Polystyrene Immobilized Ir(III) Complex as a new Material for Optical Oxygen Sensing

The luminescence spectra of tris(phenylpyridine)iridium embedded in Amberlite (polystyrene adsorbent) have been measured under various O2/N2 mixtures (total pressure = 1 atm). It is shown that the Stern‐Volmer plots are downward curved and that the curvature can be explained either by a two‐site model or by a negative deviation from Henry's law. A curve fitting procedure cannot distinguish between the two models. Using a frequency modulated blue LED and a fiber optic set‐up, O2 partial pressure of 0.4 mbar could be detected. Oxygen can be determined at 200 mbar with a 1.5% accuracy. Copyright © 1994 Wiley‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effects of a sewage plume on the biology, optical characteristics, and particle size distributions of coastal waters

The effect of a sewage plume on the biology, optical characteristics, and particle size distributions of coastal waters was evaluated around the Sand Island, Hawaii, outfall diffuser. In situ physical and biooptical data and Niskin bottle samples were collected during a 1-week cruise from September 25 to October 1, 1994. One or two layers affected by sewage could be distinguished in the water column: recently discharged (''new'') sewage plume waters and ''old'' plume waters. In conditions characterized by high Froude number the distribution of chlorophyll fluorescence in new plume waters was the same as for ambient waters, while for low Froude number, chlorophyll fluorescence increased within the plume, demonstrating the importance of physical forcing on effluent and phytoplankton interactions. New plume waters were associated with at least 2.7-fold increases in particle load, high concentrations of particles larger than 70 mu m, increases in ammonium, phosphate, and silicate, and high levels of heterotrophic bacteria and Prochlorococcus compared to surrounding waters. Both new and old plume layers, but not phytoplankton layers, showed distinct increases in fluorescence for the excitation/emission (Ex/Em) wavelength pair Ex/Em = 228/340 in mm, interpreted as particulate tryptophan-like fluorescence. Such fluorescence may be useful as a new in situ real-time indicator of waters affected by effluent discharges