In recent years, the pervasive infiltration of microplastics into aquatic environments has become a pressing global concern, raising alarm about their potential impacts on ecosystems and human health. Freshwater systems, often serving as crucial sources of drinking water and biodiversity hotspots, are increasingly recognized as significant reservoirs for microplastic contamination. A groundbreaking review published in “Microplastics & Nanoplastics” by Lakchani et al. (2025) meticulously examines the methodologies employed to analyze microplastics in freshwater sediments within the Indo-Sri Lankan region—a geographic area of immense ecological and socio-economic importance. This comprehensive synthesis not only unravels the technical intricacies involved in sediment microplastic research but also contextualizes the broader environmental implications within a critical region of the world.
The authors highlight that sediments in freshwater bodies act as both sinks and sources for microplastics, capturing these particles through sedimentation processes, yet potentially releasing them back into the water column under various environmental disturbances. Given the complex dynamics of sediment interactions, the accurate quantification and characterization of microplastics embedded within sediments pose significant scientific challenges. To address these, the review scrutinizes a suite of sampling techniques, sample preparation protocols, and analytical tools that have been developed and deployed in recent years, illustrating the evolution of methodological frameworks tailored to this nuanced form of environmental sampling.
Sampling strategies delineated in the review emphasize grab sampling, core sampling, and dredging methods, each with distinct advantages and limitations depending on sediment type, water depth, and spatial heterogeneity. The authors underscore the criticality of selecting representative sampling locales to mitigate biases arising from patchy microplastic distributions. Furthermore, standardizing sample volumes and depths is essential to facilitate comparative studies. Sediment granulometry and organic matter content are also discussed as variables influencing microplastic retention and subsequent analytical detection, underscoring the necessity for contextualizing sampling data within sediment characteristics.
Upon collection, the challenge of extracting microplastics from complex sediment matrices involves meticulous sample preparation workflows designed to isolate plastics while minimizing contamination or loss of material. Lakchani and colleagues provide a deep dive into density separation methods, which exploit the lower density of most plastics relative to mineral sediments. The review evaluates common flotation fluids such as sodium chloride and zinc chloride solutions, highlighting their differential efficacies based on density gradients, toxicity profiles, and environmental safety concerns. The procedural nuances of repeated separations, sieving, and enzymatic or chemical oxidation treatments to remove organic matter reflect the intricate balancing act required to prepare samples without compromising the integrity of targeted microplastics.
Analytical methodologies for characterizing microplastics extracted from sediments are pivotal to discerning their polymer types, shapes, sizes, and potential sources. Spectroscopic techniques such as Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy take center stage in the reviewed literature, offering molecular-level identification with varying detection limits and spatial resolutions. The authors appraise the capabilities of micro-FTIR imaging and automated particle analysis systems, elucidating their roles in high-throughput quantification and morphological characterization. Challenges such as fluorescence interference, particle aggregation, and limitations in detecting nanoplastics are candidly addressed, outlining ongoing efforts to optimize detection sensitivity and specificity.
Complementing spectroscopic approaches, the review also surveys microscopic examination methods, including stereomicroscopy and scanning electron microscopy (SEM), which provide vital insights into particle morphology and surface features. These techniques are indispensable for visual discrimination between synthetic plastics and natural debris, enhancing the accuracy of microplastic enumeration. However, the manual nature and potential observer bias inherent in microscopy-based analyses remain hurdles that the scientific community continues to navigate, prompting the integration of machine learning algorithms and automated image processing to augment objectivity and throughput.
Crucially, the review by Lakchani et al. sheds light on the regional specificity of microplastic pollution in the Indo-Sri Lankan context. The authors detail how rapid urbanization, intensive agriculture, and diverse industrial activities in the region contribute to the complexity of microplastic sources and pathways. The hydrological connectivity of rivers and estuarine systems exacerbates the dispersal of microplastics, with seasonal monsoon patterns influencing sediment transport and deposition dynamics. This geographical focus accentuates the interplay between environmental factors and anthropogenic pressures, fostering a nuanced understanding of microplastic fate within freshwater sediments.
The authors advocate for the harmonization of methodological protocols across studies to generate reliable, comparable data sets that can underpin robust environmental risk assessments and policymaking. The heterogeneity of existing techniques, alongside varying detection limits and quality assurance measures, currently impedes unified conclusions about pollution levels and ecological impacts. To this end, the review proposes a framework encompassing standardized sampling designs, validated extraction protocols, and consensus on analytical modalities, aimed at fostering methodological coherence.
Significantly, the review pursues a forward-looking perspective by highlighting emerging technological innovations and methodological refinements. Techniques such as pyrolysis-gas chromatography-mass spectrometry (pyrolysis-GC-MS) and thermal extraction desorption methods are explored for their potential to complement existing analytical arsenals. These emerging approaches promise enhanced chemical specificity and size range detection, particularly for nanoplastics—an area of growing environmental concern due to their unknown ecotoxicological effects.
The discourse also navigates the ethical and practical challenges of microplastic research, including contamination control during field sampling and laboratory analysis. The pervasiveness of synthetic fibers in laboratory environments necessitates stringent procedural blanks and contamination mitigation strategies to ensure data integrity. The use of cleanrooms, procedural blanks, and lab coats made from natural fibers underscores the meticulous care required to validate microplastic measurements reliably.
Importantly, the review emphasizes the need to integrate sediment microplastic studies with broader ecological investigations, linking physicochemical data with biological exposures. Understanding the bioavailability of sediment-associated microplastics to benthic organisms and their potential trophic transfer within freshwater food webs constitutes an emergent research frontier. The coupling of methodological rigor with ecological relevance is imperative to elucidate the cascading effects of microplastics on aquatic biodiversity and ecosystem functioning.
In conclusion, this comprehensive review article serves as a pivotal resource for researchers focusing on microplastic pollution in freshwater sediments, particularly within the Indo-Sri Lankan region’s intricate environmental matrices. By consolidating diverse methodological insights and contextualizing them within regional environmental realities, Lakchani and colleagues advance the scientific community’s ability to tackle microplastic pollution with enhanced precision and contextual rigor. The implications extend beyond academic inquiry, informing regional environmental management frameworks and international efforts to mitigate plastic pollution.
As the global scientific community accelerates efforts to confront the microplastic crisis, such regionally specific, methodologically focused reviews are indispensable. They not only sharpen research focus but also spotlight critical gaps and opportunities, catalyzing collaborative innovations in analytical chemistry, environmental science, and policy domains. The microplastic conundrum, once a peripheral scientific curiosity, is now a defining environmental challenge of our time, demanding sophisticated and harmonized methodological approaches to safeguard freshwater ecosystems and human health alike.
Subject of Research: Microplastics in freshwater sediment in the Indo-Sri Lankan region
Article Title: Microplastics in freshwater sediment in the Indo-Sri Lankan region: a review of methodologies.
Article References:
Lakchani, D.T., Jayasinghe, A., Maithreepala, R.A. et al. Microplastics in freshwater sediment in the Indo-Sri Lankan region: a review of methodologies. Micropl.&Nanopl. 5, 16 (2025). https://doi.org/10.1186/s43591-025-00123-y
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