Hydrocarbon transport

The assessment of health effects due to exposure to the total petroleum hydrocarbons requires much more detailed information than what is provided by a single total petroleum hydrocarbon value. More detailed physical and chemical properties and analytical information on the total petroleum hydrocarbons fraction and its components are required. Indeed, a critical aspect of assessing the toxic effects of the total petroleum hydrocarbons is the measurement of the compounds, and the first task is to appreciate the origin of the various fractions (compounds) of the total petroleum hydrocarbons. Transport fractions are determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons and transport fractions (Chapters 8, 9, and 10). 

As is well known, when hydrocarbons transported in an inert gas such as helium are heated, carbon or pyrolytic graphite will deposit on the walls. In the HTCVD, the ethylene helps make the particles stable and, in doing so, carbon is transported into the chamber together with the silicon. It is a sort of symbiosis in the transport between the silicon and carbon. 

MOT Model for the process of Oil hydrocarbon Transport to foodchains (Payne et al., 1991). 

A. Vost and A. Maclean, Hydrocarbon transport in chylomicrons and high density lipoproteins in rat, Lipids 79 423-435 (1984). 

Pho D. B., Pennanec h M. and Jallon J. M. (1996) Purification of adult Drosophila melanogaster lipophorin and its role in hydrocarbon transport. Arch. Insect Biochem. Physiol. 31, 289-303. 

Theisen, M.O., Miller, G.C., Cripps, C., de Renobales, M. and Blomquist, G. J. (1991). Correlation of carbaryl uptake with hydrocarbon transport to the cuticular surface during development in the cabbage looper, Trichoplusia ni. Pesticide Biochem. Physiol., 40, 111-116. 

To illustrate current concepts of hydrocarbon transportation in insects, we present a scheme (Figure 5.3) showing the hypothetical transport pathways of hydrocarbons and other lipids to various tissues (Bagneres (1996) and Jurenka (2004)). 

To finish this duscussion on lipophorin biosynthesis we will mention studies on the origins of PLs, hydrocarbons, sterols, and carotenoids. It has been reported that in adult M. sexta and Rhodnius prolixm PL can be transferred from fat body to lipophorin (Van Heusden et al., 1991 Correa et al., 1992). This transfer of PL is independent of de novo synthesis of lipophorin however, the mechanism by which it occurs is unknown. Hydrocarbon transport by lipophorin has been studied only in P. ameri-cana. Katase and Chino (1982) have shown, in in vitro incubations, that a fat body rich in oenocytes, one type of cell in the hemolymph, which is the major site of hydrocarbon biosynthesis (Diehl, 1975), can release labeled hydrocarbon to lipophorin. It was also shown, using in vitro incubations, that the labeled hydrocarbon in lipophorin was delivered to the epidermis, the normal site of hydrocarbon deposition in insects. The sterols and carotenoids that are present in lipophorin must arise from the diet, because insects cannot biosynthesize either sterols or carotenoids de novo. Chino and Gilbert (1971) have shown that sterol can be transferred from the midgut to lipophorin, and the same is most likely true for carotenoids. The mechanism by which hydrocarbons, sterols, and carotenoids are transferred from either oenocytes or midgut epithelial cells to lipophorin is unknown. 

A number of methods are used for studying the sorption of basic probe molecules on zeolites to learn more about zeolite acidity. A common disadvantage of all the examinations is that adsorbed basic probe increases the electron density on the solid and, thereby, change the acidic properties of the sites examined. From this aspect it seems advantageous to probe the acid sites with a weak base, e. g., with a hydrocarbon. It was shown that adsorption of alkanes is localized to the strong Brdnsted acid sites of H-zeolites [1, 2]. However, recent results suggest that usually the diffusion in the micropores controls the rate of hydrocarbon transport [3-5]. Obviously, the probe suitable for the batch FR examination of the sites has to be non-reactive and the sorption dynamics must control the rate of mass transport. The present work shows that alkanes can not be used because, due to their weak interaction with the H-zeolites, the diffusion is the slowest step of their transport. In contrast, acetylene was found suitable to probe the zeolitic acid sites. The results are discussed in comparison with those obtained using ammonia as probe. Moreover, it is demonstrated that fundamental information can be obtained about the alkane diffusivity in H-zeolites... 

Some additional geochemical and geohydrological observations are given below in order to answer the question of whether it is likely that hydrocarbon transport in solution can be considered as a primary migration mechanism. 

The ATSDR approach, as reflected in this profile, focuses on an assessment of the health effects of petroleum hydrocarbon transport fractions, as suggested by the TPHCWG (1997a, 1997b, 1997c). 

Samples collected several miles downstream from the municipal-industrial area, however, did not reflect significant petroleum hydrocarbon transport. 

All measurements in the present contribution have been performed on large crystals of silicalite-1 and H-ZSM-5 zeolites. Use of large zeolite crystals simplifies significantly the modeling and experimental procedure because it allows one to avoid pelletizing of the crystals. This has the important advantage that no macropore diffusion has to be included in the hydrocarbon transport models and intracrystalline diffusion is the dominating process. 

Serrano-Ruiz JC, Dumesic JA (2011) Catalytic routes for the conversion of biomass into liquid hydrocarbon transportation fuels. Energ Environ Sci 4(l) 83-99... 

Chlorinated hydrocarbons Transport in refrigerated condition in specially cleansed, gas-tight sealed glass bottles. 

Polycyclic aromatic hydrocarbons Transport specially cleansed glass bottles. 

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