Metal and Metalloid Size-Fractionation Strategies in Spatial High-Resolution Sediment Pore Water Profiles

Trace metal comparative analysis of sinking particles and sediments from a coastal environment of the Jiaozhou Bay, North China: Influence from sediment resuspension

To constrain the resuspension influence to the biogeochemical behavior of trace metals (TMs) in settling materials, the concentrations and chemical speciations of macro-elements (Al, Fe, Mn) and selected particulate TMs (V, Cr, Co, Cu, Zn, Ga, Sr, Cd, Ba, Tl, Pb, U) in trap-collected particles (TCPs), surface sediments (SS) and core sediment samples (CS5) of the Jiaozhou Bay were compared. Two approaches, mass conservation method and vertical two end-members mixing model, both calculated a resuspension ratio of more than 90%. Greater TM concentrations and Al-normalization levels than SS/CS5 determined the TCPs an important TM-sink, predominantly owing to grain-size effects and TCP-specific characteristics, i.e., structural capacity of organic-Fe associations for TMs' scavenging, preferential remineralization of TM than biogenic elements in autochthonous microorganisms. Comparison revealed distinct, Fe mineral controls on TM sequestration patterns: higher metal sequestration associated with amorphous Fe oxyhydroxides, while less reactive crystalline Fe oxides hold less metal. Nevertheless, turbulent hydrodynamics muted the wide TM retention divergences between TCP and SS, which should have happened based on different Fe minerals distribution for TCP/SS. The net effect of TM release by the organic carrier phase and then adsorption principally onto Mn/Fe oxyhydroxide phase for raised overall TCP-TM concentrations was also identified.

Microorganism Assisted Synthesized Nanoparticles for Catalytic Applications

Metal and metalloid nanoparticles (NPs) have attracted substantial attention from research communities over the past few decades. Traditional methodologies for NP fabrication have also been intensely explored. However, drawbacks such as the use of toxic agents and the high energy consumption involved in chemical and physical processes hinder their further application in various fields. It is well known that some bacteria are capable of binding and concentrating dissolved metal and metalloid ions, thereby detoxifying their environments. Bioinspired fabrication of NPs is environmentally friendly and inexpensive and requires only low energy consumption. Some biosynthesized NPs are usually used as heterogeneous catalysts in environmental remediation and show higher catalytic efficiency because of their enhanced biocompatibility, stability and large specific surface areas. Therefore, bacteria used as nanofactories can provide a novel approach for removing metal or metalloid ions and fabricating materials with unique properties. Even though a wide range of NPs have been biosynthesized, and their synthetic mechanisms have been proposed, some of these mechanisms are not known in detail. This review focuses on the synthesis and catalytic applications of NPs obtained using bacteria. The known mechanisms of bioreduction and prospects in the design of NPs for catalytic applications are also discussed.