Ammonium deposited over the open ocean comes almost entirely from natural marine sources, not from human activities like agriculture, as was previously believed, a new study of rain samples taken in Bermuda suggests.

The island of Bermuda is an ideal place to study the origins of pollutants, Hastings says. The weather over the island is dominated by tropical air masses that blow in from the south. But for part of the year, when tropical high pressure shifts, air masses coming off the continental United States work their way into the region. Those air masses can contain pollutants from industry, agriculture, and other human activities on the continent.

Read the full article at