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Home / Science / The path of nitrogen pollution to streams leads through more forests (and faster) than suspected

The path of nitrogen pollution to streams leads through more forests (and faster) than suspected



A new study by research hydrologist Stephen Sebestyen from the USDA Forest Service and 29 colleagues from agencies and universities around the world is one of the largest long-term studies to track unprocessed nitrate movement in forests. Credit: Stephen Sebestyen, USDA Forest Service

Nitrogen falls to the ground in rain and snow, where it is theoretically used by forest plants and microbes. New research from a scientific collaboration led by the USDA Forest Service shows that more nitrogen from rain and snow leads to more streams than previously thought and flows downstream in the forests of the US and Canada. The study "Unprocessed atmospheric nitrate in waters of the Northern Forest region in the US and Canada" was published this week in the journal Environmental Science & Technology .

Scientists found that nitrate, a form of nitrogen that can be used by plants and microbes, occasionally moves too fast for biological uptake, resulting in "unprocessed" nitrate, which is the otherwise effective filter of Forest biology bypasses. The study combines pollutant emissions from various and sometimes distant sources such as industry, energy production, the transport sector and agriculture with forest health and water quality.

"Nitrogen is critical to the planet's biological productivity, but it will pollute and pollute ecologically if there is too much," said Stephen Sebestyen, a research hydrologist at the USDA Forest Service's Northern Research Station Rapids, Minnesota, and the lead author of the study.

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"From public land managers to forest owners, there is a great deal of interest in forest health and water quality, and our research shows widespread adverse effects that undermine efforts to manage nitrogen pollution. "

Sebestyen and 29 co-authors conducted one of the largest and longest investigations to monitor unprocessed nitrate movement in forests. Scientists from several federal agencies and twelve academic institutions in the United States, Canada, and Japan collected water samples in 1

3 states and the province of Ontario and produced more than 1,800 nitrate isotope analyzes over 21 years.

"We generally thought that nitrate pollution would not travel a great distance through a forest, as the landscape would serve as an effective filter," Sebestyen said. "This study shows that although we were right, we needed more information to be better informed." Forests consume most of the nitrate unless rain and snow melt during higher flow velocities lead to short but important windows when unprocessed nitrate flows to rivers; sometimes at unexpectedly high levels.

Excessive nitrogen contributes to the decline of forests and the growth of bad vegetation in lakes and ponds. Tree species have different tolerances for nitrogen. Too much nitrogen can change the composition of the forest and stop non-native plants. "I'm concerned with how air pollution affects forests and water basins," said Trent Wickman, an Air Resource Specialist with the USDA Forest Service Eastern Region and co-author of the study. "There are a number of federal and state programs that aim to reduce air pollution from nitrogen and airborne air." Understanding the fate of nitrogen in the air but landing in the countryside is important to understanding To assess the effectiveness of this pollution reduction program. "

Sebestyen and the co-authors of the study point out that since unprocessed nitrogen is not filtered to the extent by natural vegetation, monitoring in conjunction with this basic information is required is to give land managers a more sophisticated picture of forest health problems.


Explore further:
Track nitrate in watersheds

Further information:
Stephen D. Sebestyen et al., Unprocessed Atmospheric Nitrate in Northern Forest Region waters in the USA and Canada, Environmental Science & Technology (2019). DOI: 10.1021 / acs.est.9b01276

Magazine Reference:
Environmental Science & Technology

Provided by:
USDA Forest Service


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