共查询到20条相似文献，搜索用时 343 毫秒
1.
该文采用水平扩散池观测了水溶性盐阳离子在工程黄土中的扩散过程。结果表明：水溶性盐阳离子在土壤中的扩散性因离子种类而异,Ｃａ＾２＋的扩散系数最高,Ｍｇ＾２＋,Ｎａ＾＋,Ｋ＾＋依次降低,其由两个模型测定的平均值分别为２．６９２８×１０＾－６,２．３１２７×１０＾－６,１．６７３０×１０＾－６,０．４５０４×１０＾０－６ｃｍ＾２／ｓ。在距源溶液较近时,土壤胶体交换性Ｋ＾＋,Ｎａ＾＋,Ｍｇ６２＋均明显升高 相似文献
2.
3.
土壤离子吸附：2.主要阴阳离子的吸附特性 总被引：5，自引：0，他引：5
综述了土壤与环境中主要阴离子ＨＰＯ＾２－４，ＭｏＯ＾２－４，ＳＯ＾２－４，Ｆ＾－，Ｃｌ＾－和ＮＯ＾－３以及主要阳离子Ｋ＾＋，Ｎａ＾＋，Ｃａ＾２＋，Ｍｇ＾２＋和重金属离子Ｃｕ＾２＋，Ｚｎ＾２＋，Ｎｉ＾２＋，Ｃｏ＾２＋，Ｐｂ＾２＋等的吸附特性和研究进展。 相似文献
4.
5.
钙镁肥对番茄产量品质和养分吸收的影响 总被引：17，自引：0，他引：17
在黄棕壤型酸性菜园土壤上施用钙肥和镁肥，以及应用不同Ｃａ＾２＋，Ｍｇ＾２＋营养水平进行蕃茄试验中，钙、镁肥能显著提高番茄产量和果实中的抗坏血酸和还原糖含量，使滴定酸降低。在不同钙肥品种中，Ｃａ（ＮＯ３）２和Ｃａ（ＯＨ）２的较果较好，ＣａＣｌ２效果较差。钙、钙配合施用效果较好。营养液中Ｃａ＾２＋浓度以１６０ｍｇ／ｋｇ，Ｍｇ＾２＋浓度以４０ｍｇ／ｋｇ较适宜，高Ｃａ＾２＋，高Ｍｇ＾２＋浓度存在着离子间的 相似文献
6.
植物材料含碘量的测定 总被引：2，自引：0，他引：2
德国是世界碘缺乏区之一，对土壤和植株中的碘含量的调查显得特别重要。土壤和植株中的低含量碘（μｇ和ｎｇ水平）可根据ＳＡＮＤＥＬＬ－ＫＯＬＴＨＯＦＦ反应用分光光度计测定，其原理是在碘催化下Ａｓ（Ⅲ）将Ｃｅ（Ⅲ）还原。该反应的程度主要取决于时间和温度，也受离子（如Ｃｌ＾－、ＮＯ２＾－、ＳＣＮ＾－、Ｆｅ＾２＋、ＢｒＯ３＾－、ＭｎＯ４＾－、Ａｇ＾＋、ＣＮ＾－、Ｈｇ＾＋）和金属（如Ｏｓ）的影响。加入ＫＯＨ和Ｚ 相似文献
7.
滨海盐土脱盐过程中pH变化及碱化问题研究 总被引：25，自引：0，他引：25
对滨海重盐土室内淋洗模拟脱盐过程的分析研究结果表明：随着含盐量的下降,Ｎａ＾＋、Ｃｌ＾－、ＳＯ４＾２－、Ｃａ＾２＋和Ｋ＾＋的绝对含量都逐渐减少,ＨＣＯ３＾－逐渐增加;Ｃｌ＾－和Ｎａ＾＋的相对含量逐渐下降,而ＳＯ４＾２＋、Ｍｇ＾２＋、Ｋ＾＋特别是Ｃａ＾２＋、ＨＣＯ３＾－的相对含量逐渐增加,当含盐量降至１ｇ／ｋｇ以下时结果更加明显。由于各离子的迁移能力不同,导致土壤的盐分化学类型由Ｃｌ－Ｎａ向ＨＣＯ３－Ｃａ转化。淋洗试验中淋洗液的盐分化学类型变化滞后于土样。ｐＨ值在整个脱盐过程中先上升后下降,ｐＨ值下降时的土壤含盐量在小于１ｇ／ｋｇ范围。在ｐＨ值先上升后下降的变化过程中,Ｃａ＾２＋含量是先下降后上升,而ＨＣＯ３＾－含量是先上升后下降,残余碳酸钠（ＲＳＣ）的变化趋势也与ＨＣＯ３＾－一样,土壤ｐＨ值与可溶性Ｃａ＾２＋含 相似文献
8.
论述长江之源各拉丹冬峰东坡的尕日曲流域冈加曲巴冰川和水晶矿冰川冰、雪、水样品中的ＰＨ值、总碱度、总硬度、矿化度，以及Ｋ＾＋，Ｎａ＾＋，Ｃａ＾２＋，Ｍｇ＾２＋和ＳＯ＾２－４，Ｃｌ＾－，ＨＣＯ＾－３，ＳｉＯ２等可溶性离子的含量，同时讨论了其水化学组成类型。 相似文献
9.
10.
Fe^2＋和Mn^2＋对水稻锌吸收与运转的影响 总被引：3，自引：0，他引：3
水培试验结果表明，Ｆｅ＾２＋、Ｍｎ＾２＋对水稻锌的吸收和运转有明显的影响。高浓度Ｆｅ＾２＋或Ｍｎ＾２＋（５μｇ／ｇ）显著降低水稻吸锌量、抑制锌由根向茎、叶的运转。稻株生物量与叶片Ｆｅ／Ｚｎ比值或Ｍｎ／Ｚｎ比值有明显折负相关关系，在叶片Ｆｅ／Ｚｎ〉８或Ｍｎ／Ｚｎ〉２６时，水稻生物量明显降低。造成水稻缺锌的主要原因是土壤有效锌含量低，而高浓度Ｆｅ＾２＋和Ｍｎ＾２＋是诱发和加重水稻缺锌的重要条件。因此在 相似文献
11.
中国东部太湖地区酸性水稻土团聚体上铜的专性和非专性吸附动力学研究 总被引：1，自引：0，他引：1
The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+sorption, and the p H changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+followed a descending order of clay > coarse sand > bulk soil > silt> sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+by the bulk soil and the aggregates, which were divided into two stages(rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations(P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The p H of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the p H of the solution was minimized nearly simultaneously.The sorption progress of Cu2+by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil p H and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil. 相似文献
12.
不同培肥措施下土壤CO2释放及其动力学研究 总被引：7，自引：0，他引：7
实验室恒温密闭培养法研究了 4种培肥措施连续培肥 23年后农田土壤的CO2释放状况及其动力学特征。结果表明 ,含水量 12%至 24%范围内 ,土壤CO2释放过程完全可以用一级反应动力学方程 y =A0(1-e-kt)进行定量描述 (r2=0.9812～0.995 9,P 0.01) ;土壤CO2释放量和潜在可释放C量A0 随含水量增加呈线性增加 (r2=0.9728～0.9987,P0.01) ,速率常数k则随含水量增加呈线性降低 (r2=0.9356～0.9939,P0.01)。不同培肥措施明显影响土壤CO2释放状况及其动力学特征参数 ;NP化肥和厩肥 +NP化肥 2种培肥措施较不施肥对照明显增加了土壤CO2释放量、潜在可释放C量A0和速率常数k ;秸秆 +NP化肥培肥措施较不施肥对照显著增加了土壤CO2释放量、潜在可释放C量A0,但却显著降低了释放速率常数k ;有机无机肥料配合措施 (秸秆 +NP、厩肥 +NP)与单施NP化肥措施比较 ,明显降低了释放速率常数k。 相似文献
13.
Coupled diffusion and oxidation of ferrous iron in soils. I. Kinetics of oxygenation of ferrous iron in soil suspension 总被引：3，自引：0，他引：3
The kinetics of oxidation of iron in an aqueous suspension of a thoroughly reduced low-humus tropical rice paddy soil were followed by measuring the extractable ferrous iron in the whole suspension and in the solution. Three-quarters of the initial ferrous iron was oxidized rapidly (first-order rate constant = 9.2 × 10?5 s?1). The subsequent reaction was slow (first-order rate constant = 9.4 × 10?7 S?1) and was not studied in detail. The pH fell from 6.6 to 4.9 over the course of the fast reaction. In further experiments the rate of oxidation was followed at constant pH values in the range 6.5 to 4.5. It was concluded that the oxidation of adsorbed iron was much faster than solution iron, and that the adsorbed iron was oxidized at a rate that was nearly independent of the pH. During the reaction some ferrous iron is adsorbed on the ferric hydroxide formed. The proportion of the remaining ferrous iron adsorbed on ferric hydroxide rather than the original exchange surfaces was high at pH > 6.0 and low at pH < 5.0. The rate of oxidation of the ferrous iron was similar whether it was adsorbed on exchange sites or on the ferric hydroxide formed. Since the rate of oxidation of the iron adsorbed on ferric hydroxide was very much slower than that on ferric hydroxide formed in the absence of soil, it is suggested that the rate in soil may be controlled by diffusion of oxygen to the adsorption sites. 相似文献
14.
Studies on the removal of cadmium(II) ions from aqueous solutions by adsorption on various activated carbons [commercial activated carbon (CAC) and chemically prepared activated carbons (CPACs) from raw materials such as straw, saw dust and datesnut] have been carried out with an aim to obtain information on treating effluents containing Cd(II) ions. Factors influencing the adsorption of Cd(II) ions from aqueous solution by ACs have been investigated by following a batch adsorption technique at 30± 1 °C. The percentage removal increased with decrease in initial concentration and particle size of CPACs and an increase in contact time, dose and initial pH of the solution. Adsorption process was inhibited by the added electrolytes. The adsorption data were fitted with the Langmuir, Dubinim–Radushkevich and Freundlich isotherms and first-order kinetic equations viz., first-order, Lagergren and Bhattacharya–Venkobachar equations and intra-particle diffusion model. The kinetics of adsorption is first order with intra-particle diffusion as one of the rate determining steps. Thermodynamic parameters were obtained from equilibrium constants measured at 30, 35 and 40 °C (Error = ± 1 °C). Results of the studies on adsorption of Cd2+ ions from simulated wastewater were compared with that of CAC and Tulsion CXO-9(H), a commercial ion exchange resin/cationic resin (CR). Straw carbon showed the maximum adsorption capacity towards Cd2+ ions and a high value of rate constant of adsorption. Straw carbon is an alternative low-cost adsorbent to CAC. 相似文献
15.
HU Guo-Song 《土壤圈》1996,6(3):251-258
The kinetics of H+ releasing after Pb2+ adsorption was studied by the potentiometric method combined with the acid-base titration curve technique. Results showed that pH of latosol, red soil and kaolinite suspensions dropped sharply, and then decreased gradually. Most of the H+ exchanged, more than 60%, was displaced at the first minute after Pb2+ was added into the suspension. More H+ was released at a higher concentration of Pb2+ added for a given sample and the amount of H+ released decreased in the order of red soil > latosol > kaolinite at a given concentration. The time-dependent data of H+ releasing of latosol, red soil and kaolinite at two concentrations could be fitted best with the second-order equation among the six equations, including second-order equation, two-constant equation, Elovich equation, parabolic diffusion equation, first-order equation and exponential equation. The H+/Pb2+ exchange stoichiometry increased with time, and a stable ratio of H+/Pb2+, being 1.73, 1.92 and 2.01 for kaolinite, latosol and red soil, respectively, was reached 25 minutes later. 相似文献
16.
Mahdi Najafi Ghiri Ali Abtahi Soheila Sadat Hashemi Fatemeh Jaberian 《Archives of Agronomy and Soil Science》2013,59(12):1439-1454
The release of non-exchangeable potassium from 24 calcareous soils of divergent mineralogy, from southern Iran, was examined. Sand, silt and clay particles were fractionated after dispersion with an ultrasonic probe. Samples were extracted with 0.01 M CaCl2 for 30 successive 2-h periods. The clay fraction released the largest amount of K in each soil. Cumulative K released ranged from 175 to 723, 35 to 128, and 71 to 146 mg kg?1 contributing 20–90, 4–39 and 2–54% for clay, silt and sand fractions, respectively. The lower proportion of K released from sand and silt fractions can be explained by the presence of a high content of CaCO3 and quartz in these fractions. The release kinetics for the non-exchangeable K data showed that parabolic diffusion and power function were the best fitting kinetic models. This indicated that slow diffusion of K from the mica interlayer positions is the main rate-controlling process. Cumulative K released and constant b values of parabolic diffusion model correlated significantly with the mica content of the clay fraction. 相似文献
17.
Theoretical cation exchange equilibria relationships in a soil for a ternary system containing Na+, Ca2+ and Mg2+ are presented. The solid phase activity coefficients of cations for the three binary systems (i. e., Na+ – Ca2+, Na+ – Mg2+ and Ca2+ – Mg2+) were used to calculate the Wilson parameters. Adsorbed phase activity coefficients of Na+, Ca2+ and Mg2+ corresponding to their equivalent fractions on the adsorbed phase of A horizon of a Camborthid for the ternary system (i. e., Na+ – Ca2+ – Mg2+) were evaluated, using these Wilson parameters. Using the values of activity coefficients of adsorbed Na+, Ca2+ and Mg2+ in a ternary soil system and of thermodynamic equilibrium constants for the binary systems, the multiple linear regression relationships between the equivalent fractions of Na+, Ca2+ and Mg2+ on the adsorbed phase and their mole fractions in the equilibrium solution were obtained. The amounts of adsorbed phase cations so predicted showed a fair agreement with those observed experimentally in a ternary system. 相似文献
18.
Employing four mathematical models (first-order, parabolic-diffusion, Elovich and zero-order), kinetics of potassium desorption from eight soils with and without cropping were studied to evaluate their ability in explaining K release from soils. The decline in the soil test K in cropped soils over original soils was drastic in easily desorbable forms compared to that of strongly held forms like 3 M H2SO4 K. Results showed that parabolic diffusion as well as first-order kinetic equation explained the K release data well for both original and K depleted (cropped) soils. Elovich and zero-order equations were not suitable to describe the kinetic data. However, zero-order equation explained K release data better in case of K-depleted soils as compared to original soils. Soils with higher initial K contents registered higher release rate constants. Over the entire period of cropping the range of release rate (b) decreased from 1.26 to 1.53 × 10?2 to values ranging from 1.12 to 1.30 × 10?2 h?1. In contrast, the first-order equation, parabolic diffusion showed higher b values for cropped soils as they represent the diffusion gradient. Mica and its biotite content in both silt and clay fractions showed significant correlation (r) with b values. Similarly with the rate of K release, clay content of soils maintained significant r whereas the silt content did not. 相似文献
19.
《Communications in Soil Science and Plant Analysis》2012,43(7):897-907
The activity of zinc (Zn) ions in the soil solution bathing plant roots is controlled by the simultaneous equilibrium of several competing reactions, such as surface exchange, specific bonding, lattice penetration, precipitation reactions, and the processes leading to the desorption of surface and lattice-bound ions. Desorption of Zn in 15 calcareous soils from southern Iran, treated with 10 mg Zn kg?1 soil as zinc sulfate (ZnSO4·7H2O) and 100 mg phosphorus (P) kg?1 soil as calcium phosphate [Ca(H2PO4)2H2O] and then equilibrated and extracted with diethylentriaminepentaacetic acid (DTPA), was studied in this experiment. The results were fitted to zero-order, first-order, second-order, third-order, parabolic diffusion, two-constant rate, Elovich, and simple Elovich kinetic models. Two-constant rate, simple Elovich, and parabolic diffusion models were determined to best describe Zn-desorption kinetics. Zinc desorption increased as Zn was applied but decreased with applied P. 相似文献
20.
Mineralization of carbon and nitrogen from fresh and anaerobically stored sheep manure in soils of different texture 总被引：1，自引：0，他引：1
A sandy loam soil was mixed with three different amounts of quartz sand and incubated with (15NH4)2SO4 (60 g N g-1 soil) and fresh or anaerobically stored sheep manure (60 g g-1 soil). The mineralization-immobilization of N and the mineralization of C were studied during 84 days of incubation at 20°C. After 7 days, the amount of unlabelled inorganic N in the manure-treated soils was 6–10 g N g-1 soil higher than in soils amended with only (15NH4)2SO4. However, due to immobilization of labelled inorganic N, the resulting net mineralization of N from manure was insignificant or slightly negative in the three soil-sand mixtures (100% soil+0% quartz sand; 50% soil+50% quartz sand; 25% soil+75% quartz sand). After 84 days, the cumulative CO2 evolution and the net mineralization of N from the fresh manure were highest in the soil-sand mixutre with the lowest clay content (4% clay); 28% fo the manure C and 18% of the manure N were net mineralized. There was no significant difference between the soil-sand mixtures containing 8% and 16% clay, in which 24% of the manure C and -1% to 4% of the manure N were net mineralized. The higher net mineralization of N in the soil-sand mixture with the lowest clay content was probably caused by a higher remineralization of immobilized N in this soil-sand mixture. Anaerobic storage of the manure reduced the CO2 evolution rates from the manure C in the three soil-sand mixtures during the initial weeks of decomposition. However, there was no effect of storage on net mineralization of N at the end of the incubation period. Hence, there was no apparent relationship between net mineralization of manure N and C. 相似文献