Photolytic Release of Dissolved Vanadium and Copper from Resuspended Coastal Marine Sediments

Sunlight photolysis engenders release of dissolved vanadium (V), copper (Cu), and dissolved organic carbon (DOC) from a wide variety of resuspendable coastal marine sediments. Net photoreleases after 6 h of simulated sunlight were as high as 12 nM for Cu and as high as 15 nM for V. Release of Cu significantly correlated with sediment Cu. Photoreleased Cu (but not V) correlated with sediment Fe content, suggesting that photoreduction of Fe oxide carrier phases may be an important photoproduction mechanism for Cu. Longer term experiments showed continued release of metals that were not immediately readsorbed back onto sediments after 24 h of irradiation suggesting that photoproduced metals persist in the dissolved phase and are not immediately scavenged onto particles. Experiments utilizing differing total suspended sediment (TSS) levels show that, although higher TSS causes more photoproduction of Cu and V, the amount produced per mass of sediment is greatest at the lowest TSS. Vanadium photoproduction increased in Macondo oil-amended sediments compared to controls after a one-month incubation period suggesting that the oil may be a source of this metal to the water column. These results imply that photoproduction is an unrecognized source of the micronutrient metals Cu and V to coastal waters.