共查询到20条相似文献，搜索用时 31 毫秒
1.
Pyrolysis of two kerogens isolated from the and source rocks in the Niuzhuang sag, Dongying Depression, Bohai Bay Basin, China, was performed in a confined system. The products were extracted with solvent and separated using micro-column chromatography into group-type fractions (saturates, aromatics, resins and asphaltenes) with the kerogen residue in each case undergoing swelling with a variety of solvents. The kinetics for generation and retention of crude oil and its group-type fractions from the kerogens were studied and the kinetic parameters applied to modeling generation and retention of crude oil and its fractions from the and source rocks on the basis of burial and thermal history of the Niuzhuang sag. The results show that the “normal oil” was generated at about 4.26 Ma and 24.85 Ma ago, but expelled at about 3.96 Ma and 17.46 Ma ago, respectively, from and source rocks. The current proportions of the expelled saturates, aromatics and NSOs are about 60%, 15% and 25%, respectively. 相似文献
2.
3.
4.
5.
6.
《Applied Geochemistry》2006,21(6):887-903
The chemical compositions of the surface/ground water of Guiyang, the capital city of Guizhou Province, China are dominated by Ca2+, Mg2+, , which have been derived largely from chemical weathering of carbonate rocks (limestone and dolomite). The production of has multiple origins, mainly from dissolution of sulfate evaporites, oxidation of sulfide minerals and organic S in the strata, and anthropogenic sources. Most ground water is exposed to soil CO2 and, therefore, the H2CO3 which attacks minerals contains much soil C. In addition, the H2SO4 produced as a result of the oxidation of sulfides in S-rich coal seams and/or organic S, is believed to be associated with the chemical weathering of rocks. The major anthropogenic components in the surface and ground water include K+, Na+, Cl−, , with Cl− and being the main contributors to ground water pollution in Guiyang and its adjacent areas. The seasonal variations in concentrations of anthropogenic components demonstrate that the karst ground water system is liable to pollution by human activities. The higher content of in ground water compared to surface water during the summer and winter seasons, indicates that the karstic ground water system is not capable of denitrification and therefore does not easily recover once contaminated with nitrates. 相似文献
7.
8.
9.
10.
Paul T. Behum Liliana Lefticariu Kelly S. Bender Yosief T. Segid Andrew S. Burns Charles W. Pugh 《Applied Geochemistry》2011
This study reports changes in coal-mine drainage constituent concentrations through an anaerobic SO4-reducing bioreactor monitored over a 3-a period. The purpose of the study was to identify and monitor over time the biogeochemical mechanisms that control the attenuation of toxic compounds in the mine drainage. This information is needed to investigate bioreactor performance and longevity. The water treated at the case example site, the Tab-Simco Mine, was highly acidic with an average pH of 2.9, a net acidity of 1674 mg/L CaCO3 equivalent-CCE, and high levels of dissolved , Al, Fe and Mn. The results of this study indicated that the treatment system increased the pH of the acid mine drainage (AMD) to 6.2 and decreased the median acidity to 22.7 mg/L CCE, from 2981 to 1750 mg/L, Fe from 450.6 to 1.76 mg/L, Al from 113 to 0.42 mg/L, and Mn from 36.4 to 23.3 mg/L. Geochemical modeling indicates that the bioreactor discharge is saturated with respect to the minerals alunite, gibbsite, siderite, rhodochrosite, jarosite, and Fe hydroxide precipitates. The observed trends also include seasonal variations in reduction and a general decline in the amount of alkalinity produced. The average δ34S value of the in the untreated AMD was +7.3‰. In the bioreactor, δ34S value of increased from an average of +6.9‰ to +9.2‰, suggesting the presence of bacterial SO4 reduction processes. Preliminary results of a bacterial community analysis show that DNA sequences corresponding to bacteria capable of SO4 reduction were present in the bioreactor outflow sample. However, these sequences were outnumbered by sequences similar to bacteria capable of reoxdizing reduced sulfur species. This study illustrates the dynamic nature of metal removal in SO4-reducing bioreactor-based treatment systems. 相似文献
11.
12.
13.
14.
15.
17.
18.
Previous paleoenvironmental studies reported the δD values of a mixture of coeluting alkenones. Here, we present a semi-preparative normal-phase high-performance liquid chromatography–mass spectrometry (NP-HPLC–MS) method for purifying long chain (C37 and C38) unsaturated methyl and ethyl ketones (alkenones) on the basis of chain length and degree of unsaturation.The method was applied to purify alkenones in suspended particles and surface sediments from a site in Chesapeake Bay, eastern USA. The hydrogen isotopic composition of di- and triunsaturated C37 and C38 alkenones differed significantly on the basis of chain length and the degree of unsaturation, demonstrating the importance of gas chromatography–isotope ratio-mass spectrometry (GC–irMS) analysis of individual alkenones for accurate paleoenvironmental reconstruction. Constant fractionation factors between alkenones with different chain length but the same degree of unsaturation () and those with the same chain length but different degree of unsaturation () in all samples suggest that the values may represent hydrogen isotope fractionation associated with elongation and desaturation during alkenone biosynthesis. 相似文献
19.
The groundwater of Pomona, California, is contaminated with perchlorate (). This water is treated to reduce the concentration to less than 6 μg L−1 for compliance with California Department of Public Health drinking water regulations. A study of the isotopic composition of oxygen and chlorine in has been conducted to determine the source of the contamination. Isotopic compositions were measured for samples extracted from 14 wells, yielding ranges of δ18O values from −10.8‰ to −8.0‰, Δ17O values from +4.6‰ to +7.5‰, and δ37Cl values from −12.8‰ to −8.9‰. Evaluation of mixing proportions using published isotopic data for three end-members (synthetic, Atacama, and indigenous natural ) indicates that contamination is dominantly (85–89%) Atacama derived from past use of imported Chilean nitrate fertilizer in citrus cultivation. This interpretation is consistent with (1) aerial photography archives showing extensive citrus fields surrounding Pomona in the early- to mid-20th century, (2) mass-balance estimates for , and (3) numerical hydrologic models yielding travel-times for from fields to wells that are in the range of 15 to >100 years. The hydrologic models predict that contamination of Pomona groundwater will persist for decades into the future. 相似文献