Stephen H. Lieberman

Bioluminescence: spatial statistics in the North Atlantic

Abstract Surface bioluminescence, temperature, and chlorophyll fluorescence data for a North Atlantic transect (Copenhagen, Denmark to Wilmington, NC) were analysed statistically. Bioluminescence standard deviations were highly correlated with mean levels ( r = 0.93, P « 0.01 ); the standard deviation to mean ratio was approximately 0.5. The gamma probability distribution function (pd) with k = 4, which has a standard deviation to mean ratio of 0.5, gave a reasonable fit to the bioluminescence pds. Spectral analysis of bioluminescence data showed ocean structure (fronts, eddies, upwelling, etc.) in nearshore and North Atlantic Current waters at spatial scales >2−3 km. Structure generally was not observed at scales r = 0.67, P r = 0.76, P r = 0.98 for region averages) and with this ratio cubed ( r = 0.78, P

Multispectral fluorometric sensor for real time in-situ detection of marine petroleum spills

This paper describes the development of a fluorescence based in-situ sensor system for real time monitoring and detection of petroleum hydrocarbon contaminants in the marine environment. The system consists of an array of underwater sensors deployed just below the water surface. The sensors can detect floating product (surface sheen) from below the surface as well as detect emulsified or dissolved phase petroleum in the water column. Data from each of the sensors is transmitted to a central base station computer for display, logging, and analysis. The primary intended use of the system is to protect marine facilities from accidental petroleum discharges by providing responding authorities with immediate notification of the occurrence of a leak or spill. The detection of petroleum is based upon the fluorescence of polycyclic aromatic hydrocarbons found within petroleum derived products. The sensors utilize broadband ultraviolet excitation from a pulsed xenon lamp to generate fluorescence in contaminated sea water. The intensity of the resulting fluorescence emission is proportional to both the oil concentration in water, and/or the oil film thickness on the water surface. Multispectral fluorescence emission information is used to distinguish between several possible petroleum classes and eliminate false positive interference from non-petroleum based fluorophores such as chlorophyll. Real time qualitative identification yields an important advantage in terms of rapidly resolving questions of spill origin or in determining an appropriate response. To enable long term underwater deployment, the optical energy of the ultraviolet excitation source also serves to prevent the occurrence of biofouling on the surface of the optical Window. The results of initial testing in San Diego Harbor and at the Ohmsett wave tank facility in New Jersey demonstrate the systems ability to detect petroleum products under a variety of conditions, including the presence of strong harbor chop.

Feasibility studies for the detection of volatile organic compounds in the gas phase using microelectrode sensors

The use of microelectrode sensors to detect volatile organic compounds (VOCs) in air is demonstrated. In general, VOCs that oxidize easily to form protons gave a larger electrochemical response. The use of voltammetry for speciation and the effect of electrode size on the electrochemical response are discussed. We demonstrate that surface enhanced Raman spectroscopy (SERS) can be used to monitor the electrochemical reactions in situ and discuss its applicability in identifying the electroactive species.

pH-temperature-nutrient relationships in the eastern tropical Pacific Ocean

Abstract In November 1979, underway measurements of pH, temperature, salinity and nutrients were made in the eastern equatorial Pacific Ocean. Sixteen shallow (to 250 m) stations were also occupied across the equator on the 95 and 100° meridians. A section along the 100° meridian, from 2°S to 10°N, is discussed. It was found that surface pH correlated directly with surface temperature and this was attributed to biological rather than physico-chemical effects. Surface pH was found to increase with temperature even after nitrate was exhausted and it is suggested that the high surface pH values (to about 8.4) measured in the eastern tropical Pacific Ocean are related to nutrient recycling. Subsurface thermal and chemical measurements obtained from CTD/bottle casts made on station supported the underway surface observations. Similarities in pH-temperature profiles suggest that, in this region, net production may be estimated from steady-state temperature relationships.

Use of a neural network for the analysis of fluorescence spectra from mixtures of polycyclic aromatic hydrocarbons

The use of a software implemented backpropagation neural network is reported for the qualitative and quantitative analysis of the fluorescence emission spectra from multicomponent mixtures of polycyclic aromatic hydrocarbons (PAHs) in solution. Analysis of two types of data is described. First, a backpropagation network is developed to determine the component concentrations in a ternary mixture of PAHs. The input data provided to the network consists of sampled two-dimensional (intensity vs. emission wavelength) fluorescence spectra. A second backpropagation network is investigated for the analysis of three-dimensional time resolved fluorescence emission spectra for a binary PAH mixture. Both of the networks are trained to recognize preselected compounds. Each trained network is then used to evaluate unknown emission spectra and to determine the presence and relative concentration of the compounds it has learned to recognize. Results from analysis of two-dimensional emission spectra show that the trained network was able to successfully identify the individual components and their concentrations in solutions containing mixtures of anthracene, chrysene, and acenapthene. Analysis of three-dimensional time resolved fluorescence emission data showed that individual components could be resolved in mixtures of two spectrally similar components (anthracene and chrysene). Although a network could also be trained to recognize anthracene and chrysene in binary mixtures using their two-dimensional emission spectra, use of three-dimensional time decay spectra reduced the learning time required to train the network by a factor of three.

Relationship between chlorophyll a fluorescence and underwater light transmission in coastal waters off Southern California

Abstract The continuous measurement of underwater light attenuation was investigated as a means of estimating chlorophyll distributions in Southern California coastal waters. In contrast to previous studies at other locales, depth profiles showed that the volume attenuation coefficient ( a ) covaried nonlinearly with chlorophyll a fluorescence. However, when measured over time at a fixed depth a and chlorophyll a fluorescence were observed to be linearly related. Results are consistent with a model that considers contributions to a from nonfluorescing particles whose distributions are influenced by thermal stratification of the water column.

Application of LIBS to in-situ assessment of metal-contaminated soils

In this communication, we discuss the development of a fiber optic probe for use in field screening of waste sites that are contaminated with heavy metals. The prove, which is deployed via cone penetrometer truck, uses the principle of laser induced breakdown spectroscopy to gather qualitative and quantitative about metal contamination in-situ.