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1.
The reactions of copper and zinc with calcium carbonate surfaces 总被引：2，自引：0，他引：2
The reaction of copper and zinc were studied by adding the metal nitrate to a 4g:50ml suspension of calcite and water which had been equilibrated for two days, and then equilibrating for a further three days. Zinc behaved in a similar manner to cadmium in forming a surface-solid solution of Znχ Ca1-χ CO3 as a result of adsorption, and the pIAP of the equilibrium solutions were close to those expected from the Thorstenson & Plummer equation. However, the continuity from adsorption to precipitation was broken by the formation of Zn5 (OH)6 (CO3 )2 which has a higher stability than ZnCO3 . The CaCO3 surface appears to constrain the adsorbed Zn to conform to a carbonate structure despite its lower stability than the hydroxy carbonate.
The adsorption data for Cu can also be explained in terms of a surface-solid solution of Cuχ Ca1-X CO3 , but CuCO3 is not found naturally because of much greater stability of Cu(OH)2 , and so there is no independent value for the solubility of a CuCO3 end-member if a surface-solid solution is formed. Secondary reactions are more likely to occur for Cu, especially close to the adsorption-precipitation boundary. Continuity from adsorption to precipitation again was not found. Theory predicts that Cu is less likely to form a surface-solid solution than Zn.
Upper Chalk (calcite with 4% other minerals, mostly quartz) behaved in a similar way but with increased adsorption due to its higher surface area. 相似文献
The adsorption data for Cu can also be explained in terms of a surface-solid solution of Cu
Upper Chalk (calcite with 4% other minerals, mostly quartz) behaved in a similar way but with increased adsorption due to its higher surface area. 相似文献
2.
N. S. BOLAN J. K. SYERS R. W. TILLMAN D. R. SCOTTER 《European Journal of Soil Science》1988,39(4):493-504
The effect of lime (CaCO3 ) and phosphate additions on surface charge characteristics and their effect on the leaching of sulphate were examined for two soils (Patua loam and Tokomaru silt loam) which differed in their adsorption capacities for sulphate.
Incubation of soils with either CaCO3 (0–600 mmol kg−1 ) or phosphate (0-208 mmol kg−1 ) resulted in a two- to five-fold increase in the net negative charge and a similar decrease in the adsorption of sulphate. The effect of either lime or phosphate addition on both the surface charge and sulphate adsorption was more pronounced for the allophanic Patua soil than for the Tokomaru soil containing mainly vermiculite.
In a column experiment, liming induced the leaching of sulphur either by the desorp-tion of adsorbed sulphate or by the mineralization of organic sulphur. During a miscible displacement study, addition of either CaCO3 or phosphate resulted in an early breakthrough of sulphate in the leachate. In a pulse experiment, in which soils were incubated with sulphate (3.12 mmol kg−1 ) for 1 week and subsequently leached with water, more added sulphate was lost in the leachate of the soils previously incubated with either CaCO3 or phosphate. 相似文献
Incubation of soils with either CaCO
In a column experiment, liming induced the leaching of sulphur either by the desorp-tion of adsorbed sulphate or by the mineralization of organic sulphur. During a miscible displacement study, addition of either CaCO
3.
Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha−1 ) and liming (in 1958 and 1980, totalling 6000 kg CaCO3 ha−1 ) on CH4 uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear-cut in January 1993 and the following year one-half of each clear-cut plot was prepared by mounding. Fluxes of CH4 were measured with static chambers in the autumn before clear-cutting and during the following four summers. The average CH4 uptake during 1993–96 in the forested reference plot was 82 μg CH4 m−2 h−1 (ranging from 10 to 147 units). In the first summer after clear-cutting, the cleared plot showed 42% lower CH4 uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short-term decrease in CH4 consumption after clear-cutting was associated with increases in soil NH4 + and NO3 − concentrations. Mounding tended at first to stimulate CH4 uptake but later to inhibit it. Neither liming nor N-fertilization had significant effects on CH4 consumption. Our results suggest that over the long term, in N-limited upland boreal forest soils, N addition does not decrease CH4 uptake by the soil. 相似文献
4.
Release of potassium from some benchmark soils of India 总被引：1，自引：0，他引：1
Release of potassium from 15 surface samples of benchmark Alluvial, Red and Black soils of India to 0.01 M solutions of BaCl2 , CaCl2 , NH4 Cl and NaCl was studied in soils either untreated or pretreated with 5 × 10−3 M KCl. In the untreated soils, the efficacy of the extractants declined in the sequence: BaCl2 > NH4 Cl > CaCl2 > NaCl. Cumulative K-release was greatest from Black soils, followed by Red and Alluvial soils. From soils pretreated with 5 * 10−3 M KCl, more K was released than retained, and more 'native' K was released than that from untreated soils. Increase in the release of 'native' K decreased in the sequence: Red > Alluvial > Black soils. The amounts of surface and internal K, desorption rate constants and parabolic diffusion constants were calculated from K release to the various electrolytes. 相似文献
5.
Fate of nitrogen in cattle slurry following surface application or injection to grassland 总被引：6，自引：0，他引：6
Two field experiments commencing in winter (December) and spring (April) were conducted to determine the fate of nitrogen (N) in cattle slurry following application to grassland. In each experiment three methods of application were used: surface application, and injection ± the nitrification inhibitor, nitrapyrin. Slurry was applied at 80t ha−1 , (≡248 kg total N ha−1 in the winter experiment, and 262 kg N ha−1 in the spring experiment). From slurry applied to the surface, total losses of N through NH3 volatilization, measured using a system of wind tunnels, were 77 and 53 kg N ha−1 3 volatilization loss to ∼2 kg N ha −1 . Following surface application, loss by denitrification, measured using an adaptation of the acetylene-inhibition technique, was 30 and 5 kg N ha−1 for the two experiments. Larger denitrification losses were observed for the injected treatments; in the winter experiment the loss from the injected slurry without nitrapyrin was 53 kgN ha −1 , and with nitrapyrin 23 kgN ha−1 . Total denitrification losses for the corresponding injected treatments in the spring experiment were 18 and 14 kg N ha −1 . Apparent recoveries of N in grass herbage in both experiments broadly reflected the differences between treatments in total gaseous loss. 相似文献
6.
Caesium and strontium diffusion through sodium montmorillonite at elevated temperature 总被引：1，自引：0，他引：1
Counter ionic migration rates of dilute Cs+ and Sr2+ against sodium in a Na-montmorillonite gel are measured using a radially perfused diffusion cell. Enhanced or surface diffusion for caesium is observed both at ambient and elevated temperature. To quantify these surface diffusivities the ion-exchange properties of the diffusing species are required. Thus, exchange isotherms for caesium against sodium on montmorillonite at 22 and 90°C are given for 10−1 , 10−2 , and 10−3 M background NaCl concentrations. Caesium counterion surface diffusivities at 22 and 90°C are 2.2*10−6 and 8.0 * 10−6 cm2 s−1 , respectively. These values are found to be essentially independent of background ionic strength over the range 10−3 to 10−1 m NaCl. Experimental evidence of enhanced transport through Na-montmorillonite for the divalent cation Sr2+ is also confirmed with a surface diffusivity of 2 * 10−6 cm2 s−1 at 22°C and in 10−1 m NaCl. 相似文献
7.
Distribution coefficients of Cd, Co, Ni, and Zn in soils 总被引：17，自引：0，他引：17
Batch adsorption experiments were conducted with a mixture of solutes at low equilibrium concentrations of Cd (0.7-12.6 μg1−1 ), Co (18-118μg1−1 , Ni (22-330 μg 1−1 ), and Zn (40-1480 μg1−1 ) in 38 different soils. Statistical correlations indicated that metal sorption onto the soils was influenced by the presence of clays and hydrous oxides of Fe and Mn. Based on calculated distribution coefficients for these metals, Co will generally exhibit the highest mobility in soils, but the mobility of Zn will increase faster with decreasing pH. Two types of empirical relationships are developed from these data to estimate values for the distribution coefficients. 相似文献
8.
Influence of phosphate on cadmium sorption by calcium carbonate 总被引：1，自引：0，他引：1
Laboratory investigation was conducted to investigate the mechanism of cadmium sorption by pure calcium carbonate and to examine whether, reaction products of phosphate with calcium carbonate serve as a sink for sorption of toxic heavy metal cations like cadmium. The phosphatization of calcium carbonate (G.R) was carried out by treating it with orthophosphoric acid in Ca:P ratio of 5:3, 3:2, 4:3 and 1:1, representing the Ca–P ratios of carbonate apatite, tricalcium phosphate, octacalcium phosphate and dicalcium phosphate and then equilibrated for two months. The X-ray diffraction of the phosphate reaction products revealed that calcite along with monetite, brushite and carbonate apatite were present in each case. The cadmium was effectively retained on CaCO3 by the mechanism of chemisorption at lower Cd2+ concentrations as the pH of the equilibrium system remained constant (8.6) up to initial Cd2+ concentrations of 10−4 mol, coinciding to 100% sorption of Cd2+ from the solution. At higher concentrations, precipitation of CdCO3 on CaCO3 surface or as a separate phase predominated. Enrichment of CaCO3 with P reduced the Cd-sorption. The chemisorption of Cd probably involved the exchange of Ca2+ by Cd2+ from CaCO3 surface. The Cd2+ concentration in equilibrium solution followed the solubility diagram of CdCO3 at pH ≤ 8.6, whereas the concentration of Ca2+ started deviating from the solubility line at pH ≤ 8.2. 相似文献
9.
Predicting the rate of dissolution of lime in soil 总被引：2，自引：0，他引：2
A disc of CaCO3 was brought into contact with a column of moist acid soil, incubated for 6 days, the soil cut into thin sections, and the pH measured. The pH profile suggested that the rate of dissolution was controlled by the rate of acid-base diffusion in the soil near the interface of the soil and the CaCO3 disc.
A mechanistic model was developed, containing no arbitrary assumptions or fitting parameters, to predict the rate of neutralization of acid soil by CaCO3 particles of different size grades and at different application rates. The course of neutralization of soil at pH 3.0 and 4.9 with fine, medium and coarse grades of CaCO3 was measured and compared with the model predictions. The agreement was satisfactory within the limits imposed by experimental difficulties. 相似文献
A mechanistic model was developed, containing no arbitrary assumptions or fitting parameters, to predict the rate of neutralization of acid soil by CaCO
10.
Reaction kinetics of the adsorption and desorption of nickel, zinc and cadmium by goethite. I. Adsorption and diffusion of metals 总被引：6，自引：0，他引：6
The reactions of Ni, Zn and Cd with goethite were studied over a range of initial metal concentrations (10−6 to 10−4 M), pH values (4 to 8), reaction times (2h to 42d) and temperatures (5 to 35°C). The adsorption of metals increased with pH, reaction time and temperature. Adsorption of Ni increased relative to Zn and Cd with increasing time and temperature. The initially rapid adsorption of metals within a few hours was followed by a much slower reaction linearly related to time1/2 , interpreted as diffusion–controlled penetration of goethite. The pH–dependent relative diffusion rates (Ni > Zn > Cd) were influenced by both affinity for goethite surfaces and by ionic radius. Diffusion coefficients of the three metals ranged from about 10−19 to 10−20 cm2 s−1 . The corresponding activation energies of diffusion were also calculated (Ni 35, Cd 55, Zn 90 kJ mol−1 ). Our view about the reactions of heavy metals with goethite involves (i) adsorption of metals on external surfaces, (ii) solid–state diffusion of metals from external to internal binding sites, and (iii) metal binding and fixation at positions inside the goethite particles. The general parameters of these processes are related to the hydrolytic properties (p K values) and the ionic radii of the metals. The results show that goethite may be an efficient sink for trace metals. 相似文献
11.
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
12.
A. G. Chalmers 《Soil Use and Management》1985,1(1):17-19
Abstract. Data on lime loss and soil acidification obtained from a range of ADAS experiments are reviewed. The trials, which include drainage and lysimeter studies and long-term liming, manuring and soil management experiments, indicate a wide range of annual lime losses, with maximum rates in excess of 1000 kg ha−1 CaCO3 . 相似文献
13.
14.
The formation of CH3 ONO in 11 soils treated with HNO2 or NaNO2 in a closed system, was studied by measuring the concentration in the gas space above the soil and by absorbing CH3 ONO in HI. The gaseous concentration of CH3 ONO increased and then decreased following additions of HNO2 or NaNO2 , and the production of CH3 ONO increased with increasing concentrations of HNO2 or NaNO2 added to soils.
The amounts of CH3 ONO trapped in HI were 13.5 to 20.4 times higher than those determined by integrating under the net production curves. The evolved CH3 ONO amounted to 0.4 to 3.5% of added NO2 − , and 4.2 to 50% of the gaseous forms of N absorbed by acidic KMnO4 solution. The CH3 ONO evolved from soils was positively correlated with the methoxy content of the soils, and inversely related to soil pH, with negligible amounts being evolved from alkaline soils. The results show that CH3 ONO is a product of NO2 − decomposition in soils, and indicate that small concentrations of the gas may be produced in N–fertilized soils in which NO2 − accumulates. 相似文献
The amounts of CH
15.
S. C. JARVIS 《European Journal of Soil Science》1987,38(3):443-451
The cation composition of solutions and leachates from small-diameter laboratory soil columns was examined over a 23-week period after the addition of lime (0, 3 and 6 t ha–1 ) and/or nitrogen fertilizer (0 or 200 kg N ha–1 ) to an acid soil (pH 4.2). Water was applied at regular intervals to the surface of the columns and 17 leachate samples collected. Initially, the pH of the leachate was high (6.6) in all treatments (including those without lime) but fell rapidly to approach a steady value of 3.8. Large losses of calcium occurred from all columns; the total equivalent amounts of lime lost ranged from 0.88 (no addition) to 2.38 (with added lime) t CaCO3 ha–1 High concentrations of aluminium (181–325 μM) were present in leachates from all treatments; the addition of 200 kg N ha–1 increased the leaching of Al by 94%; addition of lime also increased the amounts of Al leached (by 52%).
The pH of the soil solution (separated by centrifugation) was influenced by treatment, especially in the top 0–40 mm of the column. Aluminium concentration was related to pH, but the form of the relationship differed amongst the treatments. 相似文献
The pH of the soil solution (separated by centrifugation) was influenced by treatment, especially in the top 0–40 mm of the column. Aluminium concentration was related to pH, but the form of the relationship differed amongst the treatments. 相似文献
16.
B. H. JAKOBSEN 《European Journal of Soil Science》1988,39(3):447-455
Pyrite and iron-rich carbonate and phosphate minerals are found in large quantities in an inland moor in western Jutland, Denmark. Sediments with up to 10.4% pyrite (FeS2 ) occur well-separated from sediments with iron-rich carbonate and phosphate minerals both reaching up to ∼6–7%. Analysis of the ground water showed that water enters the moor from different sources. Water of high alkalinity (up to 2.05 meq l−1 ) as well as water rich in sulphate (up to 79 mg l−1 ), sulphide (up to 1.75 mg l−1 ) and Fe2+ (up to 22.4 mg l−1 ) were sampled from the upper ground water flowing into the moor. On entering the moor processes within moor sediments control authigenic mineralogy, resulting in segregated mineral precipitation. 相似文献
17.
Abstract. A study was carried out to compare the impact of 6-year-old plantations of Prosopis juliflora (Swartz) D.C., Dalbergia sissoo Roxb. Ex. D.C. and Eucalyptus tereticornis Sm. on the physical and chemical properties of sodic soil in the Indo-Gangetic alluvial plains of Uttar Pradesh, India. Soil properties under the three tree species showed significant improvement through a reduction in the pH, electrical conductivity, exchangeable sodium percentage, CaCO3 and gypsum requirement, and by increase in organic C, total N, and available P and K. The six years of reclamation had achieved a marked reduction in exchangeable sodium (from 11.5 to 4.5 cmolc kg−1 ) to a depth of 1.5 m in the soil profile, whereas the levels of exchangeable calcium, magnesium and potassium had increased. There was also a significant reduction in soil bulk density (from 1.66 to 1.24 g cm−3 ) and increases in porosity, water holding capacity, field capacity, permeability and infiltration rate. The equilibrium infiltration rate after 455 min increased from 0.03 cm h−1 in the control to 0.13 cm h−1 under P juliflora and D. sissoo and 0.10 cm h−1 under E. tereticornis . It is concluded that salt-tolerant tree species have a significant impact on soil properties, which could help to rehabilitate the sodic wastelands in the region. 相似文献
18.
Olga Babourina Konstantin Voltchanskii Ian Newman Zed Rengel 《Soil Science and Plant Nutrition》2005,51(5):733-736
Potassium transport was investigated in the root elongation zone of Arabidopsis seedlings during the first minutes of Al3+ exposure, using the non-invasive MIFE microelectrode technique. To prevent pH changes during Al3+ application, and to separate aluminium from acidic stress, plants were pre-treated with 5 mM homoPIPES before addition of AlCl3 (pH 4.2). The 30-min treatment with 50 or 500 μM AlCl3 led to a significant increase in K+ efflux in solutions containing 100 μM CaCl2 . This efflux was suppressed by high concentrations of Ca2+ (10 mM) in the bathing solution. Our results suggest that elevated external Ca2+ activities can sustain K+ influx in the root elongation zone during Al3+ exposure either by maintaining [Ca2+ ]cyt or by affecting Al3+ uptake across the plasma membrane. 相似文献
19.
Uptake of K was measured using a single onion root technique with four soil cylinder diameters, and measuring changes in exchangeable K in the soil. Baldwin's model fitted the measured uptake when only exchangeable K was taken up, but that of Heming & Rowell allowed predictions of uptake of both exchangeable and non-exchangeable K (Knes ) after fitting the necessary parameters. Release of Knex occurred in both 3 mm and 6 mm cells (root densities of 14cm cm"−3 and 3.5 cm cm−3 ) in 10 days. Predictions were made for longer times and differing soil water contents: after four weeks at a water content midway between field capacity and wilting point the contribution of Knex to total uptake was significant (up to 60%) for plants with high root densities. 相似文献
20.
P. Villaverde D. Gondar J. Antelo R. López S. Fiol & F. Arce 《European Journal of Soil Science》2009,60(3):377-385
The effect of pH on the adsorption of copper (Cu), lead (Pb) and cadmium (Cd) by a peat soil was studied, and the results compared with those corresponding to cation binding by a dissolved peat humic acid (HA), and interpreted with a NICA–Donnan model. A potentiometric titration technique was used to determine the adsorption isotherms for H+ , at different ionic strengths, and for Cu2+ , Pb2+ and Cd2+ at different pH values, in a peat soil. The effect of the ionic strength on proton binding was similar for the soil (solid) organic matter and for dissolved HA. The adsorption isotherms for cation–peat and the binding curves cation–dissolved HA are almost parallel, although more cation was adsorbed per kg of C in the dissolved HA. The effect of pH on cation binding is similar for dissolved organic matter and for the organic soil. At low metal concentration the amount of adsorbed metal followed the order Cu2+ > Pb2+ > Cd2+ . The cation-binding parameters obtained with the NICA–Donnan model allow excellent simulation of the effect of pH on the adsorption of Cu, Pb and Cd ions in the studied peat soil. The binding constants for the peat suspension were greater than the corresponding generic parameters for dissolved HA. Speciation calculations showed that for Cu and Pb, the most abundant fraction was the metal adsorbed on peat, whereas for Cd the most abundant fraction was dissolved metal. 相似文献