Modeling the influence of river discharge on salt intrusion and residual circulation in Danshuei River estuary,Taiwan

A 3-D, time-dependent, baroclinic, hydrodynamic and salinity model was implemented and applied to the Danshuei River estuarine system and the adjacent coastal sea in Taiwan. The model forcing functions consist of tidal elevations along the open boundaries and freshwater inflows from the main stream and major tributaries in the Danshuei River estuarine system. The bottom friction coefficient was adjusted to achieve model calibration and verification in model simulations of barotropic and baroclinic flows. The turbulent diffusivities were ascertained through comparison of simulated salinity time series with observations. The model simulation results are in qualitative agreement with the available field data.     

A PETROGRAPHIC AND MINERAL CHEMISTRY STUDY OF THE WESTON,CONNECTICUT, CHONDRITE

The Weston meteorite is a breccia containing mostly light-colored equilibrated chondritic xenoliths and less abundant highly un-equilibrated chondritic inclusions fixed in a dark grey host of chondrules, mineral and rock fragments. Many of the inclusions show evidence of shock. Unlike most xenolithic chondrites, the Weston host contains a large fraction of considerably more equilibrated silicates than is found in the unequilibrated inclusions, suggesting either that most host silicates retain the mineral chemistry of an equilibrated source indigenous to Weston, or represent a unique fraction which equilibrated separately, prior to final agglomeration. The host silicates are similar in composition to minerals in the common xenoliths, supporting the former possibility that host chondrules and mineral fragments are derived from the xenolithic material, probably by impact fragmentation and melting. Also mixed with Weston is a small but distinct carbonaceous component including the minerals fassaite, Fespinel, forsterite, magnetite and Ca-Al-rich inclusion which are normally associated with carbonaceous chondrites.     

Strain and vorticity analysis using small-scale faults and associated drag folds

Small-scale faults with associated drag folds in brittle-ductile rocks can retain detailed information on the kinematics and amount of deformation the host rock experienced. Measured fault orientation (α), drag angle (β) and the ratio of the thickness of deflected layers at the fault (L) and further away (T) can be compared with α, β and L/T values that are calculated with a simple analytical model. Using graphs or a numerical best-fit routine, one can then determine the kinematic vorticity number and initial fault orientation that best fits the data. The proposed method was successfully tested on both analogue experiments and numerical simulations with BASIL. Using this method, a kinematic vorticity number of one (dextral simple shear) and a minimum finite strain of 2.5–3.8 was obtained for a population of antithetic faults with associated drag folds in a case study area at Mas Rabassers de Dalt on Cap de Creus in the Variscan of the easternmost Pyrenees, Spain.     

Seasonal and interannual variability of carbon dioxide and water balances of a grassland

There is great international concern over the increase of atmospheric carbon dioxide and its effect on vegetation and climate, and vice versa. Many studies on this issue are based on climate model calculations or indirect satellite observations. In contrast we present a 12-year study (1994–2005) on the net ecosystem exchange of carbon dioxide (NEE) and precipitation surplus (i.e., precipitation–evaporation) of a grassland area in the centre of the Netherlands. On basis of direct flux observations and a process-based model we study and quantify the carbon uptake via assimilation and carbon release via soil and plant respiration. It appears that nearly year-round the assimilation term dominates, which indicates an accumulation of carbon dioxide. The mean net carbon uptake for the 12-year period is about 3 tonnes C per hectare, but with a strong seasonal and interannual variability depending on the weather and water budget. This variability may severely hamper the accurate quantification of carbon storage by vegetation in our present climates and its projection for future climates.     

An Analysis of U.S. and World Oil Production Patterns Using Hubbert-Style Curves

A quantitative analytical method, using a spreadsheet, has been developed that allows the determination of values of the three parameters that characterize the Hubbert-style Gaussian error curve that best fits the conventional oil production data both for the U.S. and the world. The three parameters are the total area under the Gaussian, which represents the estimated ultimate (oil) recovery (EUR), the date of the maximum of the curve, and the half-width of the curve. The best fit is determined by adjusting the values of the three parameters to minimize the root mean square deviation (RMSD) between the data and the Gaussian. The sensitivity of the fit to changes in values of the parameters is indicated by an exploration of the rate at which the RMSD increases as values of the three parameters are varied from the values that give the best fit. The results of the analysis are as follows: (1) the size of the U.S. EUR of oil is suggested to be 0.222 × 10¹² barrels (0.222 trillion bbl) of which approximately three-fourths appears to have been produced through 1995; (2) if the world EUR is 2.0 × 10¹² bbl (2.0 trillion bbl), a little less than half of this oil has been produced through 1995, and the maximum of world oil production is indicated to be in 2004; (3) each increase of one billion barrels in the size of the world EUR beyond the value of 2.0 × 10¹² bbl can be expected to result in a delay of approximately 5.5 days in the date of maximum production; (4) alternate production scenarios are presented for world EURs of 3.0 and 4.0 × 10¹² bbl.     

Hydrogeological and multi-isotopic approach to define nitrate pollution and denitrification processes in a coastal aquifer (Sardinia,Italy)

Agricultural coastal areas are frequently affected by the superimposition of various processes, with a combination of anthropogenic and natural sources, which degrade groundwater quality. In the coastal multi-aquifer system of Arborea (Italy)—a reclaimed morass area identified as a nitrate vulnerable zone, according to Nitrate Directive 91/676/EEC—intensive agricultural and livestock activities contribute to substantial nitrate contamination. For this reason, the area can be considered a bench test for tuning an appropriate methodology aiming to trace the nitrate contamination in different conditions. An approach combining environmental isotopes, water quality and hydrogeological indicators was therefore used to understand the origins and attenuation mechanisms of nitrate pollution and to define the relationship between contaminant and groundwater flow dynamics through the multi-aquifer characterized by sandy (SHU), alluvial (AHU), and volcanic hydrogeological (VHU) units. Various groundwater chemical pathways were consistent with both different nitrogen sources and groundwater dynamics. Isotope composition suggests a mixed source for nitrate (organic and synthetic fertilizer), especially for the AHU and SHU groundwater. Moreover, marked heterotrophic denitrification and sulfate reduction processes were detected; although, for the contamination related to synthetic fertilizer, the attenuation was inefficient at removing NO₃^? to less than the human consumption threshold of 50 mg/L. Various factors contributed to control the distribution of the redox processes, such as the availability of carbon sources (organic fertilizer and the presence of lagoon-deposited aquitards), well depth, and groundwater flow paths. The characterization of these processes supports water-resource management plans, future actions, and regulations, particularly in nitrate vulnerable zones.     

An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials

Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site...     

A plausible link between the asteroid 21 Lutetia and CH carbonaceous chondrites

A crucial topic in planetology research is establishing links between primitive meteorites and their parent asteroids. In this study, we investigate the feasibility of a connection between asteroids similar to 21 Lutetia, encountered by the Rosetta mission in July 2010, and the CH3 carbonaceous chondrite Pecora Escarpment 91467 (PCA 91467). Several spectra of this meteorite were acquired in the ultraviolet to near‐infrared (0.3–2.2 μm) and in the midinfrared to thermal infrared (2.5–30.0 μm or 4000 to ~333 cm⁻¹), and they are compared here to spectra from the asteroid 21 Lutetia. There are several similarities in absorption bands and overall spectral behavior between this CH3 meteorite and 21 Lutetia. Considering also that the bulk density of Lutetia is similar to that of CH chondrites, we suggest that this asteroid could be similar, or related to, the parent body of these meteorites, if not the parent body itself. However, the apparent surface diversity of Lutetia pointed out in previous studies indicates that it could simultaneously be related to other types of chondrites. Future discovery of additional unweathered CH chondrites could provide deeper insight in the possible connection between this family of metal‐rich carbonaceous chondrites and 21 Lutetia or other featureless, possibly hydrated high‐albedo asteroids.