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61.
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
62.
Susan K. Swanson Maureen A. Muldoon Victor Polyak Yemane Asmerom 《Hydrogeology Journal》2014,22(4):851-863
Tufa-depositing springs in the southern Driftless Area of Wisconsin, USA, are used to inform the response of shallow and local groundwater flow systems to changes in climate over the last 3,000 years. The springs emanate from a shallow, unconfined, sedimentary bedrock aquifer and at stratigraphic positions similar to a shallow, perched aquifer that was identified in the eastern Driftless Area. The perched aquifer was shown to be stable under current climate conditions and over decadal time scales. This study provides further evidence of the significance of the stratigraphic interval in controlling shallow groundwater flow patterns in the region and in the stability of shallow and local groundwater flow systems over thousands of years. The tufa carbonates in three cores collected from the mounds adjacent to the springs show variations in stable isotope (δ13C, δ18O) and elemental (Mg/Ca) values that agree with well-established paleoclimate records for the region, suggesting that the springs were active and depositing tufa in the past, during climate conditions that were similar to the present and during conditions that were drier than the present. 相似文献
63.
Maureen H. Barclay 《新西兰海洋与淡水研究杂志》2013,47(1):67-80
Several species of ostracods, new to New Zealand, are described, including Darwinula sphagna n.sp. and Cypridopsis obstinata n.sp. Limnocythere duffi Hornibrook, 1955 is placed in the genus Gomphocythere Sars, 1924, and a colour variation of Newnhamia fenestrata King, 1855 is discussed. 相似文献
64.
65.
Maureen H. Lewis 《新西兰海洋与淡水研究杂志》2013,47(3):277-297
66.
Beth Ellen Clark Richard P. Binzel Ellen S. Howell Edward A. Cloutis Maureen Ockert-Bell Phil Christensen Maria Antonietta Barucci Francesca DeMeo Dante S. Lauretta Harold Connolly Jr. Alicia Soderberg Carl Hergenrother Lucy Lim Josh Emery Michael Mueller 《Icarus》2011,216(2):462-475
We present reflectance spectra from 0.4 to 2.4 μm of Asteroid (101955) 1999 RQ36, the target of the OSIRIS-REx spacecraft mission. The visible spectral data were obtained at the McDonald Observatory 2.1-m telescope with the ES2 spectrograph. The infrared spectral data were obtained at the NASA Infrared Telescope Facility using the SpeX instrument. The average visible spectrum is combined with the average near-infrared wavelength spectrum to form a composite spectrum. We use three methods to constrain the compositional information in the composite spectrum of Asteroid (101955) 1999 RQ36 (hereafter RQ36). First, we perform a least-squares search for meteorite spectral analogs using 15,000 spectra from the RELAB database. Three most likely meteorite analogs are proposed based on the least-squares search. Next, six spectral parameters are measured for RQ36 and their values are compared with the ranges in parameter values of the carbonaceous chondrite meteorite classes. A most likely meteorite analog group is proposed based on the depth of overlap in parameter values. The results of the least-squares search and the parametric comparisons point to CIs and/or CMs as the most likely meteorite analogs for RQ36, and COs and CHs as the least likely. RQ36 has a spectrally “blue” continuum slope that is also observed in carbonaceous chondrites containing magnetite. We speculate that RQ36 is composed of a “CM1”-like material. Finally, we compare RQ36 to other B-type asteroids measured by Clark et al. (Clark, B.E. et al. [2010]. J. Geophys. Res. 115, E06005). The results of this comparison are inconclusive. RQ36 is comparable to Themis spectral properties in terms of its albedo, visible spectrum, and near-infrared spectrum from 1.1 to 1.45 μm. However, RQ36 is more similar to Pallas in terms of its near-infrared spectrum from 1.6 to 2.3 μm. Thus it is possible that B-type asteroids form a spectral continuum and that RQ36 is a transitional object, spectrally intermediate between the two end-members. This is particularly interesting because Asteroid 24 Themis was recently discovered to have H2O ice on the surface (Rivkin, A., Emery, J. [2010]. Nature 464, 1322–1323; Campins, H. et al. [2010a]. Nature 464, 1320–1321). 相似文献
67.
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