Arsenic and Fluoride Variations in Groundwater of an Endorheic Basin Undergoing Land-Use Changes Vı ´ctor M. Reyes-Go ´mez • Marı ´a Teresa Alarco ´n-Herrera • Me ´lida Gutie ´rrez • Daniel Nu ´n ˜ez Lo ´pez Received: 20 May 2014 / Accepted: 3 September 2014 Ó Springer Science+Business Media New York 2014 Abstract The salt content of soil and water in endorheic basins within arid areas greatly restrict agricultural activi- ties. Despite this limitation, these lands are increasingly used to accommodate new settlements and/or agricultural practices. This study focuses on the Laguna El Cuervo closed basin of northern Mexico and its underlying aquifer, which has been found to contain high concentrations of arsenic (As) and fluoride (F). The spatial distribution of As and F, their variations with time, and the impact of drought conditions and land-use changes were investigated using well data collected from a total of 27 wells in 2007, 2010, and 2011 (As data also collected in 2005). Four of these wells were used as monitoring wells. Data also included the As content of 140 surface sediments. Results showed that 54.5 % of the wells surpassed the As limit for drinking water of 0.025 mg L -1 and that 89.0 % surpassed he F limit of 1.5 mg L -1 . Spatial analyses identified the areas in the center of the basin with the highest content of con- taminants. Principal component and correlation analyses showed a co-occurrence of As and F with r = 0.55 for the 2011 data and 0.59 for the combined data. In contrast, the relationship of As and F concentrations to droughts and changes in land use were not as clearly shown, possibly because of the short time this area has been monitored. The high As and F concentrations in the groundwater may be limiting the availability of water within this basin, espe- cially considering the greater groundwater demand fore- seen for the future. Water-conservation practices, such as drip irrigation and artificial groundwater recharge, should be considered to maintain groundwater levels supportive of agricultural practices. During the past two centuries, many arid and semiarid areas worldwide have experienced important changes in land use as humans continue to occupy and diversify the land, thus invariably stressing the availability of water and often causing water tables to decrease (Jackson et al. 2001; WHO 2005; Kafri and Yechieli 2010; Pascual-Ferrer et al. 2014). Within arid areas, a common occurrence are closed (endorheic) basins whose surface water and groundwater are enriched with salts (Gru ¨nberger 2005; Elmore et al. 2008; Kafri and Yechieli 2010; Rodrı ´guez-Rodrı ´guez et al. 2012). Groundwater mined in closed basins around the world, e.g., the United States, Mexico, China, Argentina, and Chile, report high concentrations of arsenic (As) and fluoride (F), often greater then established limits for human health (Luo et al. 1997; Welch et al. 2000; Smedley and Kinniburgh 2002; Smedley et al. 2002; Espo ´sito et al. 2011; Gonza ´lez Da ´vila 2011). However, there remain many closed basins that have not been fully characterized and where the hydrological processes are little known. Numerous closed basins in northern Mexico and the United V. M. Reyes-Go ´mez  D. N. Lo ´pez Instituto de Ecologı ´a, A.C. Red Ambiente y Sustentabilidad– Chihuahua, Miguel de Cervantes 120, Complejo Industrial Chihuahua, 31109 Chihuahua, CHIH., Mexico e-mail: victor.reyes@inecol.mx D. N. Lo ´pez e-mail: daniel.nunez@inecol.mx M. T. Alarco ´n-Herrera Centro de Investigaciones y Materiales Avanzados, Miguel de Cervantes 120, Complejo Industrial Chihuahua, 31109 Chihuahua, CHIH., Mexico e-mail: teresa.alarcon@cimav.edu.mx M. Gutie ´rrez (&) Missouri State University, Springfield, MO 65897, USA e-mail: mgutierrez@missouristate.edu 123 Arch Environ Contam Toxicol DOI 10.1007/s00244-014-0082-y