Dissolved, particulate and acid‐leachable trace metal concentrations in North Atlantic precipitation collected on the Global Change Expedition

Abstract

Rainwater samples from six precipitation events were collected on board ship during legs 3 and 4 of the Global Change Expedition over the North Atlantic Ocean and analyzed for dissolved, particulate (Al and Pb), and acid‐leachable trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn). Acid‐leachable concentrations of the elements (in 0.4% v/v HNO3) were similar to reported values from the North Atlantic and Pacific oceans which were measured using comparable acidification procedures. Concentrations of dissolved and particulate Al and Pb were determined in rain events concurrently sampled. Comparisons between acid‐leachable and total (dissolved plus particulate) trace metal concentrations suggest that the acid‐leachable fraction of metals can significantly underestimate total concentrations of crustal elements (e.g., Al) in rain). The solubilities of Al and Pb in precipitation were variable and mean solubilities of the elements were 13% and 45%, respectively. Recycled sea salt components were less than 14% for Al, Fe, Mn, Pb, Cd, Cu, and Zn, indicating that the net trace metal flux is from the atmosphere to the oceans. Deep‐sea particle fluxes for these metals through the western tropical North Atlantic exceed atmospheric deposition fluxes by a factor of 18‐41.