Assessment of the ecological risk and mobility of arsenic and heavy metals in soils and mine tailings from the Carmina mine site (Asturias, NW Spain).

An evaluation of the pollution, distribution, and mobility of arsenic and heavy metals in spoil heaps and soils surrounding the abandoned Carmina lead-zinc mine (Asturias, northern Spain) was carried out. Fractionation of arsenic was performed by an arsenic-specific sequential extraction method; while, heavy metal fractionations was carried out using the protocol of the Bureau Community of Reference (BCR) (now renamed Standards, Measurements and Testing Programme). Arsenic appeared predominantly associated with amorphous iron oxyhydroxides. Among the heavy metals, lead and zinc showed high availability since significant amounts were extracted in the nonresidual fractions; whereas, chromium, copper and nickel showed very low availability, indicating their lithogenic origins. The results showed that the extractability of heavy metals in soils is influenced mainly by the presence of iron and manganese oxides as well as by pH and Eh. Multiple pollution indices, including the enrichment factor (EF), geoaccumulation index (Igeo), ecological risk index (Er) and potential ecological risk index (PERI), were used to assess the degree of soil pollution in the mine area. All results showed that lead was the key factor causing the pollution and ecological risk in the studied area, and copper, zinc and arsenic also had significant contributions. Notably, the sites at higher risk coincided with those with high availability of arsenic and heavy metals. This study provides an integrative approach that serves as a powerful tool to evaluate the metal pollution status and potential threats to the local environment of abandoned mining areas, and the results are useful for making management decisions in these areas.

Bioaccumulation of Non-Essential Trace Elements Detected in Women's Follicular Fluid, Urine, and Plasma Is Associated with Poor Reproductive Outcomes following Single Euploid Embryo Transfer: A Pilot Study.

This study aims to determine the association of non-essential trace elements present in follicular fluid, plasma, and urine with reproductive outcomes of women undergoing intracytoplasmic sperm injection (ICSI), preimplantation genetic testing for aneuploidies (PGT-A) and single frozen euploid embryo transfer (SET/FET). This single-center, prospective cohort study included sixty women undergoing ICSI with PGT-A and SET/FET between 2018 and 2019. Urine, plasma and follicular fluid samples were collected on the vaginal oocyte retrieval day to simultaneously quantify ten non-essential trace elements (i.e., Ba, Sr, Rb, Sn, Ti, Pb, Cd, Hg, Sb, and As). We found several associations between the levels of these non-essential trace elements and clinical IVF parameters. Specifically, the increased levels of barium in follicular fluid were negatively associated with ovarian function, pre-implantation development and embryo euploidy, while elevated strontium concentrations in this biofluid were negatively associated with impaired blastulation and embryo euploidy. Elevated plasma strontium levels were negatively associated with ovarian function, fertilization and blastulation. Enhanced presence of other trace elements in plasma (i.e., rubidium and arsenic) were associated with a diminished ovarian function and limited the number of recovered oocytes, mature oocytes and zygotes, respectively. Fully adjusted models suggested significantly lower odds of achieving a live birth when increased concentrations of barium and tin were found in urine.

Arsenic partitioning among particle-size fractions of mine wastes and stream sediments from cinnabar mining districts.

Tailings from abandoned mercury mines represent an important pollution source by metals and metalloids. Mercury mining in Asturias (north-western Spain) has been carried out since Roman times until the 1970s. Specific and non-specific arsenic minerals are present in the paragenesis of the Hg ore deposit. As a result of intensive mining operations, waste materials contain high concentrations of As, which can be geochemically dispersed throughout surrounding areas. Arsenic accumulation, mobility and availability in soils and sediments are strongly affected by the association of As with solid phases and granular size composition. The objective of this study was to examine phase associations of As in the fine grain size subsamples of mine wastes (La Soterraña mine site) and stream sediments heavily affected by acid mine drainage (Los Rueldos mine site). An arsenic-selective sequential procedure, which categorizes As content into seven phase associations, was applied. In spite of a higher As accumulation in the finest particle-size subsamples, As fractionation did not seem to depend on grain size since similar distribution profiles were obtained for the studied granulometric fractions. The presence of As was relatively low in the most mobile forms in both sites. As was predominantly linked to short-range ordered Fe oxyhydroxides, coprecipitated with Fe and partially with Al oxyhydroxides and associated with structural material in mine waste samples. As incorporated into short-range ordered Fe oxyhydroxides was the predominant fraction at sediment samples, representing more than 80% of total As.

Toxic Effects of Different Coating-Related Functionalized Nanoparticles on Aquatic Organisms.

The peculiar physico-chemical characteristics of nanomaterials (NMs) and the use of different coatings to improve their expected properties result in a huge amount of nanoforms, which vary in chemical composition, size, shape and surface characteristics. This makes it almost impossible to test all the nanoforms available, and efforts have been made to establish grouping or read-across strategies. The aim of this work was to find a behavior pattern of effect among nanoforms of different metallic core nanoparticles (NPs) (TiO2, CeO2 and Ag NP) with the same coatings (sodium citrate, poly (ethylene glycol), dodecylphosphonic acid or oleylamine). Daphnia magna, rainbow trout and two fish cell lines (PLHC-1 and RTH-149) were exposed to a range of concentrations (up to 100 mg/L) of the uncoated or coated NPs. Ag NPs were the most toxic, followed by CeO2 NPs and finally by TiO2 NPs. The results show that a clear pattern of toxicity in the studied species could not be established related to the coatings. However, it was possible to confirm different inter-species sensitivities. RTH-149 was the most sensitive cell line, and Daphnia magna was more sensitive than fish. Moreover, some differences in coating-core interactions were found between the metal oxide and the metal NPs in Daphnia magna.

Carbon-based thin films as a suitable alternative to metallized films for the preparation of radioactive sources.

A new method for radionuclide labeling by the use of graphene thin films was previously presented. In this work, a comparison among low energy radioactive sources supported on carbonaceous thin films on polyvinyl chloride-polyvinyl acetate copolymer (VYNS), based on the use of aqueous solutions is investigated as a feasible alternative to the traditional metallized films avoiding the downside of the loss of many broken films. Graphene-based materials were prepared by both oxidation-exfoliation-reduction and direct graphite exfoliation routes. In addition, multiwalled carbon nanotubes (MWCNTs) thin films were also evaluated. The stability of both carbonaceous materials aqueous dispersions were studied by using ionic and non-ionic surfactants. Solid carbon-based materials were characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) whereas the colloidal nature of the aqueous dispersions was verified by the measurement of Tyndall effect and the morphology of thin films was evaluated by Scanning Electron Microscopy (SEM). 55Fe solutions were used to prepare the radioactive sources on the thin films by quantitative drop deposition. The quality of spectra was measured in a pressurized proportional counter. Results showed a resolution higher than 0.9 keV for all the tested sources. However, MWCNT-based along with non-surfactant sources presented non-adequate escape peaks and low energy tails. On the contrary, all the graphene-based sources prepared using surfactants to stabilize aqueous solutions presented an energy resolution comparable to that of the metallized source while offering notable advantages in terms of cost efficiency and reliability of the as-prepared supports.

Assessment of a sequential extraction method to evaluate mercury mobility and geochemistry in solid environmental samples.

The development of a sequential extraction method for mercury in solid environmental samples is presented. The scheme recognizes and quantifies four major phase associations of mercury: "Labile mercury species", "Hg bound to humic and fulvic complexes", "elemental Hg and bound to crystalline oxides" and "Hg sulfide and refractory species". Model solids were used in this study to evaluate different extracting solutions and to determine optimum extraction conditions. Sequential and single-step extractions were conducted to evaluate the interaction among the successive steps. Different variables such as extractant concentration, time, temperature and number of extractions were optimized for each stage when necessary. The selectivity of the selected extractions was assured through experiments with natural and synthetic matrices of some specific Hg-bearing phases. The suitability of the proposed method was evaluated by using four certified reference materials from different Hg sources, physicochemical properties and total Hg content (from 0.3µgg(-1) to 33µgg(-1)). Recovery of total Hg by the sum of fractions in reference materials showed that the accuracy of the method ranges from 85 percent to 105 percent.

Ozone and Temperature May Hinder Adaptive Capacity of Mediterranean Perennial Grasses to Future Global Change Scenarios.

Climate warming is recognized as a factor that threatens plant species in Mediterranean mountains. Tropospheric ozone (O3) should also be considered as another relevant stress factor for these ecosystems since current levels chronically exceed thresholds for plant protection in these areas. The main aim of the present study was to study the sensitivity of four Mediterranean perennial grasses to O3 and temperature based on plant growth, gas exchange parameters (photosynthesis-A, stomatal conductance-gs, and water use efficiency-WUE), and foliar macro- (N, K, Ca, Mg, P, and S) and micronutrients (B, Cu, Fe, Mn, Mo, and Zn) content. The selected species were grasses inhabiting different Mediterranean habitats from mountain-top to semi-arid grasslands. Plants were exposed to four O3 treatments in Open-Top chambers, ranging from preindustrial to above ambient levels, representing predicted future levels. Chamber-less plots were considered to study the effect of temperature increase. Despite the general tolerance of the grasses to O3 and temperature in terms of biomass growth, WUE and foliar nutrient composition were the most affected parameters. The grass species studied showed some degree of similarity in their response to temperature, more related with phylogeny than to their tolerance to drought. In some species, O3 or temperature stress resulted in low A or WUE, which can potentially hinder plant tolerance to climate change. The relationship between O3 and temperature effects on foliar nutrient composition and plant responses in terms of vegetative growth, A, gs, and WUE constitute a complex web of interactions that merits further study. In conclusion, both O3 and temperature might be modifying the adaptation capacity of Mediterranean perennial grass species to the global change. Air pollution should be considered among the driving favors of biodiversity changes in Mediterranean grassland habitats.

Bioaccumulation of CuO nanomaterials in rainbow trout: Influence of exposure route and particle shape.

The bioaccumulation potential of spherical and rod-shaped CuO nanomaterials (NMs) was assessed in rainbow trout (Oncorhynchus mykiss) exposed via water and diet following the OECD Test Guideline No. 305. Fish were exposed via diet to both NMs at concentrations of 70 and 500 mg Cu/kg for 15 days, followed by 44 days of depuration. For water-borne exposure, only the rod-shaped CuO NMs were tested at 0.08 and 0.8 mg Cu/L for 28 days, followed by 14 days of depuration. The concentration of Cu was determined in fish whole body to derive biomagnification and bioconcentration factors (BMF and BCF). Different tissues were sampled to investigate the total Cu biodistribution and target organs as well as the particle number-based bioaccumulation of CuO NMs. Estimated BMF and BCF values were below the thresholds of concern. However, shape and route influenced depuration. Following dietary exposure, there was a higher depuration of Cu from fish exposed to the rod-shaped compared to the spherical CuO NMs. A higher depuration was also observed for rod-shaped CuO NMs following the dietary exposure compared the aqueous one. Despite the much higher dietary exposure concentrations of rod-shape CuO NMs, similar Cu body burdens were reached via water. Cu was found in particulate form in different tissues. Although these NMs had a low bioaccumulation potential, differences in distribution and elimination patterns of Cu were observed depending on the exposure route and particle shape. Careful consideration of the most relevant exposure route is needed when designing a bioaccumulation experiment for testing NMs.

Comparison of Thermal and Laser-Reduced Graphene Oxide Production for Energy Storage Applications.

A way to obtain graphene-based materials on a large-scale level is by means of chemical methods for the oxidation of graphite to obtain graphene oxide (GO), in combination with thermal, laser, chemical and electrochemical reduction methods to produce reduced graphene oxide (rGO). Among these methods, thermal and laser-based reduction processes are attractive, due to their fast and low-cost characteristics. In this study, first a modified Hummer's method was applied to obtain graphite oxide (GrO)/graphene oxide. Subsequently, an electrical furnace, a fusion instrument, a tubular reactor, a heating plate, and a microwave oven were used for the thermal reduction, and UV and CO2 lasers were used for the photothermal and/or photochemical reduction. The chemical and structural characterizations of the fabricated rGO samples were performed by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy measurements. The analysis and comparison of the results revealed that the strongest feature of the thermal reduction methods is the production of high specific surface area, fundamental for volumetric energy applications such as hydrogen storage, whereas in the case of the laser reduction methods, a highly localized reduction is achieved, ideal for microsupercapacitors in flexible electronics.

Comparison of three sequential extraction procedures for fractionation of arsenic from highly polluted mining sediments.

Three sequential extraction procedures were evaluated for the study of fractionation of arsenic in environmental solid samples. The procedures considered were as follows: i) the standardized and widely recognised BCR procedure, conceived for the study of the partitioning of heavy metals; ii) the procedure developed by Manful, who adapted a phosphorus scheme for arsenic fractionation; and iii) a novel sequential extraction scheme especially devised for arsenic. The efficiency and suitability of these methods and the corresponding extraction steps for partitioning arsenic obtained from the most important solid forms were tested by application of the methods to real sediment samples heavily polluted by mining activity. Results showed the BCR scheme was inappropriate for arsenic fractionation. The procedure could, nevertheless, be a first approach for the assessment of arsenic partitioning, because its first extraction step can be regarded as adequate for the estimation of the most easily mobilizable arsenic. Although the Manful scheme results in a more differentiated arsenic pattern, some drawbacks arise from the lack of selectivity of some of the reagents used, for example overlapping of specific target phases, overestimation of adsorbed arsenate because of inadequate coprecipitation processes, and the inability to discriminate among amorphous and crystalline oxyhydroxides which are mainly responsible for arsenic retention. The novel procedure achieves the most suitable arsenic fractionation, because the main phases retaining arsenic are selectively targeted according to mobilization potential. In addition, the simplicity of its extraction steps would enable automation in a continuous flow scheme.

Arsenic contamination and speciation in surrounding waters of three old cinnabar mines.

The impact of arsenic pollution in waters from the surroundings of three abandoned Hg mines in Northern Spain, as well as reaching the Caudal River, was evaluated. For assessing the factors controlling arsenic release, an extensive study based on the physicochemical characterization and multivariate statistical analysis of waters upstream and downstream each mine site was performed. Waters downstream of the La Soterraña mine present the highest arsenic concentrations, up to 38.8 mg L(-1), coming mainly from the solubilisation of calcium, magnesium and strontium arsenates at a pH close to neutral. Although arsenic concentrations downstream of La Peña are markedly lower, these values remain too high, indicating that the encapsulation carried out in this spoil heap is insufficient. In addition, the high water flow in this point involves an extremely high input of arsenic to the surroundings (0.3 g s(-1)). Waters close to tailings from Los Rueldos suffer from acid mine drainage, provoking an important solubilisation of arsenic and heavy metals, a situation which is rapidly softened with distance. The study of arsenic speciation reveals the omnipresence of As(v) in waters from the three mines, whereas in La Peña low amounts of As(iii) were also detected. Different preservation methods for As speciation were compared, such as the addition of HCl, EDTA and the storage of samples without any additive, and no alteration of samples in any case up to nine months after the collection was observed. A study of seasonal variations of As and the main parameters affecting its concentration and speciation was completed throughout a year, showing no remarkable dependency with rainfall for any studied variable.

Preparation of feed with metal oxide nanoparticles for nanomaterial dietary exposure to fish and use in OECD TG 305.

The first step of nanomaterial accumulation in the aquatic environment is the uptake of particulate material. For substances with very low water solubility, exposure via water may be of limited relevance in comparison to the dietary route. The OECD Test Guideline 305 for bioaccumulation testing in fish using dietary exposure recommends to add substances to fish food following methodologies normally used in aquaculture (e.g. with a corn or fish oil vehicle). The feasibility of using such an approach for the testing of manufactured nanomaterials (MNs), due to their unique physical characteristics and solubility, needs to be investigated. In this study an easy, cost-effective method to prepare metal oxide nanoparticle (NP) spiked feed to give the required dietary exposure concentration to fish is described. Metal oxide NP (CeO2,TiO2 and ZnO) dispersions were prepared in oil (sunflower or olive oil) and used to soak fish feed pellets. NP surface deposition and homogeneity of distribution were analysed and confirmed. Discrepancies between nominal and measured concentrations highlighted the need to measure the achieved concentration in MN-spiked feed. The present method provides stable concentrations for bioaccumulation testing of MNs in fish through the dietary route. A method for•Fish feed preparation using nanomaterial-oil suspensions.•Homogenous spiking of nanomaterials on feed.•Nanomaterials stably maintained on feed immersed in water until eaten by fish.

Deuterium Adsorption on Free-Standing Graphene.

A suitable way to modify the electronic properties of graphene-while maintaining the exceptional properties associated with its two-dimensional (2D) nature-is its functionalisation. In particular, the incorporation of hydrogen isotopes in graphene is expected to modify its electronic properties leading to an energy gap opening, thereby rendering graphene promising for a widespread of applications. Hence, deuterium (D) adsorption on free-standing graphene was obtained by high-energy electron ionisation of D2 and ion irradiation of a nanoporous graphene (NPG) sample. This method allows one to reach nearly 50 at.% D upload in graphene, higher than that obtained by other deposition methods so far, towards low-defect and free-standing D-graphane. That evidence was deduced by X-ray photoelectron spectroscopy of the C 1s core level, showing clear evidence of the D-C sp3 bond, and Raman spectroscopy, pointing to remarkably clean and low-defect production of graphane. Moreover, ultraviolet photoelectron spectroscopy showed the opening of an energy gap in the valence band. Therefore, high-energy electron ionisation and ion irradiation is an outstanding method for obtaining low defect D-NPG with a high D upload, which is very promising for the fabrication of semiconducting graphane on large scale.

Acute toxic effects caused by the co-exposure of nanoparticles of ZnO and Cu in rainbow trout.

The toxic effects produced by the co-exposure to low- and non-toxic concentrations of zinc oxide (ZnONPs) and copper nanoparticles (CuNPs) was assessed in rainbow trout following the OECD Test Guideline 203. Four groups of trouts were exposed for 96 h to a range of concentrations (0.0425-0.34 mg/L) of CuNPs (50 nm) in combination with a fixed non-toxic concentration (1.25 mg/L) of ZnONPs (25 nm) determined from an independent concentration-response study. One additional group was exposed to the highest concentration of CuNPs alone. Behaviour and mortality were observed during the experiment. After 96 h exposure, accumulated levels of Cu and Zn in the fish were measured by ICP-MS and ICP-OES, respectively. The induction of oxidative stress in liver and gills was evaluated by the glutathione-S-transferase (GST) activity and the reduced glutathione (GSH) / oxidized glutathione (GSSG) ratio. The ethoxyresorufin-O-deethylase (EROD) activity was also assessed. The results showed that CuNPs at the highest tested concentration do not cause acute toxicity, whereas exposure to all mixtures caused mortality, which was inversely proportional to the concentration of CuNPs (from 28% to 86% survival). Accumulated levels of Cu and Zn in the fish increased with the increasing concentrations of CuNPs, suggesting that the presence of CuNPs favours the entry of Zn. In general, the GST activity increased significantly in the gills of co-exposed groups, whereas the GSH/GSSG ratio was altered in the liver. The EROD activity was not modified. In conclusion, the co-exposure to these NPs potentiates their toxicity, observing an alteration of the GST activity and GSH/GSSG ratio in gill and liver, which was more pronounced at the lowest concentration of CuNPs. The lower toxic effect observed with the highest concentrations of CuNPs coincides with a greater internalization of Zn.

Preparation of graphene thin films for radioactive samples.

A new method for the preparation of conductive thin films is presented. The metallization of VYNS films guarantees the electrical conductivity but it results in the breaking of a high proportion of them. Graphene, a two-dimensional nanostructure of monolayer or few layers graphite has attracted a great deal of attention because of its excellent properties such as a good chemical stability, mechanical resistance and extraordinary electronic transport properties. In this work, the possibilities of graphene have been explored as a way to produce electrical conductive thin films without an extra metallization process. The procedure starts with preparing homogenous suspensions of reduced graphene oxide (rGO) in conventional VYNS solutions. Ultra-sonication is used to ensure a good dispersibility of rGO. Graphene oxide (GO) is prepared via oxidation of graphite and subsequent exfoliation by sonication. Different chemically rGO were obtained by reaction with hydrazine sulfate, sodium borohydride, ascorbic acid and hydroiodic acid as reducing agents. The preparation of the thin graphene films is done in a similar way as the conventional VYNS foil preparation procedure. Drops of the solution are deposited onto water. The graphene films have been used to prepare sources containing some electron capture radionuclides ((109)Cd, (55)Fe, (139)Ce) with an activity in the order of 3kBq. The samples have been measured to test the attainable low energy electron efficiency and the energy resolution of Auger and conversion electrons by 4π (electron capture)-γ coincidence measurements. The 4π (electron capture)-γ coincidence setup includes a pressurized proportional counter and a NaI(Tl) detector. Tests with different pressures up to 1000kPa were carried out. All these tests show similar values in both parameters (efficiency and resolution) as those obtained by using the conventional metallized films without the drawback of the high percentage of broken films.

Determination of rare earth and concomitant elements in magnesium alloys by inductively coupled plasma optical emission spectrometry.

An Inductively Coupled Plasma Optical Emission Spectrometry method for simultaneous determination of Al, Ca, Cu, Fe, In, Mn, Ni, Si, Sr, Y, Zn, Zr and rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in magnesium alloys, including the new rare earth elements-alloyed magnesium, has been developed. Robust conditions have been established as nebulizer argon flow rate of 0.5mLmin(-1) and RF incident power of 1500W, in which matrix effects were significantly reduced around 10%. Three acid digestion procedures were performed at 110°C in closed PFA vessels heated in an oven, in closed TFM vessels heated in a microwave furnace, and in open polypropylene tubes with reflux caps heated in a graphite block. The three digestion procedures are suitable to put into solution the magnesium alloys samples. From the most sensitive lines, one analytical line with lack or low spectral interferences has been selected for each element. Mg, Rh and Sc have been studied as internal standards. Among them, Rh was selected as the best one by using Rh I 343.488nm and Rh II 249.078nm lines as a function of the analytical lines. The trueness and precision have been established by using the Certified Reference Material BCS 316, as well as by means of recovery studies. Quantification limits were between 0.1 and 9mgkg(-1) for Lu and Pr, respectively, in a 2gL(-1) magnesium matrix solution. The method developed has been applied to the commercial alloys AM60, AZ80, ZK30, AJ62, WE54 and AE44.

Total mercury, organic mercury and mercury fractionation in soil profiles from the Almadén mercury mine area.

Soil profiles located in the mining district of Almadén were investigated for total Hg, organic Hg fraction and Hg distribution by selective sequential extraction. A four-step sequential extraction method (labile Hg species, humic and fulvic complexes, elemental Hg and bound to crystalline oxides and Hg sulfide and refractory species) was performed. Total Hg concentrations ranged from 13 to 64 mg per kg dry mass. A clear relationship between the depth and Hg content was found since Hg concentration decreases downwards, which is indicative of anthropogenic contamination via deposition processes from nearby mine waste. Significant organic Hg concentrations were found in all the tested soil profiles ranging from 79 to 287 µg kg(-1) (dry weight). It seems that organic Hg was strongly influenced by elemental Hg (r = 0.79) and to a lesser extent by the organic carbon content (r = 0.57). The fractionation revealed that Hg exists mainly as cinnabar in the studied soils, which is one of the least available and mobile Hg species, and as elemental Hg as well. The most mobile Hg fractions only accounted for 3.2 to 7.7% of the total Hg content, with the main contribution being the humic and fulvic complexes fraction. The elemental Hg fraction increased with depth indicating a migration to deeper soil layers. In contrast, the surface layers showed an enrichment in the fraction bound to sulfide, which means that Hg is mostly deposited as cinnabar particles from non-processed ore in this area.

A methodological approach to evaluate arsenic speciation and bioaccumulation in different plant species from two highly polluted mining areas.

Arsenic accumulation and speciation in different plant species growing in two polluted sites were examined, in addition to arsenic transfer from soils to plants. The studied areas were two abandoned mercury mines in Northern Spain, La Soterraña and Los Rueldos. Plants accumulated extremely high amounts of arsenic in their tissues. Accumulation rates depend on both the grade of pollution of the site and on the plant species itself. Total arsenic concentrations varied depending on the part of the plant, with roots accumulating the most arsenic in all the studied plants (up to 1400 mg · kg(-1)). A suitable extraction method for arsenic speciation in the studied samples was developed and optimized using 0.3M orthophosphoric acid as the extracting agent in a graphite block digestion system at 90 °C for 1h. Extraction efficiencies were above 80% and speciation was not altered, since recoveries of the spiked arsenic species (As(III), As(V), DMA (dimethylarsonic acid) and MMA (monomethylarsonic acid)) were between 94 and 102%. Speciation studies were performed on the parts of each plant species by means of HPLC-ICP-MS with the results indicating no significant differences in the speciation between parts of the plants. As(V) was always the predominant species, although a non-negligible amount of As(III) was found for all samples. Little amounts of MMA and DMA occurred in certain samples. Arsenic uptake by plants depends on the plant available arsenic fraction in soils, here considered as the sum of water-soluble and phosphate-extractable fractions. Although soils from La Soterraña were less polluted, arsenic bioavailability was much higher than in Los Rueldos. Soil-to-plant transfer factors, based on total and available arsenic in soils, were evaluated for the studied plants. Dryopteris filix-mas and Calluna vulgaris (L.) Hull, from La Soterraña and Los Rueldos respectively, were the plants with the highest abilities to extract arsenic from their corresponding soils.

Arsenic pollution and fractionation in sediments and mine waste samples from different mine sites.

A characterization of arsenic pollution and its associations with solid mineral phases in sediments and spoil heap samples from four different abandoned mines in Spain is performed. Three of them were mercury mines located in the same mining district, in the province of Asturias, and the other one, devoted to arsenic mining, is in the province of León. A sequential extraction procedure, especially developed for arsenic, was applied for the study of arsenic partitioning. Very high total arsenic concentrations ranging 300-67,000 mg·kg(-1) were found. Arsenic fractionation in each mine is broadly in accordance with the mineralogy of the area and the extent of the mine workings. In almost all the studied samples, arsenic appeared predominantly associated with iron oxyhydroxides, especially in the amorphous form. Sediments from cinnabar roasted piles showed a higher arsenic mobility as a consequence of an intense ore treatment, posing an evident risk of arsenic spread to the surroundings. Samples belonging to waste piles where the mining activity was less intense presented a higher proportion of arsenic associated with structural minerals. Nevertheless, it represents a long-term source of arsenic to the environment.