Sediment trap experiment in the northern North Pacific: Undulation of settling particles

Abstract

Sediment traps were deployed at five depths for about one month during summer in the northern North Pacific. The samples were physically and chemically divided into four subsamples and analyzed for Al, Fe, Mn, Cu, Ni, Co, Cd, Ca, Mg, K, Na, Si, P, 234Th, 232Th, 230Th, 228Th, 210Po, 210Pb and 7Be. The concentrations of major components, silica and calcium carbonate, in the settling particles varied greatly with depth. Ca was more concentrated in large particles. The Al concentration in settling particles, which was somewhat smaller than that in suspended particles, increased with depth. The same tendency was observed for 210Pb and 210Po, whereas the concentration of 234Th showed a minimum value at 2.16km depth. Al fluxes were found to increase linearly with depth in deep water. These results suggest that there are two kinds of particles transporting the chemical components. One is the large biogenic particles produced near the surface. The other is the aggregates of suspended matter, which is important for the downward transport of some elements such as Al, Fe, Mn and 230Th. The observed fluxes are much larger than the net fluxes. This fact may be explained by the undulation of settling particles. Bottom sources of transition metals are also confirmed. © 1982, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.