Detecting groundwater contamination of a river in Georgia, USA using baseflow sampling     

James S. Reichard  Chandra M. Brown 《Hydrogeology Journal》2009,17(3):735-747

Algal blooms and fish kills were reported on a river in coastal Georgia (USA) downstream of a poultry-processing plant, prompting officials to conclude the problems resulted from overland flow associated with over-application of wastewater at the plant’s land application system (LAS). An investigation was undertaken to test the hypothesis that contaminated groundwater was also playing a significant role. Weekly samples were collected over a 12-month period along an 18 km reach of the river and key tributaries. Results showed elevated nitrogen concentrations in tributaries draining the plant and a tenfold increase in nitrate in the river between the tributary inputs. Because ammonia concentrations were low in this reach, it was concluded that nitrate was entering via groundwater discharge. Data from detailed river sampling and direct groundwater samples from springs and boreholes were used to isolate the entry point of the contaminant plume. Analysis showed two separate plumes, one associated with the plant’s unlined wastewater lagoon and another with its LAS spray fields. The continuous discharge of contaminated groundwater during summer low-flow conditions was found to have a more profound impact on river-water quality than periodic inputs by overland flow and tributary runoff.  相似文献   

Cartographic Constructs: A Case Study of Nantucket Island Oral Histories     

James J. Biles 《The Professional geographer》2013,65(4):541-555

The widespread adoption of neoliberal reforms during the past quarter century has had profound implications for the livelihoods of those who live and work in cities throughout Latin America. This case study of Mérida, Mexico, builds directly on recent research about the changing nature of work and the role of informality as a livelihood strategy in Latin America and attempts to explain how place-specific patterns of informal work emerge from neoliberal reforms and concomitant urban economic restructuring. Drawing on field research and a large household survey, this article reveals that general patterns of informality coincide with previous findings from Latin America: high levels of informal work; increased heterogeneity of informality; and significant mobility, with a large share of workers “opting out” of the formal sector voluntarily. However, compared with previous research in Mexico, this study shows that informal work is significantly more pervasive, particularly among women; less likely to be voluntary; and pays considerably less. In light of gender considerations and significant discrepancies between local patterns of informality and national trends, this case study casts doubt on recent World Bank encyclicals affirming the resemblance between self-employment in Mexico and microentrepreneurship in more developed countries. Moreover, the article concludes that World Bank literature conveniently overlooks the gendered nature of informal work in Latin America and the profound divergence between the express purposes of neoliberalism and its actual implications. As a result, World Bank research on informality serves to justify the neoliberal model, rather than improve the livelihoods of those who live and work in cities throughout Latin America.  相似文献   

Boundaries Make a Difference: The Effects of Spatial and Temporal Parameters on Conservation Planning*     

Patrick R. Huber  Steven E. Greco  James H. Thorne 《The Professional geographer》2013,65(3):409-425

Conservation planning and resulting ecological target identification require selection of both a planning area boundary and temporal baseline or reference condition. We examined the effects that these selections can have on resulting amount and location of identified conservation targets. A gap analysis for California was conducted using five different sets of ecoregion boundaries to identify and compare existing conservation shortfalls in major land cover type representation in protected areas using a threshold of 30 percent per ecoregion per type as the minimum required for future ecological viability. Another gap analysis was run for a single ecoregion using two temporal baselines (current and pre-1900) for the land cover followed by a comparison of identified conservation needs. We found that the boundaries of different ecoregional schemes affected both the total area needed to meet the per ecoregion land cover conservation goals and the spatial location of underprotected land cover types. Choice of temporal baseline also had a significant effect on the establishment of conservation targets for the highly human-impacted Central Valley ecoregion. To meet the given conservation threshold using a historic rather than contemporary baseline, a substantial amount of restoration is required. The results can help identify areas of both conservation needs consensus and those that vary widely based on the chosen planning boundary, as well as aid in the selection of appropriate restoration targets in degraded ecosystems. Because all landscapes are continuous in nature and planning area boundaries are discrete, similar results are likely to be found in analyses conducted in other regions.  相似文献   

A Review of “Hurricanes of the Gulf of Mexico”     

James B. Elsner 《The Professional geographer》2013,65(4):559-560

Books reviewed:

Bassin, Mark, Imperial Visions: Nationalist Imagination and Geographical Expansion in the Russian Far East, 1840 – 1865

Shortridge, James R., Our Town on the Plains: J. J. Pennell's Photographs of Junction City, Kansas, 1893 – 1922

Jakle, John A. and Sculle, Keith A., Fast Food: Roadside Restaurants in the Automobile Age

Boeschenstein, Walter, Historic American Towns along the Atlantic Coast

McKee, Jesse O., Ethnicity in Contemporary America: A Geographical Appraisal

Luciuk, Lubomyr Y., Searching for Place: Ukrainian Displaced Persons, Ottawa, and the Migration of Memory

Hausladen, Gary, Places for Dead Bodies

Phillips, Richard, Watt, Diane and Shuttleton, David, De-Centering Sexualities: Politics and Representations beyond the Metropolis

Goldin, Liliana R., Identities on the Move, Transnational Processes in North America and the Caribbean Basin

McDonald, David A., On Borders: Perspectives on International Migration in Southern Africa

Fox, Roddy and Rowntree, Kate, The Geography of South Africa in a Changing World

Takeuchi, Keiichi, Modern Japanese Geography: An Intellectual History

Amery, Hussein A., and Wolf, Aaron T., Water in the Middle East: A Geography of Peace

Karl, Thomas R., Nicholls, Neville and Ghazi, Anver, Weather and Climate Extremes: Changes, Variations, and a Perspective from the Insurance Industry

Pittman, Blair, Texas Caves  相似文献   

News From Geographic Centers     

James D. Sidaway 《The Professional geographer》2013,65(1):49-62

This paper stresses the importance of bridging the conceptual gap between tourism research and economic geography. It explains why the tourism production system has been unable to avoid its peripheral position in economic geography. The paper then focuses on the structure and organization of the principal agents comprising the tourism production system and identifies the state's pivotal role as coordinator of these agents. Lastly, it highlights two under-researched issues relating to entreprcneurship and labor pools and makes recommendations for further research.  相似文献   

Black–White and Hispanic–White Segregation in U.S. Counties     

James P. Allen  Eugene Turner 《The Professional geographer》2013,65(4):503-520

Residential segregation in metropolitan areas has been the subject of much research, but this article analyzes patterns of white–black and white–Hispanic segregation in counties across the United States. Our purpose was to understand county variations in this one dimension of inequality. Conceiving of segregation as relative inequality of access to neighborhood resources, we measured segregation in 2000 by the index of dissimilarity (D) calculated by blocks, mapped the index values, and correlated them with census variables. Three filters enabled us to eliminate counties with characteristics that could have corrupted the analyses, leaving us with more than 1,000 counties in each analysis. Both minority groups were less segregated from whites in the West and South and in metropolitan counties. Lower segregation was strongly associated with higher minority socioeconomic status and higher percentages of minorities living in housing built in the 1990s, and Hispanic–white segregation was lower where more Hispanics were U.S.-born or English proficient. The racial threat hypothesis was supported only weakly and inconsistently. Mapping made it possible to identify regional and local patterns of high and low segregation as well as the lower segregation of suburban counties in some large metropolitan areas.  相似文献   

Editorial: Jim Blaut and the trajectories of tropical geography     

Tim Bunnell  Chin Ee Ong  James D. Sidaway 《Singapore journal of tropical geography》2013,34(3):285-291

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Developing parallel procedures for line simplification     

James E. Mower 《International journal of geographical information science》2013,27(6):699-712

Abstract

This paper explores parallel programming issues that are relevant to the efficient implementation of spatial data handling procedures on current parallel computers through sample implementations of the Douglas line simplification procedure. Using source code-equivalent implementations of the Douglas procedure, this paper analyses the performance characteristics of two parallel implementations, compares their performance characteristics to those of a sequential implementation, and identifies critical components of the parallel implementations that enhance or inhibit their overall performance values. The results of this work show that the selection of appropriate interprocessor communication and load balancing strategies are crucial to obtaining large speedup values over comparable sequential implementations.  相似文献   

The instability of barotropic circular vortices     

Peter R. Gent  James C. McWilliams 《地球物理与天体物理流体动力学》2013,107(1-4):209-233

Abstract

The linear, normal mode instability of barotropic circular vortices with zero circulation is examined in the f-plane quasigeostrophic equations. Equivalents of Rayleigh's and Fjortoft's criteria and the semicircle theorem for parallel shear flow are given, and the energy equation shows the instability to be barotropic. A new result is that the fastest growing perturbation is often an internal instability, having a finite vertical scale, but may also be an external instability, having no vertical structure. For parallel shear flow the fastest growing perturbation is always an external instability; this is Squire's theorem. Whether the fastest growing perturbation is internal or external depends upon the profile: for mean flow streamfunction profiles which monotonically decrease with radius, the instability is internal for less steep profiles with a broad velocity extremum and external for steep profiles with a narrow velocity extremum. Finite amplitude, numerical model calculations show that this linear instability analysis is not valid very far into the finite amplitude range, and that a barotropic vortex, whose fastest growing perturbation is internal, is vertically fragmented by the instability.  相似文献   

The catastrophe structure of thermohaline convection in a two-dimensional fluid model and a comparison with low-order box models     

Olivier Thual  James C. Mcwilliams 《地球物理与天体物理流体动力学》2013,107(1-4):67-95

Abstract

We impose a surface forcing on the 2D, Boussinesq, thermohaline equations in a rectangular domain, in the form of equatorially symmetric cosine distributions of salinity flux and temperature. This system may be seen as an idealization of the ocean thermohaline circulation on the global scale over intervals of centuries or millenia. Multiple steady states are found numerically. They reflect the competition between the opposite signs of the temperature and salinity-driven equatorially symmetric circulations. There are also pole-to-pole, equatorially asymmetric circulations. In the control space of the temperature and salinity-flux forcing amplitudes, these equilibria form two cusp catastrophes, and transitions between stable equilibria occur through several distinct bifurcations. These catastrophes can be reproduced in simple box models connecting stirred reservoirs through capillary pipes. This steady-state analysis may provide a framework for a better understanding of climatic transitions between different stable regimes of the ocean-atmosphere system.  相似文献