Topography‐driven flow versus buoyancy‐driven flow in the U.S. midcontinent: implications for the residence time of brines

Topography‐driven flow is normally considered to be the dominant groundwater flow system in uplifted sedimentary basins. In the U.S. midcontinent region east of the Rocky Mountains, the presence of brines derived from dissolution of halite suggests that significant topography‐driven flushing has occurred to remove older brines that presumably formed concurrently with Permian evaporites in the basin. However, the presence of evaporites and brines in the modern basin suggests that buoyancy‐driven flow could limit topography‐driven flushing significantly. Here we used numerical models of variable‐density fluid flow, halite dissolution, solute transport, and heat transport to quantify flow patterns and brine migration. Results indicate the coexistence of large‐scale topography‐ and buoyancy‐driven flow. Buoyancy‐driven flow and low permeability evaporites act to isolate brines, and the residence time of the brines was found to be quite long, at least 50 Myr. The modern distribution of salinity appears to reflect near‐steady‐state conditions. Results suggest that flushing of original evaporatively‐concentrated brines occurred tens of millions of years ago, possibly concurrent with maximum uplift ca. 60 Ma. Simulations also suggest that buoyancy‐driven convection could drive chemical exchange with crystalline basement rocks, which could supply significant Ca²⁺, Sr²⁺, and metals to brines.     

The geographies of crisis: exploring accessibility to health care in Canada

There is increasing concern in Canada that the health care system is in a state of crisis. It is argued that reductions in federal government transfers to the provinces have resulted in a health care system characterized by under‐funding in key areas and policy decisions based more on provincial fiscal concerns than the health needs of their constituents. Provincial governments have responded to reduced levels in federal funding by undertaking aggressive restructuring tactics such as the closure of hospitals and the deinsuring of medical services from provincial health plans. The end result of this restructuring, as argued by the media, consumer groups and indeed some health researchers, is a state of crisis' (i.e., lower levels of accessibility, long waiting lists, overcrowding in hospitals and increasing costs of medication). One crisis theme often mentioned is that fiscal decisions of various kinds are reducing economic and geographic accessibility, one of the five principles of the Canada Health Act (CHA) that defines the very essence of the Canadian health care system. Using data from the 1998‐99 National Population Health Survey (NPHS), this paper explores the extent to which an accessibility crisis exists within the Canadian health care system by examining access to health care services and the barriers encountered in trying to access services in each of the ten provinces. The results show that approximately 6.0 percent of Canadians report access problems, with values ranging from 4.5 percent in Newfoundland to 8.3 percent in Manitoba. Regional variations in barriers to accessing care were also observed. In particular, geographic accessibility appears to be a main barrier to care in Atlantic Canada while economic accessibility emerges as a main barrier to care in Western Canada. We discuss these findings in the context of the current debates on the Canadian health care system ‘crisis’. De plus en plus de Canadiens s'inquiétent que leur systéme de soins de santé soit en état de crise. On défend l'idée selon laquelle la réduction des paiements de transfert aux provinces par le gouvernement fédéral serait responsable de l'état d'un systeme de santé caractérisé par un sous‐financement dans les domaines‐clés et des décisions politiques de santé basées, non pas sur les besoins des membres de la société canadienne, mais sur la fiscalité provinciale. Les gouvernements provinciaux ont réagi à la réduction du financement fédéral par une tactique de restructuration agressive (fermeture d'hôpitaux et retrait de services médicaux des programmes d'assurance de santé provinciaux). Selon les médias, les groupes de consommateurs et même les chercheurs en soins de santé, cette restructuration a eu pour effet un système en état de ‘crise’ (diminution de l'aecès aux services, longues fetes d'attente, hôpitaux surchargés, augmentation des coûts des médicaments etc). Un des thèmes récurrent est celui des décisions flscales de toutes sortes qui entraînent une baisse de l'accessibilité financière et géographique. Cette accessibilité est pourtant un des cinq principes de la Loi canadienne sur la santé définissant l'essence même du système de santé au Canada. Utilisant les données tirèes de l'Enquête nationale sur la santé de la population, 1998‐99 et examinant l'accès aux services de santé et les obstacles rencontrés dans les 10 provinces canadiennes, cet article évalue dans quelle mesure une crise d'accessibilité existe au sein du système de santé canadien. Les résultats démontrent qu'environ 6.0 pour cent des Canadiens ont rencontré des problèmes d'accessibilité, avec des variantes allant de 4.5 pour cent à Terre‐Neuve jusqu'à 8.3 pour cent au Manitoba. On observe aussi des variantes régionales dans les obstacles rencontrés. L'accessibilité géographique en particulier semble un obstacle mqjeur dans les régions de l'Atlantique, alors que l'accessibilite financière semble être un obstacle majeur dans l'Ouest du Canada. Ces résultats sont présentés dans le contexte des débats actuels sur l'existence dune, ‘crise’ dans le système de santé au Canada.     

LANDSCAPE CHANGE IN THE LAKE SIMCOE-COUCHICHING BASIN, 1800–1983

Census data and Trimble's erosive land use (ELU) index are used to document changes in agricultural land use and potential erosion in the Lake Simcoe—Couchiching Basin during the past two centuries. The ELU index is represented by the cover-management factor in the universal soil loss equation and takes values between 0 (no erosion) and 1.0 (accelerated erosion). Basin-wide farmland ELU scores increased prior to 1901 due to intensification of agriculture, fell between 1911 and 1961 as yields and areas under grass increased, and then increased again from 1961 onward due to expansion in corn hectarage. The 0.152 index computed in 1981 is almost as large as the largest index (0.154)computed in 1891 and illustrates the huge environmental changes in the basin since early settlement without the beginnings of a permanent and more viable system of land use. Les changements d'utilisation des sols survenus au cours des deux derniers siècles dans le bassin du Lac Simco-Couchiching de même que I'érodibilité de ces sols, font I'objet d'une évaluation à I'aide des données de re-censements et de I'indice d'érosion particulier aux dif-férentes utilisation du sol (indice de Trimble). Le facteur de gestion de la couverture dans l'équation universelle de la partie de sol figure dans cet indice dont la valeur se range entre 0 (absence d'érosion) et 1.0 (érosion en accélération). Les scores pour les terres agricoles à I'éhelle du bassin ont augmenté avant 1901 quand l'agriculture s'est intensifiée, puis ont chuté entre 1911 et 1961 à mesure que les rendements et les superficies herbacées augmentaient, et enfin ont de nouveau re-monté depuis 1961 à la suite de l'expansion des superficies plantées en maïs. L'indice obtenu pour 1981 (0.1521 est presque aussi élevé que I'indice le plus fort atteinten 1891 (0.154). ll démontre les changements considérables survenus dans I'environnement du bassin depuis le tout début de son peuplement, alors qu'aucun système d'utilisation des sols permanent et plus viable n'a encore pu èmerger.     

GENERATION OF SYNTHETIC EARTHQUAKE ACCELEROGRAMS USING SEISMOLOGICAL MODELLING: A REVIEW

A stochastically based seismological model is described in this paper and used to generate synthetic accelerograms that are considered representative of intraplate earthquake events recorded on rock. The model, whilst well publicised in the seismological literature, is discussed and reviewed in this paper from an engineering perspective. The key factors influencing the frequency properties of the Fourier spectrum of the earthquake ground motion are presented and the differences observed between regions such as between eastern and western USA axe discussed. A procedure to generate representative artificial accelerograms from the Fourier spectrum is described. Average response spectra derived from these synthetic accelerograms are then compared with a selection of response spectra derived from recorded accelerograms to test and substantiate the model. The application of the seismological modelling approach to regions outside North America and the implications of the Displacement Based prinicples on the future development of seismological modelling have been addressed and discussed in the paper.     

EVALUATING HISTOLOGICAL METHODS FOR ASSESSING HAIR FIBRE DEGRADATION

The hair shaft has increasing importance in bioarchaeology, since it is now possible to retrieve detailed biomolecular information on recent life history using individual fibres (e.g., on diet, drug use and DNA). Data on hair condition is an important cornerstone to ensuring that reliable information is obtained. The following study defines morphological features of degradative change in human terminal scalp hair using different microscopy techniques. Evidence of degradative change is translated into a ranked histology for assessing hair sample condition. The approach is applied to samples of cut modern scalp hair subjected to degradation under soil burial/simulated grave conditions.     

THE REFLEXIVE TEST OF HAYDEN WHITE'S METAHISTORY

This paper assesses Hayden White's Metahistory through the test of reflexivity; that is, it asks whether the book's “general theory of the structure of that mode of thought which is called ‘historical”’ applies, as it should, to its own history of nineteenth‐century “historical consciousness.” Most components of the theoretical apparatus—the various concepts invoked in the “theory of the historical work” and in the “theory of tropes”—fail the reflexivity test; further, it emerges that those same components are also seriously flawed on other grounds. The sole and partial exception is the concept of emplotment, which passes the reflexivity test, albeit with qualifications, but more particularly has the virtue of illuminating the traditional history of history against which Metahistory's own story was pitched; and this result provides an ironic and unexpected vindication of Metahistory's underlying vision. Thus the book's fundamental insight—that the form of historical writing is epistemologically consequential—can be retained, even though its two theories should now be set aside.     

Communities in Catchments: Implications for Natural Resource Management

Economic and social considerations in natural resource management include the need for community participation and a greater appreciation of social and economic processes in understanding environmental problems. It is anticipated that new frameworks will guide these inclusions and redirect planning and management activities to achieve environmental sustainability. This paper examines issues of participation and the nature of ‘community’ through an analysis of relevant natural resource management policy documents and a case study of a public drinking water supply catchment in Western Australia. The findings indicate that if NRM strategies are to be successful, then a much wider and more inclusive view of community is needed, one that fully captures the different stakeholder groups beyond farmers, such as town residents, indigenous people, and those involved in other land uses. We need strategies that can accommodate differences within and between communities.