Researchers from Nagoya University in Japan have reported that nitrate accumulated in soil bordering streams plays an important role in the increase of nitrate levels in stream water when it rains.
Researchers from Nagoya University in Japan have reported that nitrate accumulated in soil bordering streams plays an important role in the increase of nitrate levels in stream water when it rains. Their findings, published in the journal Biogeosciences, may help reduce nitrogen pollution and improve water quality in downstream bodies of water, such as lakes and nearshore waters.
Nitrate is an essential nutrient for plants and phytoplankton, but excessive nitrate levels in streams can damage water quality, cause eutrophication (the over-enrichment of water by nutrients), and pose health risks to animals and humans. Although it's known that nitrate levels in streams rise when it rains, the reason for this is unclear.
There are two leading theories of how stream nitrate increases when it rains. According to the first theory, the nitrate in the atmosphere dissolves in rainwater and falls directly into streams. Whereas the second theory is that, when it rains, soil nitrate in the area that borders the stream, known as the riparian zone, flows into stream water.
To further investigate the source of the nitrate, a Nagoya University research team led by Professor Urumu Tsunogai at the Graduate School of Environmental Studies, collaborating with the Asia Center for Air Pollution Research, conducted a study to analyze changes in the isotopic compositions of nitrogen and oxygen in nitrate and the increase of nitrate concentrations in a stream during rainstorms.
Read more at Nagoya University
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