Risks to Human Health from Mercury in Gold Mining in the Coastal Region of Ecuador.

Artisanal and small-scale gold mining (ASGM) plays a crucial role in global gold production. However, the adoption of poor mining practices or the use of mercury (Hg) in gold recovery processes has generated serious environmental contamination events. The focus of this study is assessing the concentration of Hg in surface waters within the coastal region of Ecuador. The results are used to conduct a human health risk assessment applying deterministic and probabilistic methods, specifically targeting groups vulnerable to exposure in affected mining environments. Between April and June 2022, 54 water samples were collected from rivers and streams adjacent to mining areas to determine Hg levels. In the health risk assessment, exposure routes through water ingestion and dermal contact were considered for both adults and children, following the model structures outlined by the U.S. Environmental Protection Agency. The results indicate elevated Hg concentrations in two of the five provinces studied, El Oro and Esmeraldas, where at least 88% and 75% of the samples, respectively, exceeded the maximum permissible limit (MPL) set by Ecuadorian regulations for the preservation of aquatic life. Furthermore, in El Oro province, 28% of the samples exceeded the MPL established for drinking water quality. The high concentrations of Hg could be related to illegal mining activity that uses Hg for gold recovery. Regarding the human health risk assessment, risk values above the safe exposure limit were estimated. Children were identified as the most vulnerable receptor. Therefore, there is an urgent need to establish effective regulations that guarantee the protection of river users in potentially contaminated areas. Finally, it is important to continue investigating the contamination caused by human practices in the coastal region.

Environmentally Friendly Photothermal Membranes for Halite Recovery from Reverse Osmosis Brine via Solar-Driven Membrane Crystallization.

Modern society and industrial development rely heavily on the availability of freshwater and minerals. Seawater reverse osmosis (SWRO) has been widely adopted for freshwater supply, although many questions have arisen about its environmental sustainability owing to the disposal of hypersaline rejected solutions (brine). This scenario has accelerated significant developments towards the hybridization of SWRO with membrane distillation-crystallization (MD-MCr), which can extract water and minerals from spent brine. Nevertheless, the substantial specific energy consumption associated with MD-MCr remains a significant limitation. In this work, energy harvesting was secured from renewables by hotspots embodied in the membranes, implementing the revolutionary approach of brine mining via photothermal membrane crystallization (PhMCr). This method employs self-heating nanostructured interfaces under solar radiation to enhance water evaporation, creating a carefully controlled supersaturated environment responsible for the extraction of minerals. Photothermal mixed matrix photothermal membranes (MMMs) were developed by incorporating graphene oxide (GO) or carbon black (CB) into polyvinylidene fluoride (PVDF) solubilized in an eco-friendly solvent (i.e., triethyl phosphate (TEP)). MMMs were prepared using non-solvent-induced phase separation (NIPS). The effect of GO or GB on the morphology of MMMs and the photothermal behavior was examined. Light-to-heat conversion was used in PhMCr experiments to facilitate the evaporation of water from the SWRO brine to supersaturation, leading to sodium chloride (NaCl) nucleation and crystallization. Overall, the results indicate exciting perspectives of PhMCr in brine valorization for a sustainable desalination industry.

Analysis of Mercury in Aquifers in Gold Mining Areas in the Ecuadorian Amazon and Its Associated Risk for Human Health.

Gold mining activity is a source of supply in many areas of the world, and especially in developing countries, it is practiced illegally and by applying unsafe techniques. Particularly in Ecuador, artisanal and small-scale gold mining (ASGM) is widespread, and it is based on the use of toxic substances, such as mercury (Hg), in gold recovery. Hg is a heavy metal that is water-insoluble, which, once mobilized, poses a threat to both the environment and human health. This study analyzes Hg concentrations in the six provinces of Napo, Sucumbíos, Orellana, Pastaza, Morona Santiago, and Zamora Chinchipe of the Ecuadorian Amazon region to conduct a human health risk assessment. Significant differences in Hg levels were found between provinces, but concentrations were below MPL imposed by Ecuadorian regulations everywhere. Nevertheless, a worrisome picture emerges, especially with regard to the most vulnerable receptors represented by the child population. There are multiple factors of incidence that may affect the possible future development of the phenomenon, and with reference to the social, economic, and environmental context of the region, it can be concluded that it may be appropriate to plan further investigation to arrive at a more comprehensive assessment. The results of this study can be used by decision makers to plan further investigation and to implement monitoring networks, risk mitigation strategies, and groundwater protection measures.

Human health risk assessment due to mercury use in gold mining areas in the Ecuadorian Andean region.

Mining activity drives economic development and has established itself as one of the main industrial spheres globally. However, illegal, and artisanal gold mining, which uses mercury (Hg), is a major source of global pollution. Hg is highly toxic and persistent in the environment, affecting human health and the ecosystem. The objective of this research is to; (a) analyze Hg concentrations in surface waters of nine provinces of the Andean region of Ecuador and compare them with the maximum permissible limits of Ecuadorian regulations, and (b) evaluate the health risk of people exposed to waters with high Hg content through residential and recreational scenarios. In this study, 147 water samples from rivers and streams were analyzed. The results revealed worrying levels of Hg, especially in the provinces of Azuay and Loja where Hg values of up to 0.0913 mg/L and 0.0387 mg/L, respectively, were detected. In addition, it was found that 45% of the samples did not meet the water quality criteria for the preservation of aquatic life, which represents a severe risk to the ecosystem. The probabilistic risk analysis yielded values that exceeded the acceptable exposure limit for adults and children in residential settings in Azuay and Loja, while in the recreational scenario the safe exposure limit was exceeded for both receptors only in the province of Azuay. The elevated presence of Hg in the provinces, mainly in Azuay and Loja, possibly related to illegal gold mining activity, represents a threat to water quality and aquatic life in the Andean region of Ecuador. Children are especially vulnerable, and effective regulation is required to ensure the safety of the population. This study provides valuable information for decision makers regarding the risk associated with Hg exposure in areas of mining activity in the Ecuadorian Andean region. In addition, it can contribute to the development of policies and strategies to control contamination in mining environments and protect human and environmental health in the region.

Tunable optical and semiconducting properties of eco-friendly-prepared reduced graphene oxide.

Wide bandgap oxidized graphenes have garnered particular interest among the materials explored for these applications because of their exceptional semiconducting and optical properties. This study aims to investigate the tunability of the related properties in reduced graphene oxide (rGO) for potential use in energy conversion, storage, and optoelectronic devices. To accomplish this, we scrutinized crucial parameters of the synthesis process such as reduction time and temperature. Our findings demonstrate that controlling these parameters makes it possible to customize the optical bandgap of reduced graphene oxide within a range of roughly 2.2 eV-1.6 eV. Additionally, we observed that reduced graphene oxide has strong and superior absorption in the visible region, which is attributable to the existence of OFGs and defects. Notably, our results indicate that the absorption coefficients of reduced graphene oxide are up to almost three times higher (7426 ml mg-1 m-1) than those observed in dispersions of exfoliated graphene and graphene oxide (GO). To complement our findings, we employed several spectroscopic and morphological characterizations, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrical measurements. The implications of our results are significant for the development and design of future semiconductors for energy conversion and optoelectronic applications.

Temperature-Dependent Optical Properties of Oxidized Graphenes.

In this study, we investigate how changing important synthesis-related parameters can affect and control the optical characteristics of graphene oxide (GO) and reduced graphene oxide (rGO). These parameters include drying time and reduction time at two different temperatures. We obtain an understanding of their impact on optical transitions, optical bandgap, absorption coefficient, and absorbance spectrum width by analyzing these factors. Accordingly, GO has an optical bandgap of about 4 eV, which is decreased by the reduction process to 1.9 eV. Both GO and rGO display greater absorption in the visible spectrum, which improves photon capture and boosts efficiency in energy conversion applications. Additionally, our results show that GO and rGO have higher absorption coefficients than those previously reported for dispersions of exfoliated graphene. Defects in GO and rGO, as well as the presence of functional oxygen groups, are the main contributors to this increased absorption. Several measurements are carried out, including spectroscopic and morphological studies, to further support our findings.

Assessment of Hg pollution in stream waters and human health risk in areas impacted by mining activities in the Ecuadorian Amazon.

Illegal gold mining activities have contributed to the release and mobilization of Hg and environmental degradation in many parts of the world. This study aims to determine the concentration of Hg in five provinces of the Amazon Region of Ecuador, in addition to assessing the risk to human health of exposed populations, applying deterministic and probabilistic methods. For this purpose, 147 water samples were collected in rivers and streams crossing and/or located near mining areas. As a result, 100% of the samples analyzed exceeded the maximum permissible limit (MPL) according to the water quality criteria for the preservation of aquatic life of the Ecuadorian regulations, while 7% of the samples exceeded the MPL for drinking water. On the other hand, considering the European Environmental Quality Standard (EQS) for surface water bodies, in our study, 100% of the samples exceed the maximum permissible limit (0.07 µg/L), and with respect to the Canadian water quality guidelines, 35% of the samples exceed the permissible limit (0.001 mg/l) for drinking water, and 100% of the samples exceed the limit for life in water bodies (0.0001 mg/l). The risk assessment revealed that the probability of developing adverse health effects from exposure to Hg is below the recommended limits according to the probabilistic assessment; this is in relation to the criterion of residential and recreational use of water resources. However, it was identified that the child population doubles the acceptable systemic risk level according to the results of the deterministic assessment in the residential scenario. This information can be used by decision-makers to implement strategies to reduce Hg contamination and exposure of the population in Ecuadorian Amazonian rivers.

A model for the adsorption process of water dissolved elements flowing into reactive porous media: Characterization and sizing of water mining/filtering systems.

This study presents a mathematical model describing the adsorption-desorption process of water dissolved elements onto reactive porous materials during filtering operations performed under dynamic flow conditions. The developed model is based on a reversible second order adsorption kinetic featuring the progressive reduction of the purifying capacity of the filtering material due to the gradual exhaustion of the active sites available for solute retention. It enables the simulation of the performances of water filtering systems through the use of parameters having a clear chemical-physical significance or it can be used for the estimation of these parameters to characterize the adsorption properties of the reactive material. Starting from the same adsorptive conceptual model used for the filtering system marked by ongoing flowing conditions, an adaptation for static systems was performed on the mathematical framework in order to process the same chemical physical parameters in both schemes. Adsorption laboratory tests were carried out to validate the developed model. Results show that the kinetic constants and adsorption capacities (a maximum of about 45 mg g-1 was obtained for the tested material) are highly comparable, both within the same experimental system, and between different experimental setup. This confirms the validity of the developed model which is able to perfectly fit the observed concentration data in all tested configurations.

Stable Supercapacitors Based on Activated Carbon Prepared from Italian Orange Juice.

The development of efficient energy storage systems is critical in the transition towards sustainable energy solutions. In this context, the present work investigates the viability of using orange juice, as a promising and sustainable precursor, for the synthesis of activated carbon electrodes for supercapacitor technologies. Through the carbonization-activation process and controlling the preparation parameters (KOH ratio and activation time), we have tailored the specific surface area (SSA) and pore size distribution (PSD) of the resulting carbon materials-crucial parameters that support supercapacitive performance. Several spectroscopic, morphological, and electrochemical techniques are used to characterize the obtained carbon materials. In particular, our optimization efforts revealed that a 5:1 KOH ratio with an activation time up to 120 min produced the highest SSA of about 2203 m2/g. Employing these optimal conditions, we fabricated symmetric coin cell supercapacitors using Na2SO4 as the electrolyte, which exhibited interesting specific capacitance (~56 F/g). Durability testing over 5000 cycles sustained the durability of the as-made activated carbon electrodes, suggesting an excellent retention of specific capacitance. This study not only advances the field of energy storage by introducing a renewable material for electrode fabrication but also contributes to the broader goal of waste reduction through the repurposing of food byproducts.

Adsorption of Mercury on Oxidized Graphenes.

Graphene oxide (GO) and its reduced form, reduced graphene oxide (rGO), are among the most predominant graphene derivatives because their unique properties make them efficient adsorbent nanomaterials for water treatment. Although extra-functionalized GO and rGO are customarily employed for the removal of pollutants from aqueous solutions, the adsorption of heavy metals on non-extra-functionalized oxidized graphenes has not been thoroughly studied. Herein, the adsorption of mercury(II) (Hg(II)) on eco-friendly-prepared oxidized graphenes is reported. The work covers the preparation of GO and rGO as well as their characterization. In a further stage, the description of the adsorption mechanism is developed in terms of the kinetics, the associated isotherms, and the thermodynamics of the process. The interaction between Hg(II) and different positions of the oxidized graphene surface is explored by DFT calculations. The study outcomes particularly demonstrate that pristine rGO has better adsorbent properties compared to pristine GO and even other extra-functionalized ones.

History, Socioeconomic Problems and Environmental Impacts of Gold Mining in the Andean Region of Ecuador.

Mining in Ecuadorian territory comprises three stages of Ecuadorian history: pre-Columbian, colonial, and republican times. In its beginnings, this activity did not have regulations or a legal foundation. The first Mining Law dates back to 1830, and it has been modified until the most recent update in 2009. The Andean region consists of 10 provinces, 9 of which have registered gold concessions, the most important of which are Loja, Azuay, and in recent years, Imbabura and Pichincha, which are the provinces with the highest number of reported concessions. The objective of this study focused on analyzing the historical and current situation of Artisanal and Small-scale Mining (ASGM) and the emergence of large-scale (industrial) mining. For the elaboration of this study, different methodological techniques were used, such as literature review, field interviews, and expert judgment validation. The main findings show that the provinces of Loja, Azuay, Imbabura, and Pichincha are the most conflictive areas in the region due to the impacts caused by mining activities. In socio-economic terms, there are conflicts between inhabitants in favor and against these activities and problems associated with human health. In environmental terms, the findings suggest historical contamination of water sources by heavy metals, which has altered the surrounding aquatic and terrestrial systems. Finally, the study concludes that implementing public policies should be promoted to balance socio-economic and environmental aspects in gold mining activities in the Andean region of Ecuador, strengthening the use of new technologies and education to raise awareness of the serious effects of mining activities.

Effects of groundwater abstraction and desalination brine deep injection on a coastal aquifer.

As a result of climate change, population increase and improvement of living standards, the water demand is annually growing drawing worldwide attention on seawater desalination to face water crisis. The total global desalination capacity is dominated by Reverse Osmosis (RO) and, often, this desalination process is fed with the brackish water extracted from coastal aquifers. After this process the desalted freshwater is obtained at a recovery factor of ca. 50%, while concentrate byproduct, named brine, is disposed back to coastal aquifers, seas, oceans or evaporative ponds, determining detrimental effects on the surrounding environment. A common approach to clean out the brine is the deep-well injection into coastal aquifers, exacerbating the seawater intrusion. The ultimate result is a reduction of the available water both in terms quantity and quality hampering the benefits of the desalination. The aim of this study is to investigate the effects of brine water injection in the Nile coastal aquifer, one of the largest underground freshwater reservoirs in the world, and to find a way to minimize and manage the environmental impact of the RO process. In order to simulate the effects of the brackish water extraction and the brine deep-injection on the Nile coastal aquifer, a combined seawater intrusion, numerical models for flow and salt transport model in aquifers and the solution-diffusion in RO practices were implemented. Different management scenarios were considered and their consequences on salt mass storage in the Nile coastal aquifer evaluated. According to the numerical results, the salinization of the coastal aquifer can be mitigated by reducing the concentration of the water feeding the reverse osmosis plant, i.e., mixing the extracted brackish water with a lower salinity water. Besides, low feed salinity leads to significant gains by decreasing the specific energy consumption of the desalination process.

Groundwater pollution assessment in landfill areas: Is it only about the leachate?

Groundwater is the environmental compartment very often involved in the broader issues related to contaminated sites characterization and reclamation. It is not uncommon to find areas in which some substances directly linked to the petrographic composition of the aquifer reach high values exceeding the limits set by the regulations. These concentrations are defined as Natural Background Levels (NBL) and the need to quantify their real contribution, in areas subject to strong anthropogenic pressures, represents an emerging problem. Global statistical analyses and laboratory testing are proposed here to distinguish between the impacts of different forcing influencing water quality in hydrogeological systems. The study focus on the application of a methodology based on the Component Separation analysis for the NBL estimation of selected chemical species in potentially contaminated aquifers flowing in the proximity of landfill areas, and on the subsequent validation of the results through experimental studies of field samples. A site located in Calabria, Italy, and constituting a typical example of an aquifer which has been subjected to possible contact with the leachate produced by waste degradation is considered. The work is keyed to NBLs characterization of aluminum, iron and manganese and to the identification of their natural component for a proper environmental assessment of the site. Estimated NBLs are consistent with the geochemical composition of site samples. The adopted methodology can represent a useful instrument to distinguish effective anthropogenic contamination from natural conditions and to define realistic environmental clean-up goals.

Effects of climate change on the design of subsurface drainage systems in coastal aquifers in arid/semi-arid regions: Case study of the Nile delta.

The influence of climate change on the availability and quality of both surface- and ground-water resources is well recognized nowadays. In particular, the mitigation of saline water intrusion mechanisms in coastal aquifers is a recurrent environmental issue. In the case of the Nile delta, the presence of sea level rise and the perspective of other human-induced stressors, such as the next operation of the Grand Ethiopian Renaissance Dam, are threats to be taken into account for guaranteeing resilient agricultural practices within the future possible scenarios. Subsurface drainage offers a practical solution to the problem of upward artesian water movement and the simultaneous downward flow of excess irrigation water, to mitigate the salinization in the root zone. Subsurface draining systems can contribute to mitigate the vulnerability to climate change and to the increased anthropic pressure insofar they are able to receive the incremented flow rate due to the foreseen scenarios of sea level rise, recharge and subsidence. This paper introduces a rational design of subsurface drainage systems in coastal aquifers, taking into account the increment of flow in the draining pipes due to future possible conditions of sea level rise, artificial recharge and subsidence within time horizons that are compatible with the expected lifespan of a buried drainage system. The approach proposed in this paper is characterized by the assessment of the incremental flow through the drains as a function of various possible scenarios at different time horizons. Our calculations show that the impact on the discharge into the existing subsurface drainage system under the new foreseen conditions is anything but negligible. Thus, future climate-related scenarios deeply impact the design of such hydraulic structures, and must be taken into account in the frame of the next water management strategies for safeguarding agricultural activities in the Nile delta and in similar coastal contexts.

Study of the adsorption of mercury (II) on lignocellulosic materials under static and dynamic conditions.

WHO has declared mercury as one of the most dangerous pollutants for human health. Unfortunately, several cases of rivers and aquifers contaminated by mercury inevitably poses the problem on how to remediate them. Considerable efforts are being addressed to develop cost-effective methodologies, among which the use of low-cost adsorbing materials. In this paper, the adsorption performances of an alternative lignocellulosic material derived from the Spanish broom plant, are presented. This plant is widely diffused in the world and its usage for Hg(II) removal from water in real working conditions requires only minimal pretreatment steps. A thoroughly investigation on the kinetics and thermodynamics of Hg(II) adsorption on Spanish broom is presented, by using Hg(II) polluted aqueous solutions specifically prepared in order to simulate typical groundwater conditions. Several batch experiments, under static conditions, were carried out in order to evaluate the effect of pH, contact time, adsorbent dosage, initial concentration, temperature. A maximum adsorption capacity of 20 mg L-1 can be obtained at pH 5, following a pseudo second order kinetics. Moreover, adsorption experiments in dynamic conditions were carried out using Spanish broom filters. Interestingly, a systematic, unconventional double S-shape breakthrough curve was observed under different experimental conditions, revealing the occurrence of two adsorption processes with different time scales. This behavior has been fitted by a bimodal Thomas model which, unlike the single Thomas fitting, gives satisfactory results with the introduction of a new parameter related to the fraction of surface active sites involved in the adsorption processes.

A Comparison of deterministic and probabilistic approaches for assessing risks from contaminated aquifers: an Italian case study.

In this article we consider the methods of deterministic and probabilistic risk analysis regarding the presence of chemical contaminants in soil, water and air, with a broader meaning than usual for the latter, as we extended the probabilistic treatment to the parameters that influence the transport to a greater extent, in particular hydraulic conductivity and partition coefficient. These parameters, to which only one value is assigned, are considered here as random variables. The objective of the study reported herein was to demonstrate that application of the probabilistic method of risk assessment is preferable to the use of the deterministic method. Both methods yield contaminant removal levels that will reduce adverse effects on human health and the environment, but results from the deterministic method are typically more conservative than necessary, and are thus more costly to achieve. In addition, we found it essential to consider the importance of random variables (the parameters influencing the flow and the transport), such as the hydraulic conductivity and the partition coefficient, when assessing health risks. Both methodologies of health risk analysis, deterministic and probabilistic, were applied to a site in southern Italy, contaminated by heavy metals. The results obtained confirm the purposes of this study.

An inverse procedure to estimate transmissivity from heads and SP signals.

Experimental hydraulic heads and electrical (self-potential) signals associated with a pumping test were used in an inverse model to estimate the transmissivity distribution of a real aquifer. Several works reported in the literature show that there is a relatively good linear relationship between the hydraulic heads in the aquifer and electrical signals measured at the ground surface. In this experimental test field, first, the current coupling coefficient was determined by the best fit between experimental and modeled self-potential signals at the end of the pumping phase. Soon afterward, with the hydraulic heads obtained from the self-potential signals, the transmissivity distribution of the aquifer was conditioned by means an inverse model based on the successive linear estimator (SLE). To further substantiate the estimated T field from the SLE analysis, we analyzed the drawdown rate, the derivative of the drawdown with respect to the ln(t), because the drawdown rate is highly sensitive to the variability in the transmissivity field. In our opinion, these results show that self-potential signals allow the monitoring of subsurface flow in the course of pumping experiments, and that electrical potentials serve as a good complement to piezometric observations to condition and characterize the transmissivity distribution of an aquifer.