1496 / 2024-09-27 19:00:16

Speciation distribution of trace metals in sea ice of Antarctic: a view from the monthly time series observation

trace metal,antarctica,sea ice

The Antarctic sea ice coverage makes up 40% of the Southern Ocean's area and serves as a significant reservoir for the marine trace metals. However, the seasonal changes in trace metal concentrations within the sea ice are not well understood. This study analyzed ice core samples collected continuously in Pridz Bay from May to December 2022 at a monthly interval. The concentrations of trace metals (Fe, Al, Mn, Ni, Cu, Zn, and Cd) in sea ice in different speciation (dissolved, total dissolvable, and total) were analyzed. The data showed that the concentrations of dissolved metals were similar to those of underlying seawater, except for Fe, which was 1-2 orders of magnitude higher than that of the underlying seawater. Based on the speciation and distribution patterns of trace metals in sea ice, we identified three groups of trace metals in this study. Among them, speciation distribution of Fe, Aland Pb was mainly dominated by the particulate phase. Iron was predominantly found in the refractory particles (RpFe=total Fe - total dissolvable Fe), while seasonal dFe concentrations ranging from 2.7-51.8 nmol/L (mean 7.4 nmol/L), only account for 2% of the total Fe. Al was usually used in tracing the lithogenic input from the continental shelf, and found predominantly in RpAl (0-363.6 nmol/L, mean 519.8 nmol/L) in this study. Mn was mainly dominated by the dMn(0.1- 27.2 nmol/L mean 2.3 nmol/L), with an overall C-type distribution in the ice core profiles. Pb was dominated by the tdPb (0.01-1.4 nmol/L, mean 0.2 nmol/L) and RpPb (0-17.7 nmol/L ,mean 0.4 nmol/L), and there is almost no dPb (0-0.4 nmol/L ,mean 0.03 nmol/L). Mn, Zn and Cd are mainly dominated in the dissolved phase, distribute as a C-shape and closely correlated with salinity. The dMn, dZn and dCd averaged 2.3 nmol/L,44.6 nmol/L,0.3 nmol/L, respectively, and corresponding to 74%, 96%, and 85% in the dissolved phase, respectively. There is a high concentration region present in the middle and upper parts of the ice core, while the surface and bottom concentrations are more stable. Ni and Cu were mainly controlled by both dissolved and particulate phses, Ni was mainly dominated by the dNi (mean 1.3 nmol/L) and RpNi (mean 1.8 nmol/L), accounted for about 49% and 49.7% of the total Ni, respectively . Cu was mainly presented in the DCu (mean 3.2nmol/L) and RpCu (mean 1.7nmol/L), accounted for about 52% and 27% of the total Cu, respectively.