Geogenic arsenic contamination of wet-meadows associated with a geothermal system in an arid region and its relevance for drinking water

Environmental fate and ecological impact of the potentially toxic elements from the geothermal springs

Potentially toxic elements from geothermal springs can cause significant pollution of the surrounding environment and pose potential risk to the ecosystem. The fate of potentially toxic elements in the water-soil-plant system in the Yangbajain geothermal field on the Tibetan Plateau, China was investigated to assess their impact on the eco-environment. The concentrations of Be, F, As, and Tl were highly elevated in the headwaters of the Yangbajain geothermal springs, and their concentrations in the local surface water impacted by the geothermal springs reached 8.1 μg/L (Be), 23.9 mg/L (F), 3.83 mg/L (As), and 8.4 μg/L (Tl), respectively, far exceeding the corresponding thresholds for surface and drinking water. The absence of As-Fe co-precipitation, undersaturated F-, and weak adsorption on minerals at high geothermal spring pH may be responsible for the As- and F-rich drainage, which caused pollution of local river. As concentrations in the leaves of Orinus thoroldii (Stapf ex Hemsl.) Bor were up to 42.7 μg/g (dry weight basis), which is an order of magnitude higher than the allowable limit in animal feeds. The locally farmed yaks are exposed to the excessive amount of F and As with high exposure risk through water-drinking and grass-feeding.

Arsenic-rich geothermal fluids as environmentally hazardous materials - A global assessment

Arsenic-rich geothermal fluids are hazardous materials of global impact, affecting different environments (groundwater, surface water, seawater, sediments, soils, atmosphere) and human and animal health. They can be released naturally or through human activities. For the first time, a systematic global assessment of geothermal arsenic (As) in fluids of the six principal types of geothermal reservoirs and their environmental impact (e.g. freshwater sources used for drinking and irrigation), distinguishing between different uses (if any), was performed based on research of the geochemical characteristics and geotectonic setting of the formation of natural geothermal reservoirs worldwide. This will assist to further improve the sustainability of geothermal energy use, which can be an excellent environmental friendly renewable energy resource for electric power production and direct heat use. Arsenic in geothermal fluids (up to several tens of mg/L) originates especially in deep seated (several kilometers) reservoirs. Proper management of geothermal fluids during exploration, exploitation, use and disposal of resulting waste products through sustainable As mitigation strategies are essential. However, more research about As speciation and volatile As is necessary to fulfil this aim. Therefore As (and its principal species) needs to be included as parameter for standard analysis and monitoring program in any project using geothermal fluids from exploration to management of resulting wastes as base to define appropriate mitigation actions.

Fate of arsenic in living systems: Implications for sustainable and safe food chains

Arsenic, a group 1 carcinogen for humans, is abundant as compared to other trace elements in the environment and is present mainly in the Earth's crust and soil. The arsenic distributions in different geographical regions are dependent on their geological histories. Anthropogenic activities also contribute significantly to arsenic release into the environment. Arsenic presents several complications to humans, animals, and plants. The physiology of plants and their growth and development are affected by arsenic. Arsenic is known to cause cancer and several types of organ toxicity, such as cardiotoxicity, nephrotoxicity, and hepatotoxicity. In the environment, arsenic exists in variable forms both as inorganic and organic species. From arsenic containing compartments, plants can absorb and accumulate arsenic. Crops grown on these contaminated soils pose several-fold higher toxicity to humans compared with drinking water if arsenic enters the food chain. Information regarding arsenic transfer at different trophic levels in food chains has not been summarized until now. The present review focuses on the food chain perspective of arsenic, which affects all components of the food chain during its course. The circumstances that facilitate arsenic accumulation in flora and fauna, as components of the food chain, are outlined in this review.

Hydrodynamic and hydrochemistry of wet meadows and shallow lakes in areas of the Patagonian basaltic plateaus, Argentina

Extra-Andean Patagonia, located in the south end of South America, is a wide arid region where the basaltic plateau landscape dominates. Associated with the basaltic plateaus, wet meadows and shallow lakes make up environments of relevance due to the ecosystemic services they provide. The aim of this work was to define the processes and factors that condition the hydrodynamics and hydrogeochemistry of wet meadows and shallow lakes in a sector of the Patagonian plateau basalts. For this, detailed geological and geomorphological studies were carried out and water was sampled at 29 points for the analysis of major ions and, in some samples, stable isotopes of the water molecule. Values of δ¹⁸O and δ²H similar to the local meteoric line in the water of wet meadows indicate that rainwater quickly infiltrates through the fractures of the basaltic plateaus and stores in the underlying sediments. Groundwater discharge occurs in the scarp zone due to changes in sediment permeability. The weathering of silicates in basalts, ion exchange in the sediment clays, and the dissolution of soluble salts provided by the dust control water chemistry of this wetland. Water from wet meadows drains into saline endorheic basins of sodium chloride composition where the isotopic signal is indicative of evaporation percentages close to 95%. The high evaporation rates cause the precipitation of evaporitic salts at the edges of shallow lakes with carbonate, sulfate, and chloride species controlled by the dominance of sodium in the water.