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1.
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2.
A worldwide data set of 1,085 samples containing organic matter of the type II/III kerogen from Carboniferous to Cenozoic was used to analyse the evolution of the hydrogen index (HI), quality index (QI), and bitumen index (BI) with increasing thermal maturity. The HImax, QImax and BImax lines were defined, based on statistical analysis and cross-plots of HI, QI and BI versus the vitrinite reflectance (%Ro) and T max (°C). The constructed HI, QI and BI bands were broad at low maturities and gradually narrowed with increasing thermal maturity. The petroleum generation potential is completely exhausted at a vitrinite reflectance of 2.0–2.2 % and T max of 510–520 °C. An increase in HI and QI suggests extra petroleum potential related to changes in the structure of the organic material. A decline in BI signifies the start of the oil window and occurs within the vitrinite reflectance range 0.75–1.05 % and T max of 440–455 °C. Furthermore, petroleum potential can be divided into four different parts based on the cross-plot of HI versus %Ro. The area with the highest petroleum potential is located in “Samples and methods” with %Ro = 0.6–1.0 %, and HI > 100. Oil generation potential is rapidly exhausted at “Results and discussion” with %Ro > 1.0 %. This result is in accordance with the regression curve of HI and QI with %Ro based on 80 samples with %Ro = 1.02–3.43 %. The exponential equation of regression can thus be achieved: HI = 994.81e?1.69Ro and QI = 1,646.2e?2.003Ro (R 2 = 0.72). The worldwide organic material data set defines two range of oil window represented by the upper and lower limits of the BI band: %Ro 0.75–1.95 %, T max 440–525 °C, and %Ro 1.05–1.25 %, T max 455–465 °C, respectively.  相似文献   

3.
Fine sediment inputs can alter estuarine ecosystem structure and function. However, natural variations in the processes that regulate sediment transport make it difficult to predict their fate. In this study, sediments were sampled at different times (2011–2012) from 45 points across intertidal sandflat transects in three New Zealand estuaries (Whitford, Whangamata, and Kawhia) encompassing a wide range in mud (≤63 μm) content (0–56 %) and macrofaunal community structure. Using a core-based erosion measurement device (EROMES), we calculated three distinct measures of sediment erosion potential: erosion threshold (? c ; N m?2), erosion rate (ER; g m?2 s?1), and change in erosion rate with increasing bed shear stress (m e ; g N?1 s?1). Collectively, these measures characterized surface (? c and ER) and sub-surface (m e ) erosion. Benthic macrofauna were grouped by functional traits (size and motility) and data pooled across estuaries to determine relationships between abiotic (mud content, mean grain size) and biotic (benthic macrofauna, microbial biomass) variables and erosion measures. Results indicated that small bioturbating macrofauna (predominantly freely motile species <5 mm in size) destabilized surface sediments, explaining 23 % of the variation in ? c (p ≤ 0.01) and 59 % of the variation in ER (p ≤ 0.01). Alternatively, mud content and mean grain size cumulatively explained 61 % of the variation in m e (p ≤ 0.01), where increasing mud and grain size stabilized sub-surface sediments. These results highlight that the importance of biotic and abiotic predictors vary with erosion stage and that functional group classifications are a useful way to determine the impact of benthic macrofauna on sediment erodibility across communities with different species composition.  相似文献   

4.
Instrumental and historical data on mainshocks for 13 seismogenic sources in western Anatolia have been used to apply a regional time- and magnitude-predictable model. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T t = 0.13 M min + 0.21 M p ? 0.15 log M 0 + 2.93 and M f = 0.87 M min ? 0.06 M p + 0.33 log M 0 ? 6.54. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.29, respectively, for the first relation, and 0.65 and 0.47, respectively, for the second relation. The positive dependence of T t on M p and the negative dependence of M f on M p indicate the validity of time- and magnitude-predictable model on the area considered in this study. On the basis of these relations and using the occurrence time and magnitude of the last main shocks in each seismogenic source, the probabilities of occurrence P(Δt) of the next main shocks during the next 50 years with decade interval as well as the magnitude of the expected main shocks were determined. The highest probabilities P 10 = 80 % (M f = 6.8 and T t = 13 years) and P 10 = 32 % (M f = 7.6 and T t = 29 years) were estimated for the seismogenic source 11 (Golhisar-Dalaman-Rhodes) for the occurrence of a strong and a large earthquake during the future decade, respectively.  相似文献   

5.
Microprobe analysis, single crystal X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray absorption spectroscopy were applied on Fe-rich osumilite from the volcanic massif of Mt. Arci, Sardinia, Italy. Osumilite belongs to the space group P6/mcc with unit cell parameters a = 10.1550(6), c = 14.306(1) Å and chemical formula (K0.729)C (Na0.029)B (Si10.498 Al1.502)T1 (Al2.706 Fe 0.294 2+ )T2 (Mg0.735 Mn0.091 Fe 1.184 2+ )AO30. Structure refinement converged at R = 0.0201. Unit cell parameter a is related to octahedral edge length as well as to Fe2+ content, unlike the c parameter which does not seem to be affected by chemical composition. The determination of the amount of each element on the mineral surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si2p, Al2p, Mg1s and Fe2p core levels, suggests that Fe presents Fe2+ oxidation state and octahedral coordination. Two peaks at 103.1 and 100.6 eV can be related to Si4+ and Si1+ components, respectively, both in tetrahedral coordination. The binding energy of Al2p, at 74.5 eV, indicates that Al is mostly present in the distorted T2 site, whereas the Mg peak at 1,305.2 eV suggests that this cation is located at the octahedral site. X-ray absorption at the Fe L2,3-edges confirms that iron is present in the mineral structure, prevalently in the divalent state and at the A octahedral site.  相似文献   

6.
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7.
The stress [crack damage stress (σ cd) and uniaxial compressive strength (σ c)] and strain characteristics [maximum total volumetric strain (ε cd), axial failure strain (ε af)], porosity (n) and elastic constants [elastic modulus (E) and Poisson’s ratio (ν)] and their ratios were coordinated with the existence of two different types (type 1 and type 2) of volumetric strain curve. Type 1 volumetric strain curve has a reversal point and, therefore, σ cd is less than the uniaxial compressive strength (σ c). Type 2 has no reversal point, and the bulk volume of rock decreases until its failure occurs (i.e., σ cd = σ c). It is confirmed that the ratio between the elastic modulus (E) and the parameter λ = n/ε cd strongly affects the crack damage stress (σ cd) for both type 1 and type 2 volumetric strain curves. It is revealed that heterogeneous carbonate rock samples exhibit different types of the volumetric strain curve even within the same rock formation, and the range of σ cd/σ c = 0.54–1 for carbonate rocks is wider than the range (0.71 < σ cd/σ c < 0.84) obtained by other researchers for granites, sandstones and quartzite. It is established that there is no connection between the type of the volumetric strain curve and values of n, E, σ cd, ν, E/(1 ? 2ν), M R = E/σ c and E/λ. On the other hand, the type of volumetric strain curve is connected with the values of λ and the ratio between the axial failure strain (ε af) and the maximum total volumetric strain (ε cd). It is argued that in case of small ε af/ε cd–small λ, volumetric strain curve follows the type 2.  相似文献   

8.
The main objective of this paper was to investigate the dewatering behaviour of a clayey uranium ore slurry. The slurry (containing 28% clay size) exhibited moderate water adsorption (w l  = 83% and w p  = 30%). Primarily composed of muscovite (46%) and quartz (30%), the clay minerals included illite (8%), chlorite (5%) and kaolinite (2%) alongside a CEC of 41 (cmol(+)/kg) with Ca2+ and Mg2+ as the dominant cations. Likewise, the high EC (17,600 μS/cm) and ionic strength (1.15 mol/L) indicated a flocculated microstructure due to the presence of SO4 2? (22,600 mg/L) and Mg2+ (1340 mg/L) in the slurry water. Settling included sedimentation and consolidation at low initial solids condition (25–35%) whereas only consolidation was observed at high initial solids contents (40–50%). The average k reduced from 1.2 × 10?6 m/s (initial s = 25%) to 5.3 × 10?8 m/s (initial s = 50%) along with a void ratio reduction from 7.4 to 2.6. Due to thixotropic strength, volume compressibility during consolidation showed apparent pre-consolidation at low effective stress (0.3–2 kPa) with a reduction in void ratio from 2.6 to 2.5. The e s was found to be 2.46 at σ′ = 2 kPa and was followed by a steeper slope with the void ratio reducing to 2.1 at σ′ = 31 kPa. Likewise, the hydraulic conductivity during consolidation decreased from 2.6 × 10?9 m/s (at e = 2.6) to 2.0 × 10?10 m/s (at e = 2.1).  相似文献   

9.
A high-pressure single-crystal X-ray diffraction study has been carried out on a P21/c natural Mg-rich pigeonite sample with composition ca. Wo6En76Fs18 using a diamond anvil-cell. The unit-cell parameters were determined at 14 different pressures to 7.14 GPa. The sudden disappearance of the b-type reflections (h + k = odd) and a strong discontinuity (about 2.8%) in the unit-cell volume indicated a first-order P21/c–C2/c phase transition between 4.66 and 4.88 GPa. The P(V) data of the P21/c phase were fitted to 4.66 GPa by a third-order Birch–Murnaghan equation of state (BM3 EoS), whereas the limited number of experimental data collected within the C2/c phase between 4.88 and 7.14 GPa were fitted using the same equation of state but with K′ constrained to the value obtained for the P21/c fitting. The equation of state coefficients are V 0 = 424.66(6) Å3, K T0 = 104(2) GPa and K′ = 8(1) for the P21/c phase, and V 0 = 423.6(1) Å3, K T0 = 112.4(8) GPa, and K′ fixed to 8(1) for the C2/c phase. The axial moduli for a, b, and c for the P21/c phase were obtained using also a BM3-EoS, while for the C2/c phase only a linear calculation could be performed, and therefore the same approach was applied for comparison also to the P21/c phase. In general the C2/c phase exhibits axial compressibilities (β c > β a >> β b) lower than those of the P21/c phase (β b > β c ≈ β a; similar to those found in previous studies in clinopyroxenes and orthopyroxenes). The lower compressibility of the C2/c phase compared with that of the P21/c could be ascribed to the greater stiffness along the b direction. A previously published relationship between P c and M2 average cation radius (i.r.) has been updated using all the literature data on P21/c clinopyroxene containing large cations at M2 site and our new data. The following weighted regression was obtained: P c (GPa) = 26(4) ? 28(5) ×  i.r (Å), R 2 = 0.97. This improved equation can be used to predict the critical pressure of natural P21/c clinopyroxene samples just knowing the composition at M2 site.  相似文献   

10.
The effects of several parameters on the simultaneous saccharification and fermentation of straw stalk for ethanol fuel production were investigated on the basis of orthogonal experiments. The parameters include temperature and time of fermentation, quantity and proportion of yeast inoculation, as well as cellulase dosage. An ethanol yield of 0.183 g/g was obtained from the straw stalk pretreated with diluted acid under determined optimum conditions. These conditions were: fermentation temperature: 38℃; fermentation time: 72 h; yeast inoculation quantity: 15%; yeast inoculation proportion: 2:1; and cellulose enzyme dosage: 20 U/g. The relationship between ethanol concentration c and fermentation time t is presented as follows, c=abt/(1+bt). The rate constant k of straw stalk hydrolysis by the cellulose enzyme depends on hydrolysis time, as described by k=k1t-h. Therefore, straw stalk hydrolysis reaction by the cellulose enzyme is fractal-like.  相似文献   

11.
In this study, the effects of salinity of infiltrating solutions on the swelling strain, compressibility, and hydraulic conductivity of compacted GMZ01 Bentonite were investigated. After swelling under vertical load using either distilled water or NaCl solutions with concentrations of 0.1, 0.5 M, and 1 M, laboratory oedometer tests were conducted on the compacted GMZ01 Bentonite. Based on the oedometer test results, hydraulic conductivity was determined using the Casagrande’s method. Results show that the swelling strain of highly compacted GMZ01 Bentonite decreases as the concentration of NaCl solution increases. The compression index C c * increases and then turns to decrease with an increase in the vertical stress or a decrease in the void ratio for different solutions, and the C c * decreases as the concentration of NaCl solution increases. The secondary consolidation coefficient C α increases linearly with the increase of the compression index C c * . Furthermore, a bi-linear relationship between the swelling index C s * and the secondary consolidation coefficient C α can be characterized clearly. The hydraulic conductivity increases as the concentration of NaCl solution increases, however, this increase can be prevented if a high confining stress is applied.  相似文献   

12.
In semiarid Sahelian region, the dynamics of soil organic carbon (SOC) and water are key to sustainable land management. This work focuses on the behaviour of carbon. A total of 33 soil profiles in four polders, ranging from 10 to 65 years in age, were sampled, analysed (0–1 m), and matched with marsh soil profiles in recent sediments considered as reference (t0) for carbon stocks determination. SOC and soil inorganic carbon (SIC) stocks show a spatial variability between polders. SOC stocks were t0 200 ± 0.8; t60 183 ± 34; and t65 189 ± 1.1 MgC·ha?1, whereas the SIC stocks were negligible. These results show the highest stocks of soil carbon observed for this climatic region. The SOC stocks were also calculated for the equivalent soil mass at a defined depth (0–0.3 m); the corrected calculation of SOC stocks (Scorr) for 2450 Mg·ha?1 of equivalent soil mass is t0 64 ± 1.9, t60 59 ± 9.8, and t65 53 ± 2.2 MgC·ha?1; the stocks decrease by ?7.8% and ?17.2% from t0 to t60 and t65. Carbon was inherited from the pre-existing·marsh and the polders have conserved high stock values.  相似文献   

13.
In this paper, we present zircon U–Pb age and Hf isotope data to document the significance of magma mixing in the formation of Late Jurassic granitoid intrusions in the eastern Qinling Orogen, China. The Muhuguan granitoid pluton from this orogen consists of monzogranite and lesser biotite granite and granodiorite, all containing abundant hornblende-rich cumulates, dioritic xenoliths, and mafic magmatic enclaves (MMEs). The monzogranite and granodiorite are intruded by a number of lamprophyre dykes. Both a cumulate and a dioritic xenolith samples have concordant zircon U–Pb ages of ca. 161 ± 1 Ma, but possess contrasting Hf isotopic compositions. The cumulate has more radiogenic zircon Hf isotopes with negative ε Hf(t) values (?7.9 to ?2.5) and T DM1 ages of 0.9–1.1 Ga, indicating its derivation likely from basaltic rocks of the Neoproterozoic to early Paleozoic Kuanping Group in the area. The dioritic xenolith has much lower zircon ε Hf(t) values of ?19.5 to ?8.8 and T DM2 ages of 2.4–1.7 Ga, consistent with a juvenile Paleoproterozoic crust source presumably represented by the metabasic rocks of the Qinling Group in the area. Individual samples of the monzogranite, MME, and a lamprophyre dyke have U–Pb ages of 150 ± 1, 152 ± 1, and 152 ± 1 Ma, respectively, demonstrating coeval mafic and felsic magmatism in the Late Jurassic. The lamprophyre dyke has homogeneous, highly negative zircon ε Hf(t) values (?29.8 to ?24.8) and Archean T DM2 ages (3.0–2.7 Ga), and its genesis is interpreted as partial melting of an ancient enriched subcontinental mantle source. Zircons from the fine-grained MME show a large range of ε Hf(t) between ?29.1 and ?9.8, overlapping values of the monzogranite and lamprophyre dyke samples. Zircon U–Pb age and Hf isotopes of the MMEs are consistent with their formation by mixing of crustal- and enriched mantle-derived magmas. The main group of zircons from the monzogranite has ε Hf(t) values (?17.9 to ?9.3) and T DM2 ages (2.3–1.8 Ga) that are compatible with the dioritic xenoliths, indicating that the former was produced by partial melting of Paleoproterozoic crustal source with involvement of mantle-derived magmas. Mafic magmatism revealed from the Muhuguan pluton indicates that the eastern Qinling Orogen was dominated by lithospheric extension during the Late Jurassic. Compilation of existing geological and geochronological data suggests that this extensional event started in Late Jurassic (ca. 160 Ma) and persisted into the Early Cretaceous until ca. 110 Ma. The Jura-Cretaceous extension may have resulted from the late Mesozoic westward subduction of the Pacific plate beneath the East Asian continental margin.  相似文献   

14.
Information on soil water storage (SWS) within soil profiles is essential in order to characterize hydrological and biological processes. One of the challenges is to develop low cost and efficient sampling strategies for area estimation of profile SWS. To test the existence of certain sample locations which consistently represent mean behavior irrespective of soil profile wetness, temporal stability of SWS in ten soil layers from 0 to 400 cm was analyzed in two land uses (grassland and shrub land), on the Chinese Loess Plateau. Temporal stability analyses were conducted using two methods viz. Spearman rank correlation coefficient (r s) and mean relative differences. The results showed that both spatial variability and time stability of SWS increased with increasing soil depth, and this trend was mainly observed at above 200 cm depth. High r s (p?<?0.01) indicated a strong temporal stability of spatial patterns for all soil layers. Temporal stability increased with increasing soil depth, based on either r s or standard deviation of relative difference index. The boundary between the temporal unstable and stable layer of SWS for shrub land and grassland uses was 280 and 160 cm depth, respectively. No single location could represent the mean SWS for all ten soil layers. For temporal stable layers, however, some sampling locations could represent the mean SWS at different layers. With increasing soil depth, more locations were able to estimate the mean SWS of the area, and the accuracy of prediction for the representative locations also increased.  相似文献   

15.
The crystallographic structures of the synthetic cheralite, CaTh(PO4)2, and its homolog CaNp(PO4)2 have been investigated by X-ray diffraction at room temperature. Rietveld analyses showed that both compounds crystallize in the monoclinic system and are isostructural to monazite LnPO4 (Ln = La to Gd). The space group is P21/n (I.T. = 14) with Z = 2. The refined lattice parameters of CaTh(PO4)2 are a = 6.7085(8) Å, b = 6.9160(6) Å, c = 6.4152(6) Å, and β = 103.71(1)° with best fit parameters R wp = 4.87%, R p = 3.69% and R B = 3.99%. For CaNp(PO4)2, we obtained a = 6.6509(5) Å, b = 6.8390(3) Å, c = 6.3537(8) Å, and β = 104.12(6)° and R wp = 6.74%, R p = 5.23%, and R B = 6.05%. The results indicate significant distortions of bond length and angles of the PO4 tetrahedra in CaTh(PO4)2 and to a lesser extent in CaNp(PO4)2. The structural distortions were confirmed by Raman spectroscopy of CaTh(PO4)2. A comparison with the isostructural compounds LnPO4 (Ln = Ce and Sm) confirmed that the substitution of the large rare earth trivalent cations with Ca2+ and Th4+ introduces a distortion of the PO4 tetrahedra.  相似文献   

16.
The speciation of CO2 in dacite, phonolite, basaltic andesite, and alkali silicate melt was studied by synchrotron infrared spectroscopy in diamond anvil cells to 1,000 °C and more than 200 kbar. Upon compression to 110 kbar at room temperature, a conversion of molecular CO2 into a metastable carbonate species was observed for dacite and phonolite glass. Upon heating under high pressure, molecular CO2 re-appeared. Infrared extinction coefficients of both carbonate and molecular CO2 decrease with temperature. This effect can be quantitatively modeled as the result of a reduced occupancy of the vibrational ground state. In alkali silicate (NBO/t = 0.98) and basaltic andesite (NBO/t = 0.42) melt, only carbonate was detected up to the highest temperatures studied. For dacite (NBO/t = 0.09) and phonolite melts (NBO/t = 0.14), the equilibrium CO2 + O2? = CO3 2? in the melt shifts toward CO2 with increasing temperature, with ln K = ?4.57 (±1.68) + 5.05 (±1.44) 103 T ?1 for dacite melt (ΔH = ?42 kJ mol?1) and ln K = ?6.13 (±2.41) + 7.82 (±2.41) 103 T ?1 for phonolite melt (ΔH = ?65 kJ mol?1), where K is the molar ratio of carbonate over molecular CO2 and T is temperature in Kelvin. Together with published data from annealing experiments, these results suggest that ΔS and ΔH are linear functions of NBO/t. Based on this relationship, a general model for CO2 speciation in silicate melts is developed, with ln K = a + b/T, where T is temperature in Kelvin and a = ?2.69 ? 21.38 (NBO/t), b = 1,480 + 38,810 (NBO/t). The model shows that at temperatures around 1,500 °C, even depolymerized melts such as basalt contain appreciable amounts of molecular CO2, and therefore, the diffusion coefficient of CO2 is only slightly dependent on composition at such high temperatures. However, at temperatures close to 1,000 °C, the model predicts a much stronger dependence of CO2 solubility and speciation on melt composition, in accordance with available solubility data.  相似文献   

17.
This study was conducted in six plots along an elevation gradient in the Qinghai spruce (Picea crassifolia Kom.) forest ecosystem of the Qilian Mountains, northwest China. Soil CO2 efflux over bare soil (R s) and moss covered soil (R s+m) were investigated from June to September in 2010 and 2011 by means of an automated soil CO2 flux system (LI-8100). The results showed that R s ranged from 1.51 to 3.96 (mean 2.64 ± 0.72) μmol m?2 s?1 for 2010, and from 1.41 to 4.09 (mean 2.55 ± 0.70) μmol m?2 s?1 for 2011. The daily change trend of R s resembled that of air temperature (T a), and there was a hysteresis between R s and soil temperature (T s). The seasonal variations of R s at lowlands (i.e., Plot 1, Plot 2 and Plot 3) were driven by soil moisture and temperature (T a and T s), while that at highlands (i.e., Plot 4, Plot 5 and Plot 6) were obviously affected by temperature. There were higher values at Plot 2 and Plot 6, which were caused by the interaction between soil moisture and temperature. In addition, soil CO2 efflux over moss covered soil (R s+m) was 8.83 % less than that over bare soil (R s), indicating that moss was another factor affecting R s. It was concluded that R s had temporal and spatial variations and was mainly controlled by temperature and soil moisture; the main determinants differed at different elevations; moss could reduce R s.  相似文献   

18.
A contemporary probabilistic seismic hazard assessment (PSHA) study for Bulgaria and the surrounding Balkan area is performed under constraints of a newly developed, fit-for-purpose historical earthquake catalogue and the theory of extreme values. Sensitivity analyses are first adopted as preparatory reviews on subsets of the adopted data to determine suitable values for the constraints of cut-off magnitude threshold, sample extreme interval and start year of catalogue data to impose on the parent database for both the full region considered as well as significant urban centres within it. Maximum estimates are then determined for magnitude recurrence hazard using Gumbel’s third asymptotic extreme values distribution for return periods of 50 and 100 years, and also these time intervals at 90 % probability of not being exceeded (PNBE). Gumbel’s first asymptotic extreme values distribution is also used with carefully selected, geographically relevant ground motion models for peak horizontal ground acceleration, PGA(h), and peak horizontal ground velocity, PGV(h), for the same return periods. The former provides direct comparison with the current EUROCODE 8 anti-seismic building code standard promoted across Europe, the previous GSHAP and SESAME hazard mapping projects as well as a number of recent studies. Sofia is forecast an upper bound magnitude of 7.33 M w (±0.78) compared with 7.31 M w (±0.55) for the full Balkan extent and 7.24 M w (±0.70) for the political triple junction area of southwest Bulgaria, viz., Bulgaria, Greece and The Former Yugoslav Republic of Macedonia. Sofia is also forecast a 475-year return period (equivalent to a 50-year return period at 90 % PNBE) magnitude of 7.27 M w, with an equivalent PGA (the standard EUROCODE 8 metric) of 156 cm s?2 and PGV of 13 cm s?1.  相似文献   

19.
Core sediments from three disturbed boreholes (JOR, GHAT, and RAJ) and two undisturbed boreholes (DW1 and DW2) were collected in the study area of the Chapai-Nawabganj district of northwestern Bangladesh for geochemical analyses. In the study area, groundwater samples from fourteen As-contained private wells and five nested piezometers at both the DW1 and DW2 boreholes were also collected and analyzed. The groundwater arsenic concentrations in the uppermost aquifer (10–40 m of depth) range from 3 to 315 μg/L (mean 47.73 ± 73.41 μg/L), while the arsenic content in sediments range from 2 to 14 mg/kg (mean 4.36 ± 3.34 mg/kg). An environmental scanning electron microscope (ESEM) with an energy dispersive X-ray spectrometer was used to investigate the presence of major and trace elements in the sediments. Groundwaters in the study area are generally the Ca–HCO3 type with high concentrations of As, but low levels of Fe, Mn, NO3 ? and SO 4 ?2 . The concentrations of As, Fe, Mn decrease with depth in the groundwater, showing vertical geochemical variations in the study area. Statistical analysis clearly shows that As is closely associated with Fe and Mn in the sediments of the JOR core (r = 0.87, p < 0.05 for Fe and r = 0.78, p < 0.05 for Mn) and GHAT core (r = 0.95, p < 0.05 for Fe and r = 0.93, p < 0.05 for Mn), while As is not correlated with Fe and Mn in groundwater. The comparatively low Fe and Mn concentrations in some groundwater and the ESEM image revealed that siderite precipitated as a secondary mineral on the surface of the sediment particles. The correlations along with results of sequential extraction experiments indicated that reductive dissolution of FeOOH and MnOOH represents a mechanism for releasing arsenic into the groundwater.  相似文献   

20.
Thermal inertia (I) is an important parameter in the Earth’s thermal study. There is no doubt that correct and up-to-date knowledge of thermal inertia particularly as it is affected by the land use/cover will provide good and useful information to agriculturists and environmental scientists. In this work, thermal inertia of Abeokuta City of Ogun State, southwestern Nigeria, was determined. Map of the study area was gridded using 2-min resolution which gave 5 × 5 sampling points from where core samples were collected. Bulk density (ρ s ), thermal conductivity (λ s ), and heat capacity (C s ) of the samples were determined. The pattern of variation of the city view of I (in the order of ×103 Jm?2 s?1/2 K?1) showed that the main urban built-up part of the study area, Abeokuta South, had the highest I mean, 0.76160 with standard deviation of 0.032547 and standard error of 0.01455541. The trend also varied along each sampling latitudinal line. It ranges between 0.509 and 0.756 on latitude 7° 14′, 0.557 and 0.768 on latitude 7° 12′, 0.642 and 0.782 on latitude 7° 10′, 0.7 and 0.794 on latitude 7° 08′, and between 0.642 and 0.728 on latitude 7° 06′. Hence, we have estimated thermal inertia of Abeokuta using the thermophysical properties of the study area. Thermal inertia tends to gradually decrease with distance from the city center (Abeokuta South). This result is promising in possible future consideration of urban ground heat energy conversion to other forms of energy.  相似文献   

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