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1.
R. S. B. GREENE P. RENGASAMY G. W. FORD C. J. CHARTRES J. J. MILLAR 《European Journal of Soil Science》1988,39(4):639-648
The effect of treatment with either gypsum or sodium chloride on the saturated hydraulic conductivity ( K s ) of repacked soil columns and modulus of rupture (MOR) was studied on surface samples of two red-brown earth soils from SE wheat belt in Australia.
When the exchangeable sodium percentage (ESP) of the two soils was increased to >80, KS was substantially reduced and MOR increased relative to the untreated soil; the values of the parameters were nearly equal for these pairs of high ESP soils. However, after treatment with gypsum the Raywood soil had a K s twice, and a MOR less than half, the corresponding values for the Glenloth soil.
Micromorphological and scanning electron microscope (SEM) observations suggest that the increase in Ks following gypsum treatment is associated with an increase in visible macropores and reduced clay dispersion; Na treatment increased dispersion at the soil surface, with the clay particles forming an impermeable surface seal and illuviation argillans. 相似文献
When the exchangeable sodium percentage (ESP) of the two soils was increased to >80, K
Micromorphological and scanning electron microscope (SEM) observations suggest that the increase in K
2.
The contribution of sorbed sodium and calcium to the self-diffusion of these cations in soils with different clay mineralogies 总被引：1，自引：0，他引：1
Self-diffusion coefficients of sodium and calcium were measured on a range of moist subsoils. The ratio of concentrations of each isotope in the liquid phase and on the surface at the water content of the diffusion run was obtained from both the extrapolation of ratios measured at a range of soil:solution ratios, and, where possible, by measurement on expressed soil solution.
The diffusion coefficients were considerably greater than would be predicted if only the liquid phase contributed to diffusion. Surface phase impedance factors, fs , were calculated for each soil. f s for sodium was between 1/5 and 1/2 of the liquid phase impedance factor, f L ; f s for calcium was between 1/9 and 1/20 of f L . Values of f s were not obviously related to the clay mineralogy, the proportion of internal to external cation adsorption, the volumetric water content, or the pH. 相似文献
The diffusion coefficients were considerably greater than would be predicted if only the liquid phase contributed to diffusion. Surface phase impedance factors, f
3.
The cationic bridging effect of the calcium ion (Ca2+ ) and the flocculating ability of clay and organic matter are crucial in the formation and stability of soil aggregates. They are therefore likely to influence the soil's saturated hydraulic conductivity ( K s ). We tested the individual effects of these factors on aggregate stability and related hydraulic properties, and studied the influence of clay mineralogy also. Samples from the surface (0–10 cm) of three contrasting soils in Trinidad were used. The soils were treated with three levels of Ca2+ and three levels of organic matter in a 3 × 3 × 3 factorial design and incubated for 14 days. Both aggregate stability and saturated hydraulic conductivity were influenced by all factor combinations. Interactions between soil type and Ca2+ revealed the importance of polyvalent cations in aggregate stability of soils with low activity minerals. The influence of organic matter varied with quantity; the more there was, the more stable the soil became, particularly in the soil containing little clay. Clay dispersion and slaking of expanding minerals occurred even with large additions of Ca2+ and organic matter, emphasizing the overall influence of mineralogy in determining the response of soils to stability treatments. 相似文献
4.
Determination of the gas diffusion coefficient D s of peat soils is essential to understand the mechanisms of soil gas transport in peatlands, which have been one of major potential sources of gaseous carbons. In the present study, we aimed at determining the D s of peat soils for various values of the air-filled porosity a and we tested the validity of the Three-Porosity Model (Moldrup et al. 2004) and the Millington-Quirk model (1961) for predicting the relative gas diffusivity, the ratio of D s to D 0 , the gas diffusion coefficient in free air. Undisturbed peat soil cores were sampled from aerobic layers in the Bibai mire, Hokkaido, Japan. The MQ model reproduced the measured D s / D 0 curves better than the TPM. The TPM, a predictive model for undisturbed mineral soils, overestimated the D s / D 0 values for peat soils, implying that in the peat soils the pore pathways were more tortuous than those in the mineral soils. Since the changes in the D s / D 0 ratios with the a values of a well-decomposed black peat soil tended to be more remarkable than those of other high-moor peat soils, the existence of a positive feedback mechanism was assumed, such that peat soil decomposition itself would increase the soil gas diffusivity and promote soil respiration. 相似文献
5.
Soil from cleaning and washing of sugar beet during processing is collected and decanted in tanks each year over a period of several months. Instead of spreading it on agricultural land, another option is to reuse the sediment for crop growth. The physical and mechanical properties of the non-structured washed soil (WS) and the efficiency of added organic matter (peat and green waste compost) were evaluated by comparison with an arable silt loam soil (AS). Water retention data were expressed in a double-exponential function which characterized soil structural and matrix pore space. The effects on saturated hydraulic conductivity and pore space morphology from applying loads of 60 and 200 kPa on two initial volumetric water contents (12 and 25%) were investigated using image analysis. WS was a silt loam with no plasticity, and its void ratio and water retention were higher than the AS before compression. However, WS had a very small amount of structural pore space and despite its higher void ratio, its hydraulic conductivity was always lower than AS after compression. Organic matter improved all the WS properties by increasing structural porosity and vertical stress resistance. Organic matter created elongated and tortuous pores and increased K s values by changing pore size distribution. During compression large pores with a radius >1500 μm disappeared in WS mixtures but were still observed in AS and were maintained by aggregate stability. 相似文献
6.
Alfisols exhibit a high degree of spatial variability in their physical properties. As a result, it is difficult to use information on physical parameters measured at one location to model larger-scale hydrologic processes. In this study, the saturated hydraulic conductivity, KS , of an Alfisol was determined on 109 undisturbed monoliths using the falling-head permeameter method. The model developed by Arya & Paris (1981) was used to calculate the pore volume from sand and clay fractions. Scaling factors were calculated from the measured Ks , sand pore-volume, clay pore-volume, clay content and effective porosity, using the similar media concept. Prediction of Ks of gravelly Alfisol using clay pore-volume is confounded by high gravel content which, when discounted, improves the prediction remarkably. The scaled mean saturated hydraulic conductivity K* for all horizons of the Alfisol was approximately l.0x 10−5 ms−1 . 相似文献
7.
人工湿地是一种常见的污水处理技术,但一直受到不可避免的堵塞问题的困扰。该研究主要以不同堵塞现象下的垂直流人工湿地模型为对象(可溶性有机物堵塞,不溶性有机物堵塞,加入抑菌剂的不溶性有机物堵塞),在轮休操作下持续测量不同时期孔隙率与渗透系数变化情况,研究3种堵塞类型的恢复规律,并对其动力学进行分析。试验结果表明在相同轮休期下,生物膜堵塞和有机颗粒堵塞恢复效果较为明显,其中,可溶性有机物堵塞、不溶性有机物堵塞装置分别轮休至第9天、第20天后基本达到较好的恢复状态,当轮休时间足够充分,这2种堵塞类型基本可以恢复至正常状态。其中可溶性有机物堵塞恢复速度最快,其次是不溶性有机颗粒堵塞。并在规律研究基础上,进一步推导了2种堵塞类型的渗透系数恢复的动力学。研究同时发现,轮休操作对无机颗粒类堵塞基本没有恢复效果。 相似文献
8.
Abstract. A rotation trial of four years' pasture followed by two years' arable was used to study the effect of cropping on the morphological and hydraulic properties of soil. An adjacent paddock in grass for the past 35 years was included as a permanent pasture reference. Initial infiltration and field saturated hydraulic conductivity ( K fs ) were least for cultivated soil and increased with increasing time under pasture. This could be explained by the contrasting porosities of resin-impregnated blocks of undisturbed soil which had been infiltrated with methylene blue dye. Small K fs values for cultivated soil resulted mainly from a thin surface crust, although pore discontinuity at the depth of the cultivation pan (130 mm) could also have contributed. Greater K fs values under short-term pasture resulted primarily from water flowing through biogenic pores connected to the surface. The greatest K fs values were in soil that had been under pasture for 35 years (P35). This was attributed to flow through biogenic pores and fissures associated with the strongly-developed subangular blocky structure. The amount of water that infiltrated the two- and four-year pasture soils (P2 and P4) under ponding was 2.5 and 5 times greater, respectively, than the soil that had been cultivated for two years (C2).
As irrigation duration cannot be varied under the border-dyking system used on the Canterbury Plains, the interval between irrigations must be varied if the same total amount of water is to be applied to each of these soils through the season. The interval should be less for the cultivated soil than for those under pasture, and should increase with increasing time under pasture (i.e. P35 > P4 > P2 > C2). 相似文献
As irrigation duration cannot be varied under the border-dyking system used on the Canterbury Plains, the interval between irrigations must be varied if the same total amount of water is to be applied to each of these soils through the season. The interval should be less for the cultivated soil than for those under pasture, and should increase with increasing time under pasture (i.e. P35 > P4 > P2 > C2). 相似文献
9.
Extraction using ethylenediaminetetraacetic acid (EDTA), and other chelates has been demonstrated to be an effective method of removal of Pb from many contaminated soils. However, column leaching of Pb from alkaline soils with EDTA has been problematic due to extremely low soil permeability. The first purpose of this study was to develop batch extraction procedures and methods of analysis of batch extraction data to provide Pb solubility information which can be used to model the column extraction of Pb from soils. The second purpose was to determine the effect of the addition of KOH and CaCl2 to K2H2EDTA extract solution on both hydraulic conductivity and Pb removal. A Pb-contaminated soil sample was collected from an abandoned battery recycling facility. Both batch shaker extractions and column leaching experiments were completed using 5 different EDTA extract solutions. When only CaCl2 was added to EDTA no change in the amount of Pb removed by batch extraction was observed. As expected, lead solubility was observed to decrease as pH was increased by the addition of KOH. However, Pb solubility was only slightly decreased by the addition of both CaCl2 and KOH. The amount of time required to leach 6.0 L of extraction solution through the soil columns varied from 2 to 33 days. The addition of CaCl2 and/or KOH resulted in increased soil hydraulic conductivity relative to the EDTA-only solution. The hydraulic conductivity was related to residual calcium carbonate content, suggesting that dissolution of CaCO3 and subsequent production of CO2 gas in the soil pores was partially responsible for the observed reductions in soil permeability. However, Pb removal was diminished with the addition of CaCl2 and KOH because of the decreased Pb solubility and also kinetic limitations associated with the shorter residence time of the extract solution in the column. 相似文献
10.
The proportion of metals in soils in equilibrium with soil solution can be determined using isotopic dilution. For this purpose, an isotope dilution mass spectrometric (IDMS) technique has been applied for the elements Cd, Cr, Cu, Mo, Ni, Pb, Tl and Zn. Conventionally, sorbed amounts of heavy metals in soils are analysed by ethylenediamine tetra-acetic acid (EDTA) extraction. The IDMS technique and EDTA extraction were both applied to 115 soil samples and compared. For Cd, Cu, Ni, Pb and Zn, the results of the IDMS technique correlated well with the results of EDTA extractions ( r s (Cd) = 0.965, r s (Cu) = 0.916, r s (Ni) = 0.878, r s (Pb) = 0.922, r s (Zn) = 0.962; all at P < 0.001). For Cd and Zn, no significant differences between the results of both methods could be observed, which suggests that EDTA and IDMS determined the same pool. EDTA extracted more Cu, Ni and Pb than was determined by IDMS (7, 26 and 13%, respectively). The correlation between EDTA extraction and IDMS for Cr was significant but weak ( r s (Cr) = 0.361). For Tl and Mo, EDTA extraction and IDMS did not correlate, and IDMS yielded larger concentrations than EDTA. This can be explained by the fact that Tl and Mo do not form stable EDTA complexes, which are essential for the EDTA technique. Recovery experiments demonstrated that added Cd, Cu, Mo, Ni, Pb, Tl and Zn could be recovered successfully by IDMS analysis (mean recovery = 103 ± 9%). Adsorption isotherms for soil samples were determined for Tl, thereby demonstrating that IDMS gave a better estimation of the native content of sorbed Tl in soils than EDTA extraction. 相似文献
11.
Abstract. We studied the effects of red deer grazing and fence-line pacing on soil losses of contaminants (suspended sediment, Escherichia coli , phosphorus) and nitrogen species (ammonia, nitrate) via overland flow and soil physical properties (macroporosity, bulk density, saturated hydraulic conductivity, K sat ) soon after (1 day) and 6 weeks after grazing on a Pallic pastoral soil in southern New Zealand. Fence-line pacing decreased the soil volume occupied by water, macroporosity and K sat , while increasing suspended sediment (to 0.226 g 100 mL−1 ), total P (to 2.0 mg L−1 ), mainly as particulate P (up to 90% of total P), and E. coli (to 3.52 log10 c.f.u. 100 mL−1 ) concentrations in overland flow at 1 day after grazing compared with soils from the rest of the paddock (0.148 g 100 mL−1 , 0.86 mg L−1 and 2.86 log10 c.f.u. 100 mL−1 , respectively). Although concentrations in overland flow were less at 6 weeks after grazing than at 1 day after grazing, losses of P, especially in fence-line soils, were still above recommended limits for surface water quality. Compared to P, losses of N species would be unlikely to have a significant impact on downstream water quality. Management strategies should be directed towards minimizing the occurrence of fence-line pacing to prevent contaminant loss and maintain water and soil quality. 相似文献
12.
Abstract. This paper describes a study of 37 farms in the Batinah region of Oman where fodder crops and date palms are grown using saline irrigation water. Soil water salinities (εs ) range from 2 to 50 dS m–1 . Soil water salinity depends on irrigation water quality and management factors such as the amount and frequency of irrigation and the area of the irrigation basin relative to the vegetation canopy. An irrigation management model for soil salinity control IMAGE has been developed, based on the salt balance of the profile assuming that the εs is in equilibrium with the irrigation water. The input parameters required to run the model include the annual water application, irrigation interval, soil textural class, potential evaporation, the ratio of crop canopy to irrigation basin area and the salinity of irrigation water. Verification of the model using rather uncertain data from a survey of the farms showed that this simple approach predicted εs to within 2.5 dS m–1 in 82% of cases. The model showed that εs was highly sensitive to the size of irrigation basin and the amount and scheduling of irrigation, and so provides a tool for optimizing salinity management. 相似文献
13.
Measuring unsaturated sorptivity and hydraulic conductivity using multiple disc permeameters 总被引：7，自引：0，他引：7
A new field method of obtaining, with minimal disturbance, the unsaturated hydraulic conductivity ( K0 ) and sorptivity ( S0 ) from unconfined disc permeameter measurements is introduced. Conventionally, the sorptivity is obtained from the initial square-root-of-time behaviour of discharge from the disc permeameter. In some cases this can be difficult to measure, in part because multi-dimensional flows approach quasi-steady state very rapidly. As an alternative we extend the ponded twin-ring method to unsaturated discs of several radii. This method has the advantage that only long-time, quasi-steady discharges are needed to obtain K0 and S0 . In the present study, the two methods are tested using data obtained for a fine sandy loam at a supply potential ( Ψ0 ) of – 35 mm and agreement is good. 相似文献
14.
《Communications in Soil Science and Plant Analysis》2012,43(9-10):2265-2278
Abstract The effect of pH on the saturated hydraulic conductivity (K) of repacked columns of two non‐sodic soils (Healaugh and Fagaga soils) was examined. The K value was greater for the Fagaga soil than for the Healaugh soil which is attributed to the difference in the amount of free iron oxides between the soils. The K values reached a maximum when the pH was close to the point of zero net charge (PZNC) (3.7 and 4.8 for the Healaugh and the Fagaga soil, respectively) and decreased on either side of these pH values. The effect of pH on K was related to its effect on surface charge. As the pH of variable‐charge soils approaches the PZNC, the net surface charge decreases resulting in flocculation and maintenance of a high K. Conversely, as the pH deviates from the PZNC, the net surface charge increases, resulting in dispersion and a decrease in K. There was a negative relationship between the amount of dispersed clay and the K values, suggesting that clay dispersion and the resulting clogging of pores decreases K in these soils. 相似文献
15.
Abstract. Uptake in grass crops of ammonium acetate lactate extractable K (KAL ) and reserve K (interlayer K + structural K) in soil was studied in 16 field experiments at different locations on a range of mineral soil types in Norway. The K uptake from soil, both from KAL and reserve K, was considerable, often even at the highest level of K fertilizer. During three years, only on the sandy soils with a low level of acid soluble K (KHNO3 minus KAL ) was there a yield response to K fertilization. The KAL values declined rapidly and flattened off at a 'minimum level' which differed with soil type. This minimum level for KAL is a useful parameter in fertilizer planning, because the grass usually took up the K in excess of the minimum level over two years. The minimum value of KAL was significantly correlated with the content of clay + silt in soil. The decrease in KAL during the growing season was closely correlated to the KAL value in spring minus the minimum value and, therefore, the amount of K supplied to the grass from the KAL fraction can be calculated. Furthermore, the KAL value for the following spring may be estimated. The release from reserve K was partially related to acid soluble K. 相似文献
16.
The unsaturated hydraulic conductivity was determined in the laboratory for some red and black soils, following water movement into a horizontal column of homogenous soil of uniform packing. A highly significant positive relationship was found between moisture content and hydraulic conductivity values in all the soils studied. Correlation coefficients calculated for the relationships between soil constituents/properties and the change in hydraulic conductivity per unit change in moisture content (regression coefficient between hydraulic conductivity and moisture content) have shown positive relationship to sand and negative relationships to silt, silt + clay, clay, carbonates, aggregates > 0.25 mm and saturated hydraulic conductivity. It is concluded that the unsaturated hydraulic conductivity decreases rapidly with decrease in moisture content and this decrease depends on the soil constituents/properties and differences between soil types are clear. 相似文献
17.
18.
Abstract. Hydraulic properties of soils after rice cropping are generally unfavourable for wheat cultivation. Poor drainage, delayed planting and oxygen stress in the root zone may adversely affect the wheat crop after lowland rice cultivation. We studied long-term effects of lantana ( Lantana spp. L.) residue additions at 10, 20 and 30 t ha−1 yr−1 (fresh biomass) on physical properties of a silty clay loam soil under rice–wheat cropping in northwest India. At the end of ten cropping cycles, soil water retention, infiltration rate, saturated hydraulic conductivity and drying rate of soil increased significantly with lantana additions. The available water capacity (AWC), on volume basis, declined at rice harvest (from 22.0 to 18.8–20.9%), but increased at wheat harvest (from 12.9 to 13.4–15.0%) after lantana treatment. The volumes of water transmission (>50 μm) and storage pores (0.5–50 μm) were greater, while the volume of residual pores (<0.5 μm) was smaller in lantana-treated plots than in controls at both rice and wheat harvest. Infiltration rate in the lantana-treated soil was 1.6–7.9 times that of the control (61 mm d−1 ) at rice harvest, and 2–4.1 times that of the control (1879 mm d−1 ) at wheat harvest. Thus lantana addition improved soil hydraulic properties to the benefit of the wheat crop in a rice–wheat cropping sequence. 相似文献
19.
A. Pedescoll P. R. Knowles P. Davies J. García J. Puigagut 《Water, air, and soil pollution》2012,223(5):2263-2275
Clogging is the main operational problem associated with horizontal subsurface flow constructed wetlands (HSSF CWs). The measurement of saturated hydraulic conductivity has proven to be a suitable technique to assess clogging within HSSF CWs. The vertical and horizontal distribution of hydraulic conductivity was assessed in two full-scale HSSF CWs by using two different in situ permeameter methods (falling head (FH) and constant head (CH) methods). Horizontal hydraulic conductivity profiles showed that both methods are correlated by a power function (FH?=?CH0.7821, r 2?=?0.76) within the recorded range of hydraulic conductivities (0?C70?m/day). However, the FH method provided lower values of hydraulic conductivity than the CH method (one to three times lower). Despite discrepancies between the magnitudes of reported readings, the relative distribution of clogging obtained via both methods was similar. Therefore, both methods are useful when exploring the general distribution of clogging and, specially, the assessment of clogged areas originated from preferential flow paths within full-scale HSSF CWs. Discrepancy between methods (either in magnitude and pattern) aroused from the vertical hydraulic conductivity profiles under highly clogged conditions. It is believed this can be attributed to procedural differences between the methods, such as the method of permeameter insertion (twisting versus hammering). Results from both methods suggest that clogging develops along the shortest distance between water input and output. Results also evidence that the design and maintenance of inlet distributors and outlet collectors appear to have a great influence on the pattern of clogging, and hence the asset lifetime of HSSF CWs. 相似文献
20.
Soil compaction and related changes of soil physical parameters are of growing importance in agricultural production. Different stresses (70, 230, 500, and 1000 kPa) were applied to undisturbed soil core samples of eight typical soils of a Saalean moraine landscape in N Germany by means of a confined compression device to determine the effect on (1) total porosity/pore‐size distribution, (2) saturated hydraulic conductivity, and (3) air conductivity to assess the susceptibility towards compaction. Different deformation behaviors after exceeding the mechanical strength particularly resulted from a combination of soil characteristics like texture and initial bulk density. The saturated hydraulic conductivity, as an indicator for pore continuity, was largely affected by the volume of coarse pores (r² = 0.82), whereas there was no relationship between bulk density and saturated hydraulic conductivity. Since coarsely textured soils primarily possess a higher coarse‐pore fraction compared to more finely textured soils, which remains at a high level even after compaction, only minor decreases of saturated hydraulic conductivity were evident. The declines in air conductivity exceeded those in hydraulic conductivity, as gas exchange in soils is, besides the connectivity of coarse pores, a function of water content, which increases after loading in dependence of susceptibility to compaction. A soil‐protection strategy should be focused on more finely textured soils, as stresses of 70 kPa may already lead to a harmful compaction regarding critical values of pore functions such as saturated hydraulic conductivity or air capacity. 相似文献