Julie R. Bradbury

Kinetic studies of lead(II) uptake by the seagrass Zostera muelleri in water by radiotracing, atomic absorption spectrometry and electrochemical techniques

Abstract Evidence was found that uptake of lead from seawater in both model and natural systems by the leaves of the seagrass Zostera muelleri does occur for live, dead and scraped leaves at all the lead concentrations tested. Positive uptake of lead was measured using the three analytical techniques of radio-tracer, differential pulse anodic stripping voltammetry and atomic absorption spectrometry; similar uptake profiles were obtained for each technique. Profiles always showed an initial rapid uptake phase followed by a gradual transition to a plateau phase at which an approximate equilibrium between lead attached to seagrass and free ionic lead in seawater was reached. The presence of active lead uptake processes was indicated in experiments which attempted to remove lead from leaves by a chelating agent.

Electrochemical reduction of the trimethyllead(IV) cation in seawater

Abstract The need to distinguish between inorganic and organic forms of lead in seawater has been widely recognized. Electrochemical techniques based on reduction at mercury electrodes or anodic stripping voltammetry have been proposed as methods for determining the various forms of lead. However, detailed investigation of the electrode process for the electrochemical reduction of the trimethyllead cation in seawater show that correct data may not necessarily be obtained with all electrochemical techniques. On the short time scale of polarography the proposed reduction mechanism is: (CH 3 ) 3 Pb + + e (CH 3 ) 3 Pb+3 Hg→Pb(amalgam)+3 CH 3 Hg(ads) 3 CH 3 Hg(ads)+3 e →3 CH 3 Hg − Data show that differential pulse polarography can be used to determine simultaneously inorganic lead and the trimethyllead cation, however, with inverse oxidation experiments involving stripping of lead (amalgam) such as reverse normal pulse voltammetry, substantial modification to the electrode process occurs in the presence of methylated mercury. Anodic stripping voltammetry therefore suffers from substantial interference, when using the: Pb(amalgam)Pb 2+ +2 e electrode process for determining the concentration of the trimethyllead cation in seawater.

Redox properties of mononuclear and triply-bridged binuclear thiolato anions of oxomolybdenum(V)

Interconversion of mononuclear [MoVO(SR)4]–(1; R = aryl or alkyl) and triply-bridged, binuclear [MoV2O2(SR)6Z]–(2; Z = OMe, OEt, or SCH2Ph) anions occurs via redox processes involving both the molybdenum and ligand thiolate centres.