排序方式： 共有9条查询结果，搜索用时 62 毫秒
1
1.
A South Australian Tertiary brown coal is fractionated into humic acid and kerogen fractions. These related samples are then subjected to a number of different analytical techniques including infrared and13C-Nuclear Magnetic Resonance spectroscopies and pertrifluoroacetic acid oxidation. Structural conclusions are drawn from an integrated consideration of the data. Brown coal aliphatic structure is concentrated in the kerogen and the solvent soluble polar acid fractions. The humic acids are the most aromatic and contain a high degree of hydrogen bonding. Only very minor amounts of long polymethylene chain structures are observed in the humic acids, in complete contrast to the kerogen fraction. Different organic detrital origins are proposed for the coal fractions. 相似文献
2.
Rock-Eval pyrolysis was performed on lithotype and depth profiles of Tertiary brown coals and a coalification profile of Permian bituminous coals. The humic acid and kerogen fractions from the coals are also investigated by this technique along with the effect of base extraction on the kerogen fraction. Structural variations between brown coal lithotypes are primarily reflected by changes in Oxygen Index Value. This result was supported by the results from the depth profile (same lithotype). A wide range of Hydrogen Indices (independent of depth) but similar Oxygen Indices were observed. The results from the Qualification profile show that the Oxygen Indices varied with rank, whereas Hydrogen Indices show a greater dependence on coal type. A plot of versus Hydrogen Index produced good correlations with the brown (0.77) and bituminous (0.90) samples lying on two separate lines intersecting at high H/C. This result (and higher correlation for bituminous samples) reflects the expected dependence of hydrogen index on oxygen content (present primarily as hydroxyl groups). A high correlation (0.95) between quantitative IR data (K 2920 cm mg?1) and Hydrogen Indices supports previous conclusions regarding the dependence of Hydrogen Indices on the aliphatic structure of the samples. 相似文献
3.
The functional groups of brown coal lithotypes, their humic acids and kerogens were investigated by elemental analysis and quantitative infrared spectroscopy using absorption coefficients.An inverse relationship is reported between the concentrations of kerogen and humic acids for each lithotype and significant variation in the levels of humic acids with lithotype are attributed to changing higher plant input and depositional environments.The structural implications of observed trends in absorption coefficients and their usefulness as a rapid method of functional group analysis has been investigated. Using this infrared technique, kerogen structures as reflected in functional group analyses were found to exhibit a dependance on lithotype, although no significant variation in the functionality of the humic acid structures was observed. 相似文献
4.
A quantitative 13C-NMR technique was applied to humic acids, isolated from total solvent extracts obtained from coals, varying in rank from lignite to medium volatile bituminous. The results from elemental analysis and 13C-NMR structural ratios are interpreted in the form of three distinct structural phases in the maturation of coal humic acids. These phases reflect the rank of the parent coals. A decrease in polar functional group content and corresponding increase in aromaticity is observed with increasing maturation of humic acid chemical structure. Limits are postulated for the oxygen content and level of aromaticity for humic acids derived from higher rank coals. 相似文献
5.
The experimental conditions allowing quantitative interpretation of liquid state 13C-NMR spectra of the humic acids, derived from the five Victorian brown coal lithotypes are described. The structure of the two classes of humic acids investigated for each lithotype vary significantly in their level of aromaticity, the level of polar functional groups and aliphatic chains attached to their polyaromatic skeletons. Variation is also observed in the degree of aromaticity and oxygen-containing functions of humic acids with lithotype. These data are interpreted in the light of paleobotanical evidence, which suggests that the lithotypes represent variations in depositional environment and input to the coal seam. 相似文献
6.
T.V. Verheyen A.G. Pandolfo R.B. Johns G.H. Mackay 《Geochimica et cosmochimica acta》1985,49(7):1603-1614
Several techniques including gas chromatography, petrography, nuclear magnetic resonance and infrared spectroscopy are applied to the investigation of pertrifluoroacetic acid oxidation of a series of Permian Australian bituminous coals in order to probe the effects of maturation on aliphatic structure. The occurrence of insoluble oxidation products is attributed to reagent blocking by carboxylated aromatic species. The combined influence of maturation and semifusinite content is reflected in the concentration and structural composition of functionalised long chain aliphatic oxidation products. 相似文献
7.
Jeroen Staelens An De Schrijver Kris Verheyen Niko E.C. Verhoest 《Journal of Hydrology》2006,330(3-4):651-662
Although the spatial heterogeneity of throughfall water (TF) under forest canopies has been related to vegetation structure in several forest types, few reports have been made of the driving factors of small-scale TF variability in deciduous stands. Therefore, the spatial variability of the amount of TF water under one dominant beech (Fagus sylvatica L.) tree was quantified in high temporal and spatial resolution over a 2-year period to examine the temporal stability of spatial TF variability and to relate spatial TF patterns to canopy cover determined photographically above each TF collector (n = 48). The spatial variability of TF was significantly higher during the leafed periods (coefficient of variation (CV) = 18%) than during the leafless periods (CV = 8%), and a strong negative relationship was observed between the CV of event TF and the TF fraction of rainfall in the open field. Geostatistical analysis showed that the cumulative TF water during the leafed periods was spatially correlated up to a distance of 3–4 m. There was a significant temporal stability of spatial TF patterns in the growing periods and in the dormant periods, but patterns differed largely between the two periods of the year. TF water during the growing periods significantly decreased with increasing canopy cover above the sampling locations (r = −0.54, p = 0.014, n = 20), but was more closely correlated with branch cover (r = −0.77, p < 0.001). However, the spatial pattern of TF during defoliated conditions was not related to the measured variation in branch cover. 相似文献
8.
A series of seven Permian Australian bituminous coals of varying rank, were examined by quantitative infrared spectroscopy, using absorption coefficients K(cmmg?1) and elemental analysis in the form of bond equivalence data. Both analytical techniques were found to be complementary in their average structural predictions. The coals were chemically fractionated into Total Solvent Extractables (T.S.E.), Solvent Extractable Humic Acids (S.E.H.A.) and insoluble Kerogens. Molecular condensation was found to decrease for the T.S.E. fractions, and increase as expected, for the insoluble kerogen fractions, as a function of increasing coal rank. The effect of aqueous base extraction upon the kerogen fraction, observable as an increase in oxygen by bond equivalence, could be related to minor changes in I.R. absorption coefficients and difference spectra. 相似文献
9.
While the hydrological balance of forest ecosystems has often been studied at the annual level, quantitative studies on the factors determining rainfall partitioning of individual rain events are less frequently reported. Therefore, the effect of the seasonal variation in canopy cover on rainfall partitioning was studied for a mature deciduous beech (Fagus sylvatica L.) tree over a 2‐year period. At the annual level, throughfall amounted to 71% of precipitation, stemflow 8%, and interception 21%. Rainfall partitioning at the event level depended strongly on the amount of rainfall and differed significantly (p < 0·001) between the leafed and the leafless period of the year. Therefore, water fluxes of individual events were described using a multiple regression analysis (ra2 > 0·85, n = 205) with foliation, rainfall characteristics and meteorological variables as predictor variables. For a given amount of rainfall, foliation significantly increased interception and decreased throughfall and stemflow amounts. In addition, rainfall duration, maximum rainfall rate, vapour pressure deficit, and wind speed significantly affected rainfall partitioning at the event level. Increasing maximum hourly rainfall rate increased throughfall and decreased stemflow generation, while higher hourly vapour pressure deficit decreased event throughfall and stemflow amounts. Wind speed decreased throughfall in the growing period only. Since foliation and the event rainfall amount largely determined interception loss, the observed net water input under the deciduous canopy was sensitive to the temporal distribution of rainfall. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
1