Identifying the sources of aerosol ammonium is essential because ammonium can impact the Earth’s radiative balance, as well as human health and biological diversity. The sources of ambient ammonia concentrations can be quantified based on the stable isotopic composition of ammonia for various endmembers. However, isotopic source apportionment of aerosol ammonium is challenging in the urban atmosphere, where there is excess ammonia and nitrogen isotopic fractionation commonly occurs.
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Cassava is a staple in the diet of more than one billion people across 105 countries, yet this “orphaned crop” has received little attention compared to popular crops like corn and soybeans. While advances in breeding have helped cassava withstand pests and diseases, cassava yields no more today than it did in 1963. Corn yields, by comparison, have more than doubled.
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Above Scandinavia, on the Atlantic side of the Arctic Ocean, mackerel, cod, and other fish native to the European coast are migrating through increasingly ice-free waters, heading deeper into the Arctic Basin toward Siberia. Thousands of miles to the west, above Alaska, kittiwakes and other polar seabirds are being supplanted by southern birds following warm waters streaming north through the Bering Strait. And midway between, above Canada, sea ice-avoiding killer whales from the Atlantic are increasingly making themselves at home in a thawing Arctic.
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