In recent years, the pervasive presence of microplastics has emerged as a formidable environmental challenge, particularly within aquatic ecosystems. The Indo-Sri Lankan region, characterized by its diverse hydrological networks and critical freshwater resources, has increasingly been at the epicenter of scientific scrutiny concerning microplastic pollution. A comprehensive review by Lakchani et al. (2025) meticulously examines the methodologies employed to detect and analyze microplastics embedded in freshwater sediments across this geographically complex area. Their work not only underscores the ecological ramifications but also exposes the methodological disparities that currently impede comprehensive assessments of microplastic contamination in these freshwater systems.
Microplastics, commonly defined as plastic particles smaller than 5 millimeters, originate from a variety of sources including the breakdown of larger plastic debris, synthetic textile fibers, and microbeads used in consumer products. Given their minute size, these particles infiltrate various environmental matrices, with sediments acting as crucial sinks. Sedimentary deposition zones in rivers and lakes essentially act as reservoirs, gradually accumulating microplastics transported by surface runoff and water currents. The geographical landscape of the Indo-Sri Lankan region presents unique sediment dynamics, including monsoon-driven flow variations and distinct lithological compositions that influence microplastic sedimentation patterns.
A significant portion of the review by Lakchani and colleagues focuses on sampling methodologies tailored for sediment-bound microplastics. Traditional approaches often involve grab sampling or coring techniques; however, the researchers highlight several limitations inherent in these methods. For instance, grab samples may not accurately reflect the heterogeneous distribution of pollutants, while coring can disturb sediment layers, potentially leading to under- or overestimation of microplastic concentrations. The authors propose optimized sampling strategies that incorporate stratified random sampling combined with high-resolution spatial mapping, aiming to capture a more representative sediment profile.
Analytical techniques for isolating and characterizing microplastics from sediment samples form a critical aspect of the discussed methodologies. Density separation stands out as a predominant strategy that exploits the lower density of plastics relative to mineral sediment particles. Various solutions such as zinc chloride, sodium iodide, and sodium chloride have been employed to facilitate this separation, each with its own advantages and limitations concerning cost, toxicity, and recovery rates. Lakchani et al. argue for a standardized protocol involving zinc chloride solutions due to their superior density and recovery efficiency, albeit noting the environmental precautions necessary for handling heavy-metal-based reagents.
Following extraction, the identification and quantification of microplastics involve a suite of spectroscopic techniques. Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy are lauded for their capability to elucidate polymer types with high specificity. The challenge, however, lies in the labor-intensive nature of these analyses, particularly when applied to large datasets generated from field samples. Recent advances in automated imaging and machine learning algorithms present promising avenues for scaling up microplastic identification, yet these are still in nascent stages within the context of sediment analysis in the Indo-Sri Lankan region.
In addition to physical characterization, the review delves into challenges posed by environmental factors that can alter the morphology and chemical composition of microplastics once deposited in sediments. Weathering processes, biofouling, and sediment diagenesis can significantly influence polymer degradation pathways, complicating the identification and risk assessment of microplastic pollution. This complexity necessitates the integration of chronological sediment dating techniques such as lead-210 and cesium-137 radionuclide analyses to unravel temporal trends in microplastic deposition.
Crucially, the biological implications of microplastic-laden sediments in freshwater ecosystems are examined. Sediments serve as habitats for benthic organisms, many of which are integral to nutrient cycling and overall ecosystem health. The ingestion and accumulation of microplastics by these organisms potentially disrupt ecological functions and introduce plastics into the food web, thereby posing risks to both aquatic biodiversity and human health via bioaccumulation. The review advocates for experimental ecotoxicological studies focused on sediment-associated microplastics to elucidate these complex interactions.
The Indo-Sri Lankan region’s socio-economic fabric is deeply intertwined with its freshwater bodies, which supply drinking water, fisheries, and agriculture. Therefore, understanding microplastic contamination in sediments not only contributes to ecological knowledge but also informs policy frameworks aimed at sustainable resource management. Lakchani et al. urge interdisciplinary collaborations among environmental scientists, policymakers, and local communities to develop context-specific mitigation strategies grounded in robust methodological practices.
From a technological standpoint, the authors emphasize the imperative need to harmonize methodologies across studies to enable meta-analyses and regional comparisons. The absence of standardized protocols has rendered cross-study data aggregation unwieldy, limiting effective policy translation. International guidance documents and best-practice frameworks, incorporating regional particularities such as sediment types and hydrological regimes, are proposed as essential steps moving forward.
Furthermore, the review highlights novel in-situ monitoring techniques that could revolutionize sediment microplastic detection. These include portable spectroscopic devices and real-time sensor arrays, which promise to reduce reliance on laborious laboratory procedures and enable more frequent, widespread monitoring efforts. Such innovations, while nascent, could substantially improve the temporal resolution of microplastic assessments and facilitate adaptive management approaches.
Importantly, the authors address the broader context of plastic pollution within the global environmental discourse. While marine environments have garnered significant attention for microplastic contamination, freshwater systems, particularly sediments, remain comparatively understudied despite their critical role as transitional zones influencing oceanic pollution loads. This shift in focus is pivotal for developing comprehensive strategies to curtail plastic proliferation.
The review’s comprehensive synthesis also includes an extensive discussion on data reporting standards, which are pivotal for enhancing the reproducibility and comparability of microplastic research. Proposals include uniform metrics for reporting particle size ranges, polymer types, and concentration units, alongside transparent documentation of methodological choices. Adoption of such standards could catalyze advancements in the emerging field of microplastic sedimentology.
Finally, the authors advocate for increased capacity building in the Indo-Sri Lankan region, emphasizing training in advanced microplastic analysis techniques and infrastructure development. Empowering local researchers and institutions is vital for sustaining long-term monitoring programs and ensuring that mitigation efforts are informed by high-quality, region-specific data.
In sum, this seminal review by Lakchani, Jayasinghe, and Maithreepala spotlights both the technical challenges and ecological imperatives associated with microplastics in freshwater sediments of the Indo-Sri Lankan region. Their rigorous assessment of methodologies sets a benchmark for future research and underscores a critical knowledge gap that demands concerted action to safeguard freshwater ecosystems from the insidious impacts of microplastic pollution.
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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