Leachate Composition Research Articles

Contaminant transport from solid waste dumps: Implications for environmental degradation with a focus on capital territory regions

Open dumping of Municipal solid waste is the main method of solid waste management in Pakistan. To investigate the impacts of leachate transportation from these waste dumps on groundwater quality, two sites were selected (I-12 in Islamabad and Lohsar in Rawalpindi), water samples were collected from existing wells during summer, winter, and rainy seasons and were analyzed for physiochemical parameters using standard methods. Most groundwater samples showed contamination and values of various parameters exceeded the desired limits set by the World Health Organization (WHO) and the National Standard for Drinking Water Quality (NSDWQ), especially during the rainy season, whereas the least contamination in groundwater samples was observed during the winter season. The results obtained were, pH: 5.75–7.87, Electrical Conductivity (EC): 103–3460 μS cm−1, Total Dissolved Solids (TDS): 436–4425 mg L−1, Total Alkalinity (TA): 190–1330 mg L−1, Total Hardness (TH): 128–676 mg L−1, Chlorides (Cl⁻): 56.7–893.3 mg L−1, Nitrates (NO₃⁻): 7.8–19.9 mg L−1, Dissolved Oxygen (DO): 6.1–20.8 mg L−1, Biological Oxygen Demand (BOD): 1.0–44.0 mg L−1 and Chemical Oxygen Demand (COD): 56–272 mg L−1. The findings suggest that the magnitude of groundwater contamination from leachate transportation is intricately influenced by factors such as leachate composition, seasonal variations and distance from the dumpsite. The contamination level reduced along the distance from the dumps. Except Copper (Cu) and Zinc (Zn), the concentration of all other heavy metals including, Iron (Fe), Chromium (Cr), Nickel (Ni), Lead (Pb), Cadmium (Cd) was found above standard appreciable limits. The t-test showed a significant difference in parameter concentrations for all seasons except for Cd and Zn. The calculation of water quality index through CCME (Canadian Council of Ministers of Environment) model revealed that all the groundwater samples around both the dump sites were of poor and marginal quality. In general, the groundwater quality of both study areas is not suitable for the drinking purpose. The study suggests regular testing and treating groundwater before use, use of engineered landfills, covering landfills with clay and vegetation and use of alternative strategies like composting and recycling for waste management.

Геохимия редкоземельных элементов и цериевая аномалия в морских осадочных карбонатах: современные представления

The article review the geochemistry of rare earth elements (REE) in sedimentary marine carbonates (limestones and dolostones) with respect to using the cerium anomaly as a proxy for redox conditions in ancient seawater. The physicochemical properties of REE and Y, the problem of normalizing their contents in sediments, behavior in the World Ocean and in chemogenic deposits, the origin of La, Ce, Eu, Gd anomalies and their calculations, sample preparation techniques, contamination problem and the influence of non-carbonate REE+Y-hosting phases to whole rock and acidic leachate compositions, as well as criteria for determining seawater-like pattern are considered.

Comparison of the PFAS and physical-chemical parameter fluctuations between an ash landfill and a MSW landfill

Studies of per- and polyfluoroalkyl substances (PFAS) fluctuations at landfills have focused on municipal solid waste (MSW) leachate. Few studies exist that evaluate fluctuations (defined by the coefficient of variation, CV) in MSW incinerator ash (MSWA) landfill leachate and that evaluate PFAS fluctuations in stormwater, groundwater, and treated liquids on-site. In this study, aqueous landfill samples (leachate, treated leachate, stormwater, gas condensate, ambient groundwater, and effluent from a groundwater remediation system) were collected from a MSW and an MSWA landfill geographically located within close proximity (less than 40 km). The objective of this study was to compare the leachate compositions between these two landfill types and to evaluate temporal variations. Results indicated that the CV of total detected PFAS concentrations in leachate was higher for the MSW landfill (CV = 43 %) compared to the MSWA landfill (CV = 16 %). The total detected PFAS concentration in MSW leachate samples (mean: 9641 ng/L) was higher than in MSWA leachate samples (mean: 2621 ng/L) (p < 0.05). Within a landfill, PFAS concentrations were correlated (rs > 0.6, p < 0.05) with alkalinity, total organic carbon (TOC), and ammonia. Results from the on-site leachate treatment system at the MSW landfill indicated reductions in COD, TOC, and ammonia; however, the ∑26PFAS concentration increased 3 % after the treatment. Overall, results demonstrated that differences between landfill types and fluctuations in PFAS within landfills should be considered when designing landfill leachate collection and treatment systems to remove PFAS. The comparative analysis in this study can provide insights into optimizing leachate management for MSW and MSWA landfills.

Role of redox conditions and thermal metamorphism in the preservation of Cr isotopic anomalies in components of non-carbonaceous chondrites

Mass-independent isotopic anomalies in meteorites are probes to the dynamics and evolution of the protoplanetary disc and the reservoirs from which planetary bodies accreted. Variable Cr nucleosynthetic compositions between meteorite groups are observed but the cause is not well understood. Investigations on presolar carriers in unequilibrated chondrites are thus required to establish these relationships. For that purpose, we analysed the Cr isotope compositions of leachates (stepwise dissolution solutions) of one ordinary chondrite and two enstatite chondrites of EL and EH subgroups previously measured for Nd and Sm isotopes. The leachates of the ordinary chondrite display large variations of their Cr isotope compositions, whereas the leachates of the enstatite chondrites show very limited variations of their nucleosynthetic compositions, confirming other studies. The Cr isotope compositions of leachates of unequilibrated chondrites are significantly modified by thermal processing and aqueous alteration under various conditions. The leachates of the enstatite chondrites are relatively homogeneous for Cr isotope composition, suggesting that presolar carriers of Cr are not stable under very reduced conditions and are likely oxidised phases. After careful examination of the role of parent body processing, we conclude that there is one predominant presolar carrier enriched in 54Cr that produced most of the nucleosynthetic variations observed in leachates. This carrier is likely depleted in the carbonaceous reservoir relative to the non-carbonaceous reservoir. The drastically different isotope compositions of Cr and heavy refractory lithophile elements such as Nd of leachates of chondrites reflect relative preservation biases of their respective presolar carriers, namely a still poorly characterised presolar oxide and silicon carbide (SiC), respectively.

Particle emissions from submerged combustion evaporation of membrane-concentrated leachate

The submerged combustion evaporation process, which is extensively utilized in the treatment of high salinity wastewater, inevitably confronts the challenge of particle emissions. These emissions significantly impact the local environment and pose substantial health risks to on-site workers. Currently, the understanding of particle emissions' characteristics and their critical conditions during direct-contact heat and mass transfer processes is limited, which hampers the development of effective strategies for particle control. Here, particles emitted from three evaporation projects with different membrane-concentrated leachate sources were first characterized. Most of the particles were ultrafine particles (≤100 nm) in the range of 6–500 nm, most of which were in the range of 30 nm and constituted 75.37%–89.98% of the total mass. The particles were mainly composed of inorganic ions (80.86%–86.88%), humus (1.95%–3.66%) and insoluble carbon (2.57%–4.26%). The particle concentrations range from 1.64 to 218.35 mg/m3, depending on factors such as bubble temperature, evaporation capacity, and leachate composition within evaporators. A model assessing particle release capacities showed an increase with rising bubble temperature and humus concentration. A critical bubble temperature of 1390 K was identified for significant particle release, highlighting the need to keep the bubble temperature below this level to manage heat-induced particle release within 2 mg/m3. Additionally, the high humus migration capacity to particles underscores the need to prioritize humus removal before evaporation in particle control strategies. The application of these strategies can significantly decrease particle emissions, fostering cleaner production during submerged combustion evaporation and other direct-contact heat and mass transfer processes.

Oxidative stress and energy metabolic response of Isochrysis galbana induced by different types of pristine and aging microplastics and their leachates

The aging process and leachate composition of different types of MPs (PS, PS-NH2, PS-COOH and PMMA) with a particle size of 1.0 μm were characterized, and marine microalgae Isochrysis galbana OA3011(I. galbana) was used as test organism to investigate the 96 h toxic effects of MPs before and after aging as well as leachate exposure. Except for polymethyl methacrylate (PMMA), all other tested microplastics showed significant aggregation in seawater, which increased with the presence of surface amino and carboxyl groups, in addition, the increase in polymer dispersibility index (PDI) values after aging reflected more severe aggregation. Fourier transform infrared spectrometer (FTIR) showed that the surface amino groups were shed during the aging of PS-NH2, which can likewise be demonstrated by the change in surface electric potential from positive to negative before and after aging. PMMA, due to the addition of plasticizers (HEHP and DIBP detected in high concentration) and its own structure, has stronger resistance to aging than the other three microplastics, and no significant aging phenomenon occurs. As for I. galbana, growth inhibition, oxidative stress and energy metabolism were tested after exposure to different microplastics and their leachate. It was found that high concentrations of A-PS had a greater negative impact on I. galbana, while the toxic effects of PS-NH2 and PS-COOH on I. galbana behaved in a diametrically opposite way before and after aging compared to PS with the inhibitory effect decreasing after aging, which was caused by the shedding of surface groups. As for PMMA, the differences in the toxic effects on microalgae before and after aging were not significant. The inhibitory effect of low concentrations of PAEs (Phthalate acid esters) in the leachate of PS-COOH on I. galbana was not significant, and the stronger inhibitory effect of 4 d L-PS-NH2 was presumed to be the shedding of positively charged groups.

Landfill leachate treatment in Malaysia: Continuous circulation motion using mixed agricultural wastes with an open grid-like Luffa's configuration

In this study, adsorbent materials from agriculture waste such as luffa, coconut husk, pineapple leaf and activated charcoal (AC) from coconut shell were synthesized and characterized. The material is termed as COLUFNAS/AC. The adsorbent material then was used to treat landfill leachate with ammonia as Total Kjeldahl Nitrogen (TKN), ammoniacal nitrogen (NH3−N), total suspended solid (TSS), turbidity, biochemical oxygen demand @5 days (BOD5), chemical oxygen demand (COD) and heavy metals with values of 2,279.2 ADMI, 417.2 mg/L, 1,0220 mg/L, 2,388 mg/L, 9,092 mg/L, 45,164 mg/L and <0.08 mg/L, respectively. The experiments were conducted at the laboratory and pilot scale. For laboratory scale, 8 PVC pipes with COLUFNAS/AC were used to treat 30 L of landfill leachate. Under 6 h operating conditions, COLUFNAS/AC was significantly reduced the TKN (44.84 %), turbidity (45.90 %), and COD (31.88 %). Therefore, the potential removal efficiency of COLUFNAS/AC at laboratory scale was further applied at pilot scale in pH adjustment and coagulation tanks for 15 days. The complex composition of leachate at pilot scale (30,605.5 m3) significantly improved the leachate quality by 11.11 %, 17.03 %, 12.92 %, 52.25 % and 55 % reduction of NH3–N, TSS, turbidity, BOD5 and COD. The pH of leachate was also changed to less acidic. Implementing COLUFNAS/AC in both tanks not only effectively saved treatment costs to 3,955.22 USD/month but also achieved the lowest operational treatment cost at just 0.22 USD/m3.

Impact of nCuO containing treated wastewater on soil microbes and dissolved organic matter in paddy field leachate

Using treated wastewater (TWW) resources in agriculture is a major pathway for disseminating nanoparticles. Copper–oxide nanoparticles (nCuO) offer potential benefits, but their presence in the environment poses risks to agricultural and environmental sustainability. This study examined soil microbial transformations and the composition of leachate dissolved organic matter (DOM) of paddy soils irrigated with nCuO-contaminated TWW at different concentrations (T2: 0.02 mgL−1, T3: 0.2 mgL−1, T4: 2.0 mgL−1) and examined the differences in Cu source (T5: 0.2 mgL−1 CuSO4). Results showed negative impacts on the absolute microbial abundance with up to 46 % reduction relative to the control treatment (T1). Changes in relative abundance of specific microbes at the genus level deviated from the corresponding phyla. Acidobacteria, Actinobacteria, Chloroflexi, and Verrucomicrobia phyla increased in the surface (0–3 cm) and subsurface (3–15 cm) layers responding differently to nCuO. In the 0–3 cm layer, Nitrospirae, Euryarchaeota, and Crenarchaeota increased, but only Dechloromonas genus from Proteobacteria increased with increasing nCuO. No significant variations were observed in the DOM composition, except in T4, which had a significantly low content of dissolved organic carbon (DOC), total dissolved nitrogen, and terrestrial humic-like and protein-like components. Ninety-eight distinct genera were identified, of which 44%, including 15 bacteria and two archaea, varied between the surface and subsurface, among treatments, and significantly correlated with more DOM parameters in the subsurface. T4 had the highest microbial diversity in the 0–3 layer, and Cu treatments slightly increased the diversity index in the subsurface. Moreover, the effects differed by Cu source, with T3 showing 10 % more reduction in the subsurface and 17 % less reduction in the surface than T5. The variable microbial responses to nCuO and their strong correlations with DOM highlight the need to consider the potential consequences of low nCuO concentrations on biogeochemical cycles.

Physical and chemical characterization and pollution index applied in the assessment of the polluting potential of leachate from urban landfills.

During the operation of the landfills, leachate should be managed with caution to avoid possible negative environmental impacts. Considering this, the present study aims to evaluate the relationship between different variables in the leachate composition and elucidate the transformation processes through which this effluent passes during the landfill's period of operation. The study was conducted with eight sanitary landfills from the state of Minas Gerais, in southeastern Brazil, and used descriptive statistical analysis, principal component analysis (PCA), correlation analysis, and calculation of the leachate pollution index (LPI). The biochemical oxygen demand (BOD5)/chemical oxygen demand (COD) ratio was between 0.20 and 0.60. We also observed a significant correlation of 0.45 between Cl- and N-NH4+, which reflects the biological degradation processes that contribute to the presence of both variables. The PCA showed that inorganic variables and organic matter dominated the first component, with coefficients above 0.65, indicating the importance of those variables in determining the general data variability. The LPI values were between 15.26 and 25.97, with BOD5, COD, and N-NH4+ having sub-indexes above 35, being the main variables that increase the pollution potential of the leachate. On the other hand, trace metals present sub-indexes below 7 due to precipitation caused by increased pH and the characteristics of the waste discarded in landfills. The study provides essential information regarding the landfill leachate characteristics and its variation over time, which can contribute to the definition of treatment technologies for this affluent in different scenarios.

Resynthesis of cathode active material from heterogenous leachate composition produced by electric vehicle (EV) battery recycling stream

Massive growth of electric vehicle (EV) sales in recent years triggers the huge demands of certain elements for lithium-ion battery (LIB) production. To sustain the supply of the elements and contribute to its circularity, LIB recycling is one of the justified routes. Although hydrometallurgy is considered as the most common process in battery recycling, improvements are still required to make the recycling process cleaner by reducing the steps and minimizing the chemical use. To achieve this goal, co-precipitation method is proposed to produce cathode active metals (CAM) of Li, Ni, Mn and Co from the leach solution. As battery chemistry is evolving fast, in near future, the dominant LiNi1/3Mn1/3Co1/3O2 (LNMC 111) type will be replaced by other types with different NMC ratios. Hence, in this study, co-precipitation was tested to recover Li, Ni, Mn and Co from various leachates with different metal compositions, simulating leachates from different battery chemistries. A hydrometallurgy flowsheet comprising four precipitation steps for metal recoveries from leach solutions was developed. In the first stage, aluminium was removed as Al(OH)3 by increasing the pH of the leachate to 5.5. Cu was removed in the next stage as sulfide by adding sodium sulfide to the supernatant obtained in the first stage. In the third stage, Ni, Mn and Co were co-precipitated as hydroxide precursor by increasing pH of supernatant to 11. The results showed that >95% of Ni, >83% Co, and >42% of Mn could be precipitated from the leaching liquor. Finally, Li is recovered from the supernatant as carbonate precipitate by adding sodium carbonate. Ni,Mn,Co(OH)2 precursor was finally mixed with Li2CO3 precipitated and calcined to resynthesize CAM showing the potential of this process to close the loop of recycling.

Leachate indicators of an elevated temperature landfill

Elevated temperature landfills (ETLFs) are municipal solid waste (MSW) landfills that have been impacted by subsurface exothermic reactions (SERs) and display unusual gas and leachate composition. Leachate quantity and quality data were analyzed to identify indicators of a SER at an ETLF in Ohio, USA. ETLF leachate generation increased from 2.04 to 14.4 m3/hectare-day (218 to 1,539 gallons/acre-day), peaking 16 months after the reaction was first noticed. The leachate generation rate for this ETLF remains about two times greater than the average Ohio MSW landfill. Several general parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) remain impacted 5 years later. Similarly, metals such as arsenic, iron, calcium, potassium, and magnesium have increased in concentration. Volatile organic compounds (VOCs) behavior was less consistent as a group of chemicals. Increases of VOCs such as acetone, benzene, and methyl ethyl ketone (MEK) also increased. Importantly, in one year, benzene exceeded its toxicity characteristic threshold meaning the leachate was a hazardous waste, substantially increasing treatment and disposal costs. It is not clear if the VOCs are produced directly by the SER or if they are an indicator that microbial processes -which would otherwise consume them- have been disrupted. ETLFs likely do not all undergo the same exothermic reaction(s) and, unlike the analysis of landfill gas composition, temporal changes in leachate constituents’ concentrations may be more important than comparing to absolute values.

Accelerated aging of polyvinyl chloride microplastics by UV irradiation: Aging characteristics, filtrate analysis, and adsorption behavior

The extensive use of plastic products by people has led to the prevalence of microplastics (MPs) in aquatic and terrestrial ecosystems. MPs will be able to undergo multiple aging processes and release dissolved organic matter (DOM) in the aquatic environment, thereby further affecting the ecosystem. Therefore, this thesis systematically investigated the photo-aging properties of polyvinyl chloride (PVC), and characterized the changes in physicochemical properties; in addition, the DOM composition and fluorescence characteristics of MPs leachate were characterized by using TOC and 3D-EEMs. Our results showed that the O/C ratio can quantitatively characterize the surface aging of MPs. Furthermore, We chose Malachite green (MG) and Sulfamethoxazole (SMX), which are abundantly present in the aqueous environment, as the target pollutants, through adsorption experiments we established the regression equations of the equilibrium adsorption capacity of aging MPs with O/C ratio or CI and mean particle size. Exploring the relationship between aging properties and the adsorption capacity of microplastics can help predict the degree of aging and accumulation of hydrophilic contaminants in the natural environment.

Optimizing pH conditions for impurity removal in closed-loop Li-ion battery recycling

The closed-loop recycling or resynthesis of spent cathode active materials is an emerging hydrometallurgy-based Li-ion battery (LIB) recycling approach. The conventional acidic leaching process generates various impurities in addition to the constituent elements of Ni, Co, Mn, and Li from spent Li[Ni1-x-yCoxMny]O2 (NCM) cathode active materials. It is well known that even a trace amount of these impurities in resynthesized cathode active materials can affect the LIB performance significantly. Therefore, this study aims at investigating the effects of impurities on the physicochemical and electrochemical characteristics of resynthesized NCM by varying pH conditions during the purification of the LIB leachate. After the purification process where the pH is raised from 1.9 to 6.5, Al, Cu, and Zn are completely removed and other impurities including Fe, Mg, Ca, Li, and Na mostly or partially remain in the leachate. The physicochemical properties and LIB performance of resynthesized NCM at different pH conditions are obtained by various analytical techniques. The composition of leachate and cathode active materials is correlated with the initial discharge capacity, rate capability, and cyclability. Resynthesized NCM from the purified leachate shows a similar initial discharge capacity to pristine NCM. While the purification condition at a high pH aggravates the rate capability, the cyclability of resynthesized NCM is enhanced. This established correlation between the pH condition for the impurity removal in the LIB leachate and the LIB performance of resynthesized NCM would trigger the successful implementation of the closed-loop recycling of spent cathode active materials.

Particle transfer mediates dermal exposure of consumers to plasticizers in eraser and pen accessories

Dermal exposure to chemicals released from daily consumer products is a rising concern, particularly for children who are susceptible to unintentional hand-to-mouth transfer and related chemical exposure risk. However, chemical transfer induced by tiny particles of intact products has yet to be adequately addressed. The objective of the present study was to determine the potentiality of particles release from intact erasers and pen grips upon dermal contact by measuring the migration rates of the embedded plasticizers (phthalates and its alternatives). The results showed that billions of particles were released from erasers (0.6–1.2 × 109) and pen grips (0.2–1.6 × 108) upon dermal contact at ambient temperature, with sizes mainly smaller than 1 μm. The composition of eraser leachates was identical to that of the corresponding bulk eraser, as confirmed by Fourier-transform infrared spectroscopy and pyrolysis. Migrated hydrophobic plasticizers may be used as indicators of particle release from erasers and pen grips. The potentiality of particle release was negatively correlated with the total plasticizer contents (r = −0.51; p < 0.05) for both erasers and pen grips. These findings indicated that particles directly released from school supplies and accessories could be a non-negligible source of human exposure to plasticizers.

Altered leaching composition of maize starch granules by irradiative depolymerization: The key role of degraded molecular structure

The molecular composition of starch leachates from starch-based foods has been recently recognised as a crucial determinant of food properties. However, there is limited knowledge on the regulation of this composition through irradiative depolymerization of starch. This research investigates the leaching behaviour of maize starch depolymerized by electron beam irradiation, and the relationship between the composition of leached starch and structures of modified starch granules. The analysis using 1H NMR spectroscopy confirmed a decrease in the degree of branching (from 4.4 % to 2.8 %), while size-exclusion chromatography identified a newly-derived amylopectin fraction of a smaller hydrodynamic radius (approximately 60–80 nm). The structural properties of the starch granules were also analysed, revealing an increased BET-area of granules and reduced total crystallinity after depolymerization. In the leachates of swollen granules, the bimodal distribution of starch molecules evolves into unimodal with the increase of the irradiative dosage, while modified starch leached more starch molecules with Rh < 10 nm. The results of principal component analysis and Pearson correlation analysis indicate that the degree of branching of degraded starch molecules, as well as the newly-derived amylopectin fraction, significantly correlates (p < 0.01) with the molecular size of leached starch molecules (Rh < 10 nm). It is thus proposed that the cleavage of α-1,6 linkage may be a critical factor in controlling the leaching process of irradiated starch granules. This study highlights the potential of irradiative degradation to control the molecular composition and structure of starch leachates, thereby optimizing the properties of starch-based foods.

Investigation with ESI FT-ICR MS on sorbent selectivity and comprehensive molecular composition of landfill leachate dissolved organic matter.

Molecular characterization of landfill leachate dissolved organic matter (LDOM) is essential for developing effective processing techniques. However, the molecular selectivity of extraction method and ionization modes often leads to the bias of molecular characterization of LDOM. Here, seven representative sorbents were selected and electrospray ionization negative ion mode (ESI (-)) and positive ion mode (ESI (+)) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to investigate the molecular composition of different LDOM samples. Obvious sorbent selectivity during extraction procedure was observed, resulting in the underestimation of molecular diversity of LDOM from 32.7% to 69.3%. Totally, 14,000-18,000 unique molecules were obtained in a single sample, indicating the unprecedented molecular diversity of LDOM. Lignins, proteins and lipids are three major molecular groups in LDOM, and N or S containing molecules occupied 83%. Although much of total organic carbon was removed during biochemical treatment process, the molecular diversity of LDOM was not reduced because a considerable of bio-recalcitrant molecules was produced. The results uncover the sorbents selectivity and ionization modes selectivity in LDOM analysis and provided a comprehensive change of LDOM molecular composition during biochemical treatment, which benefits the development of accurate methods to remove organic carbon in landfill leachate.

Closed-loop process for Zn and Cu selective recovery from MSWI bottom ash fine fraction

In 2019, 224 Mt of Municipal Solid Wastes (MSW) were produced in Europe. A significant proportion of this MSW is treated by incineration producing each year 20 Mt of Municipal Solid Waste Incineration (MSWI) Bottom Ashes (BA). While the coarsest fraction (>2mm) can be reemployed in construction field, this is not the case for the finest fraction <2 mm (30% wt.) which is intended to be landfilled. The challenges of the treatment of this solid residue are multiple. The metals of interest are dispersed within this complex matrix and the gangue is composed by a large proportion of carbonate based minerals which reduces the choice of possible leaching agents. Moreover, the large amounts of iron and aluminum imply to choose a highly selective recovery method and the economic constrains steer the process towards low-cost technologies. The aim of this work is to study the feasibility of a selective copper and zinc recovery, whose contents in the bottom ash fine fraction are comparable to low-grade ores. A four-step process was designed consisting of a flushing, a leaching, a precipitation and an electrowinning. A selective leaching step using ammonia-ammonium chloride solution was carried out to avoid an iron co-leaching. After the leaching step, the precipitation of zinc was achieved by addition of aluminum nitrate followed by an electrodeposition of copper from ammonia medium. Up to 70% of Cu and Zn could be recovered with minimal modifications of the leachate composition allowing thus its reuse. The developed process enables the recovery of metallic copper and zinc in a spinel form from a waste originally intended for landfilling.

Brand-Specific Toxicity of Tire Tread Particles Helps Identify the Determinants of Toxicity.

The widespread occurrence of tire tread particles (TPs) has aroused increasing concerns over their impacts. However, how they affect the soil fauna remains poorly understood. Here, based on systematically assessing the toxicity of TPs on soil model speciesEnchytraeus crypticusat environmentally relevant concentrations through both soil and food exposure routes, we reported that TPs affected gut microbiota, intestinal histopathology, and metabolites of the worms both through particulate- and leachate-induced effects, while TP leachates exerted stronger effects. The dominant role of TP leachates in TP toxicity was further explained by the findings that worms did not ingest TPs with a particle size of over 150 μm and actively avoided consuming TP particles. Moreover, by comparing the effects of different brands of TPs as well as new and aged TPs, we demonstrated that it was mainly TP leachates that resulted in the ubiquity of the disturbance in the worm's gut microbiota among different brands of TPs. Notably, the large variations in leachate compositions among different brands of TPs provided us a unique opportunity to identify the determinants of TP toxicity. These results provide novel insights into the toxicity of TPs to soil fauna and a reference for toxicity reduction of tires.

Biological treatment and microbial composition of landfill leachate using a compost process in an airlift bioreactor

Landfill leachate (LL) contains a large amount of toxic compounds and its treatment is currently a matter of concern. In this work, an adapted compost in different airlift bioreactors was used to depurate a complex, toxic and old landfill leachate without treatment (raw leachate) and after pretreatments (coagulation/flocculation; coagulation/flocculation and filtration; coagulation/flocculation, filtration and photo-Fenton process). After the complete pretreatments, a high removal of organic matter was achieved, with a global removal of chemical oxygen demand (COD) and humic acids of 72.4% and 83.4%, respectively; besides, copper and iron in the landfill leachate presented a total removal of 91.1% and 65.8%, respectively. On the other hand, after the contact of raw leachate with compost in the airlift, there was a decrease of COD, copper and iron, while for humic acids there was a slight increase. The same trend was observed when the leachate was submitted to the different pretreatments and subsequently subjected to the biologic process with compost. The respirometric analyses showed that the raw leachate was toxic, although this tendency decreased along the treatments, with inhibition values of 41.8%, 27.5%, 22.0% and 12.1% for raw and pretreated leachate (by coagulation/flocculation, filtration and photo-Fenton processes), respectively. Also, in order to improve our knowledge about the composition of the microbial assemblages in compost samples and their possible role in pollutants removal from LL, we analysed samples from both an adapted and a non-adapted compost before and after being in contact with the raw leachate by applying Illumina sequencing of the 16S rRNA gene. Bacteroidota, Proteobacteria, Firmicutes, Spirochaetota and Deinococcota were the most abundant phyla in all samples, being present in the 50 most abundant Amplified Sequence Variants (ASVs) of the study, which represented 56.5% of the total analysed sequences and were considered as our core community. Chryseolinea, Herbinix, Proteiniphilum, Pseudomonas and Sphaerochaeta seemed to be the most resilient genera when the compost was in contact to LL. Moreover, our results showed that the metabolisms related to chemoheterotrophy, fermentation and the nitrogen cycle were the most relevant in all samples. In general, the microbial community was able to adapt to adverse conditions and remove pollutants, as heavy metals.

Multizone Aquatic Ecological Exposures to Landfill Contaminants from a Groundwater Plume Discharging to a Pond.

While it is recognized that groundwater contaminant plumes can impact surface waters, there remains little information on the magnitude, spatial extent, and especially temporal variability of the resulting exposure to the variety of aquatic organisms, particularly for stagnant surface waters (e.g., ponds). The present study of a historic landfill plume discharging to a pond investigated contaminant exposure to multiple aquatic zones (endobenthic, epibenthic, pelagic) over approximately 1 year within a temperate climate. Landfill tracers included the artificial sweetener saccharin, ammonium, chloride, and specific conductance. Sampling of pond sediment porewater (upwelling groundwater) and continuous geophysical imaging of the subsurface showed a relatively stable plume footprint covering approximately 26% of the pond, although with spatially varying leachate composition, revealing year-round exposure to endobenthic (within sediments) organisms. Substantial and variable contaminant exposure to epibenthic organisms within the plume footprint was shown by elevated specific conductance measured directly above the sediment interface. Exposure varied daily at times and increased through winter to values representing undiluted plume groundwater. Exposure to pelagic organisms (overlying water) covered a larger area (~50%) due to in-pond circulation. The stream outlet concentrations were stable at approximately 10 times dilution for chloride and saccharin, but were substantially less in summer for ammonium due to in-pond processes. Whereas groundwater contaminants are typically assumed elevated at base flows, the outlet stream contaminant mass discharges to downstream receptors were notably higher in winter than summer, following stream flow patterns. Insights from the present study into the timings and locations of contaminant plume exposure to multiple ecological zones of a pond can provide guidance to contaminated site and aquatic ecosystem managers on improved monitoring, assessment, and remediation protocols. Environ Toxicol Chem 2023;42:1667-1684. © 2023 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.