Low Concentrations Of Trace Elements Research Articles

Emissions of trace elements during the 2012–2013 effusive eruption of Tolbachik volcano, Kamchatka: enrichment factors, partition coefficients and aerosol contribution

Gases and aerosols from the 2012–13 effusive eruption of Tolbachik basaltic volcano, Kamchatka, were sampled in February and May, 2013, from a lava tube window located 300m from the eruptive crater; temperature at the sampling point was 1060–1070°C. The chemical and isotopic compositions of the sampled gases (92.4% H2O, 3.5% CO2, 2.3% SO2 on average; δD from −25.0 to −38.6‰) correspond to a typical volcanic arc gas without dilution by meteoric or hydrothermal water. Halogen contents in the gases (1.37% HCl, 0.5% HF) were higher than average arc values. The total amount of analyzed metallic and metalloid (trace) elements in the gas exceeded 665ppm. Six most abundant trace elements, K (250ppm), Na (220ppm), Si (74ppm), Br (48ppm), Cu (21ppm) and Fe (12ppm), accounted for 95% of the total content of trace elements in the gas. The gases contained 24ppb Re, 12ppb Ag, 4.9ppb Au and 0.45ppb Pt. Refractory rock-forming elements (Mg, Al, Ca) and some other elements such as Ba and Th were transported mainly in the form of silicate microspheres and altered rock particles. The concentrations of metals in the eruptive Tolbachik gases are higher than the corresponding concentrations in high-temperature fumaroles worldwide, although the mutual ratios of the elements are approximately the same. The gas/magma partition coefficients of eleven elements exceed unity, including the non-metals F, S, Cl, Br, As, Se and Te and the rare metals Cd, Re, Tl and Bi. Despite the relatively low concentrations of trace elements in the volcanic gases at the highest temperatures, superficial magma degassing provides information on the sources and sinks of metals.

Trace metal bioindication and phytoremediation potentialities of Phalaris arundinacea L. (reed canary grass)

In the present study, the contents of trace metals (Zn, Mn, Fe, Pb, Cu, Ni, Cd, Co and Cr) in water, bottom sediments and different organs of Phalaris arundinacea L. collected from the Bystrzyca River (Lower Silesia), that flows through regions with a high anthropopressure level, were determined by atomic absorption spectrometry. The aims of this paper were to reveal various trace metal accumulation abilities of different organs of P. arundinacea and to investigate their potential use in the biomonitoring and phytoremediation of environmental trace metal pollution.Results showed that metal contents in various organs of the reed canary grass differed significantly. Trace metal concentrations found in the plant samples generally decreased in the following order: root>leaf>stem. Limited mobility and translocation of the metals once absorbed by the reed canary grass makes it an interesting species for phytostabilization of metal contaminated bottom sediments. The highest Zn and Pb concentrations were noted in P. arundinacea from agricultural fields. Also the reed canary grass from cities showed high accumulation of Pb and Zn mainly due to vehicle traffic. Plants tested from dam reservoirs and forests had low concentrations of most trace elements. The significant, positive correlations found between the content of Co and Zn in the environment and the levels of these elements in the organs of the reed canary grass indicate potential application of P. arundinacea in the biomonitoring of environmental contamination with these metals.

Chemical characterization of high-temperature arc gasification slag with a focus on element release in the environment.

High-temperature arc gasification (HTAG) has been proposed as a viable technology for the generation of energy and the production of saleable byproducts from municipal solid waste (MSW). Total concentrations of elements in HTAG slag were assessed and indicated a high partitioning of trace elements (Pb, Cd, and As) into the flue gas, an issue of concern when assessing the air pollution control residues (APCR) status as a hazardous waste. Hazardous waste leaching tests [such as the toxicity characteristic leaching procedure (TCLP)] were performed and confirmed that the slag did not meet U.S. criteria for a hazardous waste. Leaching was assessed using batch and column tests; the results revealed that Sb and Al were elevated in respect to risk-based regulatory thresholds. Slag samples were carbonated to simulate weathering effects, and although leachable concentrations of Al did decrease by an order of magnitude, Sb concentrations were found to increase. Low total concentrations of certain trace elements (As, Cd, and Pb), with respect to MSW incineration bottom ashes support the potential for reuse of HTAG slag; however, leaching of elements (Pb, Al, and Sb) in batch and column tests indicate that proper engineering controls would need to be taken to ensure protection of water supplies in a reuse application.

Fault-Controlled Lateral Fluid Flow Underneath and Into a Carlin-Type Gold Deposit: Isotopic and Geochemical Footprints

Many Carlin-type gold deposits in northern Nevada are found adjacent to steeply dipping faults that channeled hydrothermal fluids upward into mineralized regions. However, some Carlin deposits comprise gently dipping tabular ore zones lacking any obvious large, steeply dipping, feeder structure beneath them. The goal of this paper is to test whether fluid flow into such ore zones also involved largely vertical upwelling, or whether lateral fluid flow, particularly along low-angle fault structures, may have played a significant role in their formation. In this study we use carbon and oxygen isotopes in conjunction with trace element geochemistry to investigate pathways taken by hydrothermal ore-forming fluids into the tabular subhorizontal ore zones of the Pipeline deposit, a giant carbonate rock-hosted Carlin-type deposit in Nevada. We sampled deep drill holes within, below, and to the side of the main ore zone to assess the extent of lateral versus vertical fluid flow up to 600 m below mineralization. The main ore zone at the Pipeline deposit is dominated by carbonate host rocks having δ 18 O and δ 13 C values that are depleted in the heavier 18 O and 13 C isotopes compared to global background values for rocks of the same age. Depletion results from the progressive buffering of the rock by an infiltrating auriferous hydrothermal fluid. There is significant heterogeneity in the spatial pattern and relative degree of 18 O and 13 C depletion through the ore zone, most likely reflecting multiple flow paths with different total integrated fluid fluxes, path lengths, rates of fluid cooling, and possibly fluid mixing. A lack of a pervasive reduction in δ 18 O and δ 13 C values, and low concentrations of trace elements in the rocks immediately beneath the main ore zone indicate that the deposit was not a product of large-scale vertical upwelling of auriferous hydrothermal fluid directly into the mineralized region. Rather, flow was focused along preexisting low-angle thrusts, particularly the Abyss fault, with fluids flowing laterally underneath and then up into the area of the main ore zone. Enhanced permeability along these low-angle structures most likely derived from fault reactivation and the generation of fracture networks in damage zones peripheral to a relatively impermeable fault core. Such reactivation would have required suprahydrostatic fluid pressures, relatively shallow crustal depths, and a lack of more optimally oriented, high angle faults (>50°) that would otherwise have preferentially failed and focused fluid flow steeply upward.

Carbonate- and silicate-rich globules in the kimberlitic rocks of northwestern Tarim large igneous province, NW China: Evidence for carbonated mantle source

We report carbonate- and silicate-rich globules and andradite from the Wajilitage kimberlitic rocks in the northwestern Tarim large igneous province, NW China. The carbonate-rich globules vary in size from 1 to 3mm, and most have ellipsoidal or round shape, and are composed of nearly pure calcite. The silicate-rich globules are elliptical to round in shape and are typically larger than the carbonate-rich globules ranging from 2 to several centimeters in diameter. They are characterized by clear reaction rims and contain several silicate minerals such as garnet, diopside and phlogopite. The silicate-rich globules, reported here for the first time, are suggested to be related to the origin of andradite within the kimberlitic rocks. Our results show that calcite in the carbonate-rich globules has a high XCa (>0.97) and is characterized by extremely high concentrations of the total rare earth elements (up to 1500ppm), enrichment in Sr (8521–10,645ppm) and LREE, and remarkable depletion in Nd, Ta, Zr, Hf and Ti. The calcite in the silicate-rich globules is geochemically similar to those in the carbonate-rich globules except the lower trace element contents. Garnet is dominantly andradite (And59.56–92.32Grs5.67–36.03Pyr0.36–4.61Spe0–0.33) and is enriched in light rare earth elements (LREEs) and relatively depleted in Rb, Ba, Th, Pb, Sr, Zr and Hf. Phlogopite in the silicate-rich globules has a high Mg# ranging from 0.93 to 0.97. The composition of the diopside is Wo45.82–51.39En39.81–49.09Fs0.88–0.95 with a high Mg# ranging from 0.88 to 0.95. Diopside in the silicate-rich globules has low total rare earth element (REE) contents (14–31ppm) and shows middle REE- (Eu to Gd), slight light REE- and heavy REE-enrichment with elevated Zr, Hf and Sr contents and a negative Nb anomaly in the normalized diagram. The matrix of the kimberlitic rocks are silica undersaturated (27.92–29.31wt.% SiO2) with low Al2O3 (4.51–5.15wt.%) and high CaO (17.29–17.77wt.%) contents. The samples are characterized by incompatible element enrichment with high (La/Yb)N values (41–58) and remarkable negative anomalies in HFSEs (e.g. Ta, Zr, Hf). Our new data suggest that the carbonate-rich globule most likely crystallized at high-temperature and does not represent immiscible liquids, whereas the silicate-rich globules are related to carbonate-rich deuteric hydrothermal fluids during the later-stage of melt evolution. The fluids reacted with the surrounding silicate melts resulting in the formation of skarn minerals such as phlogopite, diopside and andradite. The presence of the carbonate-bearing globules indicates that the Wajilitage kimberlitic rocks are carbonate-rich and most likely derived from an enriched mantle with abundant carbonate. We correlate the carbonated mantle to metasomatism by the migration of deep-seated fluids (carbonate-rich) in response to the impingement of the early Permian mantle plume.

Characterization of Green Liquor Dregs, Potentially Useful for Prevention of the Formation of Acid Rock Drainage

Using alternative materials such as residual products from other industries to mitigate the negative effects of acid rock drainage would simultaneously solve two environmental problems. The main residual product still landfilled by sulphate paper mills is the alkaline material green liquor dregs (GLD). A physical, mineralogical and chemical characterization of four batches of GLD was carried out to evaluate the potential to use it as a sealing layer in the construction of dry covers on sulphide-bearing mine waste. GLD has relatively low hydraulic conductivity (10−8 to 10−9 m/s), a high water retention capacity (WRC) and small particle size. Whilst the chemical and mineralogical composition varied between the different batches, these variations were not reflected in properties such as hydraulic conductivity and WRC. Due to relatively low trace element concentrations, leaching of contaminants from the GLD is not a concern for the environment. However, GLD is a sticky material, difficult to apply on mine waste deposits and the shear strength is insufficient for engineering applications. Therefore, improving the mechanical properties is necessary. In addition, GLD has a high buffering capacity indicating that it could act as an alkaline barrier. Once engineering technicalities have been overcome, the long-term effectiveness of GLD should be studied, especially the effect of aging and how the sealing layer would be engineered in respect to topography and climatic conditions.

Effects of organic/inorganic amendments on trace elements dispersion by leachates from sulfide-containing tailings of the São Domingos mine, Portugal. Time evaluation

Greenhouse pot experiments were conducted over 13months to evaluate the effect of two amendment mixture doses (30 and 75Mg/ha) on the geochemical dispersion of trace elements by leaching hazardous mine wastes from the São Domingos mine. Mineralogical evolution of these materials was also evaluated. Amendment mixtures containing solid wastes from agriculture (plant remains+strawberry substrate and rockwool used for the strawberry crop) and from distillation of Ceratonia siliqua L. and Arbutus unedo L. fruits were used to improve the chemical characteristics of leachates from sulfide mine wastes. Sulfide mine wastes had acidic characteristics, as well as high electrical conductivity and total element concentrations (g/kg; Al: 54.8–61.2; Fe: 104.0–110.0; Pb: 9.0–13.8; S: 63.6–68.0; As: ≈1). These features contributed to the large capacity for leaching of hazardous elements during, at least, the first four months of incubation. In the seventh month of incubation, there was a significant decrease in the leachate concentration of the majority of hazardous elements. The addition of amendments minimised trace element dispersion in leachate percolation during the first seven months (25 to 99% reduction compared to control, depending on the element and sampling period). However, the leachate characteristics were not influenced by amendment doses and no significant differences were observed in leachate composition (control and amended treatments) after 13months. Amendment application led to differences between the solid phases of the efflorescent salts formed on the surface of the control and the amended treatments. The efflorescent salts contained very soluble aluminium sulfates, together with alunite–jarosite-group solid phases in amended samples, and copiapite-group solid phases in control. In the core materials (5 to 10cm in depth), the mineralogy was similar in both control and amended samples. The presence of various stable solid phases from alunite–jarosite-group, such as jarosite and beudantite (mainly in deeper materials), can explain the low concentrations of trace elements in the leachates after thirteen months.

Evaluating Impacts of CO2 Gas Intrusion Into a Confined Sandstone aquifer: Experimental Results

Deep subsurface storage and sequestration of CO2 has been identified as a potential mitigation technique for rising atmospheric CO2 concentrations. Sequestered CO2 represents a potential risk to overlying aquifers if the CO2 leaks from the deep storage reservoir. Experimental and modeling work is required to evaluate potential risks to groundwater quality and develop a systematic understanding of how CO2 leakage may cause important changes in aquifer chemistry and mineralogy by promoting dissolution/precipitation, adsorption/desorption, and redox reactions. Sediments from the High Plains aquifer in Kansas, United States, were used in this investigation, which is part of the National Risk Assessment Partnership Program sponsored by the US Department of Energy. This aquifer was selected to be representative of consolidated sand and gravel/sandstone aquifers overlying potential CO2 sequestration repositories within the continental US. In this paper, we present results from batch experiments conducted at room temperature and atmospheric pressure with four High Plains aquifer sediments. Batch experiments simulate sudden, fast, and short-lived releases of the CO2 gas as would occur in the case of well failure during injection. Time-dependent release of major, minor, and trace elements were determined by analyzing the contacting solutions. Characterization studies demonstrated that the High Plains aquifer sediments weremore » abundant in quartz and feldspars, and contained about 15 to 20 wt% montmorillonite and up to 5 wt% micas. Some of the High Plains aquifer sediments contained no calcite, while others had up to about 7 wt% calcite. The strong acid extraction tests confirmed that in addition to the usual elements present in most soils, rocks, and sediments, the High Plains aquifer sediments had appreciable amounts of As, Cd, Pb, Cu, and occasionally Zn, which potentially may be mobilized from the solid to the aqueous phase during or after exposure to CO2. However, the results from the batch experiments showed that the High Plains sediments mobilized only low concentrations of trace elements (potential contaminants), which were detected occasionally in the aqueous phase during these experiments. Importantly, these occurrences were more frequent in the calcite-free sediment. Results from these investigations provide useful information to support site selection, risk assessment, and public education efforts associated with geological CO2 storage and sequestration.« less

Leaching of boron, arsenic and selenium from sedimentary rocks: II. pH dependence, speciation and mechanisms of release

Sedimentary rocks excavated in Japan from road- and railway-tunnel projects contain relatively low concentrations of hazardous trace elements like boron (B), arsenic (As) and selenium (Se). However, these seemingly harmless waste rocks often produced leachates with concentrations of hazardous trace elements that exceeded the environmental standards. In this study, the leaching behaviors and release mechanisms of B, As and Se were evaluated using batch leaching experiments, sequential extraction and geochemical modeling calculations. The results showed that B was mostly partitioned with the residual/crystalline phase that is relatively stable under normal environmental conditions. In contrast, the majority of As and Se were associated with the exchangeable and organics/sulfides phases that are unstable under oxidizing conditions. Dissolution of water-soluble phases controlled the leaching of B, As and Se from these rocks in the short term, but pyrite oxidation, calcite dissolution and adsorption/desorption reactions became more important in the long term. The mobilities of these trace elements were also strongly influenced by the pH of the rock-water system. Although the leaching of Se only increased in the acidic region, those of B and As were enhanced under both acidic and alkaline conditions. Under strongly acidic conditions, the primarily release mechanism of B, As and Se was the dissolution of mineral phases that incorporated and/or adsorbed these elements. Lower concentrations of these trace elements in the circumneutral pH range could be attributed to their strong adsorption onto minerals like Al-/Fe-oxyhydroxides and clays, which are inherently present and/or precipitated in the rock-water system. The leaching of As and B increased under strongly alkaline conditions because of enhanced desorption and pyrite oxidation while that of Se remained minimal due to its adsorption onto Fe-oxyhydroxides and co-precipitation with calcite.

SULFIDE COMPOSITION AND ISOTOPIC SIGNATURE OF THE ALTAR Cu-Au DEPOSIT, ARGENTINA: CONSTRAINTS ON THE EVOLUTION OF THE PORPHYRY-EPITHERMAL SYSTEM

Sulfides and sulfosalts from the porphyry, transitional, and epithermal high sulfidation stages of the Altar Cu-(Au) deposit (San Juan, Argentina) were investigated by electron microprobe, laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS), and S isotopic analysis. Compositional differences found in the trace-element content in pyrite, chalcopyrite, and enargite from different alteration zones and depths of the system have implications in the physicochemical evolution of the hydrothermal fluids and might have potential for exploration in similar porphyry-high sulfidation epithermal environments. Low contents of most analyzed trace elements were found in chalcopyrite ± pyrite from the potassic alteration, except for Zn, Sn, and Ag in chalcopyrite, and Co and Ni in pyrite. During the phyllic alteration, cooling of the fluids and a decrease of its pH ( In the transitional veins and their selvages, early precipitation of bornite + pyrite and the weak kaolinite + quartz alteration envelope indicate a decrease in the temperature ( f S 2 . This stage was followed by a sudden increase in the f O 2 of the fluid and a slight decrease in the f S 2 , and bornite was replaced by tennantite (vein type E1). A trend toward higher f S 2 favored enargite precipitation (vein type E3). Traces of Au found in tennantite and enargite therefore indicate that fluctuations in the oxidation state of the fluids promoted gold precipitation in the Altar porphyry system. Negative S isotope values (δ 34 S: −1.7 to −3.0‰) obtained for the sulfides and sulfosalts from the potassic, phyllic, and transitional stages at Altar are consistent with oxidizing (SO 4 2− dominant) mineralizing fluids. The precipitation of sphalerite (δ 34 S = −4.4‰ and low concentration of FeS) and galena associated with calcite + anhydrite in late fractures (vein type 8) reflect cooling of the fluids and a slight increase of its pH at higher f O 2 , as the system moved to greater depths. The typical advanced argillic assemblages are not developed at the Altar porphyry deposit, indicating that fluids did not attain very low pH conditions. In contrast, enargite from the epithermal siliceous ledges located above the porphyry deposit precipitated with low pH mineral assemblages (quartz + alunite) and has a distinctive lighter δ 34 S value of −5.4‰, consistent with a decrease of temperature, pH, and/or an increase in the oxidation state of the fluids during its deposition. Enargite from the transitional stage veins of the porphyry deposit is enriched in Zn, Sb, Ag, and Bi, whereas enargite from the epithermal environment has much lower concentrations of trace elements, except for isolated inclusions of Au-Bi.

Intraluminal thrombus thickness is not related to lower concentrations of trace elements in the wall of infrarenal abdominal aortic aneurysms

BackgroundIntraluminal thrombus (ILT) formation plays a significant role in the progression of infrarenal abdominal aortic aneurysms (AAA). Potentially, as ILT thickness increases the availability of trace elements in the aneurysm wall could decrease thereby leading to oxidative stress and intensifying pro-inflammatory cytokine generation. AimTo determine if thrombus thickness is related to the concentration of trace elements in the wall of infrarenal AAA. Patients and methodsThe concentrations of trace elements in the wall of the aneurysm sack and ILT obtained from 19 consecutive patients during surgery for infrarenal AAA were determined using emission spectrometry. ResultsThe concentrations of magnesium, zinc, manganese, and lead in the wall of AAA were significantly greater than in the ILT. Only the concentration of copper was lower in the AAA wall compared with the thrombus. The concentration of calcium, phosphorus, zinc, lead, copper, and magnesium increased with ILT thickness. The concentrations of no other trace elements in the wall of AAA were found to be related to the ILT thickness. ConclusionsIntraluminal thrombus thickness is not associated with a lower concentration of trace elements in the wall of the infrarenal AAA. Thus, the intraluminal thrombus participates in the progression of AAA by mechanisms independent of trace element supply to the wall of the aneurysm sack.

Trace element partitioning in mixed-habit diamonds

Mixed-habit diamonds are a special type of crystal that form by simultaneous growth by two different mechanisms; octahedral and cuboid growth. This type of crystal growth is known to preferentially partition nitrogen into the octahedral growth sectors during growth. To identify if this fractionation occurs for any other trace element, this study applies in situ laser ablation mass spectrometry to a well-studied collection of mixed-habit diamonds. The results show high concentrations of nickel (3.6–36.4ppm) and cobalt (0.108–1.25ppm) in the cuboid sectors, whereas the octahedral sectors contain only <0.05–0.35ppm nickel and <0.014–0.03ppm cobalt. The relative enrichment of nickel in the cuboid sectors varies between 10 and 460 times. For cobalt, where the concentrations in the octahedral sector are commonly below the limit of quantification, the enrichment is estimated to be in the range of 10–100 times. There appears to be a rough linear relationship between the concentrations of the two elements in the cuboid sectors, with nickel concentrations approximately 27 times that of cobalt. This finding of nickel fractionation into the cuboid sectors is the opposite of what is seen in synthetic diamonds grown from FeNi solvents, where Ni is only found in the octahedral growth sectors. We propose that this is because the inherent lattice strain in the rough cuboid diamond growth of natural mixed-habit diamonds is greater than that in the smooth octahedral growth, making it easier to fit the large Ni and Co ions into a divacancy. In diamonds grown from metal solvents (i.e. industrial synthetic diamonds), the cube face is a smooth one, therefore the partitioning of trace elements is simply a result of the octahedral surface offering more bonding opportunities than the cube surface.Due to the extremely low concentrations of trace elements in these gem quality diamonds, many of the elements are commonly below the limit of quantification (LOQ). While we are confident that Pr, Sr, Pb, Zr, V, Cr and Zn are not fractionated by the crystal growth mechanisms of mixed-habit diamonds that affect Ni and Co, this remains to be proven for the remaining trace elements analysed. Data on the fractionation of copper are inconclusive, with 75% of data from the cuboid sectors above the LOQ and all data from the octahedral sectors below the LOQ. However, the values of the LOQ for the octahedral data are often higher than those of the cuboid data, so further investigation of Cu is necessary to confirm its behaviour.

Investigation on the gemological, physical and compositional properties of some opals from Slovakia ("Hungarian" opals)

The physical and compositional properties of some “Hungarian” opals have been investigated through several methodologies such as optical analysis, specific gravity, refractive indices, AvaSpec spectroscopy, XRPD, IR and Raman spectroscopy, LA-ICP-MS. The “Hungarian” opal deposits, now in Slovakia, represented the largest and most significant gem opal deposits in Europe from the Roman Times to XIXth century. The analysed opals include brown semiopals, white opals and hyalite. In general, chromophore elements like V, Cr, Cu, Ti, Co are present in very low concentrations and do not influence the physical properties of the opals. Elements like Na, Mg, Al, K, Ca, Sc, Cr and Fe have been detected, in variable amounts, in all the investigated samples. The semiopals can be used as ornamental and semiprecious material, are mostly made up by CT opal close to pure tridymite and lower amounts of goethite, show high trace elements contents while the REE pattern show a clear Eu negative anomaly. These opals probably formed during an hydrothermal, or late magmatic stage. The white opals are made up by amorphous opal (A), show appreciable play of color and iridescence and are surely the most relevant for gemological purposes. The most pure white opals show low contents of trace elements and a rather homogeneous composition, that can be used as geographical marker. Conversely some opals affected by contamination from host rocks show much higher trace element contents. White opals probably formed during a low temperature tectonic event. The samples of hyalite are yellowish, opaque and greasy. They are made up by CT opal show relevant content of B and As while the other trace element are quite low, and are probably of volcanic origin.

Batch and Continuous Mesophilic Anaerobic Digestion of Food Waste: Effect of Trace Elements Supplementation

Trace metals are essential for the enzyme cofactors involved in the biochemistry of methane formation and are needed in a balanced anaerobic digestion process. Food and kitchen waste generally contains low concentrations of trace elements, especially metals. As a consequence the anaerobic digestion process may result instable. The aim of this study is to evaluate the effect of metals addition on mesophilic anaerobic digestion of food waste, both in batch tests and in laboratory scale CSTR reactors. Batch anaerobic trials using source-separated food waste as substrate with inoculums of different origins were carried out under mesophilic conditions. Reactions were operated both with and without trace elements (Co, Mo, Ni, Se, W) supplementation. Supplementation with trace metals had either neutral or slightly negative effects with inoculums originating from reactors with a high background level of metals, such as those for the co-digestion of biowaste and waste activated sludge. For inoculums from reactors treating food waste only, which inherently contain low levels of trace metals, supplementation with these metals increased methane production. In particular, Mo concentrations in the range of 3-12 mg/kgTSfed and Se concentrations of 10 mg/kgTSfed increased methane production to as high as 30-40 %. Supplementation with a metal mixture (Co, Mo, Ni, Se, W) increased the methane production to the range 45-65 % for inoculums with low background concentrations of trace metals. These findings demonstrate the importance of Co, Mo, Ni, Se, W for high-performance anaerobic digestion process. Trace metals additions that showed the best batch results (100mgNi/kgTSfed, 100mgCo/kgTSfed, 6mgMo/kgTSfed, 10mgSe/kgTSfed, 10mgW/kgTSfed) were selected for CSTR experimentation. Performances of a continuous anaerobic digester fed with trace elements were compared to a “control reactor” fed with the same substrate but without metals addition. Preliminary CSTR results showed that metals addition allowed for a stable anaerobic digestion process at Organic Loading Rate greater than 3 kgVSfed m 3 •d but were not essential.

Effect of ethylenediaminetetraacetic acid (EDTA) on the bioavailability of trace elements during anaerobic digestion

The uptake of essential trace elements by methanogenic bacteria can be obstructed by precipitation in the presence of sulfides and carbonates. The objective of this study was to investigate whether the bioavailability of trace elements, and therefore the methane yield, can be improved through the use of complexing agents. Research showed that the use of EDTA as a complexing agent in the biogas process increases the solubility of essential metals and enhances their bioavailability. If the substrate of a biogas digester has a low content of trace elements, solutions of elements essential for the methanogenic bacteria have to be added to the process. If these metals are complexed with EDTA prior to their supply, the necessary amount can be reduced by up to 75% compared to the non-complexed metals. Therefore, it would be advantageous for environmental and economic reasons to complex trace elements prior to their addition to the biogas process.

Magma source and tectonics of the Xiangshanzhong mafic–ultramafic intrusion in the Central Asian Orogenic Belt, NW China, traced from geochemical and isotopic signatures

Several sulfide ore-bearing mafic–ultramafic intrusions occur along the southern margin of the Late Paleozoic Central Asian Orogenic Belt (CAOB) in north Xinjiang, NW China. Their origin, magma evolution and relationship with the Permian basalts in the region remain equivocal. In this study, we investigate the Xiangshanzhong mafic–ultramafic intrusion in eastern Tianshan, dominantly composed of diorite, hornblende gabbro, gabbro, hornblende pyroxenite, olivine websterite and lherzolite. We report the occurrence of olivine clinopyroxenite in the intrusive complex with visible pyroxene cumulate structure, high Mg, low Cr, Na, and Ti contents, and characterized by distinctively low trace element contents. Our data suggest that the clinopyroxene in the olivine clinopyroxenite probably crystallized from an earlier batch of magma. The rare earth element (REE) patterns and εNd values of the Xiangshanzhong mafic–ultramafic units suggest that these rocks represent cumulates of basaltic composition that were likely co-genetic and derived from the same magmatic source. The presence of phlogopite and amphibole, occurrence of Zr, Hf, Nb, and Ta negative anomalies, the trace element abundances of the parental magma, and the Nd isotopes (+5.9–+8.3) of whole-rocks suggest that the source of the Xiangshanzhong complexes may be a depleted mantle metasomatized by subducted slab-derived fluid or melt. Furthermore, the (87Sr/86Sr)i ratios, εNd(t) values and trace element geochemistry of whole-rock and clinopyroxene grains are consistent with those of the Permian Tuha basin basalts. The Xiangshanzhong intrusion has characteristics of both plume and subduction-related origin and we therefore speculate that the partial melting of subduction-related depleted mantle triggered by Permian plume activity during the post-collision extension regime generated the parental magmas of the Xiangshanzhong intrusion.

Resonant laser-induced breakdown spectroscopy (RLIBS) analysis of traces through selective excitation of aluminum in aluminum alloys

We investigated laser-induced breakdown spectroscopy for the detection of traces of magnesium and silicon contained in aluminum alloys by using the same 5 ns optical parametric oscillator laser pulse to ablate the sample and excite selectively an atomic transition of vaporized aluminum (Al I 309.27 nm). The excitation energy of aluminum is then transferred to all components of the gas/plasma phase via particle collisions. The optical emission of the trace elements as a function of the laser wavelength exhibits a high peak when the laser is tuned exactly to the aluminum transition. The on-resonance signal-to-noise ratio of magnesium (Mg 285.21 nm) was maximized near the off-resonance threshold fluence for detection of the magnesium line (∼1.78 J cm−2). The detection threshold of the magnesium line decreases below 1.0 J cm−2 when the laser is on resonance for a sample of aluminum alloy containing 150 ppm of magnesium. Under optimal conditions, the limits of detection of magnesium and silicon in aluminum alloy were found to be 0.75 ppm and 80 ppm, respectively, compared to 39 ppm and 5000 ppm, respectively, when the laser was off resonance at the same fluence. The limits of detection obtained by using low fluences and low energy per pulse are similar to those obtained using conventional LIBS but with much higher fluences and higher energy per pulse. The main advantage of this technique is that it allows measuring simultaneously relatively low concentrations of several trace elements while minimizing the damage to the sample.

Ore Fluid Properties and Sources from Quartz-Associated Gold at the Betze-Post Carlin-Type Gold Deposit, Nevada, United States

Quartz at the Betze-Post deposit, the largest Carlin-type gold system in the world, was examined to better understand ore fluid properties and sources that generated Carlin-type gold deposits. Detailed petrography and paragenesis investigations distinguished textural relationships, luminescence, various generations of quartz, and fluid inclusion populations; microthermometry, chemical analyses of quartz, and in situ and conventional oxygen isotope analyses of quartz provided information about hydrothermal fluid conditions as well as fluid sources and ore formation processes. Pre-, syn-, late-, and post-ore stages of quartz were distinguished during petrographic studies and confirmed by cathodoluminescence analyses. Ore-stage jasperoid and late-ore drusy quartz are spatially associated with Au-bearing pyrite; both lack luminescence. Two generations of post-ore drusy quartz overgrew ore and late-ore quartz and exhibit bright and multiply zoned luminescence. Electron probe microanalyses determined that nonluminescing ore and late-ore quartz have elevated concentrations of Al, in contrast to post-ore luminescent quartz that contains low trace element concentrations. Fluid inclusion microthermometry determined that ore-stage fluids had low salinities, generally <5 wt % NaCl equiv, and were trapped at 180° to 240°C. The δ 18O values, calculated for inclusion fluids and determined for quartz using in situ ion probe and conventional analyses, indicate that the isotopic composition of hydrothermal fluids became 18O depleted with time, from the ore stage through the late-ore stage to the post-ore stage. The δ 18O composition of each stage of quartz also varies spatially across the Betze-Post deposit, and δ 18OVSMOW values of ore-, late-ore, and post-ore stage quartz became more depleted with increasing distance from the master Post fault. These patterns are interpreted to result from increasing dilution of the 18O-enriched ore fluid by unevolved meteoric fluids over time and with increased ore fluid transport distance to the west, away from the Post fault, the master fault that transmitted hydrothermal fluids to the deposit. Oxygen isotope results are consistent with a low fluid/rock ratio during upward transport of the ore fluid via the Post fault. Below the deposit, some ore fluids were diverted into the JB Series faults, associated with the Betze ore zones, and the Shalosky fault, associated with the Screamer ore zone in the western part of the deposit. Ore fluids were increasingly diluted by meteoric fluids with distance as ore fluids traveled away from the Post fault and over time as different stages of quartz precipitated. Acidic, 180° to 240°C ore fluids accessed the level of the deposits where they reacted with the Devonian Popovich Formation and precipitated nonluminescing, Al-enriched ore-stage jasperoid and late-ore drusy quartz, along with Au and trace element-rich pyrite. Fluid-rock reaction, dissolution, and replacement of silty carbonate host rocks may have produced Al that substituted for Si in non-luminescing jasperoid and late-ore stage quartz. As the hydrothermal ore system began to cool and collapse, late-ore drusy quartz and realgar precipitated in open space as ore-stage pyrite precipitation declined. The hydrothermal system collapsed with meteoric water flooding; post-ore minerals, including luminescent, Al-poor post-ore drusy quartz and later calcite and barite, precipitated either from latest Carlin-related fluids, neutralized by infiltration of meteoric waters, or as part of a later, separate hydrothermal event.

Productive use of steelmaking by-product in environmental applications – II: Leachate geochemistry, ecotoxicity and environmental radioactivity

Detailed laboratory studies have indicated that the HIsmelt steelmaking by-product has the ability to neutralise acidity and hence, may have potential application as an environmental amendment. Prior to widespread environmental use, however, an ecotoxicological characterisation of the by-product leachate and an environmental radioactivity risk assessment are required. Ecotoxicity testing indicated that the HIsmelt steelmaking by-product softwater leachate, adjusted from its natural pH of 10.6–8.0 prior to use, was of low toxicity to Chlorella algae and the marine bacterium Vibrio fischeri, and not toxic to the cladoceran Ceriodaphnia dubia. Leachate metal concentrations in HIsmelt by-product were low. Relative to stringent health-based guidelines for Australian drinking water, the HIsmelt softwater leachate only exceeds the pH guideline of 6.5–8.5. The acidic toxicity characteristic leaching procedure (TCLP) HIsmelt leachate compares favourably with TCLP leachates from international steel-making by-products with low trace element concentrations reflecting low solid-phase concentrations. The HIsmelt steelmaking by-product exhibited low to moderate U and Th decay chain radionuclide activities with an absorbed dose rate of 65nGy/h. Given the low ecotoxicity, low leachate trace elements concentrations and acceptable radioactivity, the HIsmelt steelmaking by-product has potential applications as a construction material or as a soil amendment to ameliorate acidity. However, based on the results of the synthetic softwater leachate tests, it is likely that the HIsmelt steelmaking by-product will require mixing with other materials to reduce leachate pH prior to use as an environmental amendment.

Groundwater and river baseline quality using major, trace elements, organic carbon and Sr–Pb–O isotopes in a Mediterranean catchment: The case of the Lower Var Valley (south-eastern France)

Summary Dissolved trace and major elements, organic carbon and Pb–Sr–O isotopes have been investigated in surface and groundwater of the Var River Valley (SE France), including alluvial, conglomerate and limestone aquifers, as well as surface water. Boxplots and cumulative frequency distribution diagrams define chemical characteristics of each water group and distinguish between natural and anthropogenic range of concentrations. Low concentration of trace elements, statistical analysis of data and Pb isotopic ratios demonstrate that the measured baseline quality is close to the natural background, mainly influenced by water/rock interaction. Pb and Sr isotopes evidence specific primitive end members, buffering these two elements through leaching late Paleozoic rocks, strongly depleted in U and Rb since their formation. Arsenic undergoes geochemical processes such as sorption on clay minerals of the alluvial deposits. Sr isotopic ratios and high SO 4 2 - , Sr and Li contents show that Permo–Triassic sediments including evaporites strongly imprint surface waters and alluvial groundwaters. Limestone and conglomerate aquifers are mainly influenced by carbonate minerals, but may be locally affected by evaporite dissolution. High dissolved silica is also specific to conglomerate groundwaters. Limestone and conglomerate groundwaters are characterised by low and heterogeneous trace element compositions that may result from various residence times and rock compositions related to different sampling depth. Even if water quality is generally good for most of the investigated elements, pollution by agricultural activity (fertilisers and pesticides) in the alluvial and some limestone groundwaters has been demonstrated by high NO 3 - and Br− contents. Br− is suspected to originate from methyl bromide fertiliser. In conglomerate aquifers, NO 3 - contents may reach high levels, probably due to both agriculture and residential waste pollution. Despite the industrialization in the Low Var Valley, no significant metallic contamination could be detected and therefore, for trace elements, given parameters (min, max and median values) can be used as a baseline guide to detect future contamination.