Groundwater Flow Processes and Human Impact along the Arid US-Mexican Border, Evidenced by Environmental Tracers: The Case of Tecate, Baja California

With the increasing population, urbanization and industry in the arid area of Tecate, there is a concomitant increase in contaminants being introduced into the Tecate River and its aquifer. This contamination is damaging the usable groundwater supply and making local residents and commercial enterprises increasingly dependent on imported water from the Colorado River basin. In this study we apply a suite of chemical and isotopic tracers in order to evaluate groundwater flow and assess contamination trends. Groundwater recharge occurs through mountain-block and mountain-front recharge at higher elevations of the ranges. Groundwater from the unconfined, alluvial aquifer indicates recent recharge and little evolution. The increase in salinity along the flow path is due to interaction with weathering rock-forming silicate minerals and anthropogenic sources such as urban wastewater, residual solids and agricultural runoff from fertilizers, livestock manure and/or septic tanks and latrines. A spatial analysis shows local differences and the impact of the infiltration of imported waters from the Colorado River basin. The general trend of impaired water quality has scarcely been documented in the last decades, but it is expected to continue. Since the groundwater system is highly vulnerable, it is necessary to protect groundwater sources.Engineering and Science School of Tecnológico de Monterrey viaWater Science and Technology research group

Assessment of major ions and trace elements in groundwater supplied to the Monterrey metropolitan area, Nuevo León, Mexico

The Monterrey metropolitan area (MMA) is the third greatest urban area and the second largest economic city of Mexico. More than four million people living in this megacity use groundwater for drinking, industrial and household purposes. Thus, major ion and trace element content were assessed in order to investigate the main hydrochemical properties of groundwater and determine if groundwater of the area poses a threat to the MMA population. Hierarchical cluster analysis using all the groundwater chemical data showed five groups of water. The first two groups were classified as recharge waters (Ca-HCO3) coming from the foothills of mountain belts. The third group was also of Ca-HCO3 water type flowing through lutites and limestones. Transition zone waters of group four (Ca-HCO3-SO4) flow through the valley of Monterrey, whereas discharge waters of group 5 (Ca-SO4) were found toward the north and northeast of the MMA. Principal component analysis performed in groundwater data indicates four principal components (PCs). PC1 included major ions Si, Co, Se, and Zn, suggesting that these are derived by rock weathering. Other trace elements such as As, Mo, Mn, and U are coupled in PC2 because they show redox-sensitive properties. PC3 indicates that Pb and Cu could be the less mobile elements in groundwater. Although groundwater supplied to MMA showed a high-quality, high mineralized waters of group 5 have NO3 − concentrations higher than the maximum value proposed by international guidelines and SO4 2−, NO3 −, and total dissolved solid concentrations higher than the maximum levels allowed by the Mexican normative. © 2017, The Author(s)

Survey of 218 organic contaminants in groundwater derived from the world's largest untreated wastewater irrigation system: Mezquital Valley, Mexico

The Mezquital Valley system is the world's oldest and largest example with regard to use of untreated wastewater for agricultural irrigation. Because of the artificial high recharge associated with the Mezquital Valley aquifers, groundwater is extracted for human consumption, and there are plans to use this groundwater as a water resource for Mexico City. Thus, this study analyzed 218 organic micro-contaminants in wastewater, springs, and groundwater from Mezquital Valley. Five volatile organic compounds (VOCs) and nine semi-volatile organic compounds (SVOCs) were detected in the wastewater used for irrigation. Only two SVOCs [bis-2-(ethylhexyl) phthalate and dibutyl phthalate] were detected in all the wastewater canals and groundwater sources, whereas no VOCs were detected in groundwater and springs. Of the 118 pharmaceutically active compounds (PhACs) and 7 reproductive hormones measured, 65 PhACs and 3 hormones were detected in the wastewater. Of these, metformin, caffeine, and acetaminophen account for almost sixty percent of the total PhACs in wastewater. Nevertheless, 23 PhACs were detected in groundwater sources, where the majority of these compounds have low detection frequencies. The PhACs sulfamethoxazole, N,N-diethyl-meta-toluamide, carbamazepine, and benzoylecgonine (primary cocaine metabolite) were frequently detected in groundwater, suggesting that although the soils act as a filter adsorbing and degrading the majority of the organic pollutant content in wastewater, these PhACs still reach the aquifer. Therefore, the presence of these PhACs, together with the high levels of the endocrine disruptor bis-2-(ethylhexyl) phthalate, indicate that water sources derived from the recharge of the studied aquifers may pose a risk to consumer health. © 2018 The Author

Humedales de la Orinoquia (Colombia-Venezuela)

La conservación de la inmensa diversidad biológica de la cuenca del Orinoco depende de nuestra voluntad y del conocimiento que tengamos de sus ecosistemas acuáticos, hasta hoy apenas descritos, siendo como son, abundantes y variados a lo largo del gradiente altitudinal. Ambientes temporales y permanentes; de aguas quietas, corrientes o torrentosas; blancas, claras o negras; naturales, creados o muy transformados por el hombre, conforman un mosaico heterogéneo que da vida a las alturas paramunas y a las cimas de los tepuyes, a los piedemontes, los Llanos, la Guayana y finalmente al Delta, en la unión salobre del río Orinoco con el océano Atlántico. Para el Instituto de Investigación de Recursos Biológicos Alexander von Humboldt la Orinoquia representa un área prioritaria y de especial interés en sus metas de investigación. Los talleres binacionales 2009-2011, auspiciaron la colaboración entre ambos países y dieron origen a proyectos como el que hoy presentamos. Un libro que reúne años de trabajo y observación en los humedales de esta cuenca, gracias al aporte de investigadores de Venezuela y Colombia cuyos datos, apuntes y análisis han servido para la identificación y descripción de las grandes regiones del Orinoco, su vegetación acuática y la tipología de sus aguas. Este nuevo volumen de la Serie de Recursos Hidrobiológicos y Pesqueros Continentales, identifica y homologa decenas de ambientes acuáticos o humedales que serán a partir de esta síntesis un valioso punto de referencia, que contribuirá sin duda alguna, al proceso de delimitación de los humedales continentales de Colombia.Bogotá, D. C., ColombiaInstituto de Investigación de Recursos Biológicos Alexander von Humbold