Laser-induced Fluorescence of Pyrene and Other Polycylic Aromatic Hydrocarbons (PAH) in Seawater PDF Download

Author: Stephen M. Rudnick
Publisher:
ISBN:
Category :
Languages : en
Pages : 919

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Author: Baagi Thema Mmereki
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494026014
Category :
Languages : en
Pages : 328

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We have also measured the kinetics and products of a reaction between gas-phase ozone and anthracene adsorbed at the air-aqueous interface. The reactions at the "uncoated" air-water interface and at an interface consisting of a monolayer of various organic compounds were studied. In all the cases, the reaction follows a Langmuir-Hinshelwood mechanism, in which ozone first adsorbs to the air-aqueous interface, and then reacts with adsorbed anthracene. For typical atmospheric ozone concentrations, the estimated reactive uptake coefficient ranges from 2 x 10-8 to 3 x 10-7 depending on the nature of the air-aqueous interface. Smaller (C4, C6) carboxylic acids at the interface inhibit the reaction (compared to the "clean" water surface); 1-octanol enhances it. Under some circumstances, oxidation by ozone on aqueous surfaces may be more important in the atmosphere than gas phase oxidation by OH radicals. The fate of atmospheric semi-volatile organic compounds (SOCs) such as polycyclic aromatic hydrocarbons (PAHs) depends, in part, on their distribution between the gas phase and particulate phases, and oxidation reactions. In the daytime troposphere, photochemically produced OH radicals dominate these reactions, whereas chlorine atoms may contribute to the oxidation of certain PAHs in coastal areas. In the dark, oxidation by nitrate radicals (NO3) may also be important, whereas ozone can contribute to the oxidation both during the day and at night. We have developed a laser-induced fluorescence (LIF) method to study adsorption and oxidation of PAHs at the air-aqueous interface. This method allows to directly probe the mechanisms and extent of PAH uptake on aqueous surfaces. The kinetics of the adsorption of anthracene and pyrene onto "pure" water and water coated with an organic film were measured. The surface uptake coefficients of both PAHs are estimated to be on the order of 10-5, and increase by a factor of 2--3 for uptake to the 1-octanol coated water surface. However, the surface uptake of pyrene to a hexanoic-acid-coated aqueous surface does not display this enhancement. Resolved fluorescence spectra of pyrene adsorbed onto 1-octanol-coated surfaces indicate that pyrene is in a less polar environment than when adsorbed at the hexanoic-acid-coated surfaces.

Author: Diane LeAnna Peterson
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 9

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A fiber optic-based fluorometer system is described that uses a pulsed laser to induce fluorescence and a time-gated linear photodiode array coupled to a spectrograph for rapid measurement of fluorescence emission spectra and fluorescence decay times. Data is presented from studies conducted in San Diego Bay where the system has been used for real-time in situ measurements of temporal and spatial variability of petroleum hydrocarbons in seawater. Results show that the optical fiber fluorometer system is capable of direct quantification of low level (parts-per-billion diesel fuel marine equivalent) concentrations of petroleum hydrocarbons. Analysis times for measurement of complete fluorescence emission spectra are fast (tens of milli-seconds) and compare with the temporal response characteristics for temperature and conductivity sensors that are used for measuring standard physical hydrographic parameters. Results obtained with the fiber optic fluorometer system during a mapping study in San Diego Bay show good correlation with GC-MS analysis of total polycyclic aromatic hydrocarbons (PAHs) measured on discrete samples collected during the study ... CIVAPP: Environmental programs, CIVAPP: Marine biology, CIVAPP: Analytical chemistry.

Author:
Publisher:
ISBN:
Category : Polycyclic aromatic hydrocarbons
Languages : en
Pages : 500

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Author: Gregory Douglas
Publisher:
ISBN:
Category :
Languages : en
Pages : 28

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Real-time laser induced fluorescence (LIF) in situ measurements of soil samples provide a reliable and cost-effective screening tool for hydrocarbon site assessments. The site characterization and analysis penetrometer system (SCAPS), is a truck-mounted cone penetrometer probe modified with a sapphire window and connected to a laser by fiber optics. The pulsed nitrogen laser 337-nm excitation source induced fluorescence in polynuclear aromatic hydrocarbons (PAHs), which are present in petroleum products. The fluorescence response of these compounds is measured with a fluorometer. The SCAPS can provide continuous hydrocarbon screening measurements to soil depths greater than 100 feet. Discrete soil samples collected from SCAPS boreholes were extracted and analyzed for total petroleum hydrocarbons (TPH), by gas chromatography with flame ionization detection (GC/FID), and 16 parent and over 100 alkyl substituted PAH compounds by gas chromatography with mass spectrometry detection (GC/MS). This method provides a basis for evaluating the relationship between TFH and PAH concentrations in the soil samples and laser induced fluorescence measurements from the soil borings.

Author: R. T. Loda
Publisher:
ISBN:
Category :
Languages : en
Pages : 39

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This publication discusses the feasibility of remotely detecting gas-phase polynuclear aromatic hydrocarbons (PAHs) that might be produced during the combustion of propellant, explosive, and pyrotechnic (PEP) materials. Laboratory scale and remote laser-induced fluorescence measurements are presented.

Author: Rachel Gwen Adams
Publisher:
ISBN:
Category :
Languages : en
Pages : 188

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(Cont.) KPEWs for eleven PAHs and PCBs were found to correlate closely with octanol-water equilibrium partitioning constants (Kows; log KPEW = 1.1 log Kow-0.45, R2 = 0.85). Temperature and salinity dependence of KPEW for the chemical of interest can be predicted with that chemical's excess enthalpy of solution and Setschenow constant, respectively. DpEs for several HOCs were measured in the laboratory so that the time for equilibrium uptake in the field could be predicted. PEDs allowed for quick, in situ, time-averaged measurements of phenanthrene and pyrene at pM concentrations and PCB #52 at fM concentrations in Boston Harbor seawater. Observations of disequilibrium between sorbed HOCs (e.g., PAHs & PCBs) and the surrounding environmental waters indicate that the times for desorption are important for understanding the fate of HOCs. Settling and resuspended particles can play a significant role in the cycling of HOCs. For PAHs, like pyrene, these chemicals' strong affinity for black carbon in the environment makes the rate of desorption less certain. The desorption rate for pyrene from native Hudson River sediment was measured in the laboratory and a diffusion rate constant (effective diffusivity/particle radius2) ranging from 1. OE-7 to 5.6E-7 s-1 was measured. The results were in good agreement with a physically- and chemically-based model for estimating effective diffusivity and the rate of desorption.

Author: Sean J. Hart
Publisher:
ISBN:
Category : Polycyclic aromatic hydrocarbons
Languages : en
Pages : 786

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For HPLC and FIA, the data are analyzed by examining the summed fluorescence plots and qualitatively comparing the EEMs with standard measurements made with the same system. Species are qualitatively identified and quantitated by RAFA using pure component EEMs as standards and the EEMs measured during an analysis as the unknowns. RAFA calculated PAH concentrations in HPLC and FIA were in the near-quantitative regime, typically within a factor of 2 of the known concentration for laboratory-prepared mixtures. Several real world samples were analyzed and the results were generally acceptable: for HPLC all components were identified and all except two were quantitated to within a factor of 2. Analysis of lab mixtures by FIA yielded good agreement with known concentrations. The analysis of complex real world samples with many components provided reasonable qualitative identification of species and estimates of concentration.

Author: Timothy Grundl
Publisher:
ISBN:
Category : Contaminated sediments
Languages : en
Pages : 54

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