By Blake Jackson
New research from Penn State scientists suggests that rising temperatures and prolonged dry conditions can increase nitrate concentrations in rivers and streams, even in regions with little or no agricultural or urban development. The findings challenge the traditional understanding that nitrate pollution primarily results from agricultural runoff and human waste.
Published November 12 in the journal Science, the study used artificial intelligence (AI) and machine learning to analyze water quality data from more than 7,000 river monitoring sites worldwide. Researchers developed a model capable of estimating nitrate concentrations across approximately 2.9 million river segments, including areas with limited monitoring data.
“Right now, roughly a half billion people are living in proximity to rivers where nitrate concentrations exceed levels that can potentially lead to negative health effects,” said Li Li, the Barry and Shirley Isett Professor of Environmental Engineering at Penn State and the study's corresponding author.
“This finding implies that nitrate pollution is beyond a local management issue: it’s a broader problem directly related to climate, which is becoming increasingly hotter and drier.”
Nitrate is a common form of water pollution found in rivers, lakes, streams and groundwater. Although it naturally occurs at low concentrations, excessive amounts can damage aquatic ecosystems and threaten human health.
Elevated nitrate exposure in drinking water can cause methemoglobinemia, also known as blue baby syndrome, a potentially fatal condition that affects an infant's ability to transport oxygen through the blood.
Researchers found that climate characteristics, including average annual temperatures and rainfall, influence nitrate concentrations alongside human activities.
“Generally, we think nitrate hotspots derive from human input like fertilizer used in agricultural or wastewater from cities,” said Li.
“There’s not a lot of very-large-scale water quality work, so people don’t traditionally think about climate in terms of affecting nitrate levels. However, our new model is telling us that although human input plays a major role, long-term climate such as average annual temperature and average annual rainfall of an area contributes to environmental nitrate levels, as well.”
The research also identified elevated nitrate concentrations in arid regions, including parts of the Sahara Desert.
Scientists believe naturally occurring nitrate accumulates over time in dry environments because limited water movement prevents it from being washed away.
Kayalvizhi Sadayappan, a postdoctoral scholar at Penn State and the paper's first author, noted that current drinking water standards limit nitrate to 10 milligrams per liter.
However, researchers are examining potential long-term health risks associated with exposure at lower concentrations.
The team acknowledged that limited monitoring data from arid regions remains a challenge for global water quality assessments.
The researchers hope their findings will encourage additional monitoring, improve understanding of climate-related water pollution and help inform future environmental regulations as drought and rising temperatures become increasingly widespread.
Photo Credit: gettyimages-frantic00
Categories: Pennsylvania, Education