Accumulation processes of trace metals into Arctic sea ice: distribution of Fe, Mn and Cd associated with ice structure

• Published in: Marine Chemistry
• Main Authors: Evans, La Kenya, Nishioka, Jun
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier
• Subjects: Sea ice structure; Trace metals; Dissolved; Labile particulate; 450; Arctic; Arctic Ocean; Sea ice
• Online Access: http://hdl.handle.net/2115/80481; https://doi.org/10.1016/j.marchem.2018.11.011

Biogeochemical cycling of trace metals in sea ice is important to the productivity of the Arctic Ocean. Unfortunately, the processes by which trace metals accumulate into sea ice are poorly understood. To gain a clearer understanding of the mechanisms behind trace metal accumulation, dissolved (D, < 0.2 mu m), and labile particulate (LP = Total Dissolvable Dissolved) iron (Fe), manganese (Mn), and cadmium (Cd) concentrations were compared to the structure observed in sea ice. Samples were pre-concentrated via solid-phase extraction on NOBIAS Chelate PA-1 resin and analyzed on a Graphite Furnace Atomic Absorption Spectrometer. Using photographic analysis for the percentage of pore microstructure and delta O-18 analysis, sea ice structure was determined to be snow ice, granular ice (frazil ice), mixed ice (granular and columnar ice) and columnar ice. Salinity and nutrients were low, indicating brine drainage and multi-year ice. High trace metal concentrations in snow ice indicated meteoric snow was a source of trace metals to sea ice. High concentrations of LPFe in granular ice indicated entrainment of suspended particulate trace metals by frazil ice during the formation of the granular ice structure. Whereas the high concentrations of DFe and DMn in granular ice may have been due to reduction from LPFe and LPMn after particle entrainment, indicating chemical transformation processes. Low dissolved and labile particulate trace metal concentrations in mixed and columnar ice indicated a release due to brine drainage. Our study clearly indicates that the differences observed in trace metals among sea ice structures, showed that sea ice formation, chemical reduction and brine release were the processes driving trace metal accumulation and release in the Arctic sea ice.