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A gestão de solos contaminados em Espanha baseia-se fundamentalmente no conceito de risco inaceitável como uma obrigação legal de proteção da saúde humana. Para realizar a análise/gestão de risco de sedimentos contaminados é necessária uma profunda caracterização físico-química e mineralógica dos materiais contaminantes à superfície e em profundidade, bem como dos processos que ocorrem nas condições de alteração atuais e futuras.O objetivo deste artigo é abordar as implicações da análise de riscos para a saúde das pessoas na tomada de decisões para a gestão de risco de um solo contaminado, de modo que o risco aceitável/inaceitável é decisivo na seleção de tecnologias de recuperação desse solo para um uso especí co. Apresenta-se um exemplo que está a ser levado a cabo na Baía de Portmán, na zona mineira de La Union (Múrcia), que constitui um dos principais pontos de contaminação minero-metalúrgica do Mar Mediterrâneo, assoreada por mais de 60 Mtm de resíduos mineiros procedentes da descarga direta de estéreis da lavaria Roberto, a maior do mundo com coluna de utuação para sulfuretos (pirita, esfalerita, galena). Os recetores mais afetados pelo uso da baía são as crianças; a via mais importante de exposição é a ingestão de partículas sólidas, tendo em conta as características do material, seguida pelas exposições percutânea e respiratória. A recuperação está planeada com base na fabricação de Tecnosolo ad hoc, de acordo com o risco detetado. The management of contaminated soils in Spain is mainly based on the concept of unacceptable risk as a legal obligation to protect human health. The analyses and management of the risks in contaminated soils involves a detailed physico-chemical and mineralogical characterisation of the contaminated materials, both at the surface and at depth, as well as of the processes that take place under current and future weathering conditions.The purposes of this paper is to study the implications of risk assessment for human health in the decision-making for managing the risk of a contaminated soil such that an acceptable/unacceptable risk be decisive in the selection of technologies for remediating said soil for a specic use.An example of remediation being undertaken in Portman Bay, located in the mining district of La Unión (Murcia, Spain), is given. As a result of the mining waste discharged directly into the bay for more than 30 years, Portman Bay became one of the most contaminated spots in the Mediterranean. From the Roberto washery (the biggest sulphate – pyrite, blende, galena – tailing washery in the world, which treated about 1000 tonnes/day), tailings were discharged by pipe directly into the western part of the bay, from where currents washed them towards the shore. During its service life, the Roberto washery discharged 60 million tonnes of tailings, made up of clay, quartz, siderite, magnetite, and the remains of sphalerite, pyrite and galena, together with metals and residues of the chemical reagents used in oatation. As a result of the dumping, the whole bay lled up with waste, which also extended into the Mediterranean Sea. The most a ected receptors in this area are children, and the most important exposure route is the intake of solid particles, followed by dermal exposure and inhalation. The remediation project is based on the production of ad hoc technosols according to the detected risk. La gestión de suelos contaminados en España pivota fundamentalmente en el concepto de riesgo inaceptable como una obligación legal de protección de la salud humana. Para llevar a cabo el análisis/gestión de riesgos de los sedimentos contaminados es necesario una profunda caracterización sicoquímica y mineralógica de los materiales contaminantes en super cie y en profundidad, así como de los procesos que tienen lugar en las condiciones de alteración actuales y futuras.El objetivo de este artículo es tratar las implicaciones que tiene el análisis de riesgos para la salud de las personas en la toma de decisiones para la gestión del riesgo de un suelo contaminado, de tal manera que el riesgo aceptable/inaceptable es decisivo en la selección de las tecnologías de recuperación de dicho suelo para un uso determinado. Se expone un ejemplo que se está llevando a cabo en la Bahía de Portmán, en el distrito minero de La Unión (Murcia), constituye uno de los mayores puntos de contaminación minero-metalúrgica del Mar Mediterráneo, colmatada por más de 60 Mt (millones toneladas) de residuos mineros procedentes de vertido directo de estériles de lavadero Roberto, el mayor lavadero de otación de sulfuros (pirita, blenda, galena) del mundo. Los receptores más afectados por el uso de la Bahía son los niños; la vía de exposición más importante es la de ingesta de partículas sólidas, dadas las características del material, seguida de la dérmica y de inhalación. La recuperación se plantea mediante la fabricación de Tecnosoles ad hoc, según el riesgo detectado.

Values of pH (1:1 extract) and concentration of different metals and arsenic in the sediments studied.

In freshly deposited sulphidic mine tailings, the pH is neutral or slightly alkaline. Due to pyrite oxidation, the pH decreases to values lower than 3 at which acidophilic iron- and sulphur-oxidizing prokaryotes prevail and accelerate the oxidation processes. Portman Bay is heavily polluted as a result of historical mining and processing activities, during which time great amounts of wastes were produced, characterised by a high potentially toxic elements (PTE) content, acidic pH and minerals resulting from supergene alteration. Three soil samples were collected from the most recent exploitation stage, stored in containers for a year and moistened simulating rainfall events. The percolates obtained were collected and naturally evaporated, obtaining three efflorescence samples. The existence of bacterial activity was evaluated by scanning electron microscopy (SEM). C15 sample is characterised by copiapite small crystals generating an homogeneous, porous mass. Inside the mass of copiapite crystals, both pyrite and gypsum were also found. In this sample, a laminae of material fills the pore space. The high carbon content shown in the spectrum of this material permits to characterise it as a biofilm. In the cross section sample of C15, a noticeable lamination of copiapite crystals has been observed, probably originated by dissolution processes. A clear limit between the lamination zone and the upper zone of the efflorescence was noticed, and here arborescent forms are developed. C17 and C18 also presented copiapite crystals, but, unlike C15, they do not present lamination and are characterized by an irregular shape and massive fabric. In C17, small crystals growing in the surface of this material were observed, generating small crusts. According to the spectrum analysis, these crusts are formed by alunogen. In C18, crystals of acicular morphology are present, and appear grouped at certain points. Therefore, out of the three natural efflorescences, biotic activity was only found in C15. This efflorescence differs significantly in morphology and fabric from samples C17 and C18. Besides the morphology, the PTEs content is also different, suggesting that chemical properties of this soil favoured the organic activity. An important factor could be related to a high iron content, since, as demonstrated in similar materials, iron performs a fundamental factor for bioinducted nucleation.

The chemistry of waters is recognized as a relevant monitoring tool when assessing the adverse effects of acid mine drainage. The weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This communication deals with the leachability of potentially toxic elements (PTE) eluting from technosols formed from soils affected by mining activities and limestone filler. A total of three contaminated soils affected by opencast mining were selected and mixed with limestone filler at three percentages: 10 %, 20 % and 30 %, providing nine stabilised samples. These samples were stored in containers and moistened simulating rainfall. The percolates obtained were collected, and the PTEs content (As, Cd, Cu, Fe, Pb and Zn) was determined. Evaporation-precipitation experiments were carried out in these waters, and the mineralogical composition of efflorescences was evaluated. The study area is heavily polluted as a result of historical mining and processing activities, producing large amount of wastes, characterised by high trace elements content and acidic pH. The results obtained for the percolates after the rain episode showed that, before the stabilization approach, waters had an acidic pH, high electrical conductivity and high PTEs content. When these soils were mixed with 10, 20 and 30 % of limestone filler, the pH was neutral and the soluble trace element content strongly decreased, being under the detection limit when limestone percentage was 20 % and 30 %. The mineralogical composition of efflorescences before the stabilisation approach showed that predominant minerals were copiapite, followed by gypsum and bilinite. Other soluble sulphates were determined in lower percentage, such as hexahydrite, halotriquite or pickeringite. After the mixing with 10 % of limestone filler, the evaporates were mainly composed by gypsum and halite. Other minerals such as starkeyite (MgSO4·4(H2O), boyleite ((Zn,Mg)SO4·4H2O), tachyhidrite (CaMg2Cl6·12H2O) or bischofite (MgCl2) were quantified in low percentages. After mixing with 20 % and 30 % of limestone filler, main minerals were gypsum and halite, the presence of other phases being scarce. The addition of limestone filler to soils polluted by potentially toxic elements represents a useful and low impact strategy for reducing the soluble fractions of As, Cd, Cu, Fe, Pb and Zn. M.H.C. acknowledges the financial support of the Comunidad Autonóma de la Región de Murcia , Spain (Fundación Séneca, 19888/GERM/15)

The Sierra Minera of Cartagena-La Union is located in the Region of Murcia, Southeast of Spain. This zone presents high levels of heavy metals due to natural, geogenic reasons. In addition, the prolonged mining activity, and subsequent abandonment of farms, has had consequences on the environment, including severe affectation of the groundwater in the area. To remediate this situation, the Permeable Reactive Barrier (PRB) technology was assayed, which required in addition to the hydro-geological study of the zone, a careful optimization study for the design and construction of PRBs. For such a purpose a pilot-scale project was developed, and this communication reports some of the most relevant findings obtained after a four-years monitorization period. The selected reactive material for the PRBs was limestone filler. The filler is a waste material produced in many factories in the zone. These residues have good adsorption properties, high alkalinity, low cost and high availability, which make them suitable for use in remediation. The PRB was constituted by a 50% limestone filler and 50% sand, a proportion optimized by means of independent batch experiments. A layer of gravel was placed at the top, and on it a layer of natural soil. The barrier was designed in the form of a continuous trench, because the level of the contaminated groundwater was not very deep. In this way, the barrier could be prepared with standard excavation equipment. Parallel to the barrier, 6 wells where arranged downstream for sample collection. The pH and conductivity of the samples was measured directly in situ, and the content of Zn, Cd, Cu, Fe, and Pb were analyzed in the laboratory. All the samples collected after the PRB was constructed had basic pH values between 7.5 and 8. The conductivity was between 5 and 11 mS / cm except for the well 4, which had a value of 3.70 mS / cm. The concentration values of trace elements were below the detection limit (atomic absorption measurement) in most of cases, or showed values below normal levels of the area. Our results prove that limestone filler is suitable as the active component of PRBs barriers for sites polluted by trace elements. Following this relatively simple technology, there is no risk for human health or ecosystem, and a big cost-saving can be obtained in projects focused to the remediation of areas affected by mining activities.

Sediments from the Castilseras reservoir, located downstream of the Valdeazogues River in the Almadén mercury district were collected to assess the total mercury content associated with river sediment input from several decommissioned mines. A geochemical characterization, including the determination of total mercury content, were investigated using different physical and chemical techniques. The results obtained suggested that sediments are slightly acidic and characterized by high mercury, related to mining activities. In addition, sediments showed a silty texture and the electrical conductivity results showed moderate salinity, related to acid mine drainage (AMD) processes. The multivariate statistical analysis suggested that mercury content is positively correlated with the silt fraction in collected samples. In regard to the obtained results, we can conclude that Castilseras is one of the reservoirs with the highest mercury concentration, as a result of mining activities carried out in the zone. In this reservoir, the mercury content is diluted downstream.