Evaporative concentration of arsenic in groundwater: health and environmental implications, La Laguna Region, Mexico

Abstract

High arsenic concentrations in groundwater have been documented in La Laguna Region (LLR) in arid northern Mexico, where arsenic poisoning is both chronic and endemic. A heated debate has continued for decades on its origin. LLR consisted of a series of ancient connected lakes that developed at the end of a topographic depression under closed basin conditions. This study addresses the isotopic, chemical composition of the groundwater and geochemical modeling in the southeasternmost part of the LLR to determine the origin of arsenic. Groundwater samples were obtained from a carbonate and granular aquifers and from a clayey aquitard at terminal Viesca Lake. Results show that groundwater originated as meteoric water that reached the lakes mainly via abundant springs in the carbonate aquifer and perennial flooding of the Nazas-Aguanaval Rivers. Paleo-lake water underwent progressive evaporation as demonstrated by the enrichment of δO, δH and characteristic geochemical patterns in the granular aquifer and aquitard that resulted in highly saline (>90,000 mS/cm), arsenic-rich (up to 5000 μg/L) paleo-groundwater (>30,000 years BP). However, adsorption or co-precipitation on iron oxides, clay-mineral surfaces and organic carbon limited arsenic concentration in the groundwater. Arsenic-rich groundwater and other solutes are advancing progressively from the lacustrine margins toward the main granular aquifer, due to reversal of hydraulic gradients caused by intensive groundwater exploitation and the reduction in freshwater runoff provoked by dam construction on the main rivers. Desorption of arsenic will incorporate additional concentrations of arsenic into the groundwater and continue to have significant negative effects on human health and the environment.

Adsorption of Aqueous As (III) in Presence of Coexisting Ions by a Green Fe-Modified W Zeolite

“…The "La Laguna" region in North-Central Mexico, in the states of Durango and Coahuila, presents problems related to the high arsenic content in underground water [11,12]. In different regions of Mexico [13,14] sources of drinking water exceed 0.05 mg L −1 of total As present, higher than the The W zeolite synthesized by a green procedure from an industrial by-product with no commercial value and exchanged with Fe (II) ions resulted to be an active specie potentially useful in the formulation of reusable adsorbents able to trap the As (III) contained in underground water.…”

High-Arsenic Groundwater in Paleochannels of the Lower Yellow River, China: Distribution and Genesis Mechanisms

“…According to Figure 9, the high-As groundwater was mainly located between the rock weathering domain and evaporation domain, indicating that the hydrochemical compositions were influenced by evaporation except for the water-rock interaction. The effect of evaporation on arsenic accumulation in groundwater has been reported in many low-lying plains, such as the eastern Indus Plain [46], the Okavango Delta of Botswana [47], and Nazas and Aguanaval Rivers plain [48]. In the study area, the burial depth of the shallow groundwater table ranges between 2.0 m and 4.0 m and the hydraulic gradient is <0.3‰, which is conducive to the evaporation of shallow groundwater [28,49].…”

Arsenic in Latin America

“…Comarca Lagunera has been one of the most studied areas in Mexico, with groundwater As concentrations of up to 750 mg/L [10,23]. Although various sources have been proposed [24], it was concluded recently that the most probable one is related to extinct hydrothermal activity and sedimentary processes [23]. In addition, intensive groundwater exploitation and dam construction produced the advance of As rich water to the main granular aquifer [24].…”

“…Although various sources have been proposed [24], it was concluded recently that the most probable one is related to extinct hydrothermal activity and sedimentary processes [23]. In addition, intensive groundwater exploitation and dam construction produced the advance of As rich water to the main granular aquifer [24]. Concentrations of As and F above the Mexican drinking water standards have also been measured at Chihuahua state in northern México [25,26].…”