Evaporative evolution of a Na–Cl–NO<Subscript>3</Subscript>–K–Ca–SO<Subscript>4</Subscript>–Mg–Si brine at 95 °C: Experiments and modeling relevant to Yucca Mountain,Nevada     

Maureen?AlaiEmail author  Mark?Sutton  Susan?Carroll 《Geochemical transactions》2005,6(2):31

A synthetic Topopah Spring Tuff water representative of one type of pore water at Yucca Mountain, NV was evaporated at 95°C in a series of experiments to determine the geochemical controls for brines that may form on, and possibly impact upon the long-term integrity of waste containers and drip shields at the designated high-level, nuclear-waste repository. Solution chemistry, condensed vapor chemistry, and precipitate mineralogy were used to identify important chemical divides and to validate geochemical calculations of evaporating water chemistry using a high temperature Pitzer thermodynamic database. The water evolved toward a complex "sulfate type" brine that contained about 45 mol % Na, 40 mol % Cl, 9 mol % NO₃, 5 mol % K, and less than 1 mol % each of SO₄, Ca, Mg, ∑CO₂(aq), F, and Si. All measured ions in the condensed vapor phase were below detection limits. The mineral precipitates identified were halite, anhydrite, bassanite, niter, and nitratine. Trends in the solution composition and identification of CaSO₄ solids suggest that fluorite, carbonate, sulfate, and magnesium-silicate precipitation control the aqueous solution composition of sulfate type waters by removing fluoride, calcium, and magnesium during the early stages of evaporation. In most cases, the high temperature Pitzer database, used by EQ3/6 geochemical code, sufficiently predicts water composition and mineral precipitation during evaporation. Predicted solution compositions are generally within a factor of 2 of the experimental values. The model predicts that sepiolite, bassanite, amorphous silica, calcite, halite, and brucite are the solubility controlling mineral phases.  相似文献   

Settling fluxes in Saanich and Jervis Inlets, British Columbia, Canada: sources and seasonal patterns     

David A Timothy  Maureen Y.S SoonStephen E Calvert 《Progress in Oceanography》2003,59(1):31-73

We conducted a multi-year sediment-trap experiment in Saanich and Jervis Inlets, British Columbia, Canada. Moorings with traps positioned at three depths were placed near the mouth and toward the head of each fjord, and deployments were monthly. We present fluxes of total mass, biogenic silica (BSi), particulate organic carbon (POC) and aluminium (Al), as well as the δ¹³C signal of the POC, and we compare the sediment-trap fluxes to primary-production measurements made during the experiment.Diatomaceous silica and aluminosilicates were the primary components of the settling flux, while organic matter from marine (largely diatoms) and terrestrial sources was occasionally a significant portion of the sinking material. Fluxes of BSi and POC were highest in the spring and summer, tracing maxima in local primary production. These fluxes decreased, increased or remained constant with depth due to water-column remineralisation and variability in processes that cause fluxes to increase with depth. Al fluxes followed local precipitation and river runoff at the landward stations, and with remarkable faithfulness in Saanich Inlet. Near the mouths, there was little seasonality in Al flux, and the increases of flux with depth reveal sedimentary plumes at each fjord’s sill. Tidal and deepwater-renewal components of the plumes are evident, and the plume in Saanich Inlet was particularly intense. Fluxes of Al to deep sediment traps associated with renewal flows were also observed toward the head of each fjord.Marine δ¹³C endmembers are estimated from relationships between δ¹³C and BSi concentrations, and measures of soil δ¹³C from each fjord were available. These endmembers are used with the δ¹³C record to quantify marine and terrigenous contributions to the POC flux. Marine POC composed 54-72% of the total POC caught by shallow sediment traps in spring and summer, and 36-54% in fall and winter. Primary production and sediment-trap fluxes are used to estimate annually averaged export ratios (shallow-trap flux:autotrophic assimilation) for marine POC and Si. POC export ratios (0.092-0.14) were low for these productive waters, but they compare with other results based on sediment-trap fluxes from coastal waters where terrigenous OC has been subtracted. Export ratios of Si were calculated using an estimated Si:C assimilation ratio and, therefore, are susceptible to error, but the high results (>0.8) suggest that BSi was exported more efficiently than POC. The possibility that POC was preferentially lost after interception by sediment traps is also considered. Primary production and settling fluxes were higher in Saanich Inlet than in Jervis Inlet, while export ratios of OC and Si were similar in both fjords, away from the nepheloid layer near the sill of Saanich Inlet.  相似文献   

Ore and Alteration Types of the Gold and Copper Mineralization in the Lascogon Project, Surigao del Norte, Mindanao Island, Philippines     

Jonelle Nikolai Crisostomo    Jeddalyn Parian    Daizo Ishiyama    Redempta Baluda    Sonia Eguia    Jocelyn Galapon    Gerry Comia    Jessie Segura    Maureen Laroco    Noel Oliveros  Victor B. Maglambayan 《Resource Geology》2007,57(2):241-247

Two ore and three alteration types were identified in the Lascogon Project of Philex Gold Philippines, in Surigao del Norte, Mindanao Island, Philippines. The jasperoid ore is the host to the Carlin‐like gold mineralization in the Lascogon and Danao prospects. The ore occurs in a decalcified and silicified horizon, with minor chlorite and goethite, stibnite, pyrite and quartz crystals ranging from cryptocrystalline to botryoidal. The stringer–stockwork type Cu‐Au mineralization in the Suyoc prospect is hosted in argillized andesitic rocks of the Mabuhay Formation. The primary ore minerals are chalcopyrite with minor amounts of sphalerite. The alteration types identified are propylitic alteration, argillic alteration and silicification. The propylitized basaltic and andesitic flows of the Bacuag Formation bound the jasperoid mineralization in the Lascogon prospect. Stratigraphically, the relationship between propylitized basalts and stringer–stockwork Cu‐Au is not clear but a lateral change can be inferred from jasperoid in the center and stringer–stockwork towards the east.  相似文献   

Carbon Stores,Sinks, and Sources in Forests of Northwestern Russia: Can We Reconcile Forest Inventories with Remote Sensing Results?     

Krankina  Olga N.  Harmon  Mark E.  Cohen  Warren B.  Oetter  Doug R.  Olga  Zyrina  Duane  Maureen V. 《Climatic change》2004,67(2-3):257-272

Forest inventories and remote sensing are the two principal data sources used to estimate carbon (C) stocks and fluxes for large forest regions. National governments have historically relied on forest inventories for assessments but developments in remote sensing technology provide additional opportunities for operational C monitoring. The estimate of total C stock in live forest biomass modeled from Landsat imagery for the St. Petersburg region was consistent with estimates derived from forest inventory data for the early 1990s (272 and 269 TgC, respectively). The estimates of mean C sink in live forest biomass also agreed well (0.36 and 0.34 Mg C ha^–1 yr^–1). Virtually all forest lands were accumulating C in live biomass, however when the net change in total ecosystem C stock was considered, 19% of the forest area were a net source of C. The average net C sink in total ecosystem biomass is quite weak (0.08 MgC ha^–1 yr^–1 and could be reversed by minor increases in harvest rates or a small decline in biomass growth rates.  相似文献   

DISCUSSION OF "Delivery of Chloride and Nitrate by Ground Water to the Great Lakes: Case Study for the Door Peninsula, Wisconsin," by Douglas S. Cherkauer, Peter F. McKereghan, and Linda H. Schalch     

Kenneth R. Bradbury  Maureen A. Muldoon 《Ground water》1993,31(6):1030-1031

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Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary     

Gregory G. Shellenbarger  Maureen A. Downing-Kunz  David H. Schoellhamer 《Ocean Dynamics》2015,65(11):1477-1488

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Understanding different perspectives on the preservation of community and heritage buildings in the Wellington Region,New Zealand     

Tatiana Goded  Andrew Beaupre  Michael DeMarco  Tina Dutra  Andro Gogichaishvili  Daniel Haley  Alex Hyman  Nicholas Kepka Calvetti  John Potter  Maureen Coomer  Kim Wright  Andrew King 《Natural Hazards》2017,87(1):185-212

The Canterbury (New Zealand) earthquake sequence of 2010–2012 caused unexpectedly extreme levels of damage and disruption, being an unparalleled event in New Zealand in terms of the damage extent. Christchurch’s heritage buildings were seriously damaged during these events, with churches especially affected in 22 February 2011 M _w 6.2 earthquake. During this earthquake, a total of 84% of the heritage unreinforced stone and 81% of the clay brick masonry churches in the Canterbury region were either considered unsafe (receiving red placards) or with restricted access (yellow placards). Following the earthquakes, authorities across New Zealand are reassessing the capacity of older buildings to resist earthquakes. Current legislation requires that a building judged as earthquake prone either be strengthened by retrofitting or be demolished within a legislated number of years. Many building owners are facing the problems of owning earthquake-prone buildings and lacking the funding to upgrade. This affects both community and heritage buildings, resulting in the likely abandonment or demolition of some buildings. To address the problem of the balance between life safety and preservation in the Wellington Region, this project gathered and compared the perspectives of the general public, church communities, heritage specialists, professional engineers, and local authorities to assist in balancing the interests of these stakeholders. As a result of the findings, several recommendations have been provided that include standardizing structural assessment processes and training, feasibility of additional public funding to upgrade buildings, new signage to increase public awareness of earthquake-prone buildings, and regular communication among stakeholders to understand and resolve differences.  相似文献   

Automated Time Series Measurement of Microbial Concentrations in Groundwater-Derived Water Supplies     

David W. Owens  Randall J. Hunt  Aaron D. Firnstahl  Maureen A. Muldoon  Mark A. Borchardt 《Ground water》2019,57(2):329-336

Fecal contamination by human and animal pathogens, including viruses, bacteria, and protozoa, is a potential human health hazard, especially with regards to drinking water. Pathogen occurrence in groundwater varies considerably in space and time, which can be difficult to characterize as sampling typically requires hundreds of liters of water to be passed through a filter. Here we describe the design and deployment of an automated sampler suited for hydrogeologically and chemically dynamic groundwater systems. Our design focused on a compact form to facilitate transport and quick deployment to municipal and domestic water supplies. We deployed a sampler to characterize water quality from a household well tapping a shallow fractured dolomite aquifer in northeast Wisconsin. The sampler was deployed from January to April 2017, and monitored temperature, nitrate, chloride, specific conductance, and fluorescent dissolved organic matter on a minute time step; water was directed to sequential microbial filters during three recharge periods that ranged from 5 to 20 days. Results from the automated sampler demonstrate the dynamic nature of the household water quality, especially with regard to microbial targets, which were shown to vary 1 to 2 orders of magnitude during a single sampling event. We believe assessments of pathogen occurrence and concentration, and related assessments of drinking well vulnerability, would be improved by the time-integrated characterization provided by this sampler.  相似文献   

A comparative analysis of trace metal pollution parity between sandy and shaly soils: evidence from two mechanic villages in the Imo River basin     

Michael A. Nwachukwu  Huan Feng  Jude Alinnor  Maureen Nwachukwu 《Environmental Earth Sciences》2012,65(3):765-774

Heavy metal enrichment parity in sandy and shaly mechanic village (MV) soils was studied in order to explain the technical and economic imperatives of setting an environmentally friendly MV on either soil. Okigwe (shaly) and Nekede (sandy) mechanic village soils in the Imo River basin Nigeria were tested and compared. Spectroscopic analysis of the soil samples collected from three surface layers (L), where L1: 0–10 cm; L2: 10–20 cm and L3: 90–100 cm shows that Pb > Cu > Mn in the Okigwe MV, and Mn > Pb > Cu in the Nekede MV. Mean concentration of metals (mg kg⁻¹) in Okigwe MV are Fe: 51,291 ± 18,148, Ni: 22 ± 4, Cd: 20 ± 3, Pb: 500 ± 513, Cu: 616 ± 369, Cr: 16 ± 9, and Mn: 378 ± 207. Similarly, Nekede MV has 22,101 ± 7,273 of Fe; 8 ± 0.8 of Ni; 11 ± 4 of Cd; 320 ± 122 of Pb; 265 ± 145 of Cu; 11 ± 2 of Cr; and 350 ± 191 of Mn. Pollution factor (Pf): Okigwe MV has 0.77, and Nekede has 0.68. Pollution degree: Okigwe MV is greater in L1 and L2, while Nekede is greater in L3, with greater potentials for Pb, and Mn mobility than the Okigwe. Both have similar trends of metal distribution, and significant correlation with their background values. Low clay-silt content in Nekede MV soil suggests low sorption capacity, whereas the high clay-silt content (47–64%) of the Okigwe soil suggests lower bioavailability. Infiltration basin is not recommended in a MV on sandy soil if water table is near surface. In such case, the MV must be moved to a location where water table is >37 m, or have clay-shale material transported to the site to form impervious layer base for detention basin. For groundwater safety and sustainability, shaly soils are most recommended for MVs so that detention basin could be economically used for storm water treatment.  相似文献   

Iron Isotope Variations in Coastal Seawater Determined by Multicollector ICP-MS     

Olivier J. Rouxel  Maureen Auro 《Geostandards and Geoanalytical Research》2010,34(2):135-144

In this paper, we applied a reliable technique for measuring Fe isotope variations in coastal seawater at nanomolar levels. Iron was directly pre-concentrated from acidified seawater samples onto a nitrilotriacetic acid chelating resin and further purified using anion-exchange resin. Sample recovery, determined using a standard addition method, was essentially quantitative. Iron was then determined using a high-resolution multicollector ICP-MS (Neptune) coupled to an ApexQ desolvation introduction system. The external precision for δ⁵⁶Fe values was 0.11‰ (2s) when using total a Fe quantity between 25 and 100 ng. We initially applied this technique to measure the Fe isotope composition of dissolved Fe from several coastal environments in the north-eastern United States and we observed a range of δ⁵⁶Fe values between -0.9‰ and 0.1‰ relative to the IRMM-14 reference material. Iron isotope compositions of several reference water materials for inter-laboratory comparisons were also reported. Our results suggest that iron in coastal seawater, derived from benthic diagenesis and/or groundwater has negative Fe isotopic signatures that are distinct from other iron sources such as atmospheric deposition and rivers.  相似文献