Leachate composition and toxicity assessment: an integrated approach correlating physicochemical parameters and toxicity of leachates from MSW landfill in Delhi

Cation interception and permeability characteristics of bentonite barriers exposed to NaCl and NH4Cl solutions

High concentrations of Na+ and NH4+ in landfill leachate lead to deterioration of bentonite barrier and pose a threat to the environment. This study focused on the pollution interception and permeability characteristics of the bentonite barrier exposed to NaCl and NH4Cl solutions. Based on previous findings, salt solution concentrations were established at 74.80, 37.40, 18.70, and 9.4 mmol/L. The bentonite contents in the mixture were set at 0, 5, 10, and 15%. The results indicate that the samples exhibit better interception of NH4+ compared to Na+. This difference arises from the cation exchange sequence, the size of the hydration radius, and the hydrogen bonding of the two cations. Additionally, the difference in hydration enthalpy between the two cations leads to variations in the swelling of bentonite, resulting in a higher hydraulic conductivity coefficient in NH4Cl solution. This study shows that although bentonite barriers have better interception for NH4+, they exhibit greater hydraulic conductivity in NH4Cl solution, increasing the risk of leachate carrying other contaminants.

Characteristics and pollution potential of leachate from municipal solid waste landfills: Practical examples from Poland and the Czech Republic and a comprehensive evaluation in a global context

The formation of leachate is mainly due to the percolating of rainwater through the body of the landfill and the physical, chemical, and biological processes taking place inside the body of the landfill. The characteristics and pollution potential of leachate from the municipal solid waste (MSW) landfills in Poland (Łubna) and the Czech Republic (Zdounky) is presented. The objectives of this study are: 1) to evaluate and compare physicochemical characteristics of leachate, 2) to demonstrate the variability of leachate parameters in time, concerning stabilization phase of the landfill, 3) to present existing relationships between the characteristics of the leachate, 4) to indicate the factors determining the variability of the leachate composition. The Leachate Pollution Index (LPI) was applied to indicate temporal changes in leachate pollution, to assess polluting ability of leachate, and to compare the pollution potential of leachate. For the Łubna landfill, the minimum, maximum, and average values of LPI were: 6.10, 39.41, and 18.44, respectively. The LPI for the Łubna landfill tends to decrease in time due to stabilization of wastes. For the Zdounky landfill, temporal decreasing of LPI was not observed. The minimum, maximum, and average values of LPI were: 6.25, 14.25, and 10.11, respectively. Alkaline characteristics of leachate from both landfills indicate the mature stage of waste storage. This phenomenon was also evidenced by the Chemical Oxygen Demand (COD), ammonium (NH₄⁺), and cadmium (Cd). For both landfills, pH was negatively correlated with most of the leachate parameters. It is the task for environmental engineers to confront existing knowledge (supplemented by the results of this work) about the properties of leachate, its changes over time and its polluting potential with the possibilities of treating and managing it properly.

Health implications, distribution and source apportionment of heavy metals in road deposited dust of Jammu City in northern India

Road deposited dust (RDD) is an important indicators of heavy metal contamination in urban areas. In this study, we measured eight heavy metals (V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb) in RDD collected from 34 different locations in Jammu city represented by different land uses such as industrial, urban-residential, high-density traffic, and sub-urban locations, and evaluated their ecological and health risks. The ratio of metal concentrations in RDD to their respective background levels varied as: Cu (3.94) > Pb (3.75) > Zn (3.01) > Cr (1.75) > Ni (1.51) > Mn (1.40) > V (1.35) > Fe (1.1) suggesting Cr, Ni, Cu, Zn and Pb were enriched anthropogenically. Geospatial maps revealed a heterogeneous distribution of metals in Jammu city with metal(s) specific hotspots primarily localized around high traffic density locations and industrial clusters. The index of geoaccumulation indicated 32%, 26%, 20%, 9%, and 8%, of samples belonged to "moderately polluted" category for Zn, Cu, Pb, Cr, and Ni respectively. Health index (HI) showed low non-carcinogenic hazards of metal contamination to adults but a high hazard to children. Though the values of total carcinogenic risks (TCR) (6.53E-05 to 3.71E-04) considerably exceeded the USEPA acceptable levels (1 × 10^-6 ≤ TCR <1 × 10^-4) suggesting high carcinogenic risks of metal contamination to both adults and children. Besides potential ecological risk index (PERI) revealed that 56% of samples had PERI >40 suggesting "moderate to high ecological risk" of metal contamination in the Jammu city RDD.

Leachate decontamination through biological processes coupled to advanced oxidation: A review

The landfill leachate is considered a toxic effluent composed of recalcitrant contaminants that requires innovative alternatives for its decontamination. Coupling between advanced oxidation processes (AOPs) and aerobic biological treatments are highlighted in this research. Therefore, a bibliographic review of the research made from 2010 to 2021 was developed. These combined alternatives were applied in leachates, and it is oriented toward the analysis of knowledge gaps, trends, and future proposals of the treatment combined that contribute to researchers who wish to work on the subject. These kinds of treatments were chosen due to a bibliometric analysis made. Also, the information was searched in several scientific database. This work was found to be unpublished, as no reviews were found so far that agglomerate studies of coupling between photocatalytic and aerobic biological processes to treat leachates. Besides, AOPs are ideal for treating wastewater of complex composition, however, when it is used as the only treatment, they are usually unprofitable, which justifies their coupling with biological treatments. Subsequently, it was determined that the knowledge main gap is the lack of documentation of treatment costs, which makes it difficult to implement on a real scale. In addition to this, the couplings trends are toward doping with metallic and nonmetallic ions of the catalyst used in the photocatalytic process to improve the efficiency of these. Finally, future research should work on finding alternatives that allow the optimization of the resources used in the combined systems and on promoting the recovery of existing products in the leachate.Implications: Leachates generate several environmental impacts due to their toxic composition. Even when coupling between heterogeneous photocatalysis and biologic treatment can solve them, issues like cost analysis and the scaling-up factor have not been developed, and futures researchers should work on that. Besides, the trend founded in almost all investigations was the catalyst doping with metals and nonmetals ions, particularly when they use TiO2 because it gives the possibility of improving efficiencies just with a structural variation. Finally, these treatment combinations require more analyses and comparison of their remotion over emerging pollutants and their performance with new designs.

Mapping the impact of a large municipal waste disposal area on surface water: 1993-2017, case of Laogang, Shanghai

In China, the impact of waste disposal facilities is always a cause of concern for the government and the public. Laogang Municipal Waste Disposal Area (LMDA), Shanghai, one of the largest municipal waste disposal areas in the world was selected as case in this study, and it was attempted to analyze the changes in the surface water quality, and map the impacted area by LMDA on surrounding streams from its operation period of 1993-2017. The results showed that, during the whole period, only biochemical oxygen demand (BOD₅) showed a continuous improvement with a percentage of 85.92%, however, chemical oxygen demand (COD_cr), ammonia (NH₄⁺-N) and total phosphorus (TP) significantly improved but BOD₅ slightly deteriorated began from 2013. Using spatial analysis tools and Kendall's concordance test, COD_cr and phenol at LMDA showed a significant impact on surrounding surface water; especially, the impacted area for COD_cr decreased from 106.30 km² to 22.86 km² from 1993 to 2017, which dropped from 4.3 to 0.9 times the area of LMDA. Surprisingly, NH₄⁺-N and TP at LMDA were affected by the surrounding streams, instead of having an impact on them. Interestingly, heavy metals and non-metals such as Hg, As, Zn, and Se in the surrounding streams were unlikely affected by LMDA. The driving forces for surface water quality improvement included the eco-remediation of closed unsanitary landfills, upgrade in waste shipping and terminals, operation of sanitary landfills and incineration plants for landfill diversion. Capsule: Impacted area of municipal waste disposal area is not so large.

Micro- and Macroelements Content of Plants Used for Landfill Leachate Treatment Based on Phragmites australis and Ceratophyllum demersum

One of the key problems associated with the functioning of landfills is the generation of leachate. In order to reduce their negative impact on the environment, various treatment technologies are applied. Among them, solutions based on the use of phytotechnology deserve special attention. The aim of this study was to evaluate the impact of landfill leachate on the content of micro- and macroelements in plant material. The research was carried out in four municipal waste landfills located in Poland. Emergent macrophytes (P. australis) and submergent macrophytes (C. demersum) were used in this research. The migration and distribution of pollutants reaching the roots and shoots of P. australis from water solutions were also studied. The concentrations of heavy metals in the studied plants were low in all analysed cases. Higher metal contents could often be observed in roots rather than in shoots, but these differences were insignificant. The chemical composition of the studied plant samples was primarily related to the source of origin of the treated leachate (landfill), as clearly demonstrated by cluster analysis. In the conducted studies, no important differences were noted in the accumulation of the studied components between submergent plants (C. demersum) and emergent macrophytes (P. australis).

Exposure to Landfill Leachates Affects the Embryonic Development of Zebrafish, Danio rerio: A Case Study in Yucatan, Mexico

We report the chemical characterisation and toxic effects of municipal solid waste landfill leachates on the embryonic development of Danio rerio. The results of the Fourier transform infrared spectroscopy (FTIR) revealed the presence of nitrogen-containing groups and aromatic functional groups associated with highly toxic pollutants such as ammonia and heavy metal-humic complexes. Mortalities of up to 93 and 100% were observed in 1:64 and 1:32 landfill leachate dilutions, v/v, respectively. The hatching percentages of the fish were also severely affected, with very low percentages ranging from 0 to 33.3% for 1:32, 1:64 and 1:128 dilutions, v/v. Morphologically, a developmental arrest was evident for all treatments. This study reveals the high toxicity of landfill leachates that could contaminate the aquifer of the Yucatan Peninsula and threaten the health of living organisms.

Analysis of the possibility of conducting a comprehensive assessment of landfill leachate contamination using physicochemical indicators and toxicity test

The inevitable consequence of the operation of landfills is the emission of leachate, which is considered to be one of the main polluters of the ground and water environment. The leachate contains soluble organic compounds, inorganic contaminants, suspended solids, heavy metals and dangerous substances. The selection of the leachate disposal method requires a comprehensive assessment of its properties. Therefore, the physicochemical parameters and toxicity tests were chosen for a comprehensive assessment of the properties of leachate. Four municipal waste landfills (operational and non-operational) were selected for the study, for which multidimensional statistical analyses were carried out. The study was conducted between the period of April 2018 and December 2019. The comprehensive assessment showed that pollutants in leachate from the analyzed landfills remained at a level which did not allow them to be discharged to water or soil. The presence of substances particularly harmful to the aquatic environment (e.g AN, chromium, copper) may hinder their treatment together with household sewage, as it involves obtaining a permit required under laws. Toxicity of leachate may also be a problem, as it may persist after the treatment process is completed. The values of pH, EC and the concentrations of ON, TDS, TSS, chloride, iron and manganese had the strongest influence on the properties of leachate from all landfills. For operational landfills, these were also calcium concentrations, for non-operational ones COD, TU and the concentrations of TKN, AN, TS, sodium, potassium and magnesium. The mentioned parameters also showed strong correlation with other physicochemical properties of the leachate, which indicate their suitability for the monitoring of leachate and the aquatic environment in the vicinity of municipal waste landfills.

Evaluation of the Phytotoxicity of Leachate from a Municipal Solid Waste Landfill: The Case Study of Bukov Landfill

Municipal solid waste landfilling, landfilling process and landfill reclamation result in leachate, which may be dangerous to the environment. Municipal solid waste leachate phytotoxicity tests were performed using the toxicity test and a subchronic toxicity pot experiment by direct application of leachate to reference soil in 5, 25, and 50% concentration for a period of 28 days. White mustard (Sinapis alba L.) seeds were exposed to different leachate dilution. Leachate were collected monthly in 2018 in the period from April to September. Furthermore, pH, conductivity, and dissolved oxygen were measured. The inhibition results on Sinapis alba L. seeds in the tested leachate samples ranged from −18.02 to 39.03%. Lower concentration of leachate showed a stimulating effect (only for Sample 1 and Sample 2 at 5% concentration). It was found out that leachate taken at the landfill is phytotoxic. The results of measurements are based on rainfall which affects the quantity and quality of the leachate. The values of germinated seeds/growing plants from the subchronic toxicity pot experiment ranged from 80 to 104%; therefore, the leachate is considered phytotoxic. However, it was confirmed that leachate may be used for landfill irrigation.

Impairment of Mitochondrial-Nuclear Cross Talk in Lymphocytes Exposed to Landfill Leachate

Landfill leachate, a complex mixture of different solid waste compounds, is widely known to possess toxic properties. However, the fundamental molecular mechanisms engaged with landfill leachate exposure inducing cellular and sub-cellular ramifications are not well explicated. Therefore, we aim to examine the potential of leachate to impair mitochondrial machinery and its associated mechanisms in human peripheral blood lymphocytes. On assessment, the significant increase in the dichlorofluorescein (DCF) fluorescence, accumulation of 8-Oxo-2'-deoxyguanosine (8-oxo-dG), and levels of nuclear factor erythroid 2-related factor 2 (Nrf-2) strongly indicated the ability of the leachate to induce a pro-oxidant state inside the cell. The decrease in the mitochondrial membrane potential and alterations in the mitochondrial genome observed in leachate-exposed cells further suggested the disturbances in mitochondrial machinery. Moreover, these mitochondrial-associated redox imbalances were accompanied by the increased level of NF-κβ, pro-inflammatory cytokines, and DNA damage. In addition, the higher DNA fragmentation, release of nucleosomes, levels of polyadenosine diphosphate ADP-ribose polymerase (PARP), and activity of caspase-3 suggested the involvement of mitochondrial mediated apoptosis in leachate exposed cells. These observations were accompanied by the low proliferative index of the exposed cells. Conclusively, our results clearly indicate the ability of landfill leachate to disturb mitochondrial redox homeostasis, which might be a probable source for the immunotoxic consequences leading to plausible patho-physiological conditions in humans susceptible to such environmental exposures.