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Why can polluted lake sediments continue to affect water quality?

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lake Lake Ann in North Cascades National Park, Washington, U.S., viewed from the park's Maple Loop Trail. The North Cascades National Park is a large wilderness area that preserves majestic mountain scenery, snowfields, glaciers, and other unique natural features.

Polluted lake sediments can continue to affect water quality because the harmful materials trapped within them—such as heavy metals, pesticides, nutrients, and oil—remain potentially available for regeneration into the lake water.1

This process occurs primarily because the uppermost layers of lake sediment often contain large volumes of interstitial water. This water can hold high concentrations of pollutants and nutrients, which enhances the exchange potential between the sediment and the lake proper. Consequently, even after the initial source of pollution is removed, these legacy contaminants can be released back into the water column, necessitating careful consideration when planning measures to abate lake pollution.1