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Bamidele I. Olu-Owolabi Paul N. Diagboya Chukwunonso P. Okoli Kayode O. Adebowale 《Environmental Earth Sciences》2016,75(24):1494
In order to predict exposure risks as well as appropriate remediation strategies for pesticides in soils, knowledge of pesticides sorption processes onto various representative soils is vital. Hence, laboratory batch experiments were carried out to study sorption of a pesticide, pentachlorophenol (PCP), on five soils obtained from different sub-Saharan agro-ecological zones (AEZs) in order to understand sorption equilibrium, kinetics, and thermodynamics. Experimental data showed that sorption equilibrium was attained within 24 h. The fitting of kinetic results and equilibrium data to different models suggested partly surface adsorption and partly partitioning of PCP within voids of the various soil components. Sorption was mainly attributed to sharing or exchange of valence electrons between negatively charged PCP molecules and positively charged soil sorption sites. The sorption process was spontaneous and accompanied by decreased entropy, but was pH and temperature dependent, reducing with increase in pH and temperature. The various soils’ PCP sorption capacities were directly proportional to their cation exchange capacities. The low PCP sorption observed in these soils suggested high risk of PCP being present in soil water solution, especially at higher temperatures, which can lead to contamination of the aquifer. This risk may be higher for soils obtained from AEZs with warmer natural temperatures. 相似文献
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Saleh Ibrahim Bute Xiaoyong Yang Xueming Yang Musa Bala Girei Amuda Abdulgafar Kayode Yigan Lu 《Chemie der Erde / Geochemistry》2022,82(1):125809
This study reports a new dataset of whole-rock geochemistry, biotite chemistry, in situ zircon UPb geochronology and Hf isotope for a suite of granite and associated pegmatite samples from the Gubrunde region in the Eastern Nigeria Terrane (ENT), Nigeria. The Gubrunde granitic rocks are weakly ferroan, peraluminous and calc-alkalic to alkali-calcic in composition, and show I-type affinity. The zircon UPb geochronology gives an age of ~580 Ma for the rocks, although the presence of inherited zircons with early Pan-African ages of 696 ± 12, 647 ± 7 and 624–613 Ma are evident indicative of a complex history of their source rocks. The Gubrunde granite and the pegmatite yielded similar average Hf crustal model age TDM2 of 1.9 ± 0.1 Ga and εHf(t) values ?6.2 ± 1.2, suggesting that they may have sourced from reworked old crustal rocks with minor contributions from the mantle. The granite and the pegmatite were likely to connect by fractional crystallization under low to moderate pressure (~2.2 to 3.0 kbar) and temperature (~717 °C), and low oxygen fugacity (<ΔNNO ?1.14). The ca. 580 Ma magmatism may have been triggered by delamination of the lithospheric mantle as a consequence of crustal thinning during waning stage of the Pan-African orogeny. 相似文献
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This paper investigates the motion of a test particle around the triangular equilibrium points under the effects of radiation pressure of the second primary and its Poynting–Robertson (P–R) effect when the first primary is an oblate spheroid. It is seen that triangular points are influenced by the presence of these parameters: radiation pressure from the secondary and the incidental P–R effect and the oblateness of the first primary. The linear stability of the problem is studied and applied to the binary system RXJ 0450.1-5856, the triangular points are unstable due to positive roots in the Lyapunov sense when P–R effect is considered as against their conditional stability in the absence of P–R drag effect. 相似文献
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While empirical works that analyse rural–urban differentials in accessibility to health services are common in the developing countries, systematic studies focusing on intra-urban variations in accessibility to overall healthcare resources remain scant. Yet, many urban dwellers especially in the Sub-Saharan Africa have to travel long distances within the urban space to access basic health services. This study employs composed index of critical accessibility (CICA) to analyse differentials in access to health resources in Ibadan, a traditional African City. Data on healthcare centre location, ownership, doctors’ population were collected through field survey while spatial data on the administrative units and populated places were obtained from archival sources. Also, data on road networks was collected. Results show that the distribution of health facilities across local administrative units varies. In terms health facilities, Ibadan South West has 26 (36 %) of the total number while Ibadan South east has only 7 (9.8 %). The Doctor-Population Ratio also exhibits similar variations as Ibadan North has 20.5 as against 2.2, 1.9 and 0.3 for Ibadan SW, Ibadan NW and Ibadan NE respectively. The CICA analysis shows that 228,938 inhabitants are in high risk of negative accessibility while 49,234 are faced with condition of low risk of negative accessibility, which implies that a significant proportion of the population still finds it difficult to access basic health services as and when needed. The variations in the distribution of this deprived population are also noteworthy as the largest proportion of this group was localized in Ibadan NW. This has grave implication for the health and wellbeing of the population and raises once again the question of spatial equity in the delivery of urban public service. Curiously, these differences in the level of accessibility cut across administrative boundaries which brings to the fore the role of jurisdictional partitioning in ensuring equity in the delivery of urban public services. This opens a vista of research opportunity into the role jurisdictional partitioning in service provision in the urban centres. 相似文献
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Kayode Festus Oyedele Olubukola T. Fatuna Olakunle J. Coker 《Arabian Journal of Geosciences》2011,4(3-4):543-550
Surface geophysics and a priori information were employed to delineate the subsurface geology at Idi-oro in Abijo, Ibeju Lekki area of Lagos, Nigeria for foundation investigation purpose. Resistivity measurement was conducted using 1-D and 2-D resistivity probing techniques. The resistivity measurements were made with ABEM tetrameter model SAS 1000 system. The 1-D vertical electrical resistivity sounding data were obtained using the Schlumberger electrode array while the 2-D resistivity data were obtained using the dipole–dipole array. The interpreted results revealed three to five subsurface geological layers. This is made up of the top soil with resistivity values that vary from 132.4 to over 2,313.5 Ω?m and thickness values that range from 0.3 to 4.8 m, the fine sand with resistivity values that vary from 221.0 to 3,032.7 Ω?m and thickness values that range from 0.4 to 5.5 m, the medium sand with resistivity values that vary from 202.8 to 1,247.7 Ω?m and thickness values that range from 4.9 to 58.4 m. On the other hand, the clayey sand has the resistivity values that vary from 146.1 to 1,744.0 Ω?m and thickness values that vary from 2.2 to 26.3 m, while the coarse sand has resistivity values that vary from 238.3 to 14,313.9 Ω?m but with no thickness value because the current terminated in this layer. The resistivity data correlate well with borehole logs. On the whole, it is concluded that the investigated area has competent sand layer that can support medium to giant engineering structures with resistivity values that vary from 202 to 14,314 Ω?m and thickness values that vary from 0.8 to 58.4 m. 相似文献
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