PubMed · 3222018
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M Bangs. 1988. Oil nurses keep in step with change.. https://pubmed.ncbi.nlm.nih.gov/3222018/
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Magnetic resonance imaging (MRI) makes use of the interactions between atomic nuclei and an external, strong, magnetic field to image the distribution of these nuclei through a substance. In this study, proton MRI has been used to indicate the presence of oil in sediment. Using a multiecho spin-echo acquisition sequence, images of relative oil density, and hence concentration, and of the magnetic resonance relaxation rate, T2, were produced. T2, which is greatly influenced by molecular motion, was equated to binding between the oil and the sediment, thus, providing an almost real-time "description" of all aspects of the oil-sediment interaction including motion of the oil. The interactions among three sediments from the Tay Estuary (East Coast of Scotland) and three crude oils (Fulmar, Forties and Venezuelan) are discussed. Observation of changes in images of oil density and changes in T2, using spread sheets, allow both rates of diffusion of the oil into the sediment and changes in the binding of the oil to the sediment to be calculated. Both the Forties and Fulmar oils move more rapidly than the Venezuelan oil in all of the sediments examined, while the strength of binding is sediment dependent. Thus, the ability of MRI to distinguish between the rates of flow of the oils into the sediment and the strengths of interaction between the various sediments and oils is demonstrated.
Case reports describing sources of radioactivity lost downhole in Texas from 1956 to 2001 were obtained from the Texas Department of Health Bureau of Radiation Control and entered into a computerized database. The events of the 45-y period of analysis were characterized, examining aspects such as source type, amount of activity, location of loss, depth, and date of occurrence. Results of the study found that 316 downhole source incidents were reported to the agency during this period of time, representing a total of 426 distinct sources of radioactivity lost downhole within the boundaries of the State of Texas. The sources lost were predominantly AmBe, accounting for 74 TBq of radioactivity at the time of loss, and Cs, accounting for 16.3 TBq of radioactivity. A longitudinal analysis of the data showed the average loss per active oil and gas rig in Texas (known as "rig count") at approximately 24 losses per 1,000 rigs. Specific geographic information was largely missing from many of the records, which prevented the geolocation of wells described to contain lost radioactive sources. As a result, most wells could only be located to the county level, and no comprehensive geographical information system (GIS) map could be accurately created from the data. However, when available, source location information was standardized to permit the characterization of the sources reported as lost. This effort produced the first dedicated compendium of lost downhole sources for the State of Texas and provides an important source of information for regulatory agencies. The ability to provide prompt information about the fate and location of sources of radioactivity is important to regulatory officials, given the recent concerns about radiation source inventory control in the post 9/11 world as it relates to the possible creation of radiological dispersal devices.
Inductively coupled plasma isotope-dilution mass spectrometry (ICP-IDMS) with direct injection of isotope-diluted samples into the plasma, using a direct injection high-efficiency nebulizer (DIHEN), was applied for accurate sulfur determinations in sulfur-free premium gasoline, gas oil, diesel fuel, and heating oil. For direct injection a micro-emulsion consisting of the corresponding organic sample and an aqueous 34S-enriched spike solution with additions of tetrahydronaphthalene and Triton X-100, was prepared. The ICP-MS parameters were optimized with respect to high sulfur ion intensities, low mass-bias values, and high precision of 32S/34S ratio measurements. For validation of the DIHEN-ICP-IDMS method two certified gas oil reference materials (BCR 107 and BCR 672) were analyzed. For comparison a wet-chemical ICP-IDMS method was applied with microwave-assisted digestion using decomposition of samples in a closed quartz vessel inserted into a normal microwave system. The results from both ICP-IDMS methods agree well with the certified values of the reference materials and also with each other for analyses of other samples. However, the standard deviation of DIHEN-ICP-IDMS was about a factor of two higher (5-6% RSD at concentration levels above 100 mircog g(-1)) compared with those of wet-chemical ICP-IDMS, mainly due to inhomogeneities of the micro-emulsion, which causes additional plasma instabilities. Detection limits of 4 and 18 microg g(-1) were obtained for ICP-IDMS in connection with microwave-assisted digestion and DIHEN-ICP-IDMS, respectively, with a sulfur background of the used Milli-Q water as the main limiting factor for both methods.