Arsenic accumulation in the roots of Helianthus annuus and Zea mays by irrigation with arsenic-rich groundwater: Insights from synchrotron X-ray fluorescence imaging     

《Chemie der Erde / Geochemistry》2015,75(2):261-270

The aim of this study was to investigate the accumulation of arsenic (As) in and on roots of Zea mays (maize) and Helianthus annuus (sunflower) by means of synchrotron-based micro-focused X-ray fluorescence imaging (μ-XRF). Plant and soil samples were collected from two field sites in the Hetao Plain (Inner Mongolia, China) which have been regularly irrigated with As-rich groundwater. Detailed μ-XRF element distribution maps were generated at the Fluo-beamline of the Anka synchrotron facility (Karlsruhe Institute of Technology) to assess the spatial distribution of As in thin sections of plant roots and soil particles. The results showed that average As concentrations in the roots (14.5–27.4 mg kg⁻¹) covered a similar range as in the surrounding soil, but local maximum root As concentrations reached up to 424 mg kg⁻¹ (H. annuus) and 1280 mg kg⁻¹ (Z. mays), respectively. Importantly, the results revealed that As had mainly accumulated at the outer rhizodermis along with iron (Fe). We therefore conclude that thin crusts of Fe-(hydr)oxides cover the roots and act as an effective barrier to As, similar to the formation of Fe plaque in rice roots. In contrast to permanently flooded rice paddy fields, regular flood irrigation results in variable redox conditions within the silty and loamy soils at our study site and fosters the formation of Fe-(hydr)oxide plaque on the root surfaces.  相似文献   

铁屑微电解法深度处理医院废水     

邹红林  陈恩鉴  许汇娟 《广东海洋大学学报》2002,22(6):45-48

用铁屑微电池原理深度处理了医院废水 ,分析了废水pH、铁屑用量、反应时间对处理效果的影响。结果表明 ,最佳的反应条件为 :废水进水pH为 3.5 ,铁屑用量为 12 .5 % ,常温反应 80min。  相似文献   

Computer simulation of a semi-continuous open-pit mine haulage system     

Shiji Peng  Daxian Zhang  Yongfeng XI 《Geotechnical and Geological Engineering》1988,6(3):267-271

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The amino acid composition of estuarine colloidal material     

A.C. Sigleo  P.E. Hare  G.R. Helz 《Estuarine, Coastal and Shelf Science》1983,17(1):87-96

Amino acids were determined in estuarine colloidal and particulate material from near surface waters ranging from fresh to brackish water (12 g kg^?1 salinity). The hydrolizable amino acids and associated ammonia account for an average of 80% of the nitrogen present in colloidal samples, and approximately 75% of the nitrogen from particulate fractions of the same samples. The relative proportions of these amino acids are similar to those of a cultured estuarine diatom. There are no significant amounts of D amino acids, or non-protein amino acids characteristic of bacteria in sediments and soil. A single deep-water sample (25 m) shows some evidence of bottom mud resuspension by the presence of a possible aspartic acid-hydroxyproline dimer.  相似文献   

Magnetic cleansing of weathered/tarry oiled feathers--the role of pre-conditioners     

Dao HV  Ngeh LN  Bigger SW  Orbell JD  Healy M  Jessop R  Dann P 《Marine pollution bulletin》2006,52(12):1591-1594

Iron powder has previously been demonstrated to be effective in the removal, via magnetic harvesting, of a wide variety of oil contaminants from feathers and plumage. This study investigates the efficacy of magnetic cleansing for the removal from feathers of tarry contamination that has been allowed to weather. Clusters of feathers from Mallard duck (Anas platyrhnchos) and Little Penguin (Eudyptula minor) were completely immersed in a tarry contaminant and allowed to weather from one to fourteen days. The contaminant was removed using a magnetic cleansing protocol and the removal efficacy assessed gravimetrically. For one, seven and fourteen days of weathering, a final removal (after fourteen treatments) of more than 99% and 97% was achieved for duck feathers and penguin feathers, respectively. Repeating the experiments (for a seven-day weathering period) for both duck and penguin feathers, with the judicious application of a pre-conditioner (olive oil), further improved removal efficacy. A convenient method to screen for improved pre-conditioning agents is suggested.  相似文献   

Constraining models of the tectonic setting of the giant Olympic Dam iron oxide–copper–gold deposit, South Australia, using deep seismic reflection data     

Barry Drummond  Patrick Lyons  Bruce Goleby  Leonie Jones 《Tectonophysics》2006,420(1-2):91

In the Gawler Craton, the completeness of cover concealing the crystalline basement in the region of the giant Olympic Dam Cu–Au deposit has impeded any sufficient understanding of the crustal architecture and tectonic setting of its IOCG mineral-system. To circumvent this problem, deep seismic reflection data were recently acquired from  250 line-km of two intersecting traverses, centered on the Olympic Dam deposit. The data were recorded to 18 s TWT ( 55 km). The crust consists of Neoproterozoic cover, in places more than 5 km thick, over crystalline basement with the Moho at depths of 13–14 s TWT ( 40–42 km). The Olympic Dam deposit lies on the boundary between two distinct pieces of crust, one interpreted as the Archean–Paleoproterozoic core to the craton, the other as a Meso–Neoproterozoic mobile belt. The host to the deposit, a member of the  1590 Ma Hiltaba Suite of granites, is situated above a zone of reduced impedance contrast in the lower crust, which we interpret to be source-region for its  1000 °C magma. The crystalline basement is dominated by thrusts. This contrasts with widely held models for the tectonic setting of Olympic Dam, which predict extension associated with heat from the mantle producing the high temperatures required to generate the Hiltaba Suite granites implicated in mineralization. We use the seismic data to test four hypotheses for this heat-source: mantle underplating, a mantle-plume, lithospheric extension, and radioactive heating in the lower crust. We reject the first three hypotheses. The data cannot be used to reject or confirm the fourth hypothesis.  相似文献   

A geographical analysis of the Atalanti alluvial plain and coastline as the location of a potential tourist site, Bronze through Early Iron Age Mitrou, East-Central Greece     

Mark D. Green 《Applied geography (Sevenoaks, England)》2012,32(2):335-349

Tourism accounts for 15% of Greece’s gross domestic product. In the wake of a struggling economy many of Greece’s coastal villages have turned to tourism to supplement local economies. Preliminary analysis of structural and cultural materials recovered from an excavation on Mitrou, a small islet near the coastal village Tragana located 140 km north of Athens has established the site’s contribution to a fuller understanding of settlement practices in Central Greece from the end of the Bronze Age through the Early Iron Age. The site’s historic importance combined with its scenic coastal setting has considerable potential to be developed into an important tourist site. The physical geography of the region is the product of the complex interaction of coastal, alluvial, fluvial, and seismic processes. This investigation integrates the archaeological material with a geographical analysis employing a variety of geographical techniques (soil and sediment analysis, past climatic data, environmental surveys, and geospatial modeling) to reconstruct the geomorphological history of the site and to evaluate the area as a potential tourist site.  相似文献   

Manganese ore deposits in Koira-Noamundi province of Iron Ore Group, north Orissa, India: In the light of geochemical signature   总被引：1，自引：0，他引：1  

B.K. Mohapatra  P.P. Mishra  P.P. Singh  Rajeev 《Chemie der Erde / Geochemistry》2009,69(4):377-394

Several small Mn–Fe oxide and Mn-oxide ore bodies associated with Precambrian Iron Ore Group of rocks are located within Koira-Noamundi province of north Orissa, India. These deposits are classified into in situ (stratiform), remobilized (stratabound) and reworked categories based on their field disposition. Volcaniclastic/terrigenous shale in large geographic extension is associated with these ore bodies.The in situ ore bodies are characterised by cryptomelane-, romanechite- and hematite-dominating minerals, low Mn/Fe ratio (1.1) and relatively lower abundance of trace (1500–2500 ppm) constituents. In such type of deposits the stratigraphic conformity of oxides with the tuffaceous shale suggests precipitation of Mn and Fe at a time of decreased volcaniclastic/terrigenous contribution. The minor and trace elements were removed from solution by adsorption rather than by precipitation. Both Mn and Fe oxides when precipitated adsorb trace elements strongly but the partitioning of elements takes place during diagenesis. The inter-elemental relationship reveals that Cu, Co, Ni, Pb and Zn were adsorbed on precipitating hydrous Mn oxides and form manganates. Some of these elements probably get desorbed from Fe oxide because of their inability to substitute for Fe³⁺ in the lattice of its oxide. However, P, V, As and Mo were less partitioned and retained in Fe-oxide phase. Positive correlation between Al₂O₃ and SiO₂, MgO, Na₂O, TiO₂ and some traces like Li, Nb, Sc, Y, Zr, Th and U points to their contribution through volcaniclastic/terrigenous detritus of both mafic and acidic composition.The remobilized ore bodies are developed in a later stage through dissolution, remobilization and reprecipitation of Mn oxides in favorable structural weak planes under supergene environment. Increase in average Mn/Fe ratio (8) and trace content (5000–8500 ppm) by 5–2.5 orders of magnitude, respectively, or more above its abundance in adjoining/underlying protore is characteristic of these deposits. The newly formed Mn ores constituting lithiophorite, cryptomelane/romanechite and goethite get quantitatively enriched in traces like Cu, Co, Ni, Pb and Zn. Positive correlation between Mn, Li, Co and Zn is due to the formation of mineral of lithiophorite–chalcophanite group during redistribution and reconcentration of Mn oxide. P and V, which were present in Fe oxide, also get dissolved and reprecipitate with Fe oxyhydroxide in these ores. Some other elements like Y, Th and U show positive relation with Fe. This is probably due to leaching of these elements during chemical weathering of associated shale and getting re-adsorbed in Fe-oxyhydroxide phase.However, under oxidizing environment selective cations like Ba, K, etc. resorb from Mn-structure, resulting in the development of pyrolusite (Mn/Fe>20). In such transformation, trace metals from pyrolusitic structure expels out, resulting thereby in a considerable reduction in total trace value (<3000 ppm).The reworked ore bodies are allochthonous in nature and developed through a number of stages during terrain evolution and lateritisation. Secondary processes such as reworking of pre-existing crust; solution and remobilization; precipitation and cementation and transport, etc. are responsible for their development. Such deposits are usually very low in Mn/Fe ratio (3) and trace content (<2000 ppm).  相似文献   

清镇式铁矿矿石特征及加工技术性能探讨 ——以猫场铝土矿红花寨、白浪坝矿段铁矿床为例          下载免费PDF全文

杨明坤  张周位  杨国彬  李宏志  杨毕  苏亮广 《贵州地质》2019,36(1):95-100

贵州中部清镇、修文等地石炭系铝土矿底部的铁矿俗称为"清镇式铁矿",与黔中铝土矿共同赋存于下石炭统九架炉组之中。本文在实际勘探工作及通过勘探阶段在钻孔副样中采集的铁矿进行可选性试验基础上,以同类型的清镇市猫场铝土矿红花寨、白浪坝矿段铝土矿共生的铁矿为研究对象,指出该类型铁矿矿石自然类型为赤铁矿和褐铁矿;工业类型为需选铁矿石;矿石矿物主要为赤铁矿,部分赤铁矿水化为针柱状褐铁矿;脉石矿物则以白云石和方解石为主。矿石中可供利用的主要元素是铁,造渣组分主要是硅、铝,其次为钙、镁等。试验结果表明,该矿采用一粗一精一扫的强磁选试验可获得铁精矿TFe含量55. 58%,回收率80. 11%的良好指标,精矿中各元素含量达到H55-Ⅰ类赤铁精矿质量要求,在当前市场条件下采用推荐工艺处理该矿可获利。结论对黔中铝土矿资源的综合勘查开发具有借鉴意义。  相似文献   

Heating duration of igneous rim formation on a chondrule in the Northwest Africa 3118 CV3oxA carbonaceous chondrite inferred from micro-scale migration of the oxygen isotopes     

《Chemie der Erde / Geochemistry》2019,79(4):125524

Due to their common occurrence in various types of chondrites, igneous rims formed on pre-existing chondrules throughout chondrule-forming regions of the solar nebula. Although the peak temperatures are thought to reach similar values to those achieved during chondrule formation events, the heating duration in chondrule rim formation has not been well defined. We determined the two-dimensional chemical and oxygen isotopic distributions in an igneous rim of a chondrule within the Northwest Africa 3118 CV3_oxA chondrite with sub-micrometer resolution using secondary ion mass spectrometry and scanning electron microscopy. The igneous rim experienced aqueous alteration on the CV parent body. The aqueous alteration resulted in precipitation of the secondary FeO-rich olivine (Fa_40–49) and slightly disturbed the Fe-Mg distribution in the MgO-rich olivine phenocrysts (Fa_11–22) at about a 1 μm scale. However, no oxygen isotopic disturbances were observed at a scale greater than 100 nm. The MgO-rich olivine, a primary phase of igneous rim formation, has δ¹⁷O = −6 ± 3‰ and δ¹⁸O = −1 ± 4‰, and some grains contain extreme ¹⁶O-rich areas (δ¹⁷O, δ¹⁸O = ∼−30‰) nearly 10 μm across. We detected oxygen isotopic migration of approximately 1 μm at the boundaries of the extreme ¹⁶O-rich areas. Using oxygen self-diffusivity in olivine, the heating time of the igneous rim formation could have continued from several hours to several days at near liquidus temperatures (∼2000 K) in the solar nebula suggesting that the rim formed by a similar flash heating event that formed the chondrules.  相似文献