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1.
There are significant advantages in using indirect pedo-transfer functions, (PTFs) for the estimation of unsaturated soil properties. The pedo-transfer functions can be used for the estimation of the soil–water characteristic curve (SWCC) which in turn is used for the estimation of other unsaturated soil properties. The accuracy of the indirect pedo-transfer function method for the estimation of the SWCC depends on the PTF and the equation used to best-fit the particle-size distribution (PSD) data. The objectives of this study are to: (1) evaluate the performance of the Fredlund et al. (Can Geotech J 37:817–827, 2000) equation for best-fitting the particle-size distribution, (PSD) data, and, (2) compare the predictions made by two of the commonly used PTFs; namely, Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) and Fredlund et al. (Can Geotech J 39:1103–1117, 2002), for estimating the SWCC from the PSD. The authors used 258 measured PSDs and SWCC datasets from the Loess Plateau, China, for this study. The dataset consisted of 187 silt–loam soils, 41 loam soils, 11 silt–clay–loam soils, 10 sand–loam soils, 6 silt–clay soils, and 3 loam–sand soils. The SWCC and PSD datasets were measured using a Pressure Plate apparatus and the pipette method, respectively. The comparison between the estimated and measured particle-size distribution curves showed that the Fredlund et al. (Can Geotech J 37:817–827, 2000) equation closely prepresented the PSD for all soils in the Loess Plateau, with a lower root mean square error (RMSE) of 0.869%. The comparison between the estimated and measured water contents at the same suction showed that the Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF performed somewhat better than the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) function. The Fredlund et al. method had RMSE value of 0.039 cm3 cm−3 as opposed to 0.046 cm3 cm−3 for the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) method. The Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF produced the closest predictions for sand–loam, loam–sand, and loam soils, with a lower RMSE for gravimetric water content ranging from 0.006 to 0.036 cm3 cm−3. There were consistent over-estimations observed for silt–loam, silt–clay–loam, and slit–clay soils with RMSE values for gravimetric water content ranging from 0.037 to 0.043 cm3 cm−3. The measured and estimated air-entry values were closest when using the Fredlund et al. (Can Geotech J 39:1103–1117, 2002) PTF. The measured and estimated maximum slopes on the SWCC were closest when using the Arya and Paris (Soil Sci Soc Am J 45:1023–1030, 1981) PTF.  相似文献   

2.
Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha−1 year−1; MN, 100 kg N ha−1 year−1; LN, 50 kg N ha−1 year−1) on soil respiration compared with non-fertilization (CK, 0 kg N ha−1 year−1), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However, N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments of HN, LN, and CK treatments (Q 10 varied within 1.70–1.74) but was slightly reduced in MN treatment (Q 10 = 1.63). N fertilization increased soil CO2 emission in the order MN > HN > LN compared with the CK treatment. The positive effects reached a significant level for HN and MN (P < 0.05) and reached a marginally significant level for LN (P = 0.059 < 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July–September 2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of 0.01 on the basis of the data during the first entire year after fertilization (July 2007–June 2008). The annual total soil respiration was 53, 57, and 24% higher than in the CK plots (465 g m−2 year−1). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the second year fertilization (July–September 2008, P > 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P > 0.05).  相似文献   

3.
Excessive arsenic concentrations above the Argentinean and WHO guidelines for drinking water (10 μg L−1) affects shallow aquifers of the southern Pampean Plain (Argentina) hosted in the Pampean and the Post Pampean formations (loess and reworked loess; Plio-Pleistocene–Holocene). Health problems related to high As concentrations in drinking waters are known as Endemic Regional Chronic Hydroarsenicism. Hydrochemistry of shallow groundwaters and soil geochemistry were investigated aiming to (1) understand the partition of As in the solid phase and its relationship with unacceptable As concentrations in waters, (2) identify the provision source of As to groundwaters. Only 5% of the samples had As concentrations <10 μg L−1; in 27% As concentrations ranged from 10 to 50 μg L−1 and in 58% it reached 60–500 μg L−1. The coarse fraction (50–2,000 μm) hosts about 27% of the total As in the solid phase, being positively correlated to Ba (p < 0.01; r 2 = 0.93). About 70% is included in the <2 μm fraction and had positive correlations of As–Fe (p < 0.05; r 2 = 0.85) and As–Cr (p < 0.05; r 2 = 0.68). Soils and sediment sand fractions of vadose zones are the primary sources of As in shallow groundwater while adsorption–desorption processes, codisolution–coprecipitation, and evaporation during the dry seasons raise As concentrations in waters exceeding the guideline value for drinking water.  相似文献   

4.
In highlands of semiarid Turkey, ecosystems have been significantly transformed through human actions, and today changes are taking place very rapidly, causing harmful consequences such as soil degradation. This paper examines two neighboring land use types in Indagi Mountain Pass, Cankiri, Turkey, to determine effects of the conversion of Blackpine (Pinus nigra Arn. subsp. pallasiana) plantation from grassland 40 years ago on soil organic carbon (SOC) and soil erodibility (USLE-K). For this purpose, a total of 302 disturbed and undisturbed soil samples were taken at irregular intervals from two sites and from two soil depths of 0–10 cm (D1) and 10–20 cm (D2). In terms of SOC, conversion did not make any statistical difference between grassland and plantation; however, there were statistically significant differences with soil depth within each land use, and SOC contents significantly decreased with the soil depth (P < 0.05) and mostly accumulated in D1. SOC values were 2.4 and 1.8% for grassland and 2.8 and 1.6% for plantation, respectively, at D1 and D2. USLE-K values also statistically differed significantly with the land use, and in contrast to the statistics of SOC, there was no change in USLE-K with the soil depth. Since USLE-K was estimated using SOC, hydraulic conductivity (HC) and soil textural composition––sand (S), silt (Si), and clay (C) contents of soils––as well as SOC did not change with the land use, we ascribed the changes of USLE-K with the land uses to the differences in the HC as strongly affected by the interactions between SOC and contents of S, Si, and C. On an average, the soil of the grassland (USLE-K = 0.161 t ha h ha−1 MJ−1 mm−1) was more erodible than those of the plantation (USLE-K = 0.126 t ha h ha−1 MJ−1 mm−1). Additionally, topographic factors, such as aspect and slope, were statistically effective on spatial distribution of the USLE-K and SOC.  相似文献   

5.
Though irrigation with sewage water has potential benefits of meeting the water requirements, the sewage irrigation may mess up to harm the soil health. To assess the potential impacts of long-term sewage irrigation on soil health and to identify sensitive soil indicators, soil samples were collected from crop fields that have been irrigated with sewage water for more than 20 years. An adjacent rain-fed Leucaena leucocephala plantation system was used as a reference to compare the impact of sewage irrigation on soil qualities. Soils were analyzed for different physical, chemical, biological and biochemical parameters. Results have shown that use of sewage for irrigation improved the clay content to 18–22.7%, organic carbon to 0.51–0.86% and fertility status of soils. Build up in total N was up to 2,713 kg ha−1, available N (397 kg ha−1), available P (128 kg ha−1), available K (524 kg ha−1) and available S (65.5 kg ha−1) in the surface (0.15 m) soil. Long-term sewage irrigation has also resulted a significant build-up of DTPA extractable Zn (314%), Cu (102%), Fe (715%), Mn (197.2), Cd (203%), Ni (1358%) and Pb (15.2%) when compared with the adjacent rain-fed reference soil. Soils irrigated with sewage exhibited a significant decrease in microbial biomass carbon (−78.2%), soil respiration (−82.3%), phosphatase activity (−59.12%) and dehydrogenase activity (−59.4%). An attempt was also made to identify the sensitive soil indicators under sewage irrigation, where microbial biomass carbon was singled out as the most sensitive indicator.  相似文献   

6.
Copper contamination in soils and vegetables in the vicinity of an abandoned copper mine in China was investigated. The Cu concentrations of 93 soil samples ranged from 30.4 to 3,191 mg kg−1 soil for a mean of 816.8 mg kg−1 soil. Among 15 samples from a 0 to 20-cm soil layer used for the toxicity characteristic leaching procedure (TCLP) test, the highest value of Cu-TCLP was 133.8 mg kg−1 soil and the TCLP values were positively correlated with the total Cu content of the soils. The sequential extraction of soils in the 0–20-, 20–40-, and 40–60-cm soil layers showed that Cu existed mainly in the Fe–Mn oxide fraction, sulfide/organic fraction, and residual fraction. The copper contamination of 21 species of vegetables from in situ sampling was also examined. Cu concentrations in the edible portions of Brassica chinensis and Solanum melongena were higher than the FAO/WHO standard (40 mg kg−1 DW). The health risk of copper for local inhabitants from consuming these vegetables was assessed on the basis of the target hazard quotient. Enriched concentrations of copper were also found in situ in eight cultivars of B. chinensis planted in the fields, with two levels of Cu concentration. The results showed that there is severe copper contamination in this mine area, and the pollutant in soils show a high risk of leaching into the groundwater and diffusing through the food chain.  相似文献   

7.
Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg−1 and a range of 2.4–8.7 mg kg−1. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg−1. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ LF), susceptibility of anhysteretic remanent magnetization (χ ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils.  相似文献   

8.
Cesium and Strontium concentrations were analyzed in eight pedogenetic soil profiles developed on different rocks from a semiarid mediterranean region: La Mancha (Central Spain). Concentration activities of 137Cs and 90Sr, as for some soil properties, were also measured. The results are presented in this document: Cs concentrations range between 0.4 and 18.3 mg kg−1 and Sr varies widely between 11.0 and 3,384 mg kg−1. Therefore, it is clear that there is a broad range of concentrations and there are also values significantly higher than the average values stated by several authors. Concentrations of long-life artificial radionuclides (137Cs, 90Sr) were determined in some of the same soils. The activity concentration mean values (Bq kg−1) were ranging between 0.82 and 21.76 for 137Cs and 90Sr variations range between 6.73 and 0.35. There were no significant correlations between radionuclides and stable trace elements. The data indicate that the soils do not show significant radioactivity of these elements and therefore they do not pose a danger. By the same token, no risk of contamination by this activity was detected. Finally, spatial patterns seem to be affected by the soil type and some soil properties.  相似文献   

9.
Organic material in metal contaminated soils around an abandoned magnetite mine–smelter complex in the critical Highlands watershed protects the groundwater and surface water from contamination. Metals in these waters were consistently below local and national water standards. Two groups of soil types cover the area: (1) Group A disturbed metal-rich soils, and (2) Group B undisturbed organic soils. Chromium and nickel were more elevated than other metals with Cr more widespread than Ni. In Group A, Cr correlated strongly with sesquioxides in the lower horizons (Fe2O3: r = 0.74, p < 0.025; Al2O3: r = 0.92, p < 0.005). In Group B, Cr correlated strongly (r = 0.96, p < 0.005) with soil organic matter (SOM) in the O-horizons. Ni–Cr (Group A: 52 and 70% in O- and lower horizons, respectively; Group B: ~100% in both horizons) and V–Cr correlations (78% only in Group A lower horizons) suggest similar retention mechanisms for these elements. Average soil \textpH\textCaCl2 {\text{pH}}_{{{\text{CaCl}}_{2} }} for both groups ranged between 3.65 and 5.91, suggesting that soil acidity is determined by organic acids and solubility of Al3+ releasing H+ ions. SOM and sesquioxides contribute significantly to creating naturally occurring filtration systems, removing metals, and protecting water quality. High Ca, Fe, and Ti in Group A soils suggest slag and ash were mixed into the soils. Some low-Cr sources include magnetite, slag, and ash (100, 100 and 200 mg/kg, respectively). Constant ZrO 2 :TiO 2 ratios in the lower soils indicate soil formation from breakdown of underlying tailing rocks, contributing Cr to these layers.  相似文献   

10.
Suspended sediments concentration (SSC) in surface water derived from bottom sediment resuspension or discharge of sediment-laden rivers is an important indication of coastal water quality and changes rapidly in high-energy coastal area. Since artificial neural networks (ANN) had been proven successful in modeling a variety of geophysical transfer functions, an ANN model to simulate the relationship between surface water SSC and satellite-received radiances was employed. In situ SSC measurements from the Hangzhou Bay and the Moderate-resolution Imaging Spectroradiometer (MODIS) 250 m daily products were adopted in this study. Significant correlations were observed between in situ measurements and band 1–2 reflectance values of MODIS images, respectively. Results indicated that application of ANN model with one hidden layer appeared to yield superior simulation performance (r 2 = 0.98; n = 25) compared with regression analysis method. The RMSE for the ANN model was less than 10%, whereas the RMSE for the regression analysis was more than 25%. Results also showed that different tidal situations affect the model simulation results to some extent. The SSC of surface water in Hangzhou Bay is high and changes rapidly due to tidal flood and ebb during a tidal cycle. The combined utilization of Terra and Aqua MODIS data can capture the tidal cycle induced dynamic of surface water SSC. This study demonstrated that MODIS 250 m daily products and ANN model are useful for monitoring surface SSC dynamic within high-energy coastal water environments.  相似文献   

11.
Single-crystal electron paramagnetic resonance (EPR) spectra of a gem-quality jeremejevite, Al6B5O15(F, OH)3, from Cape Cross, Namibia, reveal an S = 1/2 hole center characterized by an 27Al hyperfine structure arising from interaction with two equivalent Al nuclei. Spin-Hamiltonian parameters obtained from single-crystal EPR spectra at 295 K are as follows: g 1 = 2.02899(1), g 2 = 2.02011(2), g 3 = 2.00595(1); A 1/g e β e  = −0.881(1) mT, A 2/g e β e  = −0.951(1) mT, and A 3/g e β e  = −0.972(2) mT, with the orientations of the g 3- and A 3-axes almost coaxial and perpendicular to the Al–O–Al plane; and those of the g 1- and A 1-axes approximately along the Al–Al and Al–OH directions, respectively. These results suggest that this aluminum-associated hole center represents hole trapping on a hydroxyl oxygen atom linked to two equivalent octahedral Al3+ ions, after the removal of the proton (i.e., a VIAl–O−–VIAl center). Periodic ab initio UHF and DFT calculations confirmed the experimental 27Al hyperfine coupling constants and directions, supporting the proposed structural model. The VIAl–O−–VIAl center in jeremejevite undergoes the onset of thermal decay at 300 °C and is completely bleached at 525 °C. These data obtained from the VIAl–O−–VIAl center in jeremejevite provide new insights into analogous centers that have been documented in several other minerals.  相似文献   

12.
The thermoelastic parameters of synthetic Ca3Al2Si3O12 grossular garnet were examined in situ at high-pressure and high-temperature by energy dispersive X-ray diffraction, using a Kawai-type multi-anvil press apparatus coupled with synchrotron radiation. Measurements have been conducted at pressures up to 20 GPa and temperatures up to 1,650 K: this P, T range covered the entire high-P, T stability field of grossular garnet. The analysis of room temperature data yielded V 0,300 = 1,664 ± 2 ?3 and K 0 = 166 ± 3 GPa for K￠0 K^{\prime}_{0} fixed to 4.0. Fitting of our P–V–T data by means of the high-temperature third order Birch–Murnaghan or the Mie–Grüneisen–Debye thermal equations of state, gives the thermoelastic parameters: (∂K 0,T /∂T) P  = −0.019 ± 0.001 GPa K−1 and α 0,T  = 2.62 ± 0.23 × 10−5 K−1, or γ 0 = 1.21 for fixed values q 0 = 1.0 and θ 0 = 823 (Isaak et al. Phys Chem Min19:106–120, 1992). From the comparison of fits from two different approaches, we propose to constrain the bulk modulus of grossular garnet and its pressure derivative to K T0 = 166 GPa and K￠T0 K^{\prime}_{T0}  = 4.03–4.35. Present results are compared with previously determined thermoelastic properties of grossular-rich garnets.  相似文献   

13.
The crystal structure of chromite FeCr2O4 was investigated to 13.7 GPa and ambient temperature with single-crystal X-ray diffraction techniques. The unit-cell parameter decreases continuously from 8.3832 (5) to 8.2398 (11) Å up to 11.8 GPa. A fit to the Birch–Murnaghan equation of state (EoS) based on the P–V data gives: K 0 = 209 (13) GPa, K′ = 4.0 (fixed), and V 0 = 588 (1) Å3. The FeO4 tetrahedra and CrO6 octahedra are compressed isotropically with pressure with their Fe–O and Cr–O bond distances decreasing from 1.996 (6) to 1.949 (7) Å and from 1.997 (3) to 1.969 (7) Å, respectively. The tetrahedral site occupied by the Fe2+ cation is more compressible than the octahedral site occupied by the Cr3+ cation. The resulting EoS parameters for the tetrahedral and the octahedral sites are K 0 = 147 (9) GPa, K′ = 4.0 (fixed), V 0 = 4.07 (1) Å3 and K 0 = 275 (24) GPa, K′ = 4.0 (fixed), V 0 = 10.42 (2) Å3, respectively. A discontinuous volume change is observed between 11.8 and 12.6 GPa. This change indicates a phase transition from a cubic (space group Fd-[`3]{\overline{3}} m) to a tetragonal structure (space group I41 /amd). At the phase transition boundary, the two Cr–O bonds parallel to the c-axis shorten from 1.969 (7) to 1.922 (17) Å and the other four Cr–O bonds parallel to the ab plane elongate from 1.969 (7) to 1.987 (9) Å. This anisotropic deformation of the octahedra leads to tetragonal compression of the unit cell along the c-axis. The angular distortion in the octahedron decreases continuously up to 13.7 GPa, whereas the distortion in the tetrahedron rises dramatically after the phase transition. At the pressure of the phase transition, the tetrahedral bond angles along the c-axis direction of the unit cell begin decreasing from 109.5° to 106.6 (7)°, which generates a “stretched” tetrahedral geometry. It is proposed that the Jahn–Teller effect at the tetrahedrally coordinated Fe2+ cation becomes active with compression and gives rise to the tetrahedral angular distortion, which in turn induces the cubic-to-tetragonal transition. A qualitative molecular orbital model is proposed to explain the origin and nature of the Jahn–Teller effect observed in this structure and its role in the pressure-induced phase transition.  相似文献   

14.
CH4 and CO2 fluxes from a high-cold swamp meadow and an alpine meadow on the Qinghai-Tibetan Plateau, subject to different degrees of degradation, were measured over a 12-month period. Air temperature, soil temperature and moisture, and the depths of the water table and thawing-freezing layer were determined. For swamp meadows, the greater the degradation, the lesser the carbon efflux. CH4 emissions at the nondegraded swamp meadow site were 1.09–3.5 and 2.5–11.27 times greater, and CO2 emissions 1.08–1.69 and 1.41–4.43 times greater, respectively, than those from moderately and severely degraded sites. For alpine meadows, the greater the degradation, the greater the CH4 consumption and CO2 emissions. CH4 consumption at the severely degraded alpine meadow site was 6.6–21 and 1.1–5.25 times greater, and CO2 emissions 1.05–78.5 and 1.04–6.28 times greater, respectively, than those from the nondegraded and moderately degraded sites. The CH4 and CO2 fluxes at both sites were significantly correlated (R 2 > 0.59, P < 0.05) with air temperature, soil temperature, and topsoil (0–5 cm depth) moisture, indicating these to be the main environmental factors affecting such fluxes.  相似文献   

15.
Chemical and structural data are reported for C2/c pyroxene phenocrysts collected from three potassic series (Group A: basanite-tephrite, Group B: tephrite-phonolitic tephrite, Group C: alkaline basalt-trachybasalt) of the Neogene alkaline volcanics (NAVs) in northeastern Turkey, in order to investigate the evolution of the magmatic plumbing system and the location of magma chamber(s) with crystallization conditions. The rock series hosting the clinopyroxene phenocrysts show generally porphyritic texture and have a variable phenocryst-rich nature (20–58%), with phenocryst assemblages characterized by cpx ± ol ± plag ± foid ± amp ± bio. The clinopyroxene phenocrysts can be chemically classified as Ti- and Fe3+-rich Al-diopsides for Groups A and B (AB-cpxs) and Ti- and Fe3+-poor Al-diopsides for Group C (C-cpxs). They have poorly variable composition, clustering in the diopside field. Structurally, the diopside groups have nearly similar a (ranging from 9.73 to 9.75 ?), V cell (437.2–440.9 ?3), and 〈beta〉 angle values (106.01°–106.23°), but some differences in polyhedral parameters and geometries of the AB-cpxs and C-cpxs have been observed. For example, the AB-cpxs are characterized by larger c (5.27–5.30 vs. 5.25–5.28 ?), V T (2.27–2.30 vs. 2.23–2.28 ?3), and V M2 (25.53–25.72 vs. 25.41–25.59 ?3) values and smaller b (8.87–8.88 vs. 8.88–8.91 ?) and V M1 (11.49–11.63 vs. 11.64–11.83 ?3) values with respect to the C-cpxs. In addition, the AB-cpxs show higher values of V M2/V M1 (2.20–2.23) due to large V M2 and small V M1 compared to the V M2/V M1 ratios of the C-cpxs (<2.19). Such differences in the crystal structure of the AB-cpxs and C-cpxs from the NAVs are partly related to different crystallization pressures, but mostly related to variation in melt composition and, possibly, the influence of other crystallizing mineral phases. In particular, R(M2-O1) and R(M1-O2) (i.e. bond lengths) differences in the clinopyroxenes of different groups support the presence of evolved host rocks with different alkaline character (i.e. silica-undersaturated Groups A–B and silica-saturated Group C). Based on the cpx-geothermobarometry, the crystallization pressures for the C-cpxs are lower than 4.5 kbars, but the AB-cpxs have relatively high-pressure values (5.6–10.6 kbars), suggesting that the AB-cpxs crystallized in higher pressure environments. The relatively higher crystallization temperatures of the AB-cpxs also indicate higher cooling rates. The P–T estimates suggest that the source regions of the clinopyroxene phenocrysts from the NAVs were crustal magma chambers in a closed plumbing system at a moderate- to low-pressure regime.  相似文献   

16.
The chemical quality of groundwater of western Haryana, India was assessed for its suitability for drinking purposes. A total of 275 water samples were collected from deep aquifer based hand-pumps situated in 37 different villages/towns of Bhiwani region. The water samples were analyzed for different physico-chemical properties, e.g., pH, total dissolved solids (TDS), total harness (TH), total alkalinity (TA), calcium, magnesium, carbonate, bicarbonate, sulphate, chloride and fluoride concentrations. In this study, the average TDS content was greater ranging 1,692 (Bhiwani block) to 2,560 mg l−1 (Siwani block), and other important parameters of water, e.g., TA (442–1,232 mg l−1), TH (437–864 mg l−1) and bicarbonate (554–672 mg l−1), were also higher than maximum permissible limit by WHO or BIS. The fluoride appeared as a major problem of safe drinking water in this region. We recorded greater fluoride concentration, i.e., 86.0 mg l−1 from Motipura village that is highest fluoride level ever recorded for Haryana state. The average fluoride concentration ranged between 7.1 and 0.8 mg l−1 in different blocks of western Haryana. On the basis of fluoride concentration, Siwani block showed the maximum number of water samples (84% of total collected samples) unsuitable for drinking purposes (containing fluoride >1.5 mg l−1) followed by Charki Dadri block (58%), Bhiwani block (52%), Bawani Khera block (33%) and Loharu block (14%). This study clearly suggest that some health deteriorating chemicals in drinking water were at dangerous level and; therefore, water quality could be a major health threat for local residents of western Haryana. The high fluoride level in drinking water has posed some serious dental health risks in local residents.  相似文献   

17.
This paper presents artificial neural network (ANN) prediction models for estimating the compaction parameters of both coarse- and fine-grained soils. A total number of 200 soil mixtures were prepared and compacted at standard Proctor energy. The compaction parameters were predicted by means of ANN models using different input data sets. The ANN prediction models were developed to find out which of the index properties correlate well with compaction parameters. In this respect, the transition fine content ratio (TFR) was defined as a new input parameter in addition to traditional soil index parameters (i.e. liquid limit, plastic limit, passing No. 4 sieve and passing No. 200 sieve). Highly nonlinear nature of the compaction data dictated development of two separate ANN models for maximum dry unit weight (γdmax) and optimum water content (ωopt). It was found that generalization capability and prediction accuracy of ANN models could be further enhanced by sub-clustered data division techniques.  相似文献   

18.
Diffusion coefficients of Cr and Al in chromite spinel have been determined at pressures ranging from 3 to 7 GPa and temperatures ranging from 1,400 to 1,700°C by using the diffusion couple of natural single crystals of MgAl2O4 spinel and chromite. The interdiffusion coefficient of Cr–Al as a function of Cr# (=Cr/(Cr + Al)) was determined as D Cr–Al = D 0 exp {−(Q′ + PV*)/RT}, where D 0 = exp{(10.3 ± 0.08) × Cr#0.54±0.02} + (1170 ± 31.2) cm2/s, Q′ = 520 ± 81 kJ/mol at 3 GPa, and V* = 1.36 ± 0.25 cm3/mol at 1,600°C, which is applicable up to Cr# = 0.8. The estimation of the self-diffusion coefficients of Cr and Al from Cr–Al interdiffusion shows that the diffusivity of Cr is more than one order of magnitude smaller than that of Al. These results are in agreement with patterns of multipolar Cr–Al zoning observed in natural chromite spinel samples deformed by diffusion creep.  相似文献   

19.
This study aims to explore the condensation and fractionation trends of persistent organic pollutants (POPs) in the karst soils. The tiankeng is a karst surface expression that can act as a focal point for introduction of contaminants to a karst aquifer, which may serve both as condenser for vapor phase POPs and as barrier/sink for particulate associated less volatile POPs. The fractionation of POPs in soils from the upper rim and floor of tiankeng is of interest in understanding the role of tiankeng in the long-distance transport of POPs. In the present study, polycyclic aromatic hydrocarbons (PAHs) in the surface soils from the upper rim and floor of Dashiwei tiankeng in Southern China were analyzed. The total PAH concentrations in soils were 23.40–190 ng g−1, with phenanthrene being the most abundant. The distribution patterns of PAH compounds in the soil samples matched well with their properties. It indicated the heavy PAHs were susceptible to retention by the floor soils of tiankeng than light PAHs. A plot of Cfloor/Crim against PAH molecular weight gave a good positive relationship in the molecular weight range of 152–276. It is suggested that the floor soils can be focal points of more concentrated PAH and deserve attention. The concentrations of total PAHs in the floor soils (43.40–190 ng g−1, mean 87.76 ng g−1) were higher than those in the upper rim (23.40–88.94 ng g−1, mean 57.74 ng g−1). In addition, there was a shift in compound pattern with an increase in the proportion of light PAHs (2–3 rings), a decrease in heavy PAHs (5–6 rings) and a relatively stable content of 4-ring PAHs. A combination of particulate scavenging and cold condensation is proposed as the major mechanism for the compositional fractionation of PAHs in the soils from the upper rim and floor of tiankeng.  相似文献   

20.
Effects of saline water irrigation on soil properties in northwest China   总被引：2，自引：1，他引：1  
Due to the lack of freshwater, highly saline groundwater was the main irrigation source in the last few decades in the Minqin Basin, which is in northwest China. The study evaluates the effects of salt accumulation on the soil physical–chemicals properties. Undisturbed and disturbed soil samples were taken from the experiment site, which was irrigated with saline water at a concentration of 0.8, 2 and 5 g L−1 (coded later as C08, C2 and C5). Undisturbed soil samples, at depths of 0–45 and 45–60 cm were taken to determine the water retention curve (WRC). Moreover, in the same place, another set of undisturbed soil samples were taken to determine the porosity and pore-size distribution (PoSD). From the WRC, the water-holding capacity of the soil was estimated. Disturbed soil samples at depths of 0–20, 0–45, 45–60 and 80–100 cm were taken to determine the index of aggregates stability in water (IC). The electrical conductivity of the saturated paste (ECe) was determined at depths of 0–30, 30–60 and 60–90 cm, during the irrigation season on C08, C2 and C5 treatments. The results show that the total porosity and the index of aggregates stability in water decrease with the increasing salinity of irrigation water, and the ECe increases with the increasing salinity of irrigation water especially in the surface soil. The water-holding capacity (WHC) of soil also increases with the increasing salinity of irrigation water.  相似文献   

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