Paula G. Coble

High‐resolution measurements of dissolved organic carbon in the Arctic Ocean by in situ fiber‐optic spectrometry

Here we report results from an extensive survey of dissolved organic carbon (DOC) in the Arctic Ocean, which was achieved by means of a high-resolution, in situ UV fluorometer deployed on a nuclear submarine. Based on a strong linear correlation observed between fluorescence (320 nm excitation, 420 nm emission) and organic carbon concentrations determined directly by high-temperature combustion, a continuous record of DOC was produced at a keel depth of 58 m along a 2900-km transect north of the Beaufort, Chukchi, East Siberian and Laptev seas. The DOC record, combined with other physical and chemical measurements, identifies areas where river waters cross the shelves and enter the circulation of the Arctic interior. Fluvial sources were found to account for 12-56% of the total DOC in parts of the upper Makarov and Amundsen basins.

Development and initial calibration of a portable laser-induced fluorescence system used for in situ measurements of trace plastics and dissolved organic compounds in seawater and the Gulf of Mexico

A portable UV laser-induced fluorescence system that uses a high pulsed repetition frequency (8-kHz) microchip laser at 266 nm, 13 switchable optical filters, and a gated photomultiplier tube detector has been developed and tested successfully for the detection of leached plastics (possibly bisphenol-A) and trace dissolved organic compounds in seawater. The instrument is 100 times more sensitive than commercial portable spectrofluorometers and measures a complete fluorescence spectrum in a moderate time period of 1-2 min. The system was tested in the Gulf of Mexico over varying water masses. In addition, fluorescence lifetime, bleaching, and temporal flow characteristics were studied.

Tracking Oil Dispersion in the Gulf of Mexico by Fluorescence Intensity (FI) and the Fluorescence Intensity Ratio (FIR)

Abstract Ultraviolet fluorescence (UVF) spectroscopy has been utilized to generate excitation-emission matrices (EEM) of thirteen reference oils (with viscosities ranging from 4 to 14,470 cP) and MC 252 source oil from the 2010 spill in the Gulf of Mexico. All of the oils were dispersed in seawater shaken in baffled flasks. The reference oils were dispersed at relatively high concentrations (650–836 ppm) by physical mixing or by using the chemical dispersant Corexit 9500 in combination with mixing. The matrices were reduced down to fluorescence intensity ratios (FIRs) obtained from two emission peaks at 340 and 445nm (with excitation fixed at 280nm), and the ratios compared to dispersed oil concentration. When oil concentrations were expressed as dispersion efficiencies, low FIRs (of less than 3 – 4) were associated with high dispersion efficiencies (greater than 40%) while FIRs greater than 3 – 4 were characteristic of oils dispersed with efficiencies of 20% or less. When the same dispersion techniques w...