Science Findings, Issue 115, August 2009. Undercover Isotopes: Tracking the Fate of Nitrogen in Streams

摘要

Excess nitrogen stemming from human activities is a common water pollutant. Fertilizer runoff, sewage, and fossil fuel emission all contain nitrogen that often ends in streams, rivers, and ultimately the ocean. Research has found that more nitrogen enters a river system than can be accounted for at its mouth, indicating that instream processing is occurring. A team of scientists conducted several experiments on streams across the country to better understand the fate of waterborne nitrogen. Sherri Johnson from the Pacific Northwest Research Station and her collaborators from Oregon State University led the Oregon-based studies. They added small amounts of two forms of a naturally occurring nitrogen isotope to streams in forested, agricultural, and urban areas. These novel experiments enabled researchers to quantify the rate at which different forms of nitrogen are processed and removed by stream organisms.