sciencehabit writes: About 1000 meters down in a remote part of the Atlantic Ocean sits an unusual legacy of humanity’s love affair with the automobile. It’s a huge mass of seawater infused with traces of the toxic metal lead, a pollutant once widely emitted by cars burning leaded gasoline. Decades ago, the United States and Europe banned leaded gas and many other uses of the metal, but the pollutant’s fingerprint lingers on—as shown by remarkably detailed new 3-D maps released this week. The 3D maps and animations are the early results of an unprecedented $300 million international collaboration to document the presence of trace metals and other chemicals in the world’s oceans. The substances, which often occur in minute quantities, can provide important clues to understanding the ocean’s past—such as how seawater masses have moved around over centuries—and its future, such as how climate change might shift key biochemical processes.