Microfibers (MFs) in aquatic and marine ecosystems adsorb toxic heavy metals and then transfer the heavy metals enriched MFs to living organisms. In this research paper, the adsorption-desorption dynamics of heavy metals onto MFs was studied by using theoretical models and experimental investigations. The adsorption of metals onto MFs was well correlated for the Freundlich model and the adsorption kinetics follows pseudo-second order rate equation. The adsorption capacity of naturally weathered MFs was 30.8 mg g-1 which is about 35% higher than the synthetic fiber of similar range of size of MFs. The leaching of heavy metals from MFs was found that 90-95% of adsorbed metals were leached within 24 h. The leaching of Ti(II) and Al(III) were slower than the other metal ions. The salinity has shown decrease in adsorption capacity of MFs for heavy metals. Based on the Nemerov pollution index (PN), the naturally weathered MFs enriched with heavy metals in sediments became heavily polluted with PN values between 2.98 and 3.49. The risk index value of 396 represents that the bottom dwellers and other marine organisms in the Narmada estuary high risk from MFs and MFs enriched with metals. This study indicates that MFs play dominant role in fate and distribution of heavy metals in the estuarine ecosystems.
Keywords: Ecological risk; Enrichment factors; Heavy metal contamination; Microfibers.
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