Physics and Chemistry of The Earth 

About: Physics and Chemistry of The Earth is an academic journal. The journal publishes majorly in the area(s): Water resources & Water quality. It has an ISSN identifier of 1474-7065. Over the lifetime, 3460 publications have been published receiving 99586 citations. The journal is also known as: Physics and chemistry of the earth.

The effect of thermal stress on source-rock quality as measured by hopane stereochemistry

Abstract: Whether or not a suspected source-rock has experienced sufficient thermal stress to have generated petroleum can be determined by GCMS analysis of the terpanes using the following criteria in both the rock extract and the pyrolyzate: (1) 22S 22R ratio of C31C33 hopanes. (2) Concentration of C29C32 β,β hopanes. (3) Ratio of 17βH 17αH trisnorhopanes. (4) Ratio of moretanes/hopanes. (5) Yield of saturates in the pyrolyzates. The use of these parameters in combination is demonstrated with a sequence of suspected source rocks of different stratigraphic horizons from the same basin, ranging from immature/poor to mature/excellent. Of specific value is the subtle graduation, particularly in the pyrolyzates, of these parameters throughout the samples of different degrees of maturity. Cross-supplementing between parameters is demonstrated.

Comparison of two different approaches of sensitivity analysis

Abstract: Due to spatial variability, budget constraints or access difficulties model input parameters always are uncertain to some extent. Therefore the knowledge of sensitive input parameters is beneficial for model development and application. It can lead to a better understanding and to better estimated values and thus reduced uncertainty. In the present paper two simple approaches of sensitivity analysis are compared by the use of the physically based, continuous time hydrological model SWAT. In both approaches, one parameter is varied at a time while holding the others fixed, but the way of defining the range of variation is different. Similar results are obtained suggesting that parameter sensitivity may be determined without the results being influenced by the chosen method. Most sensitive parameters for hydrology and water quality are the physical soil properties such as bulk density, available water capacity or hydraulic conductivity. Plant specific parameters like maximum stomatal conductance or maximum leaf area index as well as slope length, slope steepness, and curve number also show a high sensitivity. Both approaches can be considered as equivalent, as they provide the same overall ranking into more and less sensitive parameters. An identification of the sensitive parameters is possible independently from the chosen variation range.

Selected room temperature magnetic parameters as a function of mineralogy, concentration and grain size

Abstract: A data set of room temperature magnetic parameters for several iron oxides and sulphides was compiled from the available literature. The aim was to propose the most effective methods for assessing mineralogy, concentration and domain state within environmental magnetic studies. Establishing the magnetic mineralogy is essential for a correct interpretation of concentration and grain-size indicative parameters. Hematite and in particular goethite are recognised by their high (remanent) coercivities. The ratio of saturation remanent magnetisation to susceptibility is suited for assessing mineralogy; for low coercivity minerals, high values of the ratio are indicative of pyrrhotite. Greigite and maghemite both have intermediate ratios, while very low values suggest the presence of (titano)magnetite. From the concentration-dependent parameters mass specific susceptibility, saturation remanent magnetisation and susceptibility of anhysteretic remanent magnetisation, susceptibility displayed the least grain-size dependence. Therefore, it is perhaps the best indicator of concentration, under the proviso of uniform mineralogy and when paramagnetic and diamagnetic contributions are taken into consideration. All minerals showed a decrease in coercivity and remanence ratios with increasing grain size for sizes larger than one micrometer. In contrast, the coercivity of goethite showed an increase with grain size. Assessment of domain state was complicated by very small and large grains displaying similar magnetic properties.