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UPC: C/ Jordi Girona 31, (08034 - Barcelona) - IDAEA: C/ Jordi Girona 18-26, (08034 - Barcelona)

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Hydrozincite and Brianyoungite precipitation in an abandoned Zn-Pb mine in the Spanish Pyrenees: implications for natural attenuation of heavy metals

Ponente: Max Giannetta (IDAEA)

Lugar: Departamento de Ing. Civil, D2 Planta Baja Aula 001

Título: Hydrozincite and Brianyoungite precipitation in an abandoned Zn-Pb mine in the Spanish Pyrenees; implications for natural attenuation of heavy

metals

Abstract:

The Victoria Mine is located the Aran Valley, Spain, and was active until approximately 1950 when it was abandoned. The underground mine targeted mineral deposits comprised of mostly sphalerite (ZnS). Today the relict tunnels and shafts are exposed to air and flowing water prompting oxidative dissolution of the mineral deposits and microbial activity. A sampling campaign into one of the mining tunnels shows a trend of increasing dissolved metal concentrations (e.g. Cd change from 28 to 20 ppb) as a function of distance from the entrance (i.e. decreasing downgradient). White precipitates are prevalent throughout the tunnel galleries and preliminary XRD analysis results suggest that Hydrozincite and Brianyoungite are the predominant minerals. This is an indication of partial uptake of harmful metals (e.g. Cd, Ni, Li, Ti, Zn) into the crystal structure of the white precipitates, thus decreasing the mobility of the dissolved metals. The formation of these minerals may be a result of biomineralization, though further investigation is required. Moreover, microbially mediated processes (e.g. Fe oxidation and Mn oxidation) exhibited in the tunnel may contribute to the rate of ZnS dissolution. Eventually, this flowing water, still containing elevated metal concentrations, exits from the lowermost mining gallery and reconnects with the associated catchment system.

As a comparison, one of the abandoned Zn-Pb ore processing facilities in a neighboring catchment, known as Pontaut, was also sampled for dissolved metals. Rain water filters through the tailings dumps and flotation ponds before leaving the site. Here, there was no evidence of secondary white precipitates, and dissolved metal concentrations were elevated beyond that of the Victoria Mine tunnel (e.g. 127 ppb Cd).

Notably, the concentration of dissolved metals increases down gradient, contrary to the behavior of the Victoria Mine tunnel gallery. Preliminary geochemical modeling of the fluids at both sites suggest that the formation of Hydrozincite and Brianyoungite is less likely to occur at the processing facility due to lower alkalinity in comparison to the fluid in the mine. A result of this comparison between sites, we propose that the secondary mineral precipitation is helping to remediate some of the heavy metal contaminants. Both sites exhibit heavy-metal discharge concentrations above the MCL creating a risk for nearby plant and animal life. Two mushroom species in the Pontaut site, Amanita muscaria and Macrolepiota procera, were found to have dangerous Cd levels of 112 +/- 8 and 90 +/- 11 ppm, respectively. Eventually both systems flow into the Garonne River, however these concentrations are diluted to safe levels after mixing with the river.

Hydrozincite and Brianyoungite precipitation in an abandoned Zn-Pb mine in the Spanish Pyrenees; implications for natural attenuation of heavy metals  

Seminario Grupo de Hidrologia Subterranea. Unidad Asociada UPC-CSIC 

 

Seminario impartido por: Max Giannetta (IDAEA)

Dia: Jueves 30 de Enero a las 12:15

Lugar: Departamento de Ing. Civil (D2-Aula 001)

 

Abstract:

The Victoria Mine is located the Aran Valley, Spain, and was active until approximately 1950 when it was abandoned. The underground mine targeted mineral deposits comprised of mostly sphalerite (ZnS). Today the relict tunnels and shafts are exposed to air and flowing water prompting oxidative dissolution of the mineral deposits and microbial activity. A sampling campaign into one of the mining tunnels shows a trend of increasing dissolved metal concentrations (e.g. Cd change from 28 to 20 ppb) as a function of distance from the entrance (i.e. decreasing downgradient). White precipitates are prevalent throughout the tunnel galleries and preliminary XRD analysis results suggest that Hydrozincite and Brianyoungite are the predominant minerals. This is an indication of partial uptake of harmful metals (e.g. Cd, Ni, Li, Ti, Zn) into the crystal structure of the white precipitates, thus decreasing the mobility of the dissolved metals. The formation of these minerals may be a result of biomineralization, though further investigation is required. Moreover, microbially mediated processes (e.g. Fe oxidation and Mn oxidation) exhibited in the tunnel may contribute to the rate of ZnS dissolution. Eventually, this flowing water, still containing elevated metal concentrations, exits from the lowermost mining gallery and reconnects with the associated catchment system. As a comparison, one of the abandoned Zn-Pb ore processing facilities in a neighboring catchment, known as Pontaut, was also sampled for dissolved metals. Rain water filters through the tailings dumps and flotation ponds before leaving the site. Here, there was no evidence of secondary white precipitates, and dissolved metal concentrations were elevated beyond that of the Victoria Mine tunnel (e.g. 127 ppb Cd). Notably, the concentration of dissolved metals increases down gradient, contrary to the behavior of the Victoria Mine tunnel gallery. Preliminary geochemical modeling of the fluids at both sites suggest that the formation of Hydrozincite and Brianyoungite is less likely to occur at the processing facility due to lower alkalinity in comparison to the fluid in the mine. A result of this comparison between sites, we propose that the secondary mineral precipitation is helping to remediate some of the heavy metal contaminants. Both sites exhibit heavy-metal discharge concentrations above the MCL creating a risk for nearby plant and animal life. Two mushroom species in the Pontaut site, Amanita muscaria and Macrolepiota procera, were found to have dangerous Cdlevels of 112 +/- 8 and 90 +/- 11 ppm, respectively. Eventually both systems flow into the Garonne River, however these concentrations are diluted to safe levels after mixing with the river.

 

First calculation for a denitrification bioreactor in Kiruna mine, Sweden (NITREM Project: Nitrogen REMoval from waste rocks)

Seminario Grupo de Hidrologia Subterranea. Unidad Asociada UPC-CSIC

 

LURDES MARTINEZ LANDA - Investigadora UPC

 

Dia y Hora:Jueves 23 de Enero a las 12:15 h

Lugar: Departamento de Ingeniería Civil y Ambienta, Modulo D2-Aula CIHS, Planta Baja

 

Abstract:
The source of most of nitrogen cycling at an iron mine site is the ammonium nitrate – based explosives used in the excavation of the mine. Waste rock, often contains adsorbed nitrogen compounds (ammonium and nitrate) as a residues from the detonation of the explosives. Once the waste rock is deposited on the ground surface, the percolation of rain and snow-melt through the deposit will leach the nitrogen compounds, potentially impacting local recipients.
NITREM’s bioreactor technology removes nitrogen (in the form of nitrate) from the waste rock leachate. A microbial process occurs in the bioreactor, where denitrifying bacteria reduce dissolved nitrate in the treated water to harmless nitrogen gas.
In this presentation we show the results of a conservative transport test to know travel times along bioreactors and, identifying the main processes that take into account during the transport processes. The results of this work will be the base of the future reactive transport models.

Towards radium endmember characterization in the Maresme coast using column and batch experiments

a cargo de:Laura Martinez. Ph D Student

Día: Jueves 09 de Gener a las 12:15 h

Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:

Radium isotopes (223Ra, 224Ra, 226Ra, 228Ra) are one of the most widely tracers used to quantify submarine groundwater discharge (SGD) in open seas. SGD calculations are often based on the ratio of isotopic activities measured offshore and inland. While the former entails intensive sampling campaigns, the latter usually relies on painless sampling that mainly involves measuring in a preexisting well to asses the inputs, assuming that it will be representative of the radionuclide distribution in the aquifer. A proper characterization that takes into account geological heterogeneity and effects of the mixing zone, is still scarce and needed to better determine the representative radium endmember in coastal aquifers.

To identify the main aspects governing radium release in the fresh-saline water interface, we have performed a set of experiments. We use different types of sediments obtained from an experimental site located in an anthropized area northern Barcelona (Spain), few meters from the discharge of the Argentona ephemereal stream to the sea. This site is particularly interesting because it is surrounded by granitic outcrops that provides sources for Ra isotopes due to weathering and recoil, and numerous geophysical, hydrogeological and hydrochemical techniques are being carried out to characterize the coupled effects of SGD and seawater intrusion (SWI) in an alluvial coastal aquifer.

Sediment samples were taken from different depths of the alluvial aquifer of Argentona corresponding to the fresh-, mixing- and saltwater zones, respectively. Several batch and column experiments were performed using different solid/liquid ratios, fluid and sediment grain sizes. We studied the behaviour of radium activity with variable salinity: percolation at constant salinity, percolation at increasing salinity to simulate a SWI event and at decreasing salinity to mimic a freshening event. A 1D model was also implemented and represented well the SWI event.

The jigsaw analysis is still in process, but it will contribute to understand the results obtained in the radium filed sampling campaigns performed in the frame of MEDISTRAES project.

Reactive Transport modeling of Emerging Organic Contaminants (EOCs) and inorganic nutrients in columns simulating MAR fed with treated wastewater

a cargo de: Arnau Canelles. Ph D Student

Fecha: Jueves 05 de Diciembre a las 12:15 h

Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja

Abstract:

A reactive transport model has been performed for a set of laboratory columns simulating degradation of nutrients and EOCs through different MAR scenarios using treated wastewater. The experiments were constructed in a way that some reactive barriers were amended with organic carbon source (vegetable compost) in order to serve as source of nutrients and electron donor to the system and enhance redox reactions. This design simulated a potential reactive layer situated in the bottom of an infiltration pond. Three different scenarios for the reactive barrier have been modelled, with the sand-based barrier amended with: 0%, 10% and 50% compost.

 

The main geochemical processes modelled were aerobic degradation of organic matter, nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and nutrient release from compost. Most of these processes imply a Monod kinetic model using the experimental data to fit the different degradation constants and parameters. Once the main geochemical processes were modelled, we coupled them with the degradation of EOCs considering a co-metabolic degradation. It was observed that different reactive barrier compositions implied different kinetic rates of nutrients and EOCs degradation, with different kinetic processes present depending on the reactive barrier composition. The dynamics of the nutrient degradation showed changes in the EOCs degradation dynamics as well.

 

In addition, the hydrological model of the different column settings was developed using a double porosity model. This flow model showed that hydraulic properties of the column experiments changed during the experiment, suggesting significant development of a biofilm showing a reduction of porosity, increase of immobile region porosity and increase of heterogeneity. In addition, it has been observed that there is a relation between barrier composition, flow properties change, and degradation mechanics which show that a certain composition of a reactive barrier during MAR can significantly affect the degradation of nutrients and EOCs.

 

THE EFFECT OF IONIC STRENGTH ON DIFFUSION IN CLAY. MODELING SOLUTE TRANSPORT AND RETENTION IN THE DR-A EXPERIMENT AT MONT TERRI.

SEMINARIO GRUPO DE HIDROLOGIA SUBTERRÁNEA  (UPC-CSIC)

 

A cargo de: Josep Soler (Investigador CSIC) 

Día y hora: Jueves 28 de noviembre a las 12:15 h

Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja


Abstract:

In the DR-A experiment (Mont Terri, CH), synthetic porewater (NaCl-dominated, I=0.36) was circulated through a borehole for 189 days, leading to the out-diffusion of several tracers into the Opalinus Clay. The solution was then replaced with a higher-salinity solution (0.50 M NaCl + 0.56 M KCl) and circulated for another 540 days, leading to the diffusion of Cs+, Ca2+, Mg2+ and Sr2+ back into the borehole and to an increase in the out-diffusion of I-, Br- and 3H (HTO). These results were interpreted using the CrunchClay code, which includes a mean electrostatic potential model for the Electric Double Layer. Species-specific diffusion (Nernst-Planck) occurs through both bulk and EDL porosities. A 1D radial model considered a single pore diffusion coefficient (Dp=10-9 m2/s) for cations and HTO in the bulk porosity, and a smaller Dp (3×10-10 m2/s) for anions. Dp values in the EDL were smaller (10-11 m2/s), except for K+ and Cs+ (2×10-10 and 5×10-10 m2/s). Well-established multisite cation exchange was used to calculate sorption of cations on the clay.

The model reproduced the experimental results well. The increase in ionic strength caused a decrease in the EDL porosity and a consequent increase in the out-diffusion of I-, Br- and HTO. High K+ caused the displacement of Cs+, Ca2+, Mg2+ and Sr2+ from the exchange complex. The calculated tracer distribution profiles in the rock were consistent with measurements. Differences in Dp between bulk and EDL porosities may be caused by the different geometries of the diffusion pathways near the clay surfaces (EDL) and those in the centers of the pores (bulk). Pore throats where EDLs from opposite walls overlap may be the reason for the smaller Dp values for anions in the bulk porosity.

The model has shown the capability to consider changes in conditions affecting important radionuclide contaminants (e.g. 137Cs+90Sr2+129I-). Coupled multicomponent diffusion together with the electrostatic properties of the charged surfaces are essential in the development of predictive models for ion transport in clays.

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