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Ecological Intelligence

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Ecological Intelligence / Subject

extreme events

Hurricane Helene turned a background microplastic flux into an event-scale pulse

Evidence
Peer-reviewed
Geography
Western North Carolina, USA
System
Mountain headwaters / atmospheric deposition

WHAT THE EVIDENCE SAYS

Sampling at three western North Carolina sites before, during and after Hurricane Helene found storm-period microplastic deposition roughly 3–22 times pre-storm levels. The storm accounted for about 4.2%, 4.6% and 18.8% of annual deposition at the three sites, and the authors extrapolated an anomalous regional deposition pulse of roughly 3.85×10^15 particles across the affected area.

WHY IT MATTERS / OUR READ

Extreme events can compress a substantial share of an annual pollutant flux into a short window. Monitoring programs built around routine intervals may therefore miss the timing and magnitude of transport processes that matter most after major storms.

CAVEATS / UNCERTAINTY

This was a three-site observational event study. The regional particle estimate is modeled from site measurements, ecological and human-health effects were not measured, and atmospheric trajectory analysis does not fully resolve the sources of the deposited particles.

SOURCE

Integrated Environmental Assessment and Management
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At three western North Carolina monitoring sites, storm-period deposition rose 3–22× above pre-Helene levels; at one site, the storm supplied 18.8% of the year’s measured microplastics.

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Lake Geneva’s sediment record is being written by river intrusions below the surface

Evidence
Peer-reviewed
Geography
Lake Geneva / Rhône River, Switzerland and France
System
Large lake / river-lake sediment transport

WHAT THE EVIDENCE SAYS

Sediment traps at 10, 30, 50 and 100 m from 2020–2024 showed the Rhône as the primary driver of Lake Geneva sedimentation, with density-driven intrusions carrying particles below the thermocline. Floods generated the largest particle fluxes, while drought sharply reduced sediment supply and storms redistributed stored material.

WHY IT MATTERS / OUR READ

Monitoring only surface water or annual sediment totals can hide the transport pathway. Stratification and event type determine where river-borne material goes inside a large lake.

CAVEATS / UNCERTAINTY

This is one large peri-alpine lake observed from a fixed platform and its associated river network. The study resolves transport well but does not make its exact depth patterns universal to other lakes.

SOURCE

Aquatic Sciences
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Five years of depth-resolved traps show why river inflow, storms and stratification need to be monitored together rather than treating lake sedimentation as a surface process.

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