Metal-rich Stream Research Articles

Discovery of the Magellanic Stellar Stream Out to 100 kpc

The Magellanic Stream (MS)—an enormous ribbon of gas spanning 140° of the southern sky trailing the Magellanic Clouds—has been exquisitely mapped in the five decades since its discovery. However, despite concerted efforts, no stellar counterpart to the MS has been conclusively identified. This stellar stream would reveal the distance and 6D kinematics of the MS, constraining its formation and the past orbital history of the Clouds. We have been conducting a spectroscopic survey of the most distant and luminous red giant stars in the Galactic outskirts. From this data set, we have discovered a prominent population of 13 stars matching the extreme angular momentum of the Clouds, spanning up to 100° along the MS at distances of 60–120 kpc. Furthermore, these kinematically selected stars lie along an [α/Fe]-deficient track in chemical space from −2.5 < [Fe/H] <− 0.5, consistent with their formation in the Clouds themselves. We identify these stars as high-confidence members of the Magellanic Stellar Stream. Half of these stars are metal-rich and closely follow the gaseous MS, whereas the other half are more scattered and metal-poor. We argue that the metal-rich stream is the recently formed tidal counterpart to the MS, and we speculate that the metal-poor population was thrown out of the SMC outskirts during an earlier interaction between the Clouds. The Magellanic Stellar Stream provides a strong set of constraints—distances, 6D kinematics, and birth locations—that will guide future simulations toward unveiling the detailed history of the Clouds.

Perennial flow through convergent hillslopes explains chemodynamic solute behavior in a shale headwater catchment

Stream chemistry reflects the mixture of complex biogeochemical reactions that vary across space and time within watersheds. For example, streams experience changing hydrologic connectivity to heterogeneous water sources under different flow regimes; however, it remains unclear how seasonal flow paths link these different sources and regulate concentration-discharge behavior, i.e., changes in stream solute concentration as a function of discharge. At the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) in central Pennsylvania, USA, concentrations of chemostatic solutes (K, Mg, Na, Si, Cl) vary little across a wide range of discharge values while concentrations of chemodynamic solutes (Fe, Mn, Ca) decrease sharply with increasing stream discharge. To elucidate controls on chemodynamic solute behavior, we investigated the chemistry of surface water and shallow subsurface water at the SSHCZO in early autumn when discharge was negligible and concentrations of chemodynamic solutes were high. Dissolved ions, colloids, and micron-sized particles were extracted from hillslope soils and stream sediments to evaluate how elements were mobilized into pore waters and transported from hillslopes to the stream.During the study period when flow was intermittent, the stream consisted of isolated puddles that were chemically variable along the length of the channel. Inputs of subsurface water to the stream were limited to an area of upwelling near the stream headwaters, and the water table remained over a meter below the stream bed along the rest of the channel. Chemodynamic elements Fe and Mn were preferentially mobilized from organic-rich soils as a mixture of dissolved ions, colloids, and micron-sized particles; consequently, subsurface water draining organic-rich soils in the upper catchment was enriched in Fe and Mn. Conversely, Ca increased towards the catchment outlet and was primarily mobilized from stream sediments as Ca2+. Concentrations of chemostatic solutes were relatively invariable throughout the catchment.We conclude that chemodynamic behavior at SSHCZO is driven by seasonally variable connectivity between the stream and hillslope soils. During the dry season, stream water derives from a shallow perched water table (interflow) that upwells to generate metal-rich stream headwaters. High concentrations of soluble Fe and Mn at low discharge occur when metal-rich headwaters are flushed to the catchment outlet during periodic rain events. Interflow during the dry season originates from water that infiltrates through organic-rich swales; thus, metals in the stream at low flow are ultimately derived from convergent hillslopes where biological processes have concentrated and/or mobilized these chemodynamic elements. In contrast, high concentrations of Ca2+ at low discharge are likely mobilized from stream sediments that contain secondary calcite precipitates. We infer that chemodynamic solutes are diluted at high discharge primarily due to increased flow through planar hillslopes. This study highlights how spatially heterogeneous biogeochemistry and seasonally variable flow paths regulate concentration-discharge behavior within catchments.

Application of nanofiltration for acidic waters containing rare earth elements: Influence of transition elements, acidity and membrane stability

Acid mine drainage (AMD) is considered the main environmental problem in mining operation due to its acidity, metal content (Fe, Al, Zn, Cu) and onerous associated treatment cost. However, the presence of relatively high levels of added value elements (rare earth elements (REE)) could make its valorisation economically affordable. Membrane nanofiltration (NF) has been postulated as a potential recovery technology because it allows the recovery of a sulphuric acid rich stream and a metal rich stream in one step. In this study, the performance of a semi-aromatic polyamide NF membrane (NF270) in filtering model solutions containing common metals (Ca, Al, Zn) in sulphuric solutions (pH1.5–3.0) was evaluated. In a second stage, the performance was assessed with the same model solutions but also containing REE. NF270 showed high rejections for metallic ions in solution, allowing acid permeation. Ion rejection data were used to determine membrane permeances to ions using the solution-diffusion model considering reactive transport. The stability of the membrane was also studied by comparing performances of a virgin membrane with an aged membrane exposed to 1M sulphuric acid for 4weeks. Physicochemical changes of membrane properties after ageing were also analysed by ATR-FTIR, AFM and XPS.

Combined Recovery of Copper and Mitigation of Pollution Potential of a Synthetic Metal-Rich Stream Draining a Copper Mine in Brazil

A low pH sulfate-reducing bioreactor was used to selectively recover copper from synthetic pH 5 mine water draining a copper mine in Brazil, and also to remove other transition metals from solution. The design of the system used meant that a single bioreactor could be used for the process. Over 99% of the copper present was recovered as CuS in an off-line reactor vessel, while other metals (Ni, Co and Zn) were precipitated in the bioreactor vessel.

Erratum to: Zn biomineralization processes and microbial biofilm in a metal-rich stream (Naracauli, Sardinia)

Species composition of diatoms in biofilm, morphology characteristics, and site characteristics fromwhich the diatoms are known according to: Krammer and Lange-Bertalot (1991); Van Dam et al. (1994); Levkov (2009); Wojtal (2009) Instead of: Species composition of diatoms in biofilm, morphology characteristics, and site characteristics fromwhich the diatoms are known according to: 1—Krammer and Lange-Bertalot (1991); 2—Van Dam et al. (1994); 3—Levkov (2009); 4— Wojtal (2009)

Stratification and segregation features of pulverized electronic waste in flowing film concentration

Gravity separation of metals from plastics in pulverized e-waste using flowing film concentration in a shaking table was investigated. Over 51% rejection of plastics in a single stage operation was achieved under optimum conditions. The shaking table was shown to be suitable for processing ground PCBs. Pulverized e-waste containing 22% metals was enriched to around 40% metals in a single pass. Statistical models for the mass yield of metal-rich stream and its grade were developed by design of experiments. Optimization was carried out to maximize the mass yield at a target product grade and preferred operating regimes were established. Experiments were designed to prevent metal loss and over 95% recovery values were obtained under all conditions. Settling distances of metals and plastics were computed and shown to be good indicators of separation performance. Particle morphology and stratification in the troughs in between the riffles were shown to influence the separation significantly. Water flow-assisted motion of the plastics was captured and its role in determining the effectiveness of separation was described. The efficacy of tabling was well established for treating ground PCBs. The wet process was shown to be environment friendly and sustainable. It is also relatively cheap and has good potential for industrial application. However, rigorous cost estimates will be required before commercial application.

Talus fine sampling as a regional geochemical exploration technique in mountainous regions

Abstract In areas of rugged topography, extensive and rapid dilution of metal-rich stream sediment with barren material can greatly shorten dispersion trains of base metals in drainage sediments. Poor definition of anomalies among stream data can also result from sampling an area of high background metal contents. Consequently, geochemical exploration requires a sample medium which will provide material that is more representative of underlying bedrock. In certain instances, talus fines meet this requirement. Talus fines are collected at regularly spaced intervals near the base of prograding deposits, possibly in conjunction with stream sediment and geological surveys. Sampling is completed more slowly than comparable drainage surveys, but still with relative ease. Sample collection is followed by analysis using routine analytical procedures. Comparison of Cu, Mo, Pb and Zn contents of complementary pairs of stream sediment and talus fine samples from cirques, and U- and V-shaped valleys in central British Columbia shows talus fine geochemistry more successfully outlines mineral occurrences than drainage geochemistry.