A new mathematical technique for identifying potential sources of groundwater contamination     

W. R. Laton  R. J. Whitley  T. V. HromadkaII 《Hydrogeology Journal》2007,15(2):333-338

The observed hydrogeochemical condition of groundwater at a particular well is usually represented as a mixture of various sources of pollution and background conditions and is given in terms of measurements of multiple dissolved inorganic water contaminants such as total dissolved solids (TDS). Concentrations from a given set of wells can be compared against one another in a variety of ways, but the consideration as to which chemical concentrations are best related to one another is limited. In this analysis, an example is given to show that if there are a total of N concentration values, all N must be considered simultaneously in order to ascertain whether the observed conditions at the well can be explained as a mixture, and this can be done by solving a quadratic programming problem-convex hull.

---

Resumen La condición hidrogeoquímica observada en un pozo particular es generalmente resultante de la mezcla de varias fuentes de contaminación y las condiciones antecedentes y se traduce en términos de medidas de múltiples contaminantes inorgánicos disueltos tal como los sólidos totales disueltos (STD). Las concentraciones de un conjunto de pozos pueden ser comparadas unas contra otras por una variedad de métodos pero la consideración de las concentraciones químicas que mejor se relacionan es limitada. En este análisis se introduce un ejemplo que muestra que si existe un total de N valores de concentración, todos los N deben ser considerados simultáneamente a fin de establecer si las condiciones observadas en el pozo pueden ser explicadas como una mezcla. Esto se realizada por resolución de un problema cuadrático de envolvente convexa.

---

Résumé L’état hydrogéochimique des eaux souterraines observé au droit d’un puits particulier est usuellement représenté comme un mélange de diverses sources de pollutions et de bruits de fond et est donné en terme de mesures de plusieurs contaminants inorganiques dissous, comme les solides totaux dissous par exemple (STD). Les concentrations issues d’un groupe de puits peuvent être comparées entre elles de différentes manières, mais le souhait de corréler au mieux telle concentration chimique avec une autre est limité. Dans cette étude, l’exemple traité montre que s’il existe un nombre total N de valeurs de concentration, ces Nvaleurs doivent être considérées simultanément afin de déterminer si les conditions observées au puits peuvent s’expliquer en terme de mélange ; ceci peut être réalisé en résolvant un problème quadratique programmable-une enveloppe convexe.

  相似文献   

Spatial variability of E. coli in an urban salt-wedge estuary     

Dusan Jovanovic  Rhys Coleman  Ana Deletic  David McCarthy 《Marine pollution bulletin》2017,114(1):114-122

This study investigated the spatial variability of a common faecal indicator organism, Escherichia coli, in an urban salt-wedge estuary in Melbourne, Australia. Data were collected through comprehensive depth profiling in the water column at four sites and included measurements of temperature, salinity, pH, dissolved oxygen, turbidity, and E. coli concentrations. Vertical variability of E. coli was closely related to the salt-wedge dynamics; in the presence of a salt-wedge, there was a significant decrease in E. coli concentrations with depth. Transverse variability was low and was most likely dwarfed by the analytical uncertainties of E. coli measurements. Longitudinal variability was also low, potentially reflecting minimal die-off, settling, and additional inputs entering along the estuary. These results were supported by a simple mixing model that predicted E. coli concentrations based on salinity measurements. Additionally, an assessment of a sentinel monitoring station suggested routine monitoring locations may produce conservative estimates of E. coli concentrations in stratified estuaries.  相似文献   

Cycling amongst Māori: Patterns,influences and opportunities     

Rhys Jones  Bruce Kidd  Kirsty Wild  Alistair Woodward 《New Zealand geographer》2020,76(3):182-193

This paper outlines the results of mixed-methods research on Māori and cycling. Our findings suggest that Māori cycle at similar rates to Pākehā (NZ European); however conditions may differ, possibly indicating higher levels of “necessity cycling” amongst Māori. Māori experience similar barriers to cycling, including a lack of suitable cycling infrastructure, but these occur against a backdrop of stark social, economic and transport-related inequities. Particular barriers for Māori may include inflexible work conditions, concerns about neighbourhood safety, inadequate provision for social cycling, and lack of access to places of importance to Māori. We identify potential solutions, including more whānau-friendly and culturally safe cycling infrastructure, and cycling programmes designed around Māori commitments to whanaungatanga and kaitiakitanga.  相似文献   

Insights into ground response during underground coal gasification through thermo-mechanical modeling     

Wu Gao  Renato Zagor&#x; ak  Hywel Rhys Thomas 《国际地质力学数值与分析法杂志》2022,46(1):3-22

This paper presents a coupled thermo-mechanical model to investigate the ground response during underground coal gasification (UCG). The model incorporated the temporal and spatial development of temperature, the gradual growth of the cavity, and temperature-dependent material properties. Model verification was made against two benchmarks to acquire the confidence for the predictive purpose. The first exercise demonstrated the correctness of the model implemented in COMPASS. The second exercise showed that using the ash-filled cavity to represent null or empty zones is a good option in the numerical modeling and provided highly comparable results to other models. Based on the Hanna UCG trial, different cases were simulated to investigate the effects of the cavity size in the coal seam and the thermal expansion coefficient of the caprock and base rock on key features that take place during the process of UCG. A maximum temperature in the range of 1200–1500 ℃ was induced by the gasification of coal, and a cavity with a maximum length of 13.5 m was formed after 30 days of simulation. Meanwhile, small vertical displacement in the range of -5–12 mm took place near the cavity because of the thermal expansion of the geologic materials and the reduction of the overall weight with the creation of the cavity. In addition, it was found the thermal expansion coefficients can influence the thermo-mechanical response of geologic materials, but the effects were insignificant when its order of magnitude was smaller than 10^-6 K^-1.  相似文献   

Middle Pleistocene environments,landscapes and tephrostratigraphy of the Armenian Highlands: evidence from Bird Farm 1, Hrazdan Valley     

Jenni E. Sherriff  Keith N. Wilkinson  Poppy Harding  Hayley Hawkins  Rhys G. O. Timms  Daniel S. Adler  Emily J. Beverly  Simon P. E. Blockley  Boris Gasparyan  Christina J. Manning  Darren Mark  Samvel Nahapetyan  Katie J. Preece 《第四纪科学杂志》2022,37(1):6-27

The significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto-tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale.  相似文献