Significance of Atmospheric Input on Metal Concentrations in Oceanic Surface Water and Suspended Matter

摘要

Studies were conducted in order to determine if man-produced increases in air pollution will cause a significant increase in ocean surface water metal concentrations and what the quantitative significance of atmospheric flux of metals is compared to the metals flux leaving the surface layer of the ocean via particle sinking. The atmospheric input of particulate metals was estimated using oceanic air particulate chemistry data and atmospheric deposition velocity data for the natural radionuclide exp 7 Be. The atmospheric flux of metals was compared to both the downward flux of metals determined from sediment traps and the upward flux of metals to the surface layer by water mixing. The residence times of metals in the surface layer were calculated using the atmospheric or sediment trap flux. It is concluded that atmospheric input is the major source of Al, Fe, Pb, Zn and Sc to open surface water. Several metals (Al, Fe, Pb, Zn, Cd and Sc) are very reactive or insoluble and, consequently, have a short residence time (<9 yr) in the surface layer as estimated from air and mixing inputs. Residence times estimated from removal processes generally show the same trend as the residence time for input processes. However, so little sediment trap metal flux data are available, only a qualitative comparison is meaningful. Atmospheric input can account for the flux of many of the metals estimated for the minimum trap flux but not for the maximum trap flux. Several metals (V, Se, As, and Sb), present as oxy-anions, are relatively nonreactive and, consequently, their concentrations are controlled by mixing processes. The remaining metals (Mn, Cu, Ni, Cr, Co and Ag) are apparently of intermediate reactivity and their cycles are affected by both air input and mixing processes. (ERA citation 07:048090)