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Calcite carbonate sinks low-density plastic debris in open oceans
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Researchers found that calcite precipitation, a natural biogeochemical process in the ocean, causes low-density plastic debris to sink by coating particles with mineral layers that increase their density. The finding identifies a previously unrecognized mechanism for removing buoyant plastics from the ocean surface.
The vertical settling of plastic debris in oceans is poorly understood. A large share of low-density microplastics (LDMPs) are largely absent from sea surfaces. The present study employs a model that considers the potential of an overlooked microbially induced calcium carbonate precipitation (MICP) process and new motion equations for irregular LDMPs. Here we show that the motion of LDMPs in the present model, exhibiting a damped oscillation pattern, is quite different from that in biofouling models. Furthermore, LDMPs in the size range of 10-200 µm are most likely to gain sufficient density at the biofouling/MICP stage to independently sink to the ocean floor with relatively small drag coefficients, potentially explaining the selective enrichment of LDMPs in the oceanic sediment. The size and shape exhibit strong non-linear effects on the settling patterns of LDMPs. Overall, the present study highlights the importance of calcite-mediated sinking of LDMPs in open oceans.
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BiocalcificationInduces the Preferential Settlingof Small Buoyant Microplastics in Freshwater
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Researchers found that biocalcification processes involving Microcystis aeruginosa and calcium ions promote the preferential settling of small buoyant microplastics in freshwater, with incubation experiments revealing how algal-induced mineral precipitation accelerates vertical transport of particles that would otherwise remain suspended.
Modelling the sedimentation of macro-, micro- and nanoplastics in the ocean from surface to sediment
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Researchers modeled the sedimentation of macro-, micro-, and nanoplastics from the ocean surface to the seafloor, finding that biofouling and particle aggregation dramatically accelerate sinking rates and that most plastics eventually reach benthic environments.
Sinking of microbial-associated microplastics in natural waters
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Researchers investigated how microbial biofilm colonization of microplastics affects their buoyancy and sinking behavior in natural waters, finding that biological ballasting from attached microorganisms can significantly increase particle density and promote vertical transport toward sediments. The results suggest that biofouling is a key mechanism driving the removal of microplastics from surface waters.
Carbonate mineral precipitation enhances microplastic deposition in karst rivers globally
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Scientists found that tiny plastic particles in rivers stick to calcium-based minerals and sink to the river bottom, especially in areas with limestone and similar rocks. This natural process acts like a filter that traps microplastics before they reach the ocean, which could be good news since it reduces the amount of plastic pollution flowing into marine food chains. Understanding this process could help us develop better ways to remove microplastics from rivers in different geological regions.
Biocalcification Induces the Preferential Settling of Small Buoyant Microplastics in Freshwater
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This study examined how a common freshwater algae (Microcystis aeruginosa) promotes the sinking of buoyant microplastics through a process called biocalcification — where biological activity causes calcium carbonate crystals to form on the plastic surface, increasing its density. Smaller microplastics were more strongly affected than larger ones because they adsorb more of the algal secretions that serve as crystal-nucleation sites, and environmental weathering of plastics enhanced the effect further. This natural mechanism could significantly influence how quickly and where microplastics settle out of the water column in freshwater lakes.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.