The continuum and narrow line region of the NLS1 galaxy Mrk 766

We present the first spectroscopic observations in the interval 0.8-4.0 microns, complemented with HST/UV and optical spectroscopy, of the narrow line Seyfert 1 galaxy Mrk766. The NIR spectrum is characterized by permitted lines of HI, HeI, HeII and FeII, and forbidden lines of [SII], [SIII] and [FeII] among others. High ionized species such as [SiIX], [SiX], [SIX] and [MgVII] are also observed. The continuum has a complex shape, with contribution of the central engine, circumnuclear stellar population and dust. This last component is evidenced by the presence of an excess of emission peaking at 2.25 microns, fitted by blackbody function with T_bb=1200K. That temperature is close to the evaporation temperature of graphite grains. As such, it provides strong evidence of hot dust, probably very close to the nucleus. Consistent modeling of the line and broad band continuum spectrum by composite models, which account for the photoionizing flux of the central engine and shocks, shows that the shock velocities are between 100 and 500 km/s, the preshock densities between 100 and 1000 cm^-3 and the radiation fluxes from the active centre between 10^9 and 5x10^12 photons cm^-2 s^-1 eV^-1 at 1 Ryd with spectral indices $\alpha_{UV}$=-1.5 and $\alpha_X$=-0.4. Adopting silicon grains, dust-to-gas ratios are between 10^-{6} and 4x10$^{-4}$ by mass. The emitting clouds are at an average distance of 160 pc from the centre, with high velocity clouds closer and low velocity clouds farther from the centre. The N/H relative abundance could be twice solar. In constrast, Fe is depleted from the gaseous phase by a factor >2. Ratios of calculated to observed line ratios to Hbeta indicate an average contribution of the broad line region to the observed Hbeta of about 40%.Comment: 15 pages, 6 figures. Accepted to MNRA

Effectiveness of Organic Carbon Cover Systems on Sulfide-rich Tailings

Acid mine drainage (AMD) occurs when sulfide minerals oxidize; generating low pH water and the release of dissolved metals. This phenomena is of primary concern in the mining industry, where the future loading of dissolved metals from inactive mine sites could continue for decades to centuries, with recent estimates of total liability related to AMD remediation exceeding $10 billion in Canada alone (Mining Watch Canada, 2017). Traditionally, remediation of AMD generally is focused on collection and treatment of water from surface-water bodies (i.e., ponds, ditches and streams) and treatment through pH neutralization using lime (CaO). While this approach improves water quality, it represents a recurring cost for the mining companies who need to continue operating these systems after mine closure. Due to this reality, numerous approaches have been developed over the past few decades to passively mitigate and remediate AMD by limiting the supply of O2 and water to tailings rich in sulfide minerals. These passive approaches can be done through the use of: 1) cover systems by limiting O2(g) diffusion and/or O2(g) consumption; and 2) waters covers by limiting O2(g) diffusion. Examples of option 1) include biosolids, wood-waste, peat, compost, geosynthetic clay liners (GCL), covers with capillary barrier effects (CCBEs), and monolayer covers with an elevated water table; while an example of option 2) is subaqueous tailings disposal. The performance of a cover system, consisting of a 0.5 m layer of biosolids fertilizer and municipal compost underlain by a ~ 2 m layer of thickened desulfurized tailings (DST), was studied. Six locations were investigated, including four locations with a 2-layer cover system, one location with a 1-layer cover of DST only, and one location without any cover system. The DST layer had been in place for up to 12 years and the organic cover components in place between 5 and 8 years. Results demonstrated that the cover system was able to consume all atmospheric O2(g) prior to the base of the cover system, resulting in improved water quality when compared to the location without a cover system. Comparison between the locations with a 2-layer cover system and the location with a 1-layer cover revealed that the current geochemical conditions were similar, except that the organic layer consumes a portion of incoming O2(g) and leaches alkalinity to the shallow porewater; thus improving the acid-neutralizing capacity. This research shows that cover systems which use an organic layer over top of a low sulfur (S) thickened tailings layer with an elevated water table can limit oxidation of the tailings and neutralize acidity. However, in order for the organic carbon portion of this cover system to operate as an effective O2 barrier in the long-term, occasional replenishment of organic material is required

The use of an organic carbon cover system at a Cu-Ni mine in Sudbury, ON

Acid rock drainage (ARD) occurs when sulfide minerals oxidize, generating low pH water and the release of dissolved metals. This phenomenon is one of the most significant concerns in the mining industry, where the future loading of dissolved metals from inactive mine sites could continue for decades to centuries. Traditionally, remediation of ARD is focused on collection of water from surface-water bodies and treatment through pH neutralization using lime (CaO). While this approach improves water quality, it represents a recurring cost for mining companies. Therefore, numerous approaches have been developed over the past few decades to passively mitigate and remediate ARD by limiting the supply of O₂(g) and water to tailings rich in sulfide minerals. For example, some cover systems utilize organic carbon material such as biosolids, wood-waste, peat and compost. A two-layer cover system was studied at an active Cu-Ni mine site located near Sudbury, ON and comparisons were made between sites with a two-layer cover system, a one-layer cover of desulfurized tailings only, and no cover. Pore-gas results show that the organic layer consumes a portion of the O₂(g) ingress from the atmosphere, with most of the O₂(g) depletion occurring in the desulfurized tailings layer. Pore-water results show that the organic carbon layer increases the alkalinity and that the presence of the desulfurized tailings vastly improves water quality. Thus, the re-use of waste products within a cover system has the potential to sustainably manage ARD in the near term and further study on their use as a land reclamation measure is warranted.Non UBCUnreviewedOthe

Correlated multiwavelength emission from the X-ray-bright Seyfert galaxy III Zw 2

‘The definitive version is available at www.blackwell-synergy.com '. Copyright Blackwell Publishing. DOI: 10.1046/j.1365-8711.2002.05603.x [Full text of this article is not available in the UHRA]Peer reviewe