the relevant publications of PPCPs in landfill leachates, systematically summarized the occurrence of PPCPs in landfill leachates globally, evaluated the removal performances for various PPCPs by different types of on-site full-scale leachate treatment processes, and assessed the impacts of landfill leachates on PPCPs in the adjacent groundwater. In particular, influencing factors for PPCPs in landfill leachates, including the physicochemical properties of PPCPs, climate conditions, and characteristics of landfill sites (i.e., landfill ages) as well as sociological factors (i.e., economic development), were extensively discussed to understand their occurrence patterns. Future perspectives were also proposed in light of the identified knowledge gaps. To the best of our knowledge, this is the first review regarding the occurrence and removal of PPCPs from landfill leachates worldwide.

Groundwater contamination from a municipal landfill: Effect of age, landfill closure, and season on groundwater chemistry

Groundwater reservoirs continue to be threatened globally, mainly from anthropogenic activities. There is need to understand how remediation of groundwater can be influenced by site-specific factors. There are few studies, if any, that incorporate at least three site-specific factors in a single investigation of groundwater contamination from landfills. We report a study where waste age, landfill closure, and season were compared with changes in water quality, using a twenty-four-year groundwater chemistry dataset. Groundwater samples were extracted from monitoring wells and analysed for twenty-eight physicochemical parameters. Results showed discharge of both legacy pollutants and elevated inorganic pollutants into the groundwater. Among the site-specific factors, waste age was the most influential. At the landfill age of 21 years, concentrations of pollutants became close to the reference value. The result also indicated that closing the landfill caused significant decrease in concentrations of contaminants in the groundwater (P < 0.05). Season was the least influential, registering significant results only for dissolved oxygen, sulphate and chloride (P < 0.05). Lastly, the result showed strong attenuation of pollutants with distance, thereby demonstrating the feasibility of the aquifer acting as a natural treatment plant to the pollutants. This eliminates any serious environmental risk associated with the emanating leachate, but at a cost of prohibiting abstraction of the groundwater for human use, due to potential health risks.

Long-term Temporal Variations in Characteristics of Leachates from a Closed Landfill in an Arid Region

There is limited information on the effect of characteristics of soil in the arid regions on the transport of pollutants. Al-Qurain landfill site is located about 1.5 km from the Arabian Gulf shoreline in Kuwait. The site was operated as an open dump and was designed without a liner or leachate collection system. This study was performed after 35 years of the site closure to investigate the quality of soil, leachate, and groundwater in its vicinity. A total of 25 test boreholes and 17 observation wells were used for the investigation. Analysis of soil, leachate, and groundwater samples shows high concentrations of organics (COD), nutrients (nitrogen, phosphorus), heavy metals, and minerals. Aging of the landfill has its impact on performance of landfill which was reflected on the characteristics of soil, leachate, and groundwater. The principal pollutants in leachate were COD, ammonia, and heavy metals as landfill age increased. A good indicator of landfill aging was the very low (0.04) BOD/COD ratio and BOD decay rate constant of 0.027/year. Water samples were also heavily polluted and their organic content ranged between 9 and 255 mg/L as BOD and 38 and 15,052 mg/L as COD. Solids levels in the water samples from the observation wells were generally higher than those typically reported in groundwater. The results showed that the mobility of the heavy metal was largely element-dependent. The organic content of the landfill played an important role in such mobility. This suggests segregation of waste disposed in landfills and replacing the open dumps by sanitary landfills to avoid such high long-term pollution that affects the site rehabilitation plans.

Evaluating the performance of an electro-membrane bioreactor in treatment of young leachate

Leachate generated from landfill, typically contains high amounts of different pollutions. Its composition may vary according to the origin and age of landfill. In this study, the performance of a laboratory-scale submerged electro-membrane bioreactor (SMEBR), an integrated process consisting of an electro-coagulation unit and a conventional submerged membrane bioreactor (SMBR) for treating young leachate was evaluated. SMEBR and SMBR as control reactor were operated simultaneously to compare. In SMEBR, perforated aluminum (Al) electrodes were used. SMEBR was operated under electrokinetic conditions at a current density of 24 mA/cm 2 for 50 days: at 180 s/day for 25 days (Stage I) and 360 s/day for 25 days (Stage II). Chemical oxygen demand (COD), ammonia nitrogen (NH 3 –N), color and metal removal performances were evaluated for both reactors. Also, the membrane fouling was examined by monitoring the change in transmembrane pressure over time. The concentration of dissolved oxygen (DO) was determined using the oxygen uptake rate in a period covering SMEBR operating conditions. Based on the results obtained, positive effects of electrical field SMEBR were clearly observed at Stage II. At the Stage II, the removal efficiency of COD was 6–15% higher in SMEBR compared to SMBR. The average NH 3 –N removal efficiencies in SMEBR and SMBR were 86 and 78%, respectively. Following the introduction of electrical current to SMEBR, DO concentrations were measured about 0.8 mg/L lower than SMBR; however, nitrification was not affected adversely. Additionally, chemical properties of SMEBR and SMBR membranes surfaces were characterized by using the Fourier-transform infrared spectroscopy.

Sustainability analysis on landfilling and evaluation of characteristics in landfill leachate: a case study

Issues on solid waste management in the most Asian developing countries is not recent. Unfortunately, Malaysia is still practicing landfilling method to dispose the solid wastes. The apparent consequence of this method is the production of highly polluted wastewater called leachate, which can cause several inconveniences and issues. The characterization of landfill leachate is merely important because it can guide towards the possible appropriate treatment. The main focus of this study was to analyse the leachate characteristics at Simpang Renggam Landfill Site, Johor, Malaysia for five consecutive months from January to May of 2018. There were 16 analyzed parameters; namely temperature, pH, total dissolved solids (TDS), conductivity, suspended solids (SS), colour, turbidity, ammonia (NH3-N), dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), BOD5/COD ratio, as well as heavy metals (iron (Fe), chromium (Cr), arsenic (As), lead (Pb)). All parameters were analyzed according to the Standard Methods for the Examination of Water and Wastewater, and have followed the procedures of respective instruments. Leachate in SRLS could be classified as stabilized ones, by considering the characteristics and the age of landfill. SRLS is recommended to upgrade its management system for better waste disposal and leachate treatment.

Leachates From Landfill Sites In Thessaloniki, Greece: Effect Of Aging

Sanitary landfilling still is one of the most common management systems of solid urban wastes. The persistent environmental impact of landfills depends on leachate characteristics. The present study aimed at the characterisation of leachate from two landfill sites in the prefecture of Thessaloniki, Greece. Mavrorachi landfill stands in our study as a representative Greek active landfill site, that started operating in 2008. Tagarades landfill has stopped receiving waste from 2008 after 27 years of full operation. In this investigation, leachate samples were physico-chemically characterised so as to assess their pollution potential and their concentration in regard to the type and age of landfill. Elevated concentrations of inorganic and organic constituents were observed in the leachate composition. COD ranged from 2,490 mg/L to 19,700 mg/L, while the respective range for BOD was 390-14,850 mg/L during a 35-year period. The pH values of the leachate samples presented more moderate fluctuations between 7.3 and 8.5. In addition, the ammoniacal nitrogen content increased as landfill age increased, whereas heavy metals concentrations showed significant variations with a slight decreasing trend. The results presented in this paper proved that as time passed, the values of most parameters decreased as the biodegradable compounds are broken down while the refractory compounds resist to biodegradation. Thus, the age has a pronounced influence on the composition of leachate. This study also focused on quantifying the level of contamination that leachates can be potentially cause on a comparative basis by Leachate Pollution Index (LPI). LPI values showed that pollution load was declining but is still not negligible after 33 years.

Soil water characteristic curve test and saturated-unsaturated seepage analysis in Jiangcungou municipal solid waste landfill, China

In this study, an analysis of municipal solid waste (MSW) is undertaken at the Jiangcungou landfill in Xi’an, China. Using waste specimens gathered from the landfill, the soil water characteristic curve (SWCC) is determined at the laboratory, and the effects of landfill age and dry density on the SWCC parameters are analyzed. Leachate level trends during the landfill lifecycle are examined by performing saturated-unsaturated seepage analysis with the consideration of precipitation, as well as the inner source of water. These results are then summarized into three primary points. First, the shallow waste in the Jiangcungou landfill lost its water relatively quickly at small negative pressure heads, while the deep waste lost its water much more gradually. In addition, the deeper waste exhibited a lower volumetric water content when the matrix suction was less than 1.4kPa, but the result was opposite when the matrix suction was more than 2.0kPa. Second, the saturated volumetric water content and steepness of the SWCC decreased as the dry density increased, and the residual volumetric water contents increased and the inverse of the air-entry pressure decreased with increasing landfill age. Third, layers three, five and six demonstrated the highest leachate levels in the eighth landfill stage especially layer five, and these merit the greatest attention in monitoring and construction. These findings may provide a basis for the management of the Jiangcungou landfill.

Occurrence of microplastics in landfill systems and their fate with landfill age

Microplastics (MPs) are emerging pollutants that have been extensively detected in marine and terrestrial environments. Landfills are receptacles for cumulative loading of plastic waste derived from industry and households, but data on MPs occurrences in landfill systems are lacking. In the current study, the occurrence, characteristics and distribution patterns of MPs in landfills (including leachate and refuse) of the megacity Shanghai were investigated in accordance with different landfill ages (3–20 years). The results revealed that the average abundances of MPs in leachate and refuse were 8 (±3) items/L and 62 (±23) items/g, respectively. The predominant shapes and polymer types of the detected MPs were fibers and cellophane in leachate, whereas they were fragments and polyethylene in refuse. The patterns of abundance and size distribution of MPs in refuse varied from different landfill age, and different polymer MPs exhibited various occurrence patterns with increasing landfill age. Further spectra analysis suggested the presence of oxidative degradation of polyethylene MPs in the landfill process, especially for the landfill time of more than 20 years, so the fates of MPs in landfills were determined by the increase consumptions of plastics products and the degradation process of MPs in landfills. This study firstly provided a systematic overview of MPs pollution characteristics in landfill systems, and the results will foster the understanding of MPs fates over a long time scale in the environments.

Brominated flame retardants and perfluoroalkyl substances in landfill leachate from Ireland

Between June and November 2017, leachate samples were collected from 40 landfills across the Republic of Ireland. Concentrations of perfluoroalkyl substances (PFASs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) determined in these samples were within the range previously reported in other countries. Average concentrations of PFASs exceeded those of PBDEs and HBCDD; likely due to the higher water solubility of PFASs. Log-transformed concentrations of BDEs-47, 100, 153, and 183, as well as perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorobutane sulfonate (PFBS) were significantly (p < 0.05) higher in leachate from newer, lined landfills than in samples from unlined landfills. These higher concentrations in lined landfills are likely related to the fact that lined landfills are found to retain organic matter leading to a higher organic content of leachate from such landfills. This is evidenced by the significant (p < 0.05) correlation between log-transformed concentrations in leachate of most of the same contaminants and those of chemical oxygen demand (COD). Concentrations of the less water-soluble, higher molecular weight BDE-209 were not correlated with leachate COD, nor landfill age or the presence of a landfill liner. This suggests that the presence of BDE-209 in landfill leachate is driven more by physical abrasion of particles and fibres from waste articles, than dissolution into the aqueous phase. The higher concentrations of some PFASs and PBDEs in leachate from lined landfills present a challenge with respect to leachate disposal, when leachate is sent to wastewater treatment plants that do not necessarily have mechanisms in place to remove or destroy these chemicals prior to discharge into the environment. Moreover, the presence of these persistent organic chemicals in leachate from unlined landfills raises concerns about releases to the environment including groundwater over the lifetime of such landfills and beyond.