A new interdisciplinary study at Western University has shown for the first time that 70 per cent of nitrates in high mountain lakes in Utah are from human-caused sources – with fertilizers having, by far, the most impact. The research suggests these findings also apply to other mountain ranges in western North America.
Western researchers discovered these nitrates can travel hundreds of kilometres through the air, affecting biodiversity and reducing water quality, while having particular ramifications for the health of mountain ecosystems and for populations living in nearby lowlands.
“It’s frightening that these remote areas are seeing such a large human impact,” says Beth Hundey, who was the study’s lead author as a PhD student in Western’s Department of Geography. “We were surprised that there has been such a large contribution from agriculture to these remote mountain sites.”
The paper, co-authored by Geography professor Katrina Moser, Earth Sciences professor Fred Longstaffe and his former PhD student, Sam Russell, was published today in the prestigious journal, Nature Communications.
Scientists have previously inferred human influence may have led to increased nitrate concentrations in high mountain lakes; using a novel triple isotope (an atom with the same number of protons, but differing numbers of neutrons) technique, however, Western’s team is the first to prove nitrate origin.
Isotope signatures – not unlike fingerprints – distinguish various nitrate sources, including fertilizers, soil and the atmosphere. The team accomplished this task using an apparatus built and customized by Western’s Laboratory for Stable Isotope Science, led by Longstaffe, who holds the Canada Research Chair in Stable Isotope Science.
By identifying the cause of the problem, communities and governments will be able to develop effective mitigation strategies, particularly given anticipated expansion of human populations and fertilizer use.
“We’re not saying to stop using fertilizers,” says Hundey, “but knowing they have an impact on distant lakes, we can examine different ways of using and applying them.”
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