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Mine tailings are one of the primary contaminant sources of heavy metals and metalloids in the soil. Besides increasing the concentration of potentially toxic elements (PTEs), tailings may modify the edaphic conditions and decrease the buffer capacity of impacted soils. The influence of tailings may reach distances far from the impoundments depending on the transport path and the specific transport mean: air, rain (runoff and infiltration), or acid mine drainage. In this study, soil samples from various horizons were collected in trial pits along a transect, at different distances from sulfide tailings. Soil analysis included texture, organic matter, alkalinity, porous space, carbonates, pH, electrical conductivity, real density, apparent density, total sulfur, main mineralogy, and total concentrations of As, Cd, Pb, Fe, and Zn. Graphical and statistical interpretation of the results showed that real density and porous space are the leading indicators of the tailings dispersion and accumulation and that pH is not a significant parameter (all values were above the neutrality) due to the limestone abundance in the area. However, Zn and Cd concentrations had an inverse relation with pH. Differences in the concentrations of PTEs between the superficial and deep layers that increased toward the tailings were also observed. Gypsum was only present in the closest samples to the tailings and may also be an indicator of tailings' influence on soils. This study allowed us to identify general edaphic parameters as a first and quick means to determine the tailings contamination of soils.

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We reviewed over 226 studies dealing with arsenic (As) in water bodies (124 sites or regions; 5,834 samples), soils (44; 2,700), sediments (56; 765), rocks (6; 85), mine waste (25; 582), continental plants (17 (77 species); 571), continental animals (10 (32 species); 3,525) and aquatic organisms (27 (100 species) 2,417) in Mexico. In general, higher As concentrations were associated with specific regions in the states of Hidalgo (21 sites), San Luis Potosi (SLP) (19), Baja California Sur (15), Zacatecas (5), and Morelos (4). High As levels have been detected in drinking water in certain locations of Coahuila (up to 435 µg L-1) and Sonora (up to 1004 µg L-1); in continental surficial water in Puebla (up to 780 µg L-1) and Matehuala, SLP (up to 8684 µg L-1); in groundwater in SLP (up to 16,000 µg L-1) and Morelia, Michoacán (up to 1506,000 µg L-1); in soils in Matehuala, SLP (up to 27,945 µg g-1) and the Xichú mining area, Guanajuato (up to 62,302 µg g-1); and in sediments in Zimapán, Hidalgo (up to 11,810 µg g-1) and Matehuala, SLP (up to 28,600 µg g-1). In contaminated arid and semi-arid areas, the plants P. laevigata and A. farnesiana exhibit the highest As levels. These findings emphasize the human and environmental risks associated with the presence of As in such regions. A synthesis of the available techniques for the removal of As in water and the remediation technologies for As contaminated soils and sediments is given. The As occurrence, origin (geogenic, thermal, mining and anthropogenic) and evolution in specific regions is summarized. Also, the mobilization and mechanisms to explain the As variability in continental environments are concisely given. For future research, a stratified regional sampling is proposed which prioritizes critical sites for waters, soils and sediments, and biota, considering the subpopulation of foods from agriculture, livestock, and seafood. It is concluded that more detailed and comprehensive studies concerning pollution levels, as well as As trends, transfer, speciation, and toxic effects are still required.

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Arsenic transport in alluvial aquifers is usually constrained due to arsenic adsorption on iron oxides. In karstic aquifers, however, arsenic contamination may spread to further extensions mainly due to favorable hydrogeochemical conditions. In this study, we i) determined the spatial and temporal behavior of arsenic in water in an alluvial-karstic geological setting using field and literature data, ii) established whether a contaminated aquifer exists using field and literature piezometric data and geophysical analysis, iii) studied the local geology and associated arsenic contaminated water sources to specific aquifers, iv) revealed and modeled subsoil stratigraphy, and v) established the extent of arsenic exposure to the population. We found arsenic contamination (up to 91.51 mg/l) in surface and shallow groundwater (<15 m), where water flows from west to east through a shallow aquifer, paleochannels and a qanat within an alluvial-karst transition that favors the spreading and transport of arsenic along 8 km as well as the increase of arsenic exposure to the population (up to 3.6 mgAs/kghair). Results from this study contribute to understanding arsenic transport in semi-arid, mining-metallurgical, and urban environments, where the presence of karst could favor arsenic transport to remote places and exacerbate arsenic exposure and impact in the future.

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Mining is one of the main economic activities in Mexico, and Hidalgo State is one of the main areas; however, this activity produces wastes, such as mine tailings, that are disposed in deposits and may be dispersed on the soils (e.g., agricultural soils). In this study, the concentrations of As and heavy metals in maize plants cultivated in a greenhouse in two soils influenced by tailings were evaluated. Plants were grown for 165 days in the soils (one of them more polluted due to a closer distance to the tailings) and one control soil close to the study zone. Plants' growth was evaluated, and after harvesting, they were divided in six parts: root, stalk, plant leaves, cob sheath, corncob and grains. Plants showed depressed development: small height, slow growth and physiological cob immaturity. Assimilation of As and heavy metals by plants was influenced by the concentration of the contaminants but also by the availability of nutrients. Important concentrations of the metals were recorded in the harvestable parts (grain, stalk and cob sheath). The order of accumulation was Zn > Fe > Pb > As > Cd. Cadmium was not detected in grains, but a maximum concentration of As at 1.02 mg/kg and Pb at 3.9 mg/kg was measured in the dry grain. These As and Pb concentrations do not comply with CODEX Alimentarius standards for maize, which states that the cob must be free of heavy metals. In addition, Pb also exceeds the limits established by the Mexican NOM-247-SSA1-2008 regulation.

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Communities living near active volcanoes may be exposed to respiratory hazards from volcanic ash. Understanding their perception of the risks and the actions they take to mitigate against those risks is important for developing effective communication strategies. To investigate this issue, the first comparative study of risk perceptions and use of respiratory protection was conducted on 2003 residents affected by active volcanoes from three countries: Japan (Sakurajima volcano), Indonesia (Merapi and Kelud volcanoes) and Mexico (Popocatépetl volcano). The study was designed to test the explanatory value of a theoretical framework which hypothesized that use of respiratory protection (i.e., facemask) would be motivated by two cognitive constructs from protection motivation theory: threat appraisal (i.e., perceptions of harm/ worry about ash inhalation) and coping appraisal (i.e., beliefs about mask efficacy). Using structural equation modelling (SEM), important differences in the predictive ability of the constructs were found between countries. For example, perceptions of harm/ worry were stronger predictors of mask use in Japan and Indonesia than they were in Mexico where beliefs about mask efficacy were more important. The SEM also identified differences in the demographic variants of mask use in each country and how they were mediated by the cognitive constructs. Findings such as these highlight the importance of contextualising our understanding of protection motivation and, thus, the value of developing targeted approaches to promote precautionary behaviour.

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There are two principal sources of arsenic in Zimapán. Point sources are linked to mining and smelting activities and especially to mine tailings. Diffuse sources are not well defined and are linked to regional flow systems in carbonate rocks. Both sources are caused by the oxidation of arsenic-rich sulfidic mineralization. Point sources are characterized by Ca-SO(4)-HCO(3) ground water type and relatively enriched values of deltaD, delta(18)O, and delta(34)S(SO(4)). Diffuse sources are characterized by Ca-Na-HCO(3) type of ground water and more depleted values of deltaD, delta(18)O, and delta(34)S(SO(4)). Values of deltaD and delta(18)O indicate similar altitude of recharge for both arsenic sources and stronger impact of evaporation for point sources in mine tailings. There are also different values of delta(34)S(SO(4)) for both sources, presumably due to different types of mineralization or isotopic zonality in deposits. In Principal Component Analysis (PCA), the principal component 1 (PC1), which describes the impact of sulfide oxidation and neutralization by the dissolution of carbonates, has higher values in samples from point sources. In spite of similar concentrations of As in ground water affected by diffuse sources and point sources (mean values 0.21 mg L(-1) and 0.31 mg L(-1), respectively, in the years from 2003 to 2008), the diffuse sources have more impact on the health of population in Zimapán. This is caused by the extraction of ground water from wells tapping regional flow system. In contrast, wells located in the proximity of mine tailings are not generally used for water supply.

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