Sleuths search the seas for soot

Earth system scientists have taken water samples from the north Pacific, north and south Atlantic, and Arctic oceans in search of repositories of black carbon, soot from burning biomass and diesel engines, among other sources. They’ve found considerably less of the material than expected, and they’ve discovered that it exists in at least two varieties, a younger pool closer to the ocean’s surface that is absorbed into the environment in a roughly 100-year cycle and an ancient reserve that remains stable for millennia.