Factors Influencing the Stream‐Aquifer Flow Exchange Coefficient

Knowledge of river gain from or loss to a hydraulically connected water table aquifer is crucial in issues of water rights and also when attempting to optimize conjunctive use of surface and ground waters. Typically in groundwater models this exchange flow is related to a difference in head between the river and some point in the aquifer, through a “coefficient.” This coefficient has been defined differently as well as the location for the head in the aquifer. This paper proposes a new coefficient, analytically derived, and a specific location for the point where the aquifer head is used in the difference. The dimensionless part of the coefficient is referred to as the SAFE (stream‐aquifer flow exchange) dimensionless conductance. The paper investigates the factors that influence the value of this new conductance. Among these factors are (1) the wetted perimeter of the cross‐section, (2) the degree of penetration of the cross‐section, and (3) the shape of the cross‐section. The study shows that these factors just listed are indeed ordered in their respective level of importance. In addition the study verifies that the analytical correct value of the coefficient is matched by finite difference simulation only if the grid system is sufficiently fine. Thus the use of the analytical value of the coefficient is an accurate and efficient alternative to ad hoc estimates for the coefficient typically used in finite difference and finite element methods.     

Calibrating multi-frequency acoustic backscatter systems for studying near-bed suspended sediment transport processes

The utilisation of sound backscattered from sediments in suspension, to measure profiles of near-bed particle size and concentration, has been gaining increasing acceptance and usage by sedimentologists and coastal engineers over the past two decades. To obtain the sediment parameters from the backscattered signal requires an inversion to be conducted on the signal and this necessitates a system calibration. The calibration can be carried out by detailed acoustic and electronic measurements, or alternatively by measuring the backscattering from suspensions with known scattering characteristics. Here, we explore the latter approach and describe in some detail the calibration of a triple frequency acoustic backscatter system. The aim is to provide coastal scientists involved in using acoustics as a tool for sediment transport research, with a clear exposition of the calibration process. Suspensions of glass spheres of varying particle size were used as the calibration scatterers. To interpret the signal backscatter from the suspension of glass spheres a simple model for sphere scattering is presented. The results show that consistent calibration results can be obtained in a relatively simple and robust manner.     

Probing the magma plumbing of Erebus volcano,Antarctica, by open-path FTIR spectroscopy of gas emissions

Gas emissions from Erebus volcano, Antarctica, were measured by open-path Fourier transform infrared spectroscopy to understand degassing of its magmatic system. Two degassing phonolite lava lakes were present in the summit crater during observation in December 2004. We report analyses of H₂O, CO₂, CO, SO₂, HF, HCl and OCS, (in order of molar abundance) in the plumes. Variations in the proportions of these species strongly reflect the dynamics of degassing, and sourcing of gas from different depths in the magmatic network. The highest observed ratios of CO₂ and H₂O are consistent with gas extracted from the melt at a depth of up to ∼ 2 km below the lava lakes. Magma degassing above this depth contributes to a higher H₂O/CO₂ proportion in the airborne plume. The ratio therefore reflects the balance of deeper vs. shallower contributions of volatiles and, possibly, a combination of closed- and open-system degassing. We observe a strong contrast in HF content in emissions from the two lava lakes, which we attribute to differing levels of magma ascent and/or cooling and crystallization of the magma supply. Fluxes of all gas species were determined using independent SO₂ flux determinations and measured gas ratios. In the case of CO₂ and water, ∼ 1 and ∼ 0.4 m³ s^− 1, respectively, of parental basanite magma are required to sustain the calculated output. The discrepancy between the two figures is readily explained by sequestration of part of the magma supply at depth such that it only partially degasses its complement of water.     

印尼Ertsberg地区斑岩型、矽卡岩型、交代型矿床中的贵金属矿物学

印度尼西亚伊里安查亚中西部的 Ertsberg地区位于新几内亚岛中央山脉中,距阿拉弗拉海120km.本区的矿床为新几内亚地区主要的Au±Cu矿床,包括多组矿体,与这些矿体相伴的是侵入于中-新生代沉积序列的年龄为4~2.5 Ma的过渡成分侵入体     

An Augmented Norm Activation Model: The Case of Residential Outdoor Water Use

Understanding the factors that influence voluntary conservation is critical for developing effective residential water conservation policy. Previous work drawing on Schwartz’s Norm Activation Model (NAM) has been useful to understand some of these factors. However, one’s relationship with the broader community impacted by consumptive decisions has often been overlooked. Similarly, scholars have emphasized the importance of contextual factors not captured in the NAM. In this study we hypothesize and test an augmented NAM that incorporates community attachment, along with contextual variables (sociodemographic and household infrastructure), to understand the factors that lead to the development of moral obligations to conserve water and their relationship with residential outdoor water use. Results indicate personal norms, defined as a moral obligation to conserve water, are negatively related to outdoor water use, and that community attachment is a predictor of personal norms. Contextual factors are found to have an influence on outdoor water use.     

Prospectivity Modeling for Cambrian–Ordovician Hydraulic Fracturing Sand Resources Around The Llano Uplift,Central Texas

Cambrian–Ordovician strata in Central Texas are a major source of specialty sand for hydraulic fracturing and have potential to play a bigger role in proppant supply to markets in and around Texas. Sandstone in the Hickory Member of the Riley Formation is suitable in compressive strength, as well as grain size and shape to be used as proppant. The Hickory sandstone forms the basal sequence that non-conformably overlies the Precambrian basement and is a complex succession of terrestrial and transgressive marine arkosic to quartz arenitic sands and silts. The quantity and location of sand resources in the Central Texas Frac Sand district is illustrated through geospatial volumetric techniques and estimated at 5 billion tonnes of proppant material. The prospectivity modeling of favorable characteristics of existing resource locations is applied to determine new sites for resource development and locate and quantify the abundance of prospective natural sand resources in the Central Texas Frac Sand district.