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Of recent, adsorption process has gained a lot of attention as a cheap and effective means of removing trace metals from wastewater prior to discharge into water bodies. Being flexible in design and operation, the process has enabled an optimal recovery of trace metals such that the treated effluents meet the desired standards for waste disposal. Mercury is a toxicant released into the environment from natural and anthropogenic sources. It is notorious for having an unusual tendency to bio‐accumulate and persist in the food chain. Presence of mercury in food, especially those of aquatic sources has drastic implications on human health. Therefore, efforts have been made to develop and optimize low‐cost activated carbon (AC) as adsorbents for scavenging mercury from aqueous effluents. Herein, how mercury accumulates across the food chain, its health implications, and the recent advancement in the use of low‐cost ACs as adsorbent for trapping mercury from wastewater are highlighted. Relationship between the mercury removal efficiency and the surface morphology of the adsorbents as well as the influence of prevailing experimental condition on the sorption process were addressed. Challenges and future prospects of the use of low‐cost adsorbents in addressing mercury pollution in the environment are discussed.  相似文献   
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Tight conglomerate reservoirs have complex pore structure and strong heterogeneity which could bring great difficulties in the identification of oil and wa  相似文献   
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This paper provides an overview of regional geochemical mapping using stream sediments from central and south-western Nigeria. A total of 1569 stream sediment samples were collected and 54 major and trace elements determined by ICP-MS and Au, Pd and Pt by fire assay. Multivariate statistical techniques (e.g., correlation analysis and principal factor analysis) were used to explore the data, following appropriate data transformation, to understand the data structure, investigate underlying processes controlling spatial geochemical variability and identify element associations. Major geochemical variations are controlled by source geology and provenance, as well as chemical weathering and winnowing processes, more subtle variations are a result of land use and contamination from anthropogenic activity.  相似文献   
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A combination of vertical electrical soundings (VES), 2D electrical resistivity imaging (ERI) surveys and borehole logs were conducted at Magodo, Government Reserve Area (GRA) Phase 1, Isheri, Southwestern Nigeria, with the aim of delineating the different aquifers present and assessing the groundwater safety in the area. The Schlumberger electrode array was adopted for the VES and dipole-dipole array was used for the 2D imaging. The maximum current electrode spread (AB) was 800 m and the 2D traverse range between 280 and 350 m in the east-west direction. The thickness of impermeable layer overlying the confined aquifer was used for the vulnerability ratings of the study area. Five lithological units were delineated: the topsoil, clayey sand, unconsolidated sand which is the first aquifer, a clay stratum and the sand layer that constitutes the confined aquifer horizon. The topsoil thickness varies from 0.6 to 2.6 m, while its resistivity values vary between 55.4 and 510.6 Ω/m. The clayey sand layers have resistivity values ranging from 104.2 to 143.9 Ω/m with thickness varying between 0.6 and 14.7 m. The resistivity values of the upper sandy layer range from 120.7 to 2195.2 Ω/m and thickness varies from 3.3 to 94.0 m. The resistivity of the clay layer varies from 11.3 to 96.1 Ω/m and the thickness ranges from 29.6 to 76.1 m. The resistivity value of the confined aquifer ranges between 223 and 1197.4 Ω/m. The longitudinal conductance (0.0017–0.02 mhos) assessment of the topsoil shows that the topsoil within the study area has poor overburden protective capacity, and the compacted impermeable clay layer shows that the underlying confined aquifer is well protected from contamination and can be utilized as a source of portable groundwater in the study area. This study therefore enabled the delineation of shallow aquifers, the variation of their thicknesses and presented a basis for safety assessment of groundwater potential zones in the study area.  相似文献   
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This paper presents data and preliminary interpretations on the diagenesis of Early Paleozoic continental margin deposits along a traverse of the Quebec Appalachians near Quebec City, Canada. Regional variations in diagenesis were studied using the thermal maturation of organic matter in shales (reflectance measured on asphaltic bitumen, 105 samples) and illite crystallinity (330 samples). These revealed a regional southeastward increase in grade from the late middle and late stage of diagenesis to epimetamorphism, which is reflected in the distinction of four zones: Zone I representing the late middle diagenetic stage has a mean reflectance in oil (R0) between 1.0 and 1.5% and illite crystallinity between 5.5 and 8.0 mm. Zone II (late diagenetic stage) is characterized by R0=1.5–2.6% and illite crystallinity between 3.5 and 5.5 mm. Anomalously poor illite crystallinities in Zone II (i. e. 5.5 to 8.0 mm) were obtained for black shales, in which improvement of crystallinity lags behind red and green shales. Zone II is subdivided into subzones IIA and IIB. In the former, reflectance and illite crystallinity increase, within individual nappes, as a function of age or depth of burial. In the latter no such dependence is observed, instead diagenetic grade increases regionally in a southeastward direction as it does in zones III and IV. Zone III represents the anchizone in which observed reflectance values R0 range from 2.6 to 4.0% and illite crystallinities from 2.0 to 3.1 mm. In Zone IV (epizone) illite crystallinity is less than 2.0 mm (In terms of reflectance the anchi-zone/epizone boundary was not defined). Zones I and IIA are anomalous in that lower tectonic units are diagenetically less altered than higher tectonic units: R0 varies from 1.71 to 2.30% for the highest tectonic unit (Cambrian Chaudière Nappe), 1.53 to 1.90% (Cambro-Ordovician Bacchus Nappe) and 1.08 to 1.46% (Lower Ordovician Pointe-de-Lévy Nappe) for the middle tectonic units, and 1.01 to 1.15% for the lowest tectonic unit (Middle Ordovician Quebec Promotory Nappe). Thermal maturation and mineral diagenesis in zone IIA are probably due solely to sedimentary burial at the original site of deposition (by an estimated 6 to 7 km of younger sediments) because in this zone the highest diagenetic grade occurs in the highest tectonic unit. Diagenesis in the nappes of zone I probably required additional tectonic burial by the higher nappes because original sedimentary thicknesses that once overlay these Lower and Middle Ordovician rocks appear insufficient to have caused the observed degree of diagenesis. Diagenesis in zone IIA, therefore, was most likely formed entirely before orogenesis; in zone I it is probably partly pre-orogenic in origin and has been transported during nappe-movement. In contrast, diagenesis and metamorphism in zones IIB to IV are interpreted as related to regional synorogenic heating in conjunction with the Taconic orogeny. Thermal maturation levels in zone I indicate that the rocks have not yet passed the “oil window” which is of interest for petroleum exploration in Quebec. An extended English version of this paper is in preparation for the Bulletin of Canadian Petroleum Geology (Ogunyomi et al., ms.).  相似文献   
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In this study, an assessment of the lithogenic concentrations of trace metals in soils and saprolite over basement rock units in Ibadan, SW-Nigeria is presented in respect of bedrock types and geochemical controls on the weathering-associated release of trace metals. Consequently, soil, weathered and fresh rock samples from the Precambrian Basement of SW Nigeria were collected from three different bedrock units within Ibadan metropolis and subjected to mineralogical and geochemical analyses. The analytical results revealed major proportions of oxides in the range of 18–20% Al2O3, 2–6% Na2O and 1–6% K2O for weathered profiles over granite-gneiss and pegmatite units, compared to 2–3% Al2O3, <0.5% Na2O and <1.0% K2O over schist-quartzite. For the trace elements, weathered profiles on granite-gneiss and schist-quartzite settings exhibit similar enrichment trends (enrichment factor, EF l) for most of the trace elements, unlike the pegmatite bedrock. However, enrichments are relatively greater in the top soil unit compared to the intermediate saprolite unit, especially for Pb, Ni, Zn, Cr, Co, Rb, Sr and Ba, a situation attributed to leaching and redistribution within the weathered profiles through pedogenetic process and percolating groundwater.Furthermore, the estimated weathering indices using Ruxton Ratio (RR = {SiO2/Al2O3}) and Chemical Index of Alteration (CIA = 100{Al2O3/[Al2O3 + CaO + Na2O + K2O]}) revealed RR of 2.9–3.7 and CIA of 54–73% for granite-gneiss and pegmatite units, implying medium levels of weathering, compared to RR of 30.8–35.5 and CIA of >60% for schist-quartzite units, which suggest weak chemical weathering. Also, the estimated high percentage loss, especially for Pb, Rb, Sr, Ba relative to the bedrocks, shows that the trace elements can be mobilized within the weathering profiles even at a low degree of chemical weathering. Such weathering-induced release of trace metals is of environmental significance as natural lithogenic input sources and as background reference for future monitoring of possible human/anthropogenic impacts.  相似文献   
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