Is a great iron fertilization experiment already underway? | 7/3/2018 | Staff
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It's no secret that massive dust storms in the Saharan Desert occasionally shroud the North Atlantic Ocean with iron, but it turns out these natural blankets aren't the only things to sneeze at. Iron released by human activities contributes as much as 80 percent of the iron falling on the ocean surface, even in the dusty North Atlantic Ocean, and is likely underestimated worldwide, according to a new study in Nature Communications.

"People don't even realize it," said lead author Dr. Tim Conway, Assistant Professor at the USF College of Marine Science, "but we've already been doing an iron fertilization experiment of sorts for many decades."

Fuels - Biofuels - Release - Iron - Aerosol

Burning fossil fuels, biofuels, and forests all release iron, which can be transported as an aerosol over large distances from land into the guts of the North Atlantic and beyond. But human-derived iron aerosols have been nearly impossible to see in the data—until now. The team used the isotope ratios of iron in the atmosphere to 'fingerprint' whether the iron came from Saharan desert dust or human sources such as cars, combustion, or fires.

"Despite much research, iron chemistry is still something of a black box in the ocean," Conway said. Iron, a trace element, is found in exceedingly low amounts in the ocean; one liter of seawater contains 35 grams of salt but only around one billionth of a gram of iron. This makes it very hard to measure. The iron is also hard to sample without risking contamination, especially if working on a rusty ship.

Iron - Lands - Dissolves - Ocean - Challenges

Trying to establish how much atmospheric iron lands on and dissolves in the ocean presents even more challenges, with storms, seasons, and land use all changing how much dust gets blown from the continents. Digesting dust particles in the lab to see how much iron dissolves is also problematic, and has...
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