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The phosphogypsum (PG) stacks located at Huelva (SW Spain) store about 100 Mt of PG, and covers a surface of 1000 ha. It has been very well established in many studies that this waste contains significant U-series radionuclides concentrations, with average activity concentrations rounding the 650, 600, 400 and 100 Bq kg−1 for 226Ra, 210Po, 230Th and 238U, respectively. However, the radionuclide transfer from this repository into the environment by the aquatic pathway will depend on the mobility of each radionuclide. The mobility of the natural radionuclides (U-isotopes, Th-isotopes, 226Ra, and 210Po) contained in the PG piles were evaluated by using the optimized BCR sequential extraction procedure (BCR “Community Bureau of Reference”). The radionuclides were measured in the liquid fractions by alpha-particle spectrometry with semiconductor PIPS detectors. In addition, to validate the obtained results, waters from different locations of the PG piles (pore-water, perimeter channel and edge outflow leachates) were taken and the alpha emitter radionuclides determined. Uranium presents the highest mobility, being its total mobile fraction in the PG around 70%, while 210Po and 226Ra present an intermediate mobility of (around 50% and 30%, respectively). And finally, the Th-isotopes have very low mobility (mobile fraction

Determining the availability of natural radionuclides in environmental conditions is increasingly important in order to evaluate their toxicity. A validated procedure is necessary to ensure the comparability and accuracy of the results obtained by different laboratories. For that, an optimised BCR sequential extraction procedure has been applied to the certified reference material (CRM), coded as BCR-701, and their resulting liquid and solid fractions were subjected to an exhaustive chemical and radioactivity characterisation. In this sense, several material characterisation techniques were used for chemical, mineralogical, and radioactive characterisation, in order to gain basic information about the obtained fractions. In accordance with the results of this work, the BCR sequential extraction procedure has been validated for the most significant alpha-emitter natural radionuclides (210Po, 234U, 238U, 230Th, 232Th, and 226Ra). It has been demonstrated that their mobility is related to the speciation under environmental conditions and the type of radionuclide; we have even found differences between radionuclides of the same element, such as the cases of the pairs 234U238U and 230Th232Th, for the BCR-701. In addition, we found that radium was mainly bound to the reducible fraction (Fe and Mn-oxyhydroxides), uranium to the oxidizable fraction (organic matter and sulphides), and that the polonium and thorium isotopes had a high affinity with the particulate phase (non-mobile fraction).

Commercial copper (Cu) is obtained by a hydro-pyrometallurgical process, where the Cu anodes obtained in the furnaces (Cu > 99.5%) are enriched up to 99.99% in “cathodes” by electrorefining at an electrolysis plant. During this process, some impurities accumulate in the electrolyte, mainly arsenic (As), which decrease the quality of the Cu cathode. For this reason, the electrolyte is sent to an electrolyte cleaning plant (ECP) for its purification. Electrolyte sludge (ES) is produced in the last stage of purification and is recirculated back to the furnace due to the high Cu content. This recirculation involves a severe problem of As accumulation in the industrial process. The objective of this work was to develop a procedure to fully dissolve the ES, removing the As and recovering its Cu content. The ES dissolution process was optimised (dissolution efficiency > 99%) in H2SO4 (1.4 M)/HNO3 (1.8 M) medium using a 1:20 g mL−1 solid-to-liquid ratio. As was removed from the ES solution by its precipitation as iron (III) arsenate, with high efficiency (more than 70%). After As removal, the Cu can be precipitated as copper sulphate, which is used in several applications.

Mercury (Hg) accumulation capacity was assessed in three plant species ( Axonopus compressus , Erato polymnioides , and Miconia zamorensis ) that grow on soils polluted by artisanal small-scale gold mines in the Ecuadorian rainforest. Individuals of three species were collected at two sampling zones: i) an intensive zone (IZ, 4.8 mg Hg kg -1 of soil) where gold extraction continues to occur, and ii) a natural zone (NZ, 0.19 mg Hg kg -1 of soil). In addition, the percentage of arbuscular mycorrhizal fungi (AMF) colonization was determined in plant roots and seven fungal morphotypes isolated from rhizospheric soil. Results suggest a facilitation role of native and pollution adapted AMF on Hg phytoaccumulation. E.g., E. polymnioides increased Hg accumulation when growing with greater AMF colonization. We concluded that E. polymnioides is a good candidate for the design of microbe-assisted strategies for Hg remediation at gold mining areas. The consortia between E. polymnioides and the AMF isolated in this study could be instrumental to get a deeper understanding of the AMF role in Hg phytoaccumulation.

The industry devoted to the production of phosphoric acid by using as raw material sedimentary phosphate rock (PR) is considered as a NORM activity (Naturally Occurring Radioactive Materials), due to the high levels of U-series radionuclides contained in this ore, which are 1–2 orders of magnitude higher than those in unperturbed soils. This fact allowed us to develop a deep characterization of the raw materials, wastes, main intermediate materials, and final products obtained at a typical phosphoric acid factory. The elemental composition (major, minor and trace elements), radionuclide concentrations, grain size distribution, mineralogy and micro-structural composition were analyzed. The aim of this characterization was to obtain information for operators and maintenance personnel involved in clean-up and waste management operations. The highest concentrations of some heavy metals and radionuclide activity concentrations were found in the “scales” (or internal incrustations)from the pipes that carry either phosphoric acid (PA) or the phosphogypsum waste (PG). The highest concentrations where found for 226Ra and 40K,with values up to 9 and 5 Bq g−1, respectively. In addition, high concentrations of many toxic heavy metals and trace elements, such as Cd, Cr, Ni, Sr, Y, V, Zn, Th, and U, were found in some sludge samples. The shielding effect of the containers/vessels/pipes has an essential role in the measured external dose in the intermediate products. The radiological implications of natural radionuclides with higher activity showed that if the maximum particulate matter concentration established in the Spanish regulation is verified, and taking into account the most conservative scenario, the annual limit of 1 mSv y−1 is not exceeded.