Investigating feedbacks between natural metal-binding organic ligands and particle dissolution in central California coast seawater

The roles of naturally occurring Fe- and Cu-ligands in particle dissolution were investigated during a 24-hour shipboard incubation experiment amended with various natural particles. The incubation seawater, collected from surface waters of the central Californian coast in July 2014, was amended with the Fe(II)-containing mineral biotite, the Fe(III)-mineral hematite, and resuspended nepheloid layer particles in separate treatments. Nepheloid layer particles were isolated via in situ filtration of bottom boundary layer waters overlying the central California shelf during the same cruise. Replicates of each particle type were incubated in both filtered and unfiltered surface seawater to provide insight on the role of ambient plankton communities on both the speciation of Fe and Cu and on the short-term dissolution of the particles. Samples for Fe- and Cu-binding ligands were analyzed from the 10-minute, 12-hour and 24-hour time points. Copper- and Fe-binding ligand analyses were performed by competitive ligand equilibration – cathodic stripping voltammetry (CLE–CSV), salicylaldoxime was used as the added competitive ligand for both metals. Dissolved concentrations of Fe and Cu were measured by ICP-MS analysis. Results from this experiment will be presented in the context of recently published studies looking at the influence of model Fe-binding ligands on aerosol dissolution in surface seawater. Altogether, these data emphasize the importance of ligands, and especially Fe-binding ligands, on particle dissolution in seawater.