Advection-diffusion scavenging

Figure 1. Plot of the scavenging rate constants derived from advection-diffusion--scavenging models against the stability constant for simple hydroxo complexes, Ki...

Figure 8.24 The advection-diffusion model (Craig, 1974) in a water column of depth Z, mixing length lm, and scavenging length /s. Concentrations [left, equation (8.8.8)] and fluxes [right, equation (8.8.9)] in the water column for the IJZ values labeled on the curves.

The intensified scavenging that occurs at ocean boundaries lowers the concentrations of dissolved °Th and Pa in deep waters several-fold relative to those found in open-ocean regions (Anderson et al. 1983b). Consequently, eddy diffusion and advection of deep waters from the open ocean toward ocean margins causes a net supply of dissolved Pa and °Th at a ( Taxs/ °Thxs) much greater than 0.093, and potentially as high as... 

U throughout the water colutim. The length of gray arrows represents the size of the fluxes illustrating that °Th is rapidly scavenged everywhere, while Pa can be advected or transported by diffusion (not shown) from areas of low to high productivity. Sedimentary Pa/ °Th is therefore a fimction of both the productivity and the net lateral transport of Pa by ocean circulation. 

The concentration of small ions in the atmosphere is determined by 1) the rate of ion-pair production by the cosmic rays and radioactive decay due to natural radioactive substances, 2) recombination with negative ions, 3) attachment to condensation nuclei, 4) precipitation scavenging, and 5) transport processes including convection, advection, eddy diffusion, sedimentation, and ion migration under the influence of electric fields. A detailed differential equation for the concentration of short-lived Rn-222 daughter ions including these terms as well as those pertaining to the rate of formation of the... 

Simple mass budget relationships developed by Coale and Bruland (1985) to evaluate scavenging rates and residence times hold inherent assumptions, including steady-state conditions and negligible fluxes of " Th by advection or diffusion. Even though these conditions may apply at certain times and in certain places, there are many... 

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