MARINE SCAVENGING - THE RELATIVE IMPORTANCE OF MASS-TRANSFER AND REACTION-RATES

We present an analysis of factors regulating the scavenging rate of tr ace elements and nutrients by settling particles in the ocean. The ove rall process limiting marine scavenging rates is determined by compari ng the relative kinetics of dissolved phase mass transfer and particle -associated sorption rates. Measured scavenging and uptake rates of a variety of marine particle types are then compared to theoretically ca lculated mass transfer rate constants. Our calculations show that for most marine environments, sorption rates are much slower than external mass transfer of dissolved species. External mass transfer is therefo re not the limiting process. Particle-associated processes such as ads orption, intraparticle reactions, and particle repackaging must contro l the overall scavenging rates observed in the ocean.