Amit Shiuly

Plastic waste is a major source of microplastic (MP) pollution, posing adverse environmental and public health risks. This study assessed MP abundance in 24 urban ponds and lakes within the Kolkata Municipal Corporation, India, during the post- and pre-monsoon seasons of 2022–2023. Results showed that MP concentrations were significantly higher in the post-monsoon season (20 ± 3.46 items L⁻¹; ANOVA, p < 0.05), with red, white, and black particles being the most prevalent. MPs prevalently ranged between 500 and 1000 µm with fibers constituting 58–59% of the total MPs. Fourier-transform infrared (FTIR) analysis identified polyethylene (PE) as the dominant polymer. MP abundance showed negative correlations with dissolved oxygen and turbidity, and positive associations with pH, TDS, BOD₅, and total coliform counts. A Support Vector Machine (SVM) model was developed for morphology-based MP classification, achieving an accuracy of 89%. Additionally, remote sensing and GIS techniques were used to develop index-based models for water-body identification and MP quantification (items L⁻¹) using spectral data from Sentinel-2 imagery. These models demonstrated high validation accuracy of 98.01% and 92.60%, respectively. Metal analysis of sediment and MPs of water detected chromium, suggesting possible MP–metal interactions within sediments. Although the Pollution Load Index (PLI) indicated relatively low contamination levels, the Polymer Hazard Index (PHI) exceeded 1000, indicating substantial ecological risk. Future studies should focus on long-term monitoring, socio-economic and health impact assessments and development of effective mitigation strategies particularly addressing plastic-waste derived-MPS. Graphical Abstract

The disposal of tannery sludge (TS), a hazardous by-product of the leather industry, poses serious environmental concerns but also offers potential for sustainable cementitious applications. This study evaluates the use of TS as a partial replacement for cement in concrete production at substitution levels of 0%, 6%, 12%, 18%, 24%, and 30%. Experimental results reveal that a 12% TS replacement of cement in concrete provides optimal performance, achieving a 28-day compressive strength of 37.6 MPa compared to 31.4 MPa for the control mix. Durability assessments further demonstrate significant improvements at 12% replacement, including reduced sorptivity, enhanced resistance to chloride ion ingress, and higher acid resistance. These enhancements are may be the formation of additional C–S–H and C–A–H gels, which densify the matrix. Improved carbonation resistance and effective heavy-metal immobilization further confirm the environmental safety of the modified mix. Microstructural analyses (XRD, SEM-EDX, TGA-DTG, FTIR) support these findings, showing reduced porosity and improved C–S–H formation. Further life cycle assessment (LCA) was conducted whilerarely a notable reduction in CO₂ emissions and land-use impact at 12% replacement, aligning with sustainability targets. A Cost analysis further reveals a 7% reduction in material cost per cubic meter. Overall, the findings establish that the tannery sludge, when used in controlled proportions, can serve as a sustainable, safe, and economically viable alternative to ordinary Portland cement in concrete production.