Professor Meredith Hastings and her colleagues from Brown University conducted a study to determine the extent of pollution caused by human activities that also found an ammonium deposit in the open ocean near Bermuda.

The study, which was based on rainwater samples taken in Bermuda over two years, suggests that a deposit of ammonium over the open ocean is being produced completely from natural marine sources and not from the activities of people.

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"That was a bit of a surprise," said Hastings, the Joukowsky Assistant Professor of Earth, Environmental, and Planetary Sciences and one of the study's co-authors.

"We have some sense of what the ammonium emissions are in the United States, so we would expect to see that signature in Bermuda, but we don't see it."

Hasting said the findings don't necessarily mean that emissions of ammonium are lower than previously expected. One possibility is that the ammonium was just deposited near the continent before it reached Bermuda, which is some 600 miles off the coast.

Either way, the results suggest people aren't adding the anticipated amount of ammonium into the ocean as some scientists have previously assumed, Hastings said.

Understanding the contribution of humans to the ammonium levels in the ocean is important as ammonia is a source of nitrogen. High nitrogen levels in oceans and rivers can disrupt natural aquatic ecosystems.

"We see a lot of deleterious effects of increased nitrogen pollution on our waterways and our drinking water," said Hastings, who is also a fellow in Brown's Institute for the Study of Environment and Society.

"So if you want to make policy to limit emissions and reduce these pollution impacts, we need to have a good handle on what sources are natural and what are anthropogenic."

TagsAmmonium, Brown University, marine life, Ammonium deposit, Bermuda, Nitrogen, Ecosystem