Impact of municipal solid waste disposal on the surface water and sediment of adjoining wetland Deepor Beel in Guwahati, Assam, India

Microbial diversity, enzyme activity, metal contamination, and their responses to environmental drivers in an Indo-Burmese freshwater wetland

Seasonal fluctuations can influence many biotic and abiotic parameters in wetland environments. Present research on wetlands do not serve as a comprehensive model for understanding these seasonal influences, especially in Northeast India, where wetland ecosystems remain understudied. That being, our study investigated the seasonal, spatial, depth-wise variations of enzyme activity (xylanase, invertase, and cellulase), microbial community, and heavy metal concentrations [chromium (Cr), cadmium (Cd), lead (Pb), and iron (Fe)] in the sediments of Deepor Beel. Our results show, seasons rather than sediment layers influence all parameters. Enzyme activities peaked during post-monsoon (POM), with xylanase showing highest activity throughout (0.01-132.94 mmol/min/g). Culture independent bacterial diversity study based on next generation sequence (NGS) analysis revealed a steady decrease in unique amplicon sequence variants (ASVs) from pre-monsoon (PRM) (31), followed by POM (22) and finally monsoon (MON) (2). Bacteria consistently outnumbered archaea throughout the study. Heavy metals peaked during PRM, with Fe reaching 1416-1200 mg kg-1. Cr exceeded US EPA limit in all seasons, while Pb and Cd surpassed the limits during PRM and MON. Pearson's correlation showed that TC, TN, C/N ratio, and EC significantly influenced enzyme activity during PRM and POM. Correlations between microbial community and environmental parameters revealed enzyme activities, C/N ratio and TC to positively influence many microbial genera. In contrast, certain genera showed tolerance to elevated concentrations of Cd, Pb, and Fe. Our findings have considerable implications for predicting the dynamics of abiotic and biotic factors related to the carbon cycle as a consequence of seasonal change.

Assessment of reproductive, genotoxic, and cytotoxic effects of leachate-contaminated water in male mice

Leachate-contaminated water (LCS) poses significant health risks due to its heavy metal content and altered physicochemical properties. This study examined the physicochemical parameters and heavy metal levels in LCS and assessed its reproductive toxicity, genotoxicity, and cytotoxic effects in exposed mice. Groups of mice (n = 5) were orally administered 100 μL of 30 % and 70 % LCS (v/v) twice daily for 35 days. Drinking water served as a negative control, and cyclophosphamide (Cyp) (20 mg/kg bw) as a positive control. On day 36, the mice were weighed, sacrificed, and their testicular weight, sperm count, sperm morphology, viability, acrosome integrity, and serum testosterone were examined. Oxidative stress in the testes, histopathological changes, and serum markers for liver and kidney function (SGOT, SGPT, and creatinine) were also assessed. Genotoxic effects were evaluated using a micronuclei (MN) assay. Analysis of the leachate showed altered physicochemical parameters and elevated heavy metal levels. Exposure to LCS led to a significant decrease in relative testis weight, sperm count, normal sperm morphology, viability, acrosome integrity, and serum testosterone levels. It also caused a notable increase in MDA levels and a decrease in catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) levels, along with histological changes in the testes of LCS-treated mice compared to controls. Additionally, there was a significant rise in MN formation in RBCs and elevated levels of liver enzymes and creatinine, indicating liver and renal toxicity. Histological alterations in the liver and kidneys were also observed in LCS-exposed mice. These findings suggest that LCS induces reproductive toxicity, genotoxicity, and cytotoxicity in male subjects.

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 pyrolysis potential of Indian municipal solid waste and legacy waste via physicochemical and thermochemical characterization

This study explores the viability of utilizing municipal solid waste (MSW) and legacy waste as a renewable energy source through pyrolysis, akin to solid fuels. The heating value of MSW and legacy waste were found to be 37737.89 and 40432.84 kJ/kg, respectively. Proximate analysis shows that MSW fits within Tanner diagram parameters, eliminating the need for auxiliary fuel in pyrolysis. With 47.6 % and 44.16 % lignin content in MSW and legacy waste were deemed suitable for char production. Thermal degradation resulted in mass losses of 68 % for MSW and 82 % for legacy waste. The kinetic and thermodynamic assessment indicates lower activation energy (Ea) and Gibbs free energy (ΔG) for MSW (5.72 kJ/mol and 170.37 kJ/mol, respectively) compared to fossil fuels, suggesting faster reactions without additional energy requirement. MSW emerges as a promising alternative to fossil fuels, aligning with the United Nations' 2030 Sustainable Development Goals.

Ameliorative effect of natural floating island as fish aggregating devices on heavy metals distribution in a freshwater wetland

Growing human population and climate change are leading reasons for water quality deterioration globally; and ecologically important waterbodies including freshwater wetlands are in a vulnerable state due to increasing concentrations of pollutants like heavy metals. Given the declining health of these valuable resources, the present study was conducted to evaluate the effect of natural floating island in the form of fish aggregating devices (FADs) made of native weed mass on the distribution of heavy metals in the abiotic and bio compartments of a freshwater wetland. Lower concentrations of surface water heavy metals were observed inside the FADs with a reduction of 73.91%, 65.22% and 40.57-49.16% for Cd, Pb and other metals (viz. Co, Cr, Cu, Ni and Zn), respectively as compared to outside FAD. These led to 14.72-55.39% reduction in the heavy metal pollution indices inside the FAD surface water. The fish species inside the FADs were also found less contaminated (24.07-25.07% reduction) with lower health risk indices. The study signifies the valuable contribution of natural floating island as FADs in ameliorating the effect of heavy metals pollution emphasizing the tremendous role of the natural floating islands in sustainable maintenance of freshwater wetlands for better human health and livelihood.

Drivers of Residents’ Home Composting Intention: Integrating the Theory of Planned Behavior, the Norm Activation Model, and the Moderating Role of Composting Knowledge

Home composting is judged as an effective municipal waste management option in which household contribution is essential, but it has a low adoption. The objectives of the study were to determine the factors that influence home composting intention and identify the moderating role of composting knowledge in the model, using the combined model of the theory of planned behavior (TPB) and norm activation model (NAM). A structured questionnaire was applied to a sample of 367 residents of Isfahan city, Iran, randomly selected. Data were analyzed using cluster analysis, discriminant analysis, PLS-SEM, and PLS-MGA. Cluster analysis grouped the three clusters based on the constructs of the integrated model, and this result was confirmed by discriminant analysis. Findings show that attitude, subjective norm, and perceived behavior control can predict the intention to compost. Study results confirmed the positive effect of awareness of the consequences of composting on ascribed responsibility to compost at home, of responsibility to the personal norm, and of the personal norm on intention to compost at home. Furthermore, it was observed that composting knowledge moderates the relationship between subjective norm and behavioral intention, and the one between perceived behavioral control and behavioral intention. The integrated model had more predictive power than the TPB model. The fit statistic of the integrated model was good and 71% of the variance for intention behavior toward home composting. The insights on factors affecting residents’ intention to compost obtained from this study can be used in measures and programs that reinforce and stimulate home composting.