This work investigates the electrochemical role of water in the research of deep eutectic solvent (DES) based on urea and choline chloride. The motivation comes from the growing use of this DES, and on reports where a characteristic voltammetric cathodic pre-wave is observed. However, there has been no direct study to verify if such interpretation of the pre-wave is appropriate. In this regard, cyclic voltammetry has been used in this paper to interrogate the reactions inducing the appearance of the pre-wave. These experiments have been carried out using reline (the eutectic mixture of urea and choline chloride) melts containing different amounts of water, compounds which can be incorporated as impurities from air, or as decomposition products of reline. The analyses showed that a pre-wave in voltammograms in reline originates from water electroreduction accompanied with a subsequent choline hydroxide formation. In this sense, reline behaves like a typical mixture of organic solvent + alkali cation salt + water. The voltammetric signal depends on water content in reline. Importantly, this offers a possibility for in-situ electrochemical determination of water content in reline, provided that a calibration curve is constructed.

Mining environmental liabilities (MEL) are of great concern because of potential risks to ecosystems and human health. In this research, the environmental risk (RI) related to MEL existing in three artisanal and small-scale gold-mining areas of Ecuador was evaluated. For this purpose, data of 167 MEL including landfills, mining galleries, tailing deposits, and mineral processing plants from Macuchi, Tenguel–Ponce Enriquez, and Puyango mining areas, were analyzed. The risk assessment related to the presence of waste deposits was carried out based on the methodology proposed by the Spanish Geological Survey. Moreover, the procedure outlined in the Environmental Risk Assessment Guide of the Ministry of Environment of Peru for nonwaste deposits was applied. The highest RI values were identified in Puyango and Tenguel–Ponce Enriquez. Thus, they were both categorized as priority control areas requiring intervention and rehabilitation plans. The MEL that require a high level of intervention include waste deposits and mine entrances associated with potentially toxic elements. Moreover, the point risk maps showed that rivers in the studied areas have a potential pollution risk. This study provides risk levels associated with MEL in mining areas from Ecuador. This information could be used for environmental management and pollution mitigation.

Groundwater is a strategic resource, which is experiencing a growing threat of contamination worldwide. This study aimed to assess the vulnerability of the groundwaters in the basins of the rivers Gala, Tenguel, and Siete in the Ponce Enriquez mining area, considering as a hypothesis that anthropogenic activities (mainly mining and agricultural) conducted in the area generate a high risk of contamination. Vulnerability to contamination was quantified using the DRASTIC and GOD methods. In addition, the risk of contamination (Rc) was calculated considering the vulnerability index (IV) and the danger index (IP). Geographic information system (GIS) environment was used for the spatial analysis and the generation of vulnerability maps. The DRASTIC method showed that the negligible-to-low vulnerability category was predominant (50.7% of the area), followed by moderate vulnerability (25.6%), and high-to-extreme vulnerability (23.7%). Regarding the GOD method, the low and medium vulnerability categories were predominant in 41.4% and 27.5% of the area, respectively. Both methods agree that the center area, where the mining activities are located, has a vulnerability ranging from negligible to moderate. The IP was low in the eastern zone (58.7 km2) and ranged from moderate (426.2 km2) to high in the central and western zones (371.1 km2), where mining activities predominate. The RC revealed that 20% of the study area corresponded to a high contamination index; from which, 87% comes from agricultural activities, 9% from mining activities, and 4% due to shrimp farms and urban areas. This is the first study that evaluates the vulnerability to the contamination of groundwater in a mining area of Ecuador. The results of this research can serve as a baseline for future research, since the methodology used provides information on the priority areas for the protection of aquifers, considering the current land use in the study area.

Granting access to drinking water has been a challenge because 47% of the worldwide population is not connected to a drinking water distribution network in rural settlements. This study aimed to evaluate the contaminant removal efficiency in a conventional water treatment facility in the Austro region of Ecuador, Paute, to identify the treatment units requiring hydraulic resizing. Water samples were collected from each treatment unit to characterize the physical-chemical and microbiological parameters, and the dimensions of the treatment ponds for hydraulic evaluation purposes. Water hardness, electrical conductivity, SO42−, and Fe2+ were the main issues found in the water, which failed to comply with Ecuadorian technical guidelines. The treatment units, such as the flocculator, rapid sand filter, and storage tank, were resized to meet the demand of the future population. In addition, the residual free chlorine was measured as insufficient in the community’s tap water, showing an unprotected water distribution system to microbiological contamination. No disinfection by-products were found despite the existence of biodegradable organic matter. The findings of this research propose improvements in the deployed treatment practices to provide the community with drinking water in accordance with the Sustainable Development Objectives (SDG 3 and SDG 6).

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