Vertical transport processes of an acid-iron waste in a MERL stratified mesocosm

The vertical transport of the Fe particles formed after an acid-Fe waste mixes with seawater and the impact of the waste on the trace metal composition of seawater were examined in a stratified tank at the MERL facility of the University of Rhode Island. Two acid-Fe waste additions were made to one of the stratified tanks at concentrations comparable to those observed after the initial dispersion of the waste in the ocean (10 super(5) dilution); a second stratified tank was maintained as a control. The removal of the Fe waste from the water column was due to settling of the Fe particles through the pycnocline; biological transport of the Fe particles was not an important removal mechanism. The kinetic behavior of the Fe particles was different after the two waste additions; gravitational settling was the rate-limiting step after the first addition, whereas flocculation was the rate-limiting step after the second waste addition. The first acid-Fe waste addition apparently altered the properties of the seawater, possibly stripping organic substances from the water column.