30 research outputs found
Water Supply Source Evaluation in Unmanaged Aquifer Recharge Zones: The Mezquital Valley (Mexico) Case Study
The Mezquital Valley (MV) hosts the largest unmanaged aquifer recharge scheme in the world. The metropolitan area of Mexico City discharges ~60 m3/s of raw wastewater into the valley, a substantial share of which infiltrates into the regional aquifer. In this work, we aim to develop a comprehensive approach, adapted from oil and gas reservoir modeling frameworks, to assess water supply sources located downgradient from unmanaged aquifer recharge zones. The methodology is demonstrated through its application to the Mezquital Valley region. Geological, geoelectrical, petrophysical and hydraulic information is combined into a 3D subsurface model and used to evaluate downgradient supply sources. Although hydrogeochemical variables are yet to be assessed, outcomes suggest that the newly-found groundwater sources may provide a long-term solution for water supply. Piezometric analyses based on 25-year records suggest that the MV is close to steady-state conditions. Thus, unmanaged recharge seems to have been regulating the groundwater balance for the last decades. The transition from unmanaged to managed recharge is expected to provide benefits to the MV inhabitants. It will also be likely to generate new uncertainties in relation to aquifer dynamics and downgradient systems
Nitrate mass balance in agricultural areas of intensive fertilizer application: the North Maresme aquifer system case study (Spain)
Nitrate pollution is a worldwide problem in groundwater, as it may limit water supply and increase health risk when high concentrations are present. The North Maresme coastal alluvial groundwater-dependent agrosystem, one of the most heavily nitrate polluted aquifers in Spain, is located 70 km northeast from Barcelona. Field monitoring campaigns performed in this aquifer yielded nitrate concentrations up to ten times the permitted limit for drinking water suggested by the World Health Organization (50 mg/l), with a maximum concentration of 567 mg/l and a mean of 137.5 mg/l. Nitrate contamination was quantified by means of a mass balance, taking into account the main hydrogeological and anthropogenic processes that control the behavior of this ion in the aquifer, such as recharge, groundwater extraction, irrigation and fertilizer application to crops. Nitrate balance is an integrative approach for assessing nitrate loading based on linking different sources of nitrates to a groundwater balance. This methodology considers nitrate as a conservative ion because the geological-geochemical medium behaves under oxidant conditions. Results show that the studied aquifer system receives, yields and retains approximately 935, 844 and 91 tons of NO3- / year, respectively. This methodology can be applied to other nitrate-contaminated aquifers with similar conditions to improve management of fertilizers practices in areas of intensive agriculture
Binational reflections on pathways to groundwater security in the Mexico–United States borderlands
Shared groundwater resources between Mexico and the United States are facing unprecedented stressors. We reflect on how to improve water security for groundwater systems in the border region. Our reflection begins with the state of groundwater knowledge, and the challenges groundwater resources face from a physical, societal and institutional perspective. We conclude that the extent of ongoing cooperation frameworks, joint and remaining research efforts, from which alternative strategies can emerge, still need to be developed. The way forward offers a variety of cooperation models as the future offers rather complex, shared and multidisciplinary water challenges to the Mexico–US borderlands
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Discovery of Endangered Mexican Blindcat, Prietella phreatophila, in Texas: Implications for International Groundwater Management and Evolution of the Regional Karst Aquifer Biota
Paper presented July 15, 2017 at the annual Joint Meeting of Ichthyologists and Herpetologists in Austin, Texas, USA (http://conferences.k-state.edu/JMIH-Austin-2017/).
The oral presentation of this content mentioned questions about the taxonomy and phylogenetic position of Prietella lundbergi and the only specimens attributed to P. lundbergi apart from the holotype. Since the presentation, we obtained high resolution CT scans of both the holotype and a specimen (TNHC 25767) from Cueva del Nacimiento del Río Frio, not far north of the type locality. The anatomy revealed in those CT scans suggests that these specimens represent a single species, and that P. lundbergi is only remotely related to Prietella phreatophila, which would be consistent with results of Wilcox, T.P., F.J. Garcı́a de León, Dean A. Hendrickson, and D.M. Hillis. 2004. “Convergence among Cave Catfishes: Long-Branch Attraction and a Bayesian Relative Rates Test.” Molecular Phylogenetics and Evolution 31 (3): 1101–13. doi:10.1016/j.ympev.2003.11.006). Thus, further research is in progress by Hendrickson, Lundberg, Luckenbill and Arce that may result in taxonomic revision removing P. lundbergi from Prietella.Mexican blindcat, Prietella phreatophila, described in 1954 from a cave system near the town of Múzquiz in central Coahuila state, and considered a Mexican endemic, was listed by the U.S. Fish and Wildlife Service as a foreign endangered species (protected "wherever found") in 1970. Explorations in the 1990s discovered many new localities extending nearly to the international border, and in 2016 the species was discovered in Amistad National Recreation Area (ANRA) in Texas, just north of the international border near Del Rio. Not only does the discovery support the aquifer of this fish being an internationally shared resource, but the stygobitic invertebrate biota found with the fish indicates a potentially large extent of the aquifer, and thus possibly the fish, in Texas. Invertebrate faunal connections (historic or current) extend from the Amistad Lake area of the new occurrence west into the Trans-Pecos region and east into the Edwards Aquifer of central Texas. We explore implications of this for both water management and evolutionary history of this and other blind ictalurids, and suggest that population genetic studies of both stygobitic fishes and invertebrates could help hydrogeologists better define often difficult to map aquifer extents and interconnections. While NPS is continuing to support the cave explorations of ANRA that produced the Texas discovery, we propose a broader bi-national sampling effort for both the fish and invertebrates extending well beyond the current known distribution of P. phreatophila. We also pointed out questions about phylogenetic relatedness of P. phreatophila and P. lundbergi further south, as well as the possibility of a monophyletic clade of blindcats, including those of the Edwards Aquifer, Satan and Trogloglanis. If substantiated, that evolutionary history would imply broader historic inter-aquifer connections ranging from the San Antonio area as far south as southernmost Tamaulipas. Finally, we report establishment of a small captive population of Prietella phreatophila at San Antonio Zoo for research and possibly eventual conservation applications.U.S. National Park Service; San Antonio Zoo; University of Texas at Austin College of Natural Sciences and Department of Integrative BiologyIntegrative Biolog
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Discovery of the Mexican Blindcat, Prietella phreatophila, in the U.S., and an update on its rangewide conservation status
presented at the 2017 meeting of the Texas Academy of Science at Mary Hardin Baylor University, Belton, TexasMexican blindcat, Prietella phreatophila, was described in 1954 from a single locality in Northern Coahuila, México. Long listed as endangered by the Mexican federal government, it was listed by the U.S. Fish and Wildlife Service as a foreign endangered species in 1970, and the most recent (1996) update of its assessment for the IUCN Red List considers it endangered as well. Explorations in the late 1990s discovered many new localities extending nearly to the international border, and a captive population established provided insights into the species’ basic biology and behavior. In 2016 the species was discovered in a cave in the Amistad National Recreation Area (ANRA), just north of the Río Grande in Texas. The 1970 listing instantly gave the TX population full protection under the U.S. Endangered Species Act. The species’ subterranean and mostly inaccessible habitat endows it with extremely low detectability and its actual range is likely broader than physical sampling of specimens has revealed. We review all prior and new knowledge of the species and its habitat to provide an updated international reassessment of its overall conservation status and threats, which most notably include aquifer depletion and contamination in both the Mexican and U.S. portions of its known range. A live captive population of two specimens collected in 1997 in Coahuila and one Texas specimen is now at the San Antonio Zoo, we are working with NPS to further explore ANRA caves and hope eventually to return to Coahuila to more fully update the species’ conservation status.Integrative Biolog
Surfactants-based remediation as an effective approach for removal of environmental pollutants—A review
Deterioration of environmental quality and equilibrium by rampant industrial expansion, accelerated urbanization and unchecked population growth has become a high-priority concern. The release of an alarming number of toxic polluting agents such as volatile organic compounds, dyes, heavy metals, pharmaceuticals, pesticides, industrial wastes, and personal care products due to natural or anthropogenic activities pose direct adverse effects on human health and living entities. This issue is inescapably increased because of the lack of efficient technologies for the proper disposal, management, and recycling of waste. It is of paramount importance to track alternative solutions to address these pollution problems for an eco-sustainable environment. Conventional remediation techniques are either inefficient, cumbersome or restricted due to certain techno-economic limitations. Environmental compatibility and high pollutant-removal efficacy make surfactants valuable for removal of organic pollutants and toxic heavy metal ions from different mediums. In this review, we present recent and up-to-date information on micelles/surfactants-assisted abatement of a vast number of toxic agents of emerging concern from water/wastewater including volatile organic compounds, personal care products, pharmaceutically active residues, toxic metals, dye pollutants, pesticides, and petroleum hydrocarbons. Based on the literature survey, it can be concluded that micelles-assisted water and soil treatment technology can have a better future on large-scale decontamination of wastewater. Though bio-surfactants are environmentally friendlier matrices and have successfully been employed for environmental decontamination; their large-scale applicability is challenging owing to high costs. Additional research efforts on the development and employment of novel bio-surfactants might render wastewater treatment technology greener, smarter and economical
Non-Darcian flow experiments of shear-thinning fluids through rough-walled rock fractures
Understanding non-Darcian flow of shear-thinning fluids through rough-walled rock fractures is of vital importance in a number of industrial applications such as hydrogeology or petroleum engineering. Different laws are available to express the deviations from linear Darcy law due to inertial pressure losses. In particular, Darcy’s law is often extended through addition of quadratic and cubic terms weighted by two inertial coefficients depending on the strength of the inertia regime. The relations between the effective shear viscosity of the fluid and the apparent viscosity in porous media when inertial deviations are negligible were extensively studied in the past. However, only recent numerical works have investigated the superposition of both inertial and shear-thinning effects, finding that the same inertial coefficients obtained for non-Darcian Newtonian flow applied in the case of shear-thinning fluids. The objective of this work is to experimentally validate these results, extending their applicability to the case of rough-walled rock fractures. To do so, flow experiments with aqueous polymer solutions have been conducted using replicas of natural fractures, and the effects of polymer concentration, which determine the shear rheology of the injected fluid, have been evaluated. Our findings show that the experimental pressure loss-flow rate data for inertial flow of shear-thinning fluids can be successfully predicted from the empirical parameters obtained during non-Darcian Newtonian flow and Darcian shear-thinning flow in a given porous medium
Revisiting groundwater overdraft based on the experience of the Mancha Occidental Aquifer, Spain
Aquifers provide a reliable freshwater source in arid and semiarid regions, where droughts are common and irrigated crops present significant water requirements, so intensive pumping is generally needed. Over-extraction leads to dropping water tables, which in turn threatens the survival of groundwater-dependent ecosystems and water supplies. This calls for strategies to channel hydrological, environmental, agricultural, political and social change. Based on the experience of the Mancha Occidental aquifer, Spain, this paper explores some of the complexities of managing groundwater, dealing with the long-term changes that intensive groundwater use has generated in the region. The Mancha experience shows how environmental conservation may drive social and economic change at the regional scale for periods spanning several decades. What makes this case study unique, however, is the combination of social and environmental conflicts, most of which stem from the prevalence of illegal water use, and their detrimental effect on Ramsar wetlands. The situation exposed a paradox, namely that subsidies for farmers to cut down on water use were actually detrimental to the welfare of groundwater-dependent ecosystems. The unexpected (and timely) occurrence of extreme rainfall events in recent times, after 40 years of ineffective management measures and sustained environmental degradation, enabled the aquifer and its associated wetlands to recover spectacularly to a near-pristine condition. As groundwater-dependent wetlands are highly sensitive ecosystems, it is concluded that it is up to society to decide how much environmental damage can be tolerated in exchange for the social and economic benefits of groundwater-based development
Free-product plume distribution and recovery modeling prediction in a diesel-contaminated volcanic aquifer
Light non-aqueous phase liquids (LNAPL) represent one of the most serious problems in aquifers contaminated with petroleum hydrocarbons liquids. To design an appropriate remediation strategy it is essential to understand the behavior of the plume. The aim of this paper is threefold: (1) to characterize the fluid distribution of an LNAPL plume detected in a volcanic low-conductivity aquifer (∼0.4 m/day from slug tests interpretation), (2) to simulate the recovery processes of the free-product contamination and (3) to evaluate the primary recovery efficiency of the following alternatives: skimming, dual-phase extraction, Bioslurping and multi-phase extraction wells. The API/Charbeneau analytical model was used to investigate the recovery feasibility based on the geological properties and hydrogeological conditions with a multi-phase (water, air, LNAPL) transport approach in the vadose zone. The modeling performed in this research, in terms of LNAPL distribution in the subsurface, show that oil saturation is 7% in the air–oil interface, with a maximum value of 70% in the capillary fringe. Equilibrium between water and LNAPL phases is reached at a depth of 1.80 m from the air–oil interface. On the other hand, the LNAPL recovery model results suggest a remarkable enhancement of the free-product recovery when simultaneous extra-phase extraction was simulated from wells, in addition to the LNAPL lens. Recovery efficiencies were 27%, 65%, 66% and 67% for skimming, dual-phase extraction, Bioslurping and multi-phase extraction, respectively. During a 3-year simulation, skimmer wells and multi-phase extraction showed the lowest and highest LNAPL recovery rates, with expected values from 207 to 163 and 2305 to 707 l-LNAPL/day, respectively. At a field level we are proposing a well distribution arrangement that alternates pairs of dual-phase well-Bioslurping well. This not only improves the recovery of the free-product plume, but also pumps the dissolve plume and enhances in situ biodegradation in the vadose zone. Thus, aquifer and soil remediation can be achieved at a shorter time. Rough calculations suggest that LNAPL can be recovered at an approximate cost of 10/l
Remediation of a diesel-contaminated soil from a pipeline accidental spill: enhanced biodegradation and soil washing processes using natural gums and surfactants
Purpose This paper addresses the application of bioproducts produced by plants (locust bean, guar, and mesquite seed gums) to enhance remediation processes of different nature: soil washing and biodegradation methodologies. Materials and methods These natural gums were tested at laboratory scale to remove total petroleum hydrocarbons-diesel fraction (TPH-diesel) from oil-contaminated volcanic soils sampled from a polluted site in an agricultural area of western Mexico. TPH-diesel removal by natural gums was compared to common synthetic surfactants. Results and discussion There is a strong evidence of contamination caused by the presence of TPH-diesel at a concentration of 32,100 mg/kg, which is above the legal limit of 1,200 mg/kg for agricultural soils in Mexico. Regarding the surfactant soil washing experiments, ionic surfactants showed removal rates above the control test of about 78.51 % (Maranil LAB), 71.27 % (Texapon 40), 60.13 % (SDS), and 48.19 % (Surfacpol G). In contrast, some nonionic surfactants showed removal rates below soil-washing background rate (40 %). On the other hand, natural gums showed interesting and promising results. Guar gum and locust bean gum showed efficiencies of 54.38 % and 53.46 %, respectively. Biodegradation experiments confirmed the effectiveness of natural gums as biodegradation enhancers in diesel-contaminated soils. Specifically, guar gum showed an excellent performance. An 82 % TPH-diesel removal rate was achieved for a very low gum concentration (2 ppm). In this particular context, reported surfactant concentrations to assist biodegradation are, in general, higher. Conclusions This work demonstrated the applicability of natural gums as soil remediation enhancers in diesel-contaminated systems. Particularly, guar gum might represent a cost-effective alternative for biodegradation enhancement processes