Arsenic and selenium mobilisation from organic matter treated mine spoil with and without inorganic fertilisation

Organic matter amendments are applied to contaminated soil to provide a better habitat for revegetation and remediation, and olive mill waste compost (OMWC) has been described as a promising material for this aim. We report here the results of an incubation experiment carried out in flooded conditions to study its influence in As and metal solubility in a trace elements contaminated soil. NPK fertilisation and especially organic amendment application resulted in increased As, Se and Cu concentrations in pore water. Independent of the amendment, dimethylarsenic acid (DMA) was the most abundant As species in solution. The application of OMWC increased pore water dissolved organic-carbon (DOC) concentrations, which may explain the observed mobilisation of As, Cu and Se; phosphate added in NPK could also be in part responsible of the mobilisation caused in As. Therefore, the application of soil amendments in mine soils may be particularly problematic in flooded systems. (C) 2012 Elsevier Ltd. All rights reserved.

Tunnel spoil classification and applicability of lime addition in weak formations for muck reuse

Tunnel construction planning requires careful consideration of the spoil management part, as this involves environmental, economic and legal requirements. In this paper a methodological approach that considers the interaction between technical and geological factors in determining the features of the resulting muck is proposed. This gives indications about the required treatments as well as laboratory and field characterisation tests to be performed to assess muck recovery alternatives. While this reuse is an opportunity for excavations in good quality homogeneous grounds (e.g. granitic mass), it is critical for complex formation. This approach has been validated, at present, for three different geo-materials resulting from a tunnel excavation carried out with a large diameter Earth Pressure Balance Shield (EPB) through a complex geological succession. Physical parameters and technological features of the three materials have been assessed, according to their valorisation potential, for defining re-utilisation patterns. The methodology proved to be effective and the laboratory tests carried out on the three materials allowed the suitability and treatment effectiveness for each muck recovery strategy to be defined. © 2014 Elsevier Ltd.

The Secret Life of Oilbirds: New Insights into the Movement Ecology of a Unique Avian Frugivore

Background: Steatornis caripensis (the oilbird) is a very unusual bird. It supposedly never sees daylight, roosting in huge aggregations in caves during the day and bringing back fruit to the cave at night. As a consequence a large number of the seeds from the fruit they feed upon germinate in the cave and spoil.

Field fluxes and speciation of arsines emanating from soils

The biogeochemical cycle of arsenic (As) has been extensively studied over the past decades because As is an environmentally ubiquitous, nonthreshold carcinogen, which is often elevated in drinking water and food. It has been known for over a century that micro-organisms can volatilize inorganic As salts to arsines (arsine AsH(3), mono-, di-, and trimethylarsines, MeAsH(2), Me(2)AsH, and TMAs, respectively), but this part of the As cycle, with the exception of geothermal environs, has been almost entirely neglected because of a lack of suited field measurement approaches. Here, a validated, robust, and low-level field-deployable method employing arsine chemotrapping was used to quantify and qualify arsines emanating from soil surfaces in the field. Up to 240 mg/ha/y arsines was released from low-level polluted paddy soils (11.3 ± 0.9 mg/kg As), primarily as TMAs, whereas arsine flux below method detection limit was measured from a highly contaminated mine spoil (1359 ± 212 mg/kg As), indicating that soil chemistry is vital in understanding this phenomenon. In microcosm studies, we could show that under reducing conditions, induced by organic matter (OM) amendment, a range of soils varied in their properties, from natural upland peats to highly impacted mine-spoils, could all volatilize arsines. Volatilization rates from 0.5 to 70 µg/kg/y were measured, and AsH(3), MeAsH(2), Me(2)AsH, and TMAs were all identified. Addition of methylated oxidated pentavalent As, namely monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA), to soil resulted in elevated yearly rates of volatilization with up to 3.5% of the total As volatilized, suggesting that the initial conversion of inorganic As to MMAA limits the rate of arsine and methylarsines production by soils. The nature of OM amendment altered volatilization quantitatively and qualitatively, and total arsines release from soil showed correlation between the quantity of As and the concentration of dissolved organic carbon (DOC) in the soil porewater. The global flux of arsines emanating from soils was estimated and placed in the context of As atmospheric inputs, with arsines contributing from 0.9 to 2.6% of the global budget.

Arsenic speciation in the earthworms Lumbricus rubellus and Dendrodrilus rubidus

Two species of earthworm, Lumbricus rubellus Hoffmeister and Dendrodrilus rubidus (Savigny) collected from an arsenic-contaminated mine spoil site and an uncontaminated site were investigated for total tissue arsenic concentrations and for arsenic compounds by liquid chromatography-mass spectrometry (LC-MS) and liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). For L. rubellus, whole-body total tissue arsenic concentrations were 7.0 to 17.0 mg arsenic/ kg dry weight in uncontaminated soil and 162 to 566 mg arsenic/kg dry weight in contaminated soil. For D. rubidus, whole-body tissue concentrations were 2.0 to 5.0 mg arsenic/kg dry weight and 97 to 321 mg arsenic/kg dry weight, respectively. Arsenobetaine was the only organic arsenic species detected in both species of earthworms, with the remainder of the extractable arsenic being arsenate and arsenite. There was an increase in the proportion of arsenic present as arsenobetaine in the total arsenic burden. Lumbricus rubellus and D. rubidus have similar life styles, both being surface living and litter feeding. Arsenic speciation was found to be similar in both species for both uncontaminated and contaminated sites, with dose-dependent formation of arsenobetaine. When L. rubellus and D. rabidus from contaminated sites were incubated in arsenic-free soils, the total tissue burden of arsenic diminished. Initially, L. rubellus from the tolerant populations (from the contaminated site) eliminated arsenic in the first 7 d of exposure before accumulating arsenic in tissues, whereas nontolerant populations (from the uncontaminated site) accumulated arsenic linearly. The tolerant and nontolerant L. rubellus eliminated tissue arsenic linearly over 21 d when incubated in uncontaminated soil.

Interactions between earthworms and arsenic in the soil environment:a review

Chemical pollution of the environment has become a major source of concern. In particular, many studies have investigated the impact of pollution on biota in the environment. Studies on metalliferous contaminated mine spoil wastes have shown that some soil organisms have the capability to become resistant to metal/metalloid toxicity. Earthworms are known to inhabit arsenic-rich metalliferous soils and, due to their intimate contact with the soil, in both the solid and aqueous phases, are likely to accumulate contaminants present in mine spoil. Earthworms that inhabit metalliferous contaminated soils must have developed mechanisms of resistance to the toxins found in these soils. The mechanisms of resistance are not fully understood; they may involve physiological adaptation (acclimation) or be genetic. This review discusses the relationships between earthworms and arsenic-rich mine spoil wastes, looking critically at resistance and possible mechanisms of resistance, in relation to soil edaphic factors and possible trophic transfer routes.

Arsenic-speciation in arsenate-resistant and non-resistant populations of the earthworm, Lumbricus rubellus

Arsenic speciation was determined in Lumbricus rubellus Hoffmeister from arsenic-contaminated mine spoil sites and an uncontaminated site using HPLC-MS, HPLC-ICP-MS and XAS. It was previously demonstrated that L. rubellus from mine soils were more arsenate resistant than from the uncontaminated site and we wished to investigate if arsenic speciation had a role in this resistance. Earthworms from contaminated sites had considerably higher arsenic body burdens (maximum 1,358 mg As kg-1) compared to the uncontaminated site (maximum 13 mg As kg-1). The only organo-arsenic species found in methanol/water extracts for all earthworm populations was arsenobetaine, quantified using both HPLC-MS and HPLC-ICP-MS. Arsenobetaine concentrations were high in L. rubellus from the uncontaminated site when concentrations were expressed as a percentage of the total arsenic burden (23% mean), but earthworms from the contaminated sites with relatively low arsenic burdens also had these high levels of arsenobetaine (17% mean). As arsenic body burden increased, the percentage of arsenobetaine present decreased in a dose dependent manner, although its absolute concentration rose with increasing arsenic burden. The origin of this arsenobetaine is discussed. XAS analysis of arsenic mine L. rubellus showed that arsenic was primarily present as As(III) co-ordinated with sulfur (30% approx.), with some As(v) with oxygen (5%). Spectra for As(III) complexed with glutathione gave a very good fit to the spectra obtained for the earthworms, suggesting a role for sulfur co-ordination in arsenic metabolism at higher earthworm arsenic burdens. It is also possible that the disintegration of As(III)-S complexes may have taken place due to (a) processing of the sample, (b) storage of the extract or (c) HPLC anion exchange. HPLC-ICP-MS analysis of methanol extracts showed the presence of arsenite and arsenate, suggesting that these sulfur complexes disintegrate on extraction. The role of arsenic speciation in the resistance of L. rubellus to arsenate is considered.

Resistance to copper toxicity in populations of the earthworms Lumbricus rubellus and Dendrodrilus rubidus from contaminated mine wastes

Two arsenic and heavy metal-contaminated mine spoil sites, at Carrock Fell, Cumbria, United Kingdom, and Devon Great Consols Mine, Devon, United Kingdom, have been found to support populations of the earthworms Lumbricus rubellus Hoffmeister and Dendrodrilus rubidus (Savigny). Lumbricus rubellus and D. rubidus collected from the Devon site and an uncontaminated site were kept for 28 d in uncontaminated soil and in soil containing 750 mg/kg CuCl2, the state of the specimens being recorded using a semiquantitative assessment of earthworm health (condition index). The condition index remained high for all specimens except those of L. rubellus and D. rubidus from uncontaminated sites, which displayed 100% mortality. Bioavailability of Cu in the soils from one uncontaminated and two contaminated sites and in the uncontaminated soil treated with CuCl2 was determined using sequential extraction. Soils from Devon Great Consols had the greatest availability of Cu, Carrock Fell the lowest. Total tissue Cu for L. rubellus and D. rubidus from the contaminated sites did not change significantly for each species during the experiment. Total tissue concentrations of Cu for L. rubellus and D. rubidus from uncontaminated sites increased significantly during the first 7 d, after which mortality was 90%, making it impossible to continue the analysis.

Soil conditioning for EPBMs

Nowadays, the Earth Pressure Balanced (EPB) shields are used more and more caused by both the mechanical development of the machines and the more effective use of additives such as foams and polymers. These additives are used to condition spoil in the screw conveyor. A crucial component of EPB tunnelling applications is ground conditioning. Thus, in order to permit quantitative measurements of the conditioned ground behavior, it is necessary to develop and use a test able to simulate the extraction of earth from the chamber with a screw conveyor. This reliable test procedure can provide quantitative parameters that can really describe the conditioned soil behavior.

Soil conditioning of sand for EPB applications:A laboratory research

EPB tunnelling requires the application of soil conditioning to increase its field of applicability particularly for cohesionless soils. Choosing the most suitable conditioning set for the various soils requires the use of a feasible laboratory test which can permit to define the characteristics of the conditioned soils and provide measurable data. A series of tests has been carried out using a laboratory screw conveyor device which was designed for this purpose and which simulates the extraction of the spoil from a pressure chamber in a similar way as in EPB tunnelling. The tested soils were medium-grain sands with varying amounts of silt and the tested conditioned mixtures were obtained with different water contents and amounts of foam. A simple slump test was also used to analyze the global characteristics of the conditioned soils. The test has shown that the proposed laboratory procedure permits a quantitative comparison to be made between different conditioning amounts and agents on the basis of measurable parameters. © 2007 Elsevier Ltd. All rights reserved.

Soil Conditioning and Ground Monitoring for Shield Tunnelling

Soil conditioning consists of mixing and remolding the natural material during the mechanical excavation of tunnels, generally at low depth, with additives, in order to obtain suitable properties of plasticity and consistency for the excavated material, so becoming able to apply a counterpressure against natural earth pressure and groundwater flow towards the excavation chamber. The assessment and the control of the soil parameters and of machine performance are fundamental for a regular and safe excavation, also with regards to surface stability. This paper mainly focus on testing approach aimed to the proper soil conditioning with EPB shields, whose results have been validated at real scale. The influence of the water content and the amount of conditioning foam has been studied by the Authors. A proper definition of conditioning parameters can allow to extend the application field of Earth Pressure Balance (EPB) tunnel machines to various grain soil distribution, even in weak rock formations (e.g. siltstone or flysch). Importance of conditioning is reflected also on the possibility of a proper spoil disposal or better for its reuse.

Contaminants in surface water and sediments around the Tynagh Mine, Galway, Ireland.

A former silver mine in Tynagh, Co. Galway, Ireland is one of the most contaminated mine sites in Europe with maximum concentrations of Zn, As, Pb, Mn, Ni, Cu, and Cd far exceeding guideline values for water and sediment. The aims of this research were to 1) further assess the contamination, particularly metals, in surface water and sediment around the site, and 2) determine if the contamination has increased 10 years after the Environmental Protection Agency Ireland (EPAI) identified off-site contamination. Site pH is alkaline to neutral because CaCO3-rich sediment and rock material buffer the exposed acid generating sulphide-rich ore. When this study was compared to the previous EPAI study conducted 10 years earlier, it appeared that further weathering of exposed surface sediment had increased concentrations of As and other potentially toxic elements. Water samples from the tailings ponds and adjacent Barnacullia Stream had concentrations of Al, Cd, Mn, Zn and Pb above guideline values. Lead and Zn concentrations from the tailings pond sediment were 16 and 5 times higher, respectively, than concentrations reported 10 years earlier. Pb and Zn levels in most sediment samples exceeded the Expert Group (EGS) guidelines of 1000 and 5000 mg/kg, respectively. Arsenic concentrations were as high as 6238 mg/kg in the tailings ponds sediment, which is 62 and 862 times greater than the EGS and Canadian Soil Quality Guidelines (CSQG), respectively. Cadmium, Cu, Fe, Mn, Pb and Zn concentrations in water and sediment were above guideline values downstream of the site. Additionally, Fe, Mn and organic matter (OM) were strongly correlated and correlated to Zn, Pb, As, Cd, Cu and Ni in stream sediment. Therefore, the nearby Barnacullia Stream is also a significant pathway for contaminant transport to downstream areas. Further rehabilitation of the site may decrease the contamination around the area.

Arbuscular mycorrhizal fungi confer enhanced arsenate resistance on Holcus lanatus

The role of arbuscular mycorrhizal fungi (AMF) in arsenate resistance in arbuscular mycorrhizal associations is investigated here for two Glomus spp. isolated from the arsenate-resistant grass Holcus lanatus. Glomus mosseae and Glomus caledonium were isolated from H. lanatus growing on an arsenic-contaminated mine-spoil soil. The arsenate resistance of spores was compared with nonmine isolates using a germination assay. Short-term arsenate influx into roots and long-term plant accumulation of arsenic by plants were also investigated in uninfected arsenate resistant and nonresistant plants and in plants infected with mine and nonmine AMF. Mine AMF isolates were arsenate resistant compared with nonmine isolates. Resistant and nonresistant G. mosseae both suppressed high-affinity arsenate/phosphate transport into the roots of both resistant and nonresistant H. lanatus. Resistant AMF colonization of resistant H. lanatus growing in contaminated mine spoil reduced arsenate uptake by the host. We conclude that AMF have evolved arsenate resistance, and conferred enhanced resistance on H. lanatus.

Survival and behaviour of the earthworms Lumbricus rubellus and Dendrodrilus rubidus from arsenate-contaminated and non-contaminated sites

Two arsenic- and heavy metal-contaminated mine-spoil sites, at Carrock Fell, Cumbria and Devon Great Consols Mine, Devon, were found to support populations of the earthworms Lumbricus rubellus Hoffmeister and Dendrodrilus rubidus (Savigny). L. rubellus and D. rubidus collected from the Devon site and an uncontaminated site were kept for 28 days in uncontaminated soil and in soil containing sodium arsenate (494 mg As kg^-1). The state of the specimens was recorded every 7 days using a semi-quantitative assessment of earthworm health (condition index, C. I.). The C. I. remained high for all specimens except those of L. rubellus and D. rubidus from uncontaminated sites, which displayed 60 and 10% mortality, respectively. L. rubellus collected from the Carrock Fell site, and L. rubellus and D. rubidus from an uncontaminated site, burrowed as rapidly into soil containing up to 1235 mg As kg^-1 in the form of sodium arsenate as into uncontaminated soil when placed on the soil surface. When earthworms were allowed a choice between uncontaminated soil and soil contaminated with sodium arsenate in concentrations of up to 1235 mg As kg^-1, the threshold concentration for avoidance of contaminated soil was lower for L. rubellus and D. rubidus from uncontaminated soil than for specimens from contaminated soil. There was no significant effect of pH on soil discrimination. The LC₅₀ concentration of As for L. rubellus from Devon Great Consols was significantly higher (P < 0.001) than for L. rubellus from the uncontaminated site: 1510 and 96 mg As kg^-1, respectively. © 2001 Elsevier Science Ltd. All rights reserved.

Phosphorus nutrition of arsenate-tolerant and nontolerant phenotypes of velvetgrass

Velvetgrass (Holcus lanatus L.), also known as Yorkshire fog grass, has evolved tolerance to high levels of arsenate, and this adaptation involves reduced accumulation of arsenate through the suppression of the high affinity phosphate-arsenate uptake system. To determine the role of P nutrition in arsenate tolerance, inhibition kinetics of arsenate influx by phosphate were determined. The concentration of inhibitor required to reduce maximum influx (V(max)) by 50%, K₁, of phosphate inhibition of arsenate influx was 0.02 mol m^-3 in both tolerant and nontolerant clones. This was compared with the concentration where influx is 50% of maximum, a K(m), for arsenate influx of 0.6 mol m^-3 for tolerants and 0.025 mol m^-3 for nontolerants and, therefore, phosphate was much more effective at inhibiting arsenate influx in tolerant genotypes. The high affinity phosphate uptake system is inducible under low plant phosphate status, this increasing plant phosphate status should increase tolerance by decreasing arsenate influx. Root extension in arsenate solutions of tolerant and nontolerant tillers grown under differing phosphate nutritional regimes showed that indeed, increased plant P status increased the tolerance to arsenate of both tolerant and nontolerant clones. That plant P status increased tolerance again argues that P nutrition has a critical role in arsenate tolerance. To determine if short term flux and solution culture studies were relevant to As and P accumulation in soils, soil and plant material from a range of As contaminated sites were analyzed. As predicted from the short-term competition studies, P was accumulated preferentially to As in arsenate tolerant clones growing on mine spoil soils even when acid extractable arsenate in the soils was much greater than acid extractable phosphate. Though phosphate was much more efficient at competing with arsenate for uptake, plants growing on arsenate contaminated land still accumulated considerable amounts of As. Plants from the differing habitats showed large variation in plant phosphate status, pasture plants having much higher P levels than plants growing on the most contaminated mine spoil soils. The selectivity of the phosphate-arsenate uptake system for phosphate compared with arsenate, coupled with the suppression of this uptake system enabled tolerant clones of the grass velvetgrass to grow on soils that were highly contaminated with arsenate and deficient in phosphate.