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Wolfe, P. (1959). The Simplex Method For Quadratic Programming. Econometrica, 27, 170.
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Vogel, J. C., Talma, A. S., & Heaton, T. H. E. (1981). Gaseous nitrogen as evidence for denitrification in groundwater. Journal of Hydrology, 50, 191–200.
Abstract: By investigating the nitrate, oxygen, nitrogen and argon concentrations and 15N14N ratios in artesian groundwater with radiocarbon ages ranging up to 27,000 yr. a process of very slow denitrification in a confined aquifer is demonstrated. The calculated nitrogenisotope fractionation factor associated with this reaction is comparable to that reported for bacterial cultures in vitro and in vivo.
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Heaton, T. H. E., Talma, A. S., & Vogel, J. C. (1983). Origin and history of nitrate in confined groundwater in the western Kalahari. Journal of Hydrology, 62(1), 243–262.
Abstract: Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr.
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Heaton, T. H. E., Talma, A. S., & Vogel, J. C. (1983). Origin and history of nitrate in confined groundwater in the western Kalahari. Journal of Hydrology, 62(1), 243–262.
Abstract: Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr.
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Heaton, T. H. E. (1984). Sources of the nitrate in phreatic groundwater in the western Kalahari. Journal of Hydrology, 67(1), 249–259.
Abstract: Elevated levels of nitrate occur in phreatic groundwater in the western Kalahari, Namibia. Nitrate in water containing 0.4–3.1 meq NO−3l−1, of widespread occurrence, has δ15N values in the range +4.9 to +8.0‰, suggesting natural derivation from the soil. The sporadic occurrence of very high levels of nitrate (> 4 meq NO−3l−1), which has δ15N between +9.3 to +18.7‰, reflects pollution derived from animal waste. The importance of considering the possible isotopic effects of denitrification, and the significance of leaching in the nitrogen budget of the Kalahari soil, are also discussed.
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Rubin, R. (1988). Water conservation methods in Israel’s Negev desert in late antiquity. Journal of Historical Geography, 14(3), 229–244.
Abstract: Settlement in Israel’s Negev desert historically has been dependent on water conservation techniques. Fieldwork carried out on settlement sites constructed during the Byzantine period, when agriculture and trade flourished, revealed a variety of water installations some of which are in use today. Perennial springs in the Negev are generally small and difficult of access. Cisterns were the most common conservation devices and came in both large, enclosed and single, open forms. Cisterns were common particularly in the towns, where they were usually built as part of house foundations. Dams were discovered at several sites but proved to be inefficient and easily abandoned because of evaporation and siltation problems. Public reservoirs were part of the structure of the largest towns and were open and among the larges structures uncovered at settlement sites. Wells were distributed widely throughout the desert and were part of the only conservation system that did not depend directly on surface rainfall. A qanat system was located in the eastern Negev dating from the late settlement period before the area was abandoned at the turn of the eighth century. These various water systems raise questions about their builders and their origins, and suggests that builders originating in more humid Mediterranean environments tended to produce less adaptable installations than builders derived from the south or the east.
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Uhrie, J. L., Drever, J. I., Colberg, P. J. S., & Nesbitt, C. C. (1996). In situ immobilization of heavy metals associated with uranium leach mines by bacterial sulfate reduction. Hydrometallurgy, 43(1), 231–239.
Abstract: Laboratory experiments with mixed populations of sulfate-reducing bactreria were shown to mediate the removal of milligrams/liter concentrations of uranium, selenium, arsenic and vanadium from aqueous solution via reduction, precipitation and adsorption. Results of laboratory experiments with active sulfidogenic biomass suggest that injection of sulfate and a source of carbon could enhance anaerobic microbial activity in and around uranium leach mines leading to in situ immobilization contaminating metals.
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Lightfoot, D. R. (1996). Moroccan khettara: Traditional irrigation and progressive desiccation. Geoforum, 27(2), 261–273.
Abstract: A 300 km network of khettara (qanat) subsurface irrigation channels was excavated in the Tafilalt basin beginning in the late 14th century. More than 75 of these chains provided perennial water following the breakup of the ancient city of Sijilmassa. Khettara continued to function for much of the northern oasis until the early 1970s, when new technologies and government policies forced changes. Data on origins, maintenance, and current use were collected from archival sources, aerial photographs, Landsat imagery, and from interviews. Insufficient water resources and unsustainable practices have dramatically lowered the water table, drying up khettara. This has resulted in a loss of local control over water resources, abandonment of a sustainable irrigation system, and progressive desiccation.
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Wilson, G. B., & McNeill, G. W. (1997). Noble gas recharge temperatures and the excess air component. Applied Geochemistry, 12(6), 747–762.
Abstract: The calculation of a groundwater recharge temperature based on the dissolved concentrations of Ne, Ar, Kr and Xe requires a correction for noble gas supersaturation due to excess air entrainment. This entrainment is commonly attributed to the recharge process or to air contamination at the wellhead during sample collection. With the exception of some local studies, most work has concentrated on interpretation of the recharge temperature or quantification of the radiogenic content for palaeoclimatic and dating purposes. The magnitude and source of the excess air is not directly relevant to these studies and so is often ignored. In this work, excess air Ne and other data have been calculated from new and published noble gas data sets for several groundwater systems. For younger groundwaters which have been recharged under one broad climatic regime, the amount of air entrainment increases according to lithology in the order granites, sandstones and limestones respectively. A negative correlation between precipitation and excess air entrainment is identified in at least one aquifer, and some of the mechanisms which may influence the entrainment process are discussed.
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Ubierna, J. A. J. (1998). Tunnel heritage in Spain: Roots of the underground. Tunnelling and Underground Space Technology, 13(2), 131–141.
Abstract: Spain has deep roots in the underground. The territory of myth and legend, of cave and tunnel, has existed in Spain since that ancient time overwhelmed with shreds of fog, where all was myth around heros like Túbal Hércules, Gárgoris and Abidis. The underground evokes strong links with life and death, light and darkness, and has served as a source of inspiration for art through the centuries. The history of tunnels in Spain reflects the mosaic of cultures that have inhabited Iberia from prehistoric times till today. This contribution on the subterranean History of Spain traces the country’s heritage in the form of natural caves, troglodyte dwellings, mining, crypts, galleries in fortresses and castles, aqueducts, qanats, cellars, and other landmarks.
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