Atmospheric inputs of trace metals to the northeast Atlantic Ocean: the importance of southeasterly flow

The study of aerosols and rainwater presented here demonstrates that episod ic atmospheric deposition events associated with southeasterly flow are qua ntitatively significant for large areas of the North Atlantic Ocean. This p aper considers aluminium and manganese, with predominantly crustal sources, and lead and zinc, which are mobilised into the atmosphere primarily throu gh anthropogenic activity. High levels of all trace metals are associated w ith southeasterly flow from Europe as the air passes over heavily populated and industrialised regions before reaching the northeast Atlantic Ocean. F luxes calculated using the 1% HNO3 acid soluble metal concentration show th at, although the climatological norm for this area is westerly flow, short- lived southeasterly transport events dominate the input of trace metals to this ocean region. This material may be toxic to phytoplankton or may be re present a new source of nutrients to the biological community. A significan t decrease in atmospheric lead levels in polluted air is seen between June 1996 and May 1997, reflecting the decrease in use of leaded fuels in Europe . Comparing atmospheric flux values to sediment trap metal fluxes shows tha t the atmosphere represents the dominant source of zinc to the deep ocean, whereas an additional, non-atmospheric, manganese source this required, per haps from mobilisation of sedimentary material from the continental shelf o r long range advection of manganese rich Saharan material. (C) 2001 Publish ed by Elsevier Science B.V.