Landfill Soil Research Articles

Compositional-geochemical characterization and multi-element pollution and risk assessment of potentially toxic elements in the urban landfill soil

Urban areas are characterized by the presence of various pollution sources including landfills. During the recent decade, urban landfills were investigated as a source of pollution by potentially toxic elements and potential deposits for landfill mining. The contents of Cr, V, Ti, Ca, K, Mo, Zr, Sr, Rb, As, Zn, Cu, Co, Fe, Mn, Pb, Ba in soils of Vanadzor city landfill site (VL) were determined using the X-ray fluorescence spectrometer to assess multi-element pollution and ecological risk and to identify potentially toxic elements geochemical associations through the application of compositional data analysis. The results showed that Cr, Mo, Zn, Cu, and Pb displayed significant values (>100%) of coefficient of variation suggesting their anthropogenic origin. Moreover, these elements, except Cr, displayed outliers and extreme values in the same sampling sites located directly on the reclaimed part of the landfill. The median contents of Zn, Pb, Cu, Cr, Cd, and As exceeded the global median values by 8.2, 9.8, 19.0, 4.6, 6.1, and 4.5 times, respectively. The multi-element pollution assessment showed that an extremely hazardous level of pollution was observed on the reclaimed part of the VL. From this site, a trend of decrease in the pollution level was observed in the eastern and western directions. In contrast, an allowable level of pollution was observed in the northern part - toward the direction of the above-located hill. The VL was found to be in an inferior ecological condition (a very high level of potential ecological risk was observed), which might also have a negative impact on the ecosystems located in its vicinity. The hierarchical clustering has revealed that the studied elements are grouped in two geochemical associations: a naturally formed - Co, Fe, V, Ti, Mn, Sr, Zr, Rb, K, Ba, As; and an anthropogenic one - Zn, Pb, Cu, Ca.

Enlarging effects of microplastics on adsorption, desorption and bioaccessibility of chlorinated organophosphorus flame retardants in landfill soil particle-size fractions

Chlorinated organophosphorus flame retardants (Cl-OPFRs) and microplastics (MPs) are emerging pollutants in landfills, but their synergistic behaviors and triggering risks were rarely focused on, impeding the resource utilization of landfill soils. This study systematically investigated the adsorption/desorption behaviors, bioaccessibility and human health risks of Cl-OPFRs in landfill soil particle-size fractions coexisted with MPs under simulated gastrointestinal conditions. The results showed that the adsorption capacity and bioaccessibility of Cl-OPFRs in humus soil were higher than that in subsoil. MPs promoted the adsorption of tris(1-chloro-2-methylethyl) phosphate (TCPP) and tris(1,3-dichloro-2-propyl) phosphate (TDCPP) in landfill soils by up to 34.6 % and 34.1 % respectively, but inhibited the adsorption of tris(2-chloroethyl) phosphate (TCEP) by up to 43.6 %. The bioaccessibility of Cl-OPFRs in landfill soils was positively correlated with MPs addition ratio but negatively correlated with the KOW of Cl-OPFRs, soil organic matter and particle size. MPs addition increased the residual concentration of Cl-OPFRs and significantly increased the bioaccessibility of TCEP and TDCPP by up to 33.1 % in landfill soils, resulting in higher carcinogenic and noncarcinogenic risks. The study presents the first series of the combined behavior and effects of MPs and Cl-OPFRs in landfill soils, and provides a theoretical reference for landfill risk management.

Efficiency of Microorganisms and Effectiveness of Biodegradation Techniques on LDPE Plastics: A Systematic Review

Introduction The aim of the research was to demonstrate the efficiency of microorganisms and the effectiveness of biodegradation techniques on Low-density polyethylene (LDPE) plastics. The research question was: What is the efficiency of LDPE-degrading microorganisms and the effectiveness of biodegradation techniques? Methods The systematic review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Articles were obtained from Scopus, Web of Science (WOS), Embase, and Google Scholar. The DeCS/Mesh search terms were: Low-density polyethylene, efficiency, biodegradation, microbial consortia, fungi, bacteria. Inclusion criteria were: scientific articles that included bacteria, fungi, and microbial consortia reported as LDPE degraders that report the percentage of weight loss; articles published from January 2010 to October 2022, and publications in Spanish and English with open access. Exclusion criteria were: studies that do not report gravimetry, the biodegradation time of LDPE, and the genus or species of the polyethylene-degrading microorganism. Results Out of 483 studies found, 50 were included in this Systematic Review (SR). The most frequent study techniques were scanning electron microscopy (SEM), gravimetry, and fourier transform infrared spectroscopy (FTIR), and in the case of microorganisms, the most studied belonged to the genus Pseudomonas, Bacillus, and Aspergillus. Regarding the isolation place, the most frequent mentioned in the reviewed articles were landfill soil and sanitary landfill soil. The efficiency of LDPE-degrading microorganisms was higher in bacteria such as Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp., which obtained a range of DE of 9.00-70.00%, 24.00-64%, 1.15 – 61.00%, 45.00%, and 1.5-40% with DT of 4-150, 120, 4-150, 30, and 30-120 days, respectively; in the case of fungi, the main microorganisms are Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii with efficiencies of 54.34, 48.78, and 46.34%, in 90 days, respectively; and the most efficient microbial consortia were from Enterobacter spp. and Pantoea sp. with 38.00 – 81.00%, in 120 days; and, Pseudomonas protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp. with 55. 00 – 75.00% in 120 days. Conclusions The most efficient microorganisms in LDPE degradation are Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp.; in fungi Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii; and in microbial consortia, those formed by Enterobacter spp. and Pantoea sp., and that of P. protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp.; and the most effective techniques used in LDPE biodegradation are SEM, gravimetry, and FTIR.

Characterization of methanogens from landfill samples: implications for sustainable biogas production

This case study aimed to isolate and identify methanogenic bacteria from landfill soil, mud, and leachate samples to assess their role in anaerobic digestion and biogas production. Anaerobic digestion involves the breakdown of organic matter by a diverse group of bacteria under oxygen-free conditions, resulting in the production of methane and carbon dioxide. The collected samples from the landfill were cultured in a modified mineral salt medium (MSM). Microscopic observations revealed distinct coccus and bacillus morphologies of the isolated methanogenic bacteria. Gas production experiments and substrate utilization studies identified two types of methanogens. Methanosarcina sp., which utilized acetate and methanol for methane production, and Methanobacterium sp., utilizing hydrogen and carbon dioxide, as well as acetate. Scanning electron microscope (SEM) analysis confirmed the different morphotypes of the isolated methanogens. The study findings demonstrated the presence of diverse methanogens in the landfill environment, contributing to anaerobic digestion and biogas production.

Isolation of Microbes from Landfill Soil of Gorakhpur, Uttar Pradesh, India

This study focuses on the isolation and characterization of microbes from landfill soil in Gorakhpur, India. Landfills are a major source of soil pollution, and understanding the microbial composition in these environments is crucial for assessing soil quality and developing remediation strategies. Microorganisms can degrade numerous of organic pollutants owing to their metabolic machinery and to their capacity to adapt to inhospitable environment. Thus, microorganisms are major players in site remediation. However, their efficiency depends on many factors, including the chemical nature and the concentration of pollutants, their availability to microorganisms, and the physio-chemical characteristics of the environment. The research identified a diverse microbial community in the landfill soil, with predominant bacterial representatives including Gamma-proteobacteria, firmicutes, and bacteroids. Gram staining revealed the prevalence of gram-positive bacilli, along with distinct fungal species. These findings emphasize the potential of microorganisms in degrading organic pollutants and transforming various compounds in landfill soil. By elucidating the microbial diversity in landfill sites, this study provides insights for sustainable waste management practices and environmental conservation efforts. One of the major cause of soil pollution are landfills. There are the sites designated for dumping rubbish, garbage, or other sorts of solid wastes. Because most of these waste materials are non-biodegradable, they heap in the landfills where they stay for years, impacting on soil quality and polluting the land. The aim of this study is to isolate and investigate the role of microorganisms in a particular landfill area of Gorakhpur, Uttar Pradesh and to identify the microbial community found in that particular area.

Microbial Allies in Plastic Degradation: Specific bacterial genera as universal plastic-degraders in various environments

Microbiological degradation of polymers offers a promising approach for mitigating environmental plastic pollution. This study (i) elucidated the diversity and structure of bacterial microbiomes from distinct environments (landfill soil, sewage sludge, and river water) characterized by specific physicochemical parameters, and (ii) utilized environment-derived microbial cultures enriched with microplastics (MPs) to investigate the degradation of polymers and identify culturable bacterial strains contributing to the plastisphere. We found that alpha diversity was notably higher in river water (∼20%) compared to landfill soil and sewage sludge. Dominant phyla included Pseudomonadota in sewage sludge (39.1%) and water (23.7%), while Actinomycetota prevailed in soil (38.5%). A multistage experiment, involving successive subcultures of environmental microbiomes exposed to polypropylene (PP), polyvinyl chloride (PVC), polycarbonate (PC), and polylactic acid (PLA), facilitated the assessment of MPs degradation processes. Analysis of carbonyl indices CIs and FTIR spectra revealed substantial structural changes in the treatment PVC-landfill soil, as well as in PLA- and PC-sludge enriched cultures. Further, using enriched cultures as a source of microorganisms, the study obtained 17 strains of plastic degraders from landfill soil, 14 from sewage sludge, and 6 from river water. Remarkably, similar bacterial genera were isolated across environmental microbiomes regardless of the MPs substrate used in enriched cultures. Among the 37 identified strains, Pseudomonadota predominated (64.86%) and were accompanied by Bacteroidota (16.22%), Actinomycetota (13.51%), and Bacillota (5.41%). This study highlights the complex relationship between microbiome diversity and the biodegradation efficiency of plastics, showing the potential for using microbial communities in the plastic pollution management.

Efficiency of Microorganisms and Effectiveness of Biodegradation Techniques on LDPE Plastics: A Systematic Review.

The aim of the research was to demonstrate the efficiency of microorganisms and the effectiveness of biodegradation techniques on Low-density polyethylene (LDPE) plastics. The research question was: What is the efficiency of LDPE-degrading microorganisms and the effectiveness of biodegradation techniques? The systematic review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Articles were obtained from Scopus, Web of Science (WOS), Embase, and Google Scholar. The DeCS/Mesh search terms were: Low-density polyethylene, efficiency, biodegradation, microbial consortia, fungi, bacteria. Inclusion criteria were: scientific articles that included bacteria, fungi, and microbial consortia reported as LDPE degraders that report the percentage of weight loss; articles published from January 2010 to October 2022, and publications in Spanish and English with open access. Exclusion criteria were: studies that do not report gravimetry, the biodegradation time of LDPE, and the genus or species of the polyethylene-degrading microorganism. Out of 483 studies found, 50 were included in this Systematic Review (SR). The most frequent study techniques were scanning electron microscopy (SEM), gravimetry, and fourier transform infrared spectroscopy (FTIR), and in the case of microorganisms, the most studied belonged to the genus Pseudomonas, Bacillus, and Aspergillus. Regarding the isolation place, the most frequent mentioned in the reviewed articles were landfill soil and sanitary landfill soil. The efficiency of LDPE-degrading microorganisms was higher in bacteria such as Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp., which obtained a range of DE of 9.00-70.00%, 24.00-64%, 1.15 - 61.00%, 45.00%, and 1.5-40% with DT of 4-150, 120, 4-150, 30, and 30-120 days, respectively; in the case of fungi, the main microorganisms are Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii with efficiencies of 54.34, 48.78, and 46.34%, in 90 days, respectively; and the most efficient microbial consortia were from Enterobacter spp. and Pantoea sp. with 38.00 - 81.00%, in 120 days; and, Pseudomonas protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp. with 55. 00 - 75.00% in 120 days. The most efficient microorganisms in LDPE degradation are Enterobacter spp., Pantoea spp., Pseudomonas spp., Escherichia coli, and Bacillus spp.; in fungi Neopestalotiopsis phangngaensis, Colletotrichum fructicola, and Thyrostroma jaczewskii; and in microbial consortia, those formed by Enterobacter spp. and Pantoea sp., and that of P. protegens, Stenotrophomonas sp., B. vallismortis and Paenibacillus sp.; and the most effective techniques used in LDPE biodegradation are SEM, gravimetry, and FTIR.

Enhancing heavy metal phytoremediation in landfill soil by Chrysopogon zizanioides (L.) roberty through the application of bacterial-biochar pellets

This work investigated the performance of bacterial-biochar pellets (BBP) on promoting heavy metal phytoremediation by Chrysopogon zizanioides (L.) Roberty planted in landfill soil. Micrococcus sp. MU1, an indole-3-acetic acid (IAA)-producing bacterium, was incorporated into biochar pellets (MU1-BBP). MU1-BBP contained a high number of viable bacterial cells with 90 % viability after storage at 4°C for two months. In addition, it had a greater survival capability in heavy metals-contaminated landfill soil than MU1-free cells. The application of MU1-BBP significantly promoted the growth performance and chlorophyll synthesis of C. zizanioides planted in landfill soil. Cd, Cu, Pb and Zn were mostly retained in the roots relative to the shoots of C. zizanioides. The accumulation of Cd, Cu, Pb, and Zn in the roots of C. zizanioides were significantly boosted by MU1-BBP inoculation. Plants with MU1-BBP inoculation enhanced the accumulation coefficient (AC) of all four heavy metals. The values of AC values of Cd, Cu, and Zn in C. zizanioides with MU1-BBP inoculation were greater than 1.0. However, translocation factors of all four metals were low. The findings suggest C. zizanioides may be a good heavy metal phytostabilizer. The findings support the potential of bacterial-biochar pellets to enhance the efficiency of heavy metal phytostabilization of C. zizanioides in landfill sites.

Chitinophaga pollutisoli sp. nov., isolated from contaminated sediment.

A Gram-stain-negative, yellow-pigmented, and facultatively aerobic bacterium, designated strain GPA1T, was isolated from plastic waste landfill soil in the Republic of Korea. The cells were non-motile short rods exhibiting oxidase-negative and catalase-positive activities. Growth was observed at 15-40 °C (optimum, 30 °C), at pH 6.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 0-2.5 % (w/v) NaCl (optimum, 0 %). Menaquinone-7 was the sole respiratory quinone, and iso-C15 : 0, C16 : 1 ω5c, and iso-C17 : 0 3-OH were the major cellular fatty acids (>10 % of the total fatty acids). Phosphatidylethanolamine was identified as a major polar lipid. Phylogenetic analyses based on 16S rRNA gene sequences and 120 concatenated marker protein sequences revealed that strain GPA1T formed a distinct lineage within the genus Chitinophaga. The genome of strain GPA1T was 6078 kb in size with 53.8 mol% G+C content. Strain GPA1T exhibited the highest similarity to Chitinophaga rhizosphaerae T16R-86T, with a 98.6 % 16S rRNA gene sequence similarity, but their average nucleotide identity and digital DNA-DNA hybridization values were 82.5 and 25.9 %, respectively. Based on its phenotypic, chemotaxonomic, and phylogenetic characteristics, strain GPA1T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga pollutisoli sp. nov. is proposed. The type strain is GPA1T (=KACC 23415T=JCM 36644T).

Study on Antibiotic Resistance Profiles Exhibited by Vibrio Species Isolated from Landfill Soils in Zaria Metropolis, Northern Nigeria

Study’s Novelty/Excerpt This study investigates the occurrence and antibiotic resistance profiles of Vibrio species isolated from landfill soils in Zaria Metropolis, with a focus on environmental reservoirs of antibiotic resistance. The research uniquely identifies a high prevalence of Vibrio cholerae non-O1 among the isolates and reveals significant multidrug resistance (MDR), particularly against Ampicillin, while also showing complete susceptibility to Gentamicin and Chloramphenicol. These findings highlight the potential for landfills to serve as environmental reservoirs of antibiotic resistance, underscoring the need for further research to understand the implications for public health and environmental management. Full Abstract Antibiotic resistance in bacteria presents a major risk to public health and the environment. Infections caused by Vibrio species continue to be a serious public health concern. This study investigated the occurrence and antibiotic resistance profiles of Vibrio species isolates from landfill soils in Zaria Metropolis. A total of one hundred and twenty (120) soil samples were collected from designated landfills in four locations in Sabon-Gari, Samaru, Tudun-Wada, and Zaria City. Vibrio species were isolated using Thiosulphate citrate bile salt sucrose (TCBS) agar. Bacteriological analysis of the soil samples revealed 9(7.50%) Vibrio species isolates with Vibrio cholerae non-O1 exhibiting the highest prevalence of 4 (3.33%) among all isolates. Using the Kirby-Bauer method, the isolates were tested for susceptibility against ten commonly used antibiotics belonging to three different classes. The highest resistance was to Ampicillin (88. 89%), while all the isolates (100%) showed susceptibility to Gentamicin and Chloramphenicol. Five isolates (55.56%) were Multidrug Resistance (MDR). The highest Multidrug Resistance (MDR, 60%) was observed in Vibrio cholerae non-O1. The isolate resistant to the highest number of antibiotics was obtained from the Tudun-Wada sample location. Three isolates (33.33%) showed resistance to 4 antibiotics, while 2 isolates, 1(11.11%) each were resistant to 5 and 6 antibiotics. The isolates were Multiple Antibiotic Resistance (MAR) to 4-6 antibiotics, and four different phenotypic resistance profiles were observed among them. The origin and varying levels of resistance to multiple antibiotics indicated could be traced to the faecal constituent of the waste in landfills produced by people or animals that have been treated indiscriminately with various antibiotics or items containing residual antimicrobial agents disposed of in dump soils, highlighting the potential environmental reservoirs of antibiotic resistance and call for further research to understand the implications for public health and environmental management.

Assessment of Possibly Toxic Elements in Landfill Soils and Their Impacts on the Ecosystem in Alice, South Africa

Soil contamination by metallic components is an obscure, detrimental, protracted, and irreparable predicament. Dumping of waste containing heavy metals into landfills, fertilizer and pesticide application, and coal combustion results in high toxicity of metallic elements, and their continuous accumulation in soil pollutes the environment, which, in turn, poses a threat to human health. The specimens were subsequently dehydrated, processed for mineralization, and carefully examined microscopically by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX), which examined their mineral substance, crystalline configuration, and chemical composition. Thirteen (13) elements were detected, and only eight (8) metals were discovered (K, Mg, Na, Ca, Al, Fe, Au, Ba), including non-metals (C, O, Cl, P) and a metalloid (Si). The concentrations of possibly toxic elements obtained showed no consistent succession, as they fluctuated across the examined sites. The Al concentration ranged from 3.78 ± 0.23 wt% to 10.23 ± 0.31 wt%, while the Fe concentration fluctuated from 4.14 ± 0.40 wt% to 13.13 ± 1.07 wt%. Na and Mg levels were present in all samples, but their availability was minimal, at less than 2.0 wt%, ranging between 1.44 ± 0.20 wt% and 0.31 ± 0.08 wt%. The concentrations of Ca and K were low in all soil samples, ranging from 0.91 ± 0.14 wt% to 5.56 ± 0.47 wt% for Ca and from 1.32 ± 0.25 wt% to 4.87 ± 0.18 wt% for K. During the investigation at the designated and control areas, it was discovered that the concentrations of potentially hazardous metals exceeded the accepted limits established by the World Health Organization (WHO) > 100 ppm. The findings provide proof of metallic contaminants in the study region, which calls for proper monitoring, management, and remedial measures of metal-tainted sites, since the residents of this locality are at a significantly elevated risk of experiencing adverse effects due to their heightened exposure to these elements. As a result of that, there is an imperative need to monitor and regulate this area regularly and appropriately. The study recommends sustainable farming practices, where farmers could use natural fertilizers and compost, as well as, the implementation of proper waste management, effective recycling techniques, and proper disposal of substances containing heavy metals as byproducts. Further implement remediation techniques that effectively and safely restore soils contaminated by metals in an environmentally sustainable and economically efficient manner.

The essential role of aggregation for the emulsifying ability of a fungal CYS-rich protein

Biosurfactants are in demand by the global market as natural commodities suitable for incorporation into commercial products or utilization in environmental applications. Fungi are promising producers of these molecules and have garnered interest also for their metabolic capabilities in efficiently utilizing recalcitrant and complex substrates, like hydrocarbons, plastic, etc. Within this framework, biosurfactants produced by two Fusarium solani fungal strains, isolated from plastic waste-contaminated landfill soils, were analyzed. Mycelia of these fungi were grown in the presence of 5% olive oil to drive biosurfactant production. The characterization of the emulsifying and surfactant capacity of these extracts highlighted that two different components are involved. A protein was purified and identified as a CFEM (common in fungal extracellular membrane) containing domain, revealing a good propensity to stabilize emulsions only in its aggregate form. On the other hand, an unidentified cationic smaller molecule exhibits the ability to reduce surface tension. Based on the 3D structural model of the protein, a plausible mechanism for the formation of very stable aggregates, endowed with the emulsifying ability, is proposed.Key points• Two Fusarium solani strains are analyzed for their surfactant production.• A cationic surfactant is produced, exhibiting the ability to remarkably reduce surface tension.• An identified protein reveals a good propensity to stabilize emulsions only in its aggregate form.

Microplastic pollution in landfill soil: Emerging threats the environmental and public health.

Insufficient knowledge about the decomposition of microplastics from plastic waste in landfills hinders community involvement in waste management and sorting, posing a new threat to the environment and public health. The present study identifies, characterizes, and quantifies the microplastics in landfills soil sample to determine the latest threats posed by microplastics in the environment, particularly in landfills that are close to residential areas. This research is a descriptive study, with soil samples taken from six points in landfill site in Depok City. The abundance and shape of microplastics were characterized using a microscope, while the microplastic types were identified using Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the abundance of microplastics in the Depok City landfill soil was 60,111.67 particles/kg, with the largest percentage being fragments at 63 %. FTIR functional group characterization showed the presence of plastic types, such as Polyethylene (PE), Polyvinyl Chloride (PVC), Polystyrene (PS), Polypropylene (PP), Polyethylene Terephthalate (PET), and Polyamide. The differences in waste types entering the Depok Landfill caused variations in the number, shape, and type of microplastic samples, and this study provides a foundation for mitigating and biodegrading microplastics in the landfill to minimize environmental impact and protect public health.

Searching for bacterial plastitrophs in modified Winogradsky columns

IntroductionPlastic pollution has surged due to increased human consumption and disposal of plastic products. Microbial communities capable of utilizing plastic as a carbon source may play a crucial role in degrading and consuming environmental plastic. In this study, we investigated the potential of a modified Winogradsky column (WC) to enrich Connecticut landfill soil for plastic-degrading bacteria and genes.MethodsBy filling WCs with landfill soil and inorganic Bushnell Haas medium, and incorporating polyethylene (PE) strips at different soil layers, we aimed to identify bacterial taxa capable of degrading PE. We employed high-throughput 16S rRNA sequencing to identify the microbes cultivated on the plastic strips and the intervening landfill soil. We used PICRUSt2 to estimate the functional attributes of each community from 16S rRNA sequences.Results and discussionAfter 12 months of incubation, distinct colors were observed along the WC layers, indicating successful cultivation. Sequencing revealed significant differences in bacterial communities between the plastic strips and the intervening landfill-soil habitats, including increased abundance of the phyla Verrucomicrobiota and Pseudomonadota (néé Proteobacteria) on the strips. Based on inferred genomic content, the most highly abundant proteins in PE strip communities tended to be associated with plastic degradation pathways. Phylogenetic analysis of 16S rRNA sequences showed novel unclassified phyla and genera enriched on the plastic strips. Our findings suggest PE-supplemented Winogradsky columns can enrich for plastic-degrading microbes, offering insights into bioremediation strategies.

Evaluation of Tolerance and Uptake of Cd and Mn for Microfungi Aspergillus flavus, Aspergillus oryzae, and Aspergillus terreus Isolated from Landfill Soil Collected from Bangar, La Union Philippines

Excessive deposition of heavy metals into the environment due to anthropogenic activities necessitates an eco-friendly clean-up strategy. Among microorganisms, limited studies have been made on the mycoremediation potential of microfungi. This paper evaluated three landfill microfungal isolates of Aspergillus species for tolerance and uptake to Cd and Mn. Culture media optimization was also performed for the evaluation of the tolerance index and heavy metal analysis of soil samples from the landfill site. Among the nine heavy metals analyzed, Mn and Fe were detected in relatively high amounts, while Cd, Ni, and Cu were detected in a moderate range. Luxuriant mycelial growth of A. oryzae (MK120548.1) and A. flavus (MH864264.1) was observed in potato dextrose agar while A. terreus (MH047280.1) grew best in potato sucrose agar. In terms of tolerance index, A. oryzae (MK120548.1) and A. flavus (MH864264.1) demonstrated high tolerance to Cd up to 10 mg/kg. A. oryzae (MK120548.1) showed high tolerance to Mn up to 1,000 mg/kg while A. flavus (MH864264.1) exhibited a very high 10,000 mg/kg tolerance. In terms of metal uptake, A. oryzae (MK120548.1) showed the highest metal uptake of up to 654 mg/kg of Cd, while A. terreus (MH047280.1) exhibited the highest metal uptake of 997 mg/kg ofMn. With these findings, A. oryzae (MK120548.1), A. flavus (MH864264.1), and A. terreus (MH047280.1) have considerable mycoremediation potential. Bioremediation studies in conjunction with plants can be explored to further assess the potential of these Aspergillus species.

Bioprospecting of Polyhydroxy butyrate (PHB) from Bacillus thuringiensis KUMBNGBT-41 by using Agro-industrial wastes

The diverse group of chemicals used in making of plastic is known to be highly toxic and poses a serious threat to the biosphere. These substances besides hitting hard to ecosystem cause an array of problems like birth defects, cancer, damage of nervous and immune systems. The present research work was aimed to isolate and characterize PHB producing bacteria from landfill soil sample collected from Sanehally, Chitradurga district and qualitatively screened by using viable staining techniques. Quantitative estimation was examined by using solvent extraction method. The PHB producing bacteria were characterized based on morphological, biochemical and molecular identification and confirmed as Bacillus thuringiensis strain KUMBNGBT-41 (Accession No. MW040075). Growth parameters were optimized for biomass production using various conditions such as media-nutrient broth, incubation time-72hrs, temperature-37˚C, pH-7.0, carbon source-glucose, nitrogen source-ammonium chloride and carbon to nitrogen ratio as 4:1. The low-cost production media was used for PHB production by cheaper substrates in submerged fermentation. PHB was analysed and quantified by using UV-Visible spectrophotometer at 200-600nm.

Mechanical Properties of Rubberised Geopolymer Concrete.

The environmental impact of non-biodegradable rubber waste can be severe if they are buried in moist landfill soils or remain unused forever. This study deals with a sustainable approach for reusing discarded tires in construction materials. Replacing ordinary Portland cement (OPC) with an environmentally friendly geopolymer binder and integrating crumb rubber into pre-treated or non-treated geopolymer concrete as a partial replacement of natural aggregate is a great alternative to utilise tire waste and reduce CO2 emissions. Considering this, two sets of geopolymer concrete (GPC) mixes were manufactured, referred to as core mixes. Fine aggregates of the core geopolymer mixes were partially replaced with pre-treated and non-treated rubber crumbs to produce crumb rubber geopolymer concrete (CRGPC). The mechanical properties, such as compressive strength, stress-strain relationship, and elastic modulus of a rubberised geopolymer concrete of the reference GPC mix and the CRGPC were examined thoroughly to determine the performance of the products. Also, the mechanical properties of the CRGPC were compared with the existing material models. The result shows that the compressive strength and modulus of elasticity of CRGPC decrease with the increase of rubber content; for instance, a 33% reduction of the compressive strength is observed when 25% natural fine aggregate is replaced with crumb rubber. However, the strength and elasticity reduction can be minimised using pre-treated rubber particles. Based on the experimental results, stress-strain models for GPC and CRGPC are developed and proposed. The proposed models can accurately predict the properties of GPC and CRGPC.

Geochemical fractionation of iron in paper industry and municipal landfill soils: Ecological and health risks insights

Industrial processes and municipal wastes largely contribute to the fluctuations in iron (Fe) content in soils. Fe, when present in unfavorable amount, causes harmful effects on human, flora, and fauna. The present study is an attempt to evaluate the composition of Fe in surface soils from paper mill and municipal landfill sites and assess their potential ecological and human health risks. Geochemical fractionation was conducted to explore the chemical bonding of Fe across different fractions, i.e., water-soluble (F1) to residual (F6). Different contamination factors and pollution indices were evaluated to comprehend Fe contamination extent across the study area. Results indicated the preference for less mobile forms in the paper mill and landfill, with 26.66% and 43.46% of Fe associated with the Fe–Mn oxide bound fraction (F4), and 57.22% and 24.78% in the residual fraction (F6). Maximum mobility factor (MF) of 30.65% was observed in the paper mill, and 80.37% in the landfill. The enrichment factor (EF) varied within the range of 20 < EF < 40, signifying a high level of enrichment in the soil. The individual contamination factor (ICF) ranged from 0 to >6, highlighting low to high contamination. Adults were found to be more vulnerable towards Fe associated health risks compared to children. The Hazard Quotient (HQ) index showed the highest risk potential pathways as dermal contact > ingestion > inhalation. The study offers insights into potential Fe contamination risks in comparable environments, underscoring the crucial role of thorough soil assessments in shaping land use and waste management policies.

Assessment of metal pollution and effects of physicochemical factors on soil microbial communities around a landfill

The physicochemical properties, chemical fractions of six metals (Cu, Zn, Pb, Cd, Cr, and Mn), and microbial communities of soil around a typical sanitary landfill were analyzed. The results indicate that soils around the landfill were from neutral to weak alkalinity. The contents of organic matter (OM), total nitrogen (TN), total phosphorous (TP), and activities of catalase, cellulase, and urease were significantly higher in landfill soils than those in background soils. Negative correlations were found between pH and metals. Cr was the dominant metal. Cu, Pb, Cr, and Mn were accumulated in the nearby farmland soils. Cd had the highest percentage of exchangeable fraction (33.7%−51.8%) in landfill and farmland soils, suggesting a high bioavailability to the soil environment affected by the landfill. Pb, Cr, and Mn existed mostly in oxidable fraction, and Cu and Zn were dominant in residual fraction. There was a low risk of soil metals around the landfill based on the RI values, while according to RAC classification, Cd had high to very high environmental risk. The MisSeq sequencing results showed that Actinobacteria, Proteobacteria, Chloroflexi, and Acidobacteria were the dominant phyla of bacteria, and the most abundant phylum of fungi was Ascomycota. The NMDS analysis revealed that the landfill could influence soil fungal communities more intensely than bacterial communities. TN, cellulase, and bioavailable metals (Pb-Bio and Cr-Bio) were identified to have main influences on microbial communities. Pb-Bio was the most dominant driving factor for bacterial community structures. For fungi, Pb-Bio was significantly negatively related to Olpidiomycota and Cr-Bio had a significantly negative correlation with Ascomycota. It manifests that bioavailable metals play important roles in assessing environmental risks and microbial community structures of soil around landfill.

Microbes Isolated from Landfill Soil Utilize Polyethylene Terephthalate (PET) as Their Sole Source of Carbon: An Unexplored Possibility of Bioremediation in Bangladesh

Plastic products are so extensively used that they continue to strain the already overburdened waste management system and, inevitably, the global climate. Biodegradation is a sustainable remedy. Here, we report a few microorganisms isolated from landfill soil near Dhaka that thrive especially on polyethylene terephthalate (PET) polymers. Soil samples were subjected to three enrichment cycles that contained no carbon except PET. Pure isolates were recovered and incubated on minimal agar containing PET as the sole carbon. A morphological examination was carried out. Potential PET-degrading enzyme sequences from the isolates and other microalgae were analyzed for homology using BLASTP and TBLASTN, and multiple sequence alignment (MSA) was performed to assess conserved domains. Six isolates were obtained. Two isolates grew around the PET film but did not grow sufficiently in other areas of the minimal agar. Two other isolates with greenish pigmentation flourished around the PET film as well as on other areas of the agar. One of the green cells resembled Aphanocapsa, with irregular shapes and occasionally brown dense bodies, while the others looked round like Microcystis. Homology analysis revealed the hypothetical PETases in green cells contained the highly conserved catalytic triad (Ser-His-Asp) at the active site, as always found in alpha-beta hydrolase fold containing enzymes. Microbes isolated from two landfill sites in the vicinity of Dhaka have been adapted to utilize PET as a carbon source. In the future, sequencing and further characterization would be necessary to validate the findings. Microalgal systems demand increased focus, given their potential to offer valuable resources for bioremediation.