Compositional Changes of Aromatic Steroid Hydrocarbons in Naturally Weathered Oil Residues in the Egyptian Western Desert

Naturally weathered oil residues from an arid dumpsite in Al-Alamein, Egypt were analyzed for monoaromatic and triaromatic steranes to demonstrate the utility of biomarker compounds in assessing the chemical composition changes during the degradation of the released oil residues in a terrestrial environment. The characterizations of individual aromatic compounds were based on gas chromatography/mass spectrometry (GC/MS) analyses. The results showed that triaromatic sterane distributions were similar in the oil residues of varying weathering degradation extents and correlated with a fresh crude oil sample of the Western Desert-sourced oil. Molecular ratios of triaromatic sterane compounds (ratios of C 28 20R /C 28 20S , C 27 20R /C 28 20R , and C 28 20S /[C 26 20R + C 27 20S ]) were proved to be suitable for source identification. Major changes in chemical compositions during weathering of the oil residues were the depletion of short chain mono- and tri-aromatic steranes in samples that had undergone extensive degradation. The results of triaromatic sterane distribution are in good agreement with weathering classification based on the analyses of saturate and aromatic hydrocarbons and the ratios of n -alkanes, PAHs and saturate biomarker compounds.     

Oil Identification Based on a Goodness-of-Fit Metric Applied to Hydrocarbon Analysis Results

Assessment of environmental damage following accidental oil spills requires reliable oil identification methods. Results from hydrocarbon analyses of environmental samples are often difficult to interpret, because of the changes in oil composition (or weathering) that follows release into the environment, and because of confounding by hydrocarbons from other sources. To a first-order approximation, weathering proceeds according to simple first-order loss-rate (FOLR) kinetics for polycyclic aromatic hydrocarbons (PAH) based on molecular size. This relationship between relative weathering rate and molecular size can be exploited to infer the initial PAH composition of spilled oils, and this information can be combined with results for weathering-invariant analytes to substantially increase the precision and accuracy of hydrocarbon source recognition methods. The approach presented here evaluates a goodness-of-fit metric between the measured hydrocarbon composition of an environmental sample and a suspected source, after correcting for PAR weathering losses based on FOLR kinetics. Variability from analytical and sampling error may thus be accounted for, and source identifications can be expressed as objective probability statements. This approach is illustrated by application to four independent case studies.     

Round Robin Study--Oil Spill Identification

As part of the ongoing work to develop new guidelines for oil spill identification for the European Committee for Standardization (CEN), a Round Robin test was arranged by SINTEF in co-operation with the Norwegian General Standardizing Body (NAS). Twelve laboratories from ten countries participated in the Round Robin study. They include: Denmark, Finland, France, Germany, the Netherlands, Norway, Scotland, Sweden, Wales, and the U.S.A. The analytical methodology used for the Round Robin testing is a result of the ongoing project "Revision of the Nordtest Methodology for Oil Spill Identification". The analytical methodology is described in the AMOP proceedings 2002. Seven oil samples (two artificially weathered "spill" samples and five possible sources) were analyzed following the recommended analytical protocols. The Round Robin study was a "difficult case", because the two spill samples and three of the suspected sources were highly correlated to one another. These samples were from the same oil field in the North Sea, but from different production wells. The present paper summarizes the Round Robin study, and demonstrates the potential of this methodology as a strong technically defensible tool in oil spill identification due to its ability to distinguish qualitatively similar oils from a spill and any available candidate source.     

An experimental study on the burning rate of a continuously released n-heptane spill fire on an open water surface

Spill fires are common during oil product storage and transportation after a loss of containment. Since the burning fuel is moving and the fuel depth is quite shallow, the burning rate in a spill fire is different from that of a pool fire with a static burning zone. Unlike pool fires, which have been studied for decades and have well-established correlations for burning rate, research on spill fires is inadequate. In this paper, continuously released n-heptane spill fire experiments were conducted on open water surfaces with varying fuel discharge rates. The pool diameters were measured, and the spill fire burning rates were estimated based on a dynamic balance between fuel supply and combustion. The burning rates in n-heptane pool fires from the literature were reviewed and compared with the estimated burning rates in spill fires of the same dimension. The spill fire burning rate was found to be close to that in a pool fire during the initial burning phase but lower than that in a bulk burning pool fire and that in a “fuel-level-controlled” pool fire. The distinction between the burning rates of spill fires and pool fires is explained by the heat balance analysis of the fuel layer. A model for the spill fire burning rate was proposed accordingly. The results calculated with the presented model are closer to the measured data than those calculated with pool fire models.     

Modelling spills of water-reactive chemicals

This paper describes part of a programme of work undertaken at the Health and Safety Laboratory (HSL) to investigate the behaviour of selected water-reactive chemicals. Following an accidental release, such substances react exothermically with any water present, generating acidic vapours. The STAWaRS (Source Term Assessment of Water Reactive Substances) software was developed for the Health and Safety Executive (HSE) by ESR Technology to model this complex process. The aims of the study described here were to provide experimental validation of the heats of hydrolysis used within STAWaRS, and to perform sensitivity studies on selected STAWaRS input parameters.The heat of hydrolysis of acetyl chloride was measured and showed good correlation with the value used within STAWaRS. Some of the variables that influence the severity of acetyl chloride spills are examined, with reference to predictions made by the STAWaRS model. The heats of hydrolysis of titanium tetrachloride previously measured at HSL are also discussed, and the effect of adopting these experimentally derived values for modelling spills is shown for a hypothetical land use planning case. This study demonstrates the importance of using experimentally validated values for STAWaRS input parameters.     

美国海岸警备队的溢油鉴别系统

介绍了美国海岸警备队溢油鉴别系统的发展概况，溢油鉴别策略、原理、方法，溢油鉴别数据的产生与解释、分析报告，影响溢油鉴别的因素以及溢油鉴别系统的发展方向。     

构建海洋石油开采溢油危机防控体系之我见

随着海洋石油勘探开发的迅速发展,海上溢油事故屡有发生。针对我国现行管理体制设计上的弊端,提出了在构建海洋石油勘探开发溢油危机防控管理体系的实践中,必须着力健全完善溢油事故宏观防控、溢油问题科技保障、溢油风险预测评估、溢油危机应急处置4个方面工作机制的对策。     

An experimental and modeling study of continuous liquid fuel spill fires on water

The spread of burning fuel spilled from oil product containers during offshore storage and transportation may cause large damage and trigger further accidents. Some analytical models already exist to predict the spread and burning behavior of liquid fuel spill fires, however, few experimental studies have been conducted to verify the model results. In this paper, continuous n-heptane spill fire experiments were conducted in a rectangular trench covered with water. The burning area, fuel spread rate, and thermal flux with different discharge flow rates and ignition delay times were investigated by both experimental and modeling means. The spill fire burning area, with 5 typical phases during burning, has a quasi-steady value which is directly proportional to the discharge rate but irrelevant to the ignition delay times. The steady burning rate, as the ratio of discharge rate over burning area, was estimated. A spread model was modified to simulate the spread of continuous liquid fuel spill fires in a one-dimensional channel, based on the balance between gravity and viscous forces. A cuboid solid flame model was used to compute the thermal flux from spill fires. The burning fuel spread and the heat flux calculated by the models agree with the experimental results.     

WATER TRANSFER AND ECONOMIC DEVELOPMENT

An aspect of water resource development that has currently generated a good deal of interest among economists relates to the ‘economics of water transfer.’ Some recent investigations in this connection have studied the impact of transferring water from conventional uses (mainly agricultural) to newly emerging uses (e.g., pollution abatement, recreational, and industrial). The results of these studies indicate that water transfer contributes to economic growth, both directly and indirectly.     

Modeling of a cryogenic liquid pool boiling by CFD simulation

A boiling model is developed by Computational Fluid Dynamics (CFD) code to calculate the source term of a cryogenic liquid spill. The model includes the effect of the changing ground temperature on the vaporization rate of the cryogenic liquid. Simulations are performed for liquid nitrogen. The model can describe different boiling regimes (film, transition and nucleate). The heat flux calculated for each boiling regimes are compared to the experimental data from literature. The developed numerical model seems to have a good ability to predict the heat flux for the film boiling stage. Model development is still necessary to improve the prediction of the nucleate boiling regime. Overall, the approach shows very promising results to model the complex physical phenomena involved in in the vaporization of cryogenic liquid pool spilled on ground.