The origin of arsenic in waters and sediments from Papallacta Lake area in Ecuador

This chapter focuses on characterizing sources of arsenic (As) in the vicinity of Papallacta lake, Ecuador. Some of these sources are geothermal water discharges. Arsenic concentrations in these geothermal waters range from 1090 to 7853 μg/l and temperatures range from 13.8 to 63.0◦C. Arsenic concentrations were determined in water and sediment from the Tambo river, the main tributary of Papallacta lake. Arsenic concentrations are greater than 62 μg/l in water and up to 128 mg/kg in sediments. In comparison, total As concentrations in the shallow lake water during the dry season range from 220 to 369 μg/l. At depth, the As distribution was nearly homogeneous and fluctuated between 289 and 351 μg/l. Analyses of the lake sediments indicate that As concentrations vary between 60 and 613 mg/kg. From this study, it can be concluded that discharges of geothermal waters to the Tambo river are the main natural sources of As in Papallacta lake

Occurrence, health effects and remediation of arsenic in groundwaters of Latin America

At least 4 million people depend on drinking water with toxic arsenic (As) concentrations in Argentina, Bolivia, Chile, Mexico and Peru, which primarily originate from geogenic sources. In other Latin-American countries, the occurrence of the problem and/or the number of exposed people is still unknown. This chronic As exposure is associated with neurological and dermatological problems as well as carcinogenic effects. In contrast to urban areas, practically no action has been taken by the authorities to mitigate the As problem for the rural population, which often depends on As-contaminated water as their only available drinking water resource. This lack of interest has slowed the development of low-cost remediation methods for small communities or single houses. However, various suitable remediation techniques have been developed at the laboratory scale. In a limited number of cases these techniques have been tested and proven in the field and have helped to mitigate As problems. Examples of remediation techniques include solar oxidation methods, phytoremediation, and the use of natural materials as adsorbents for As removal from drinking water. Therefore, the problem is not a technological one, since viable solutions are already available. The problem lies in convincing the responsible authorities to consider the As occurrence as a natural health risk and support the development and the application of remediation methods for rural areas

Flora del bosque seco en la provincia del Carchi

Este documento aporta con información técnica y científica de las especies registradas en el bosque seco (BmMn01) de la comunidad El Rosal, parroquia La Concepción, cantón Mira provincia del Carchi. La información que se presenta en el texto fue facilitada por informantes clave de la comunidad, con base al conocimiento ancestral que ellos poseen, respecto del valor de uso de las plantas registradas en la investigación. El texto tiene como fin brindar información técnica y científica de 41 especies vegetales del bosque seco de la Comunidad jurídica El Rosal, parroquia La Concepción, cantón Mira, provincia del Carchi - Ecuador. Estas especies están descritas por familia, nombre científico, nombre común, hábito y una breve descripción de la especie. Además, se registró información con respecto al hábito ecológico y usos locales, dentro de los que destacan al aporte social, cultural, medicinal y ambiental. El texto presenta fotografías de diferentes partes de la planta; ilustración que ayudará a la identificación para futuras y similares investigaciones

Arsenic in volcanic geothermal fluids of Latin America

Numerous volcanoes, hot springs, fumaroles, and geothermal wells occur in the Pacific region of Latin America. These systems are characterized by high As concentrations and other typical geothermal elements such as Li and B. This paper presents a review of the available data on As concentrations in geothermal systems and their surficial discharges and As data on volcanic gases of Latin America. Data for geothermal systems in Mexico, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Ecuador, Bolivia, and Chile are presented. Two sources of As can be recognized in the investigated sites: Arsenic partitioned into volcanic gases and emitted in plumes and fumaroles, and arsenic in rocks of volcanic edifices that are leached by groundwaters enriched in volcanic gases. Water containing the most elevated concentrations of As are mature Na-Cl fluids with relatively low sulfate content and As concentrations reaching up to 73.6mgL -1 (Los Humeros geothermal field in Mexico), but more commonly ranging from a few mgL -1 to tens of mgL -1. Fluids derived from Na-Cl enriched waters formed through evaporation and condensation at shallower depths have As levels of only a few μgL -1. Mixing of Na-Cl waters with shallower meteoric waters results in low to intermediate As concentrations (up to a few mgL -1). After the waters are discharged at the ground surface, As(III) oxidizes to As(V) and attenuation of As concentration can occur due to sorption and co-precipitation processes with iron minerals and organic matter present in sediments. Understanding the mechanisms of As enrichment in geothermal waters and their fate upon mixing with shallower groundwater and surface waters is important for the protection of water resources in Latin America

Preparation of polymer-supported hydrated ferric oxide based on Donnan membrane effect and its application for arsenic removal

In the present study a novel technique was proposed to prepare a polymer-supported hydrated ferric oxide (D201-HFO) based on Donnan membrane effect by using a strongly basic anion exchanger D201 as the host material and FeCl-HCl-NaCl solution as the reaction environment. D201-HFO was found to exhibit higher capacity for arsenic removal than a commercial sorbent Purolite ArsenX. Furthermore, it presents favorable adsorption selectivity for arsenic removal from aqueous solution, as well as satisfactory kinetics. Fixed-bed column experiments showed that arsenic sorption on D201-HFO could result in concentration of this toxic metalloid element below 10 μg/L, which was the new maximum concentration limit set recently by the European Commission and imposed by the US EPA and China. Also, the spent D201-HFO is amenable to efficient regeneration by NaOH-NaCl solution