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a b s t r a c tComposition and distribution of tricyclic terpanes, tetracyclic terpanes and hopane in crude oils from Tarim, Turpan, Ordos and Qaidam basins, NW China, were investigated, and some new source dependent parameters were developed and evaluated. C 19 and C 20 tricyclic terpanes are more abundant in terrigenous oils, with C 24 tetracyclic terpane dominant. Relatively higher carbon number tricyclic terpanes, especially C 23 tricyclic terpane, are often the dominant homologues in crude oils from saline lacustrine and marine sources. On the whole, the relative content of C 23 tricyclic terpane of crude oils follow the order of saline lacustrine oils > marine oils > freshwater lacustrine oils > terrigenous oils for C 19e23 tricyclic terpane. Some new parameters based on the tricyclic/hopane and tetracyclic/tricyclic terpane as well as tetracyclic/hopane ratios, could be used to distinguish the oils and source rocks with similar maturity deposited in different sedimentary environments.

a b s t r a c t a r t i c l e i n f oNine units in new-born intertidal zone of the Yellow River estuary, China were examined for concentrations of heavy metals (Pb, Cr, Cu, Zn and Ni) in sediments and plants. Heavy metal levels in surface sediments were in the order of Zn N Pb ≈ Cr N Cu ≈ Ni and generally increased in a seaward direction except for Z6 (Tamarix chinensis-Suaeda salsa zone) and Z7 (S. salsa-T. chinensis zone) units. Significant differences in metal concentrations of the 9 units were observed in the profiles (p b 0.01). Heavy metal levels in the shoots or roots of different plants decreased in the order of Zn N Cu N Pb N Ni N Cr and differed among plants or tissues. The roots at Z2 (Calamagrostis pseudophragmites zone), Z3 (Imperata cylindrical zone) and Z4 (Phramites australis zone) units accumulated greater metals than shoots [TFs (translocation factors) b 1], while the shoots at Z1 (Sparganium minimum-Potentilla supina zone), Z7 and Z8 (S. salsa zone) units accumulated greater metals than roots (TFs N 1), implying that intertidal plants showed different pathways in metal accumulation and internal transportation. Except for Pb, the concentrations of Cr, Cu, Zn and Ni in sediments were lower than the criteria of Class I recommended by the Environmental Quality Standard for Soils of China. Although heavy metal levels in intertidal zone were generally the lowest (Cr, Cu, Zn and Ni) or relatively moderate (Pb) compared with other estuaries or bays in Asia and Europe, high eco-toxic risk of Pb and Ni exposure still could be observed at Z4, Z6 and Z9 (mudflat zone) units. S. salsa was more suitable for the potential biomonitor or phytoremediation of all five heavy metals if intertidal sediments was seriously contaminated with increasing of pollutants loading in the Yellow River estuary.

A suite of 16 crude oil samples from 13 oilfields in the Qaidam Basin were analyzed using techniques including gas chromatography and gas chromatography ‐ mass spectrometry. Biomarker compositions and parameters were used to investigate the palaeoenvironmental and depositional conditions and to correlate the oils with eachother. Oils from the western Qaidam Basin have pristane/phytane (Pr/Ph) ratios of less than 0.7, and contain abundant gammacerane, C27 steranes, 4‐methyl steranes and long‐chain tricyclic terpanes. C29 sterane 20S/(20S+20R) and ββ/(ββ+αα) ratios show that the western Qaidam oils have variable maturities ranging from immature to mature. Oils from the northern Qaidam Basin, by contrast, have Pr/Ph ratios greater than 3, low gammacerane contents, and relatively abundant C29 steranes, bicyclic terpanes and alkylcyclohexanes. C29 sterane 20S/(20S+20R) and ββ/(ββ+αα) ratios indicate that the northern Qaidam oils are mature. δ13C values, which range from ‐25.4‰ to ‐28.3‰ with the exception of one oil from the north (‐3l.6‰), are similar for oils from both the northern and western parts of the Qaidam Basin. The oils'carbon isotope compositions are similar to those of the organic matter in potential source rocks. The western Qaidam oils are inferred to have originated from Tertiary source rocks deposited under anoxic and saline‐hypersaline lacustrine conditions with dominant algal organic matter. The northern Qaidam oils are interpreted to be derived from Jurassic source rocks which were deposited in a freshwater lacustrine environment and which are dominated by terrigenous organic matter.

Pyrolysis of lignite was conducted at high temperatures from 400 to 700℃ and high pressures of 1 and 3 GPa in a closed system in order to investigate pressure and temperature effects on organic matter maturation. The data indicated that the total yield of liquid hydrocarbons decreased with increasing pressure and the maximum of production was obtained at a higher temperature. The alkanes show more mature characteristics with increasing temperature at a given pressure, conversely, high pressure significantly hinders the thermal evolution of geological organic matter. The experimental results also demonstrated that the relative abundance of high molecular weight hydrocarbons may exist under the conditions of the lower lithosphere, which not only breaks through the traditional concept that alkanes mainly present at stage of "oil window", but also enhances the possibility to find the oil in the high temperature and pressure areas.

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