Early diagenesis and accumulation of redox-sensitive elements in East Siberian Arctic Shelves

Abstract

The Arctic shelf makes up half of the area within the Arctic Ocean. It plays an important role in the global carbon cycle, whilst its part in the recycling process of redox-sensitive elements (RSEs) is still not clear. This study has selected nine sediment cores, 30 to 40 cm in length, covering a wide area over the East Siberian Arctic Shelves (ESAS) and analyzed a suite of RSEs (S, Mn, Mo, U, V, Cd) in the sediments, along with Al, Fe, total organic carbon (TOC), grain size, and sedimentation rate. The redox environment in surface sediments was clearly divided based on the S and Mn contents of the cores, ranging from being more oxidized on the western East Siberian Sea shelf, to more reduced on the Chukchi Sea shelf. TOC also showed an increasing trend eastward in the study region. Statistically significant correlations were found between Cd and S, V and Fe, Mo and Mn, and U and TOC, implying their close relationships during early diagenetic processes at the sediment-water interface. Across the study area, authigenic accumulation occurred for all RSEs, except Mn. The estimated authigenic accumulation fluxes for Mo, U, V, and Cd over the entire ESAS are 0.21 ± 0.09, 0.086 ± 0.043, 11.0 ± 9.2 and 0.019 ± 0.014 × 108 mol y−1, respectively, which are comparable to values reported in suboxic marginal sediments for Mo, U, and Cd, but exceptionally high for V. Although the sampling resolution was coarse and there are uncertainties in the sedimentation rates and detrital background values of V, we propose the authigenic accumulation flux for V on the broad and shallow ESAS may be a significant but missing sink term for the global V cycle.