ABSTRACT
This chapter outlines the mathematical theory of transport-reaction modeling as applied to metals in surface sediments. Surface sediments are not the passive recipients of particulate metals settling out of the water column. Rather, they act as biogeochemical reactors in which the deposited metals participate in a variety of processes, including microbial reactions, redox transformations, adsorption-desorption exchanges, and the precipitation and dissolution of minerals. Most chemical transformations affecting metals in surface sediments are driven, directly or indirectly, by the decomposition of organic detritus deposited from the water column. Because surface sediments are open, non-equilibrium systems, a kinetic description which accounts for reaction and transport is required. The accurate description of the distributions, transformations and transport of metal species in surface sediments requires a combination of approaches and methodologies. Field-based measurements offer an integrated record of the interaction of the sedimentological, biological and geochemical processes that affect metal cycling.
