FLUX OF SURFACE-ACTIVE ORGANIC-COMPLEXES OF COPPER TO THE AIR-SEA INTERFACE IN COASTAL MARINE WATERS

Concentrations of surface-active organic complexes of copper in coasta l seawater were used to estimate their transport from the water column to the air-sea interface by molecular diffusion and bubble scavenging . Under average wind conditions observed in Massachusetts Bay, molecul ar diffusion to the air-sea interface was the primary transport mechan ism. Estimated diffusion flux rates ranged from 3.8 to 210 x 10(-17) m ol Cu cm(-2) s(-1) , with a mean value of 62 x 10(-17) mol Cu cm(-2) s (-1). Temporal variability in the flux rates was directly related to e stimated rates of primary production, presumably due to the biological production of surface-active organic matter within the bulk water. Fl ux rates due to bubble scavenging were generally 3 orders of magnitude less than those observed for diffusion, with a mean value of 2.3 x 10 (-19) mol cm(-2) s(-1) for particulate Cu and 3.7 x 10(-19) mol cm(-2) s(-1) for dissolved Cu. Temporal variability of the estimated bubble- mediated fluxes reflected sensitivity to changes in wind stress, as we ll as the variablility in concentration of the surface-active forms of copper. Residence times of copper in the sea-surface microlayer, base d on a comprehensive estimate of the flux of copper from bulk water an d atmospheric sources, ranged from 2 min during a phytoplankton bloom period to 21 min during the winter months. Estimates of the flux of su rface active forms of copper from the water column to the air-sea inte rface suggest that the entire inventory of copper within the surface m ixed layer of Massachusetts Bay can be cycled through the microlayer w ithin approximately 50 days. This is of the same timescale as the resi dence time of copper within the surface mixed layer of Massachusetts B ay, indicating that a major portion of copper within the surface mixed layer will be transported to the microlayer before removal from the m ixed layer. The formation and transport of surface-active forms of cop per may significantly influence the biogeochemical behavior of copper and, perhaps, other metals within the surface mixed layer.