The AGN fuelling/feedback cycle in nearby radio galaxies - IV. Molecular gas conditions and jet-ISM interaction in NGC 3100

This is the fourth paper of a series investigating the AGN fuelling/feedback processes in a sample of eleven nearby low-excitation radio galaxies (LERGs). In this paper we present follow-up Atacama Large Millimeter/submillimeter Array (ALMA) observations of one source, NGC 3100, targeting the 12CO(1-0), 12CO(3-2), HCO+(4-3), SiO(3-2) and HNCO(6-5) molecular transitions. 12CO(1-0) and 12CO(3-2) lines are nicely detected and complement our previous 12CO(2-1) data. By comparing the relative strength of these three CO transitions, we find extreme gas excitation conditions (i.e. Tex ≳ 50 K) in regions that are spatially correlated with the radio lobes, supporting the case for a jet-ISM interaction. An accurate study of the CO kinematics demonstrates that, although the bulk of the gas is regularly rotating, two distinct non-rotational kinematic components can be identified in the inner gas regions: one can be associated to inflow/outflow streaming motions induced by a two-armed spiral perturbation; the second one is consistent with a jet-induced outflow with vmax ≈ 200 km s−1 and $\dot{M}\lesssim 0.12$ M⊙ yr−1. These values indicate that the jet-CO coupling ongoing in NGC 3100 is only mildly affecting the gas kinematics, as opposed to what expected from existing simulations and other observational studies of (sub-)kpc scale jet-cold gas interactions. HCO+(4-3) emission is tentatively detected in a small area adjacent to the base of the northern radio lobe, possibly tracing a region of jet-induced gas compression. The SiO(3-2) and HNCO(6-5) shock tracers are undetected: this - along with the tentative HCO+(4-3) detection - may be consistent with a deficiency of very dense (i.e. ncrit > 106 cm−3) cold gas in the central regions of NGC 3100.

Dynamic Behavior of Air Void during the Discharge of Cohesive Powder in a Hopper Using a Rubber Air Spring

An unstable discharge rate occurs during dry fine powder discharge from a hopper because of the significant two-phase solid/gas interactions that occur in powder flows. In addition, the air bubble phenomenon may occur in a silo during fine powder discharge. In this study, we conducted experiments using a semi-conical dual-structure hopper, and examined the effects on the hopper internal flow structure, cavity fluid pressure, pressure inside the airtight cavity section, and the powder discharge rate when changes are made in the position of the supplied air injection port and the solenoid valve open/close timing. From the experimental results, it was confirmed that an appropriate pressure supply port position exists, and the change in expansion/contraction of the flexible container due to air vibration is determined by the balance between the amount of air inserted and the amount of air discharged, and does not affect the presence or absence of powder so much. Furthermore, as the pressure value in the airtight void is directly related to the change in the expansion and contraction of the flexible container, the maximum amplitude value of the pressure in the airtight void can be kept high and constant at the time of opening and closing the solenoid valve.

Stable Bromine Isotopic Composition of Coal Bed Methane (CBM) Produced Water, the Occurrence of Enriched 81Br, and Implications for Fluid Flow in the Midcontinent, USA

This study characterizes the δ37Cl, δ81Br, and 87Sr/86Sr of coal bed methane produced fluids from Pennsylvanian Cherokee Group coals of the Cherokee Basin in southeast Kansas, USA. The δ37Cl, δ81Br, and 87Sr/86Sr values range between −0.81 and +0.68‰ (SMOC), −0.63 and +3.17‰ (SMOB), and 0.70880 and 0.71109, respectively. A large percentage of samples have δ81Br above +2.00‰. Two fluid groups were identified on the basis of K/Br, Br/Cl, and Ca/Mg ratios, temperature, He content, δ2H, δ18O, δ81Br, and 87Sr/86Sr. Both fluid groups have geochemical similarities to fluids in Cambrian, Ordovician, and Mississippian units. Lower salinity and higher temperature fluids from deeper units are leaking up into the Cherokee Group and mixing with a higher salinity fluid with higher δ81Br and more radiogenic 87Sr/86Sr. Variation in δ37Cl indicates an unknown process other than mixing is affecting the salinity. This process does not appear to be related to evaporation, evaporite dissolution, or diffusion. Insufficient data are available to evaluate halide–gas or water–rock interaction, but halide–gas interactions are not likely a significant contributor to high δ81Br. Rather, interactions with organically bound bromine and soluble chloride within the coal could have the strongest effect on δ37Cl and δ81Br values.

Leaching of trace metals (Pb, Zn) from contaminated tailings: New insight from a modelling approach

<p>Reclamation measurements are commonly applied to mitigate the leaching of metal pollutants in order to reduce the risk for humans and the environment. Organic and/or inorganic amendments are often recommended to stabilize tailings and to reduce leaching of contaminants. In a recent microcosm percolation experiment (Thouin et al., 2019), the addition of a mining slurry called ochre and manure, either alone or in combination, drastically reduced the leaching of several metal pollutants, notably Pb. Nevertheless, the biogeochemical processes involved in the immobilization of metal pollutants remain unknown, preventing the management of this remediation technique from being optimized and its extension to other sites.  To fill this gap, a multicomponent reactive model was developed to simulate and forecast the impact of amendments on the leaching of metal pollutants. This model accounts for the following biogeochemical processes: kinetically-controlled dissolution and precipitation reactions, sorption reactions (i.e. surface complexation reactions), water-gas interactions and microbially-driven redox reactions with an explicit microbial growth. For all treatments, simulations revealed that Pb reactivity followed dynamic patterns driven by watering steps. The decrease in Pb concentration in the leachates of amended tailings compared to untreated tailings was also accurately reproduced. In untreated tailings, Pb reactivity is mainly controlled by the dissolution of Pb-bearing mineral phases. These reactions were maintained in thermodynamic disequilibrium due to the renewal of pore solution at each watering step. In amended tailings, this pattern was strengthened as the iron oxides contributed by ochre maintained a low Pb concentration in pore solution by sorbing released Pb. Sorption reactions were enhanced by the increase in pH induced by the dissolution of calcium carbonate initially present in ochre. The latter reaction was partially counterbalanced in tailings amended with manure as organic matter provided sufficient energy to fuel microbial aerobic respiration, leading to the release of protons. Pb desorption was promoted by this pH drop. By providing a better understanding of the effect of amendment, this multicomponent reactive model is a powerful tool to optimize the reclamation of tailings, in order to limit contaminant transfer to the environment.</p><p>Thouin H. et al. (2019), Appl. Geochem. 111, 104438</p>

Understanding the Origin and Mixing of Deep Fluids in Shallow Aquifers and Possible Implications for Crustal Deformation Studies: San Vittorino Plain, Central Apennines

Expanding knowledge about the origin and mixing of deep fluids and the water–rock–gas interactions in aquifer systems can represent an improvement in the comprehension of crustal deformation processes. An analysis of the deep and meteoric fluid contributions to a regional groundwater circulation model in an active seismic area has been carried out. We performed two hydrogeochemical screenings of 15 springs in the San Vittorino Plain (central Italy). Furthermore, we updated the San Vittorino Plain structural setting with a new geological map and cross-sections, highlighting how and where the aquifers are intersected by faults. The application of Na-Li geothermometers, coupled with trace element and gas analyses, agrees in attributing the highest temperatures (>150 °C), the greatest enrichments in Li (124.3 ppb) and Cs (>5 ppb), and traces of mantle-derived He (1–2%) to springs located in correspondence with high-angle faults (i.e., S5, S11, S13, and S15). This evidence points out the role of faults acting as vehicles for deep fluids into regional carbonate aquifers. These results highlight the criteria for identifying the most suitable sites for monitoring variations in groundwater geochemistry due to the uprising of deep fluids modulated by fault activity to be further correlated with crustal deformation and possibly with seismicity.

Controlled sample environment for studying solid–gas interactions by in situ powder X-ray diffraction

A sample cell for powder X-ray diffraction studies with in situ applied pressure and control of temperature is demonstrated. The cell is based on a previously reported design and consists of a glass or quartz capillary glued into a Swagelok weld gland; this configuration can hold up to 100 bar (1 bar = 100 kPa). The cell is placed in contact with a copper plate for control of temperature between −30 and 200°C. This is achieved by Peltier elements, heat cartridges and a refrigerated circulating bath. This work mainly focuses on the temperature control system. Commissioning tests were performed in a custom-made small/wide-angle X-ray diffractometer at the Norwegian University of Science and Technology. The system is easily portable to synchrotron facilities.