Soluble iron conservation and colloidal iron dynamics in a hydrothermal plume

Iron (Fe) limits or co-limits primary productivity and nitrogen fixation in large regions of the world's oceans, and the supply of Fe from hydrothermal vents to the deep ocean is now known to be extensive. However, the mechanisms that control the amount of hydrothermal Fe that is stabilized in the deep ocean, and thus dictate the impact of hydrothermal Fe sources on surface ocean biogeochemistry, are unclear. To learn more, we have examined the dispersion of total dissolvable Fe (TDFe), dissolved Fe (dFe) and soluble Fe (sFe) in the buoyant and non-buoyant hydrothermal plume above the Beebe vent field, Caribbean Sea. We have also characterized plume particles using electron microscopy and synchrotron based spectromicroscopy. We show that the majority of dFe in the Beebe hydrothermal plume was present as colloidal Fe (cFe = dFe − sFe). During ascent of the buoyant plume, a significant fraction of particulate Fe (pFe = TDFe − dFe) was lost to settling and exchange with colloids. Conversely, the opposite was observed in the non-buoyant plume, where pFe concentrations increased during non-buoyant plume dilution, cFe concentrations decreased apparently due to colloid aggregation. Elemental mapping of carbon, oxygen and iron in plume particles reveals their close association and indicates that exchanges of Fe between colloids and particles must include transformations of organic carbon and Fe oxyhydroxide minerals. Notably, sFe is largely conserved during plume dilution, and this is likely to be due to stabilization by organic ligands, in contrast to the more dynamic exchanges between pFe and cFe. This study highlights that the size of the sFe stabilizing ligand pool, and the rate of iron-rich colloid aggregation will control the amount and physico-chemical composition of dFe supplied to the ocean interior from hydrothermal systems. Both the ligand pool, and the rate of cFe aggregation in hydrothermal plumes remain uncertain and determining these are important intermediate goals to more accurately assess the impact of hydrothermalism on the ocean's carbon cycle. This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean – GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González

Preparation and characterization of acrylic polymer–nanogold nanocomposites from 3-mercaptopropyltrimethoxysilane encapsulated gold nanoparticles

100學年度張朝欽升等參考著作[[abstract]]In this study, acrylic polymer–nanogold nanocomposites and their cast films were prepared from an acrylic copolymer and 3-mercaptopropyltrimethoxysilane (MPS) stabilized gold nanoparticles by a sol–gel reaction. The acrylic copolymer was synthesized from methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). The Si–OMe groups of MPS on the surface of gold nanoparticles (MPS–Au) provided the further reaction with the same groups of MSMA, hence the covalent bonds between polymers and MPS–Au nanoparticles were formed. FE-SEM images show MPS–Au nanoparticles are dispersed well in the prepared nanocomposites, and no large aggregation is occurred. TGA results indicate that the decomposed temperatures (Td) of low Au-content (0.1 wt.%) nanocomposites are higher than these of the acrylic copolymer and high Au-content (1.0 wt.%) nanocomposites. The temperature of maximum decomposed rate (Tp) of each prepared nanocomposite is higher than that of the acrylic copolymer. The hardness of the cast film increases with increasing the Au content. The results show the improved thermal stability and application potentials of the prepared acrylic polymer–nanogold nanocomposites.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙