The chemistry and vertical flux of particles in the northeastern Gulf of Alaska

Abstract

The physical and chemical compositions of settling particles and underlying sediments collected from a pristine coastal environment south of Icy Bay in the northeastern Gulf of Alaska were compared to investigate the processes affecting the compositions, flux, and early diagenesis of the materials. Settling particles were collected with three self-closing sediment traps moored vertically approximately 30 km offshore. Sediments collected by gravity coring at the site were dated by 210Pb geochronology. Total particulate Al, Si, Cr, Mn, Fe, Ni, Cu, Zn, and Pb were determined on all samples by flameless atomic absorption and standard colorimetric procedures. Total C and N were determined by dry combustion gas chromatography. A dilute hydrogen peroxide oxidation dissolution treatment was used to study element associations with labile particulate organic matter. A selective biogenic SiO 2 dissolution treatment also was employed to determine the biogenic SiO 2 fraction. Results suggest that the sediment traps efficiently collected settling particles. The elemental accumulation rates, remineralization of particulate organic matter, and remobilization of trace elements, notably Cu, were quantified by comparing the composition of the trapped materials with the underlying sediments. The majority of the remineralization appears to occur within the sediments below the zone influenced by resuspension, presumably as a result of biological activity.