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Nanomaterials could mean more algae outbreaks for wetlands, waterways

The last 10 years have seen a surge in the use of tiny substances called nanomaterials in agrochemicals such as pesticides and fungicides. The idea is to provide more disease protection and better yields for crops, while decreasing the amount of toxins sprayed on agricultural fields. But when combined with nutrient runoff from fertilized cropland and manure-filled pastures, these "nanopesticides" could also mean more toxic algae outbreaks for nearby streams, lakes and wetlands, a new study finds. Too small to see with all but the most powerful microscopes, engineered nanomaterials are substances manufactured to be less than 100 nanometers in diameter, many times smaller than a hair's breadth. Their nano-scale gives them different chemical and physical properties from their bulk counterparts, including more surface area for reactions and interactions. Most of the 260,000 to 309,000 metric tons of nanomaterials produced worldwide each year are eventually disposed in landfills, according to a previous study. But of the remainder, up to 80,400 metric tons per year are released into soils, and up to 29,200 metric tons end up in natural bodies of water. To find out how the combined effects of nutrient runoff and nanoparticle contamination would affect eutrophication -- an essential process in the formation of algal blooms -- researchers set up 18 separate 250-liter tanks with sandy sloped bottoms to mimic small wetlands. Over the course of the experiment, big algal blooms were more than three times more frequent and more persistent in tanks where nanoparticles and nutrients were added together than where nutrients were added alone. Nutrient-fueled algal blooms eventually reduce oxygen levels to the point where fish and other organisms can't survive, creating dead zones in the water. Some algal blooms also release toxins that can make pets and people who swallow them sick.

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