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1.
A comparison of measured and theoretical soil acidity diffusion coefficients over a wide range of pH
The soil acidity diffusion coefficients have been measured at two Pco2 levels with values in the range 2–70 × 10?9 cm2 s?1. The coefficient passed through an ill-defined minimum in the pH range 5–6.5. Theoretical values, calculated on the basis that the only significant acid-base carriers in the soil were the H3O+ -H2O and H2CO3-HCO?3 pairs, agreed well with the experimental values over the whole pH range at Pco2= 0.005 atm. Agreement was not so good however at a CO2 pressure of 0.0003 atm., especially in the neutralalkaline pH range. This was thought to be due to difficulties in maintaining this level of CO2 throughout the soil samples. 相似文献
2.
C. BLOOMFIELD 《European Journal of Soil Science》1972,23(1):1-16
Aerating pyritic soils causes acidification and the forrnation of acid sulphate soils, or cat-clay. The Oxidation of pyrite in soils is associated with the deposition in tile drains of a form of ochre quite distinct from that formed by the action of filamentous iron bacteria. Pyrite-derived ochre results from the action of Thiobacillus ferrooxidans, which, below pH 3.5–4.0, catalyses the Oxidation of Fe2+ and pyrite. In soils less acid than c. pH 4, pyrite oxidizes relatively slowly by chemical reactions to Fe2+ and SO24?. Under these conditions iron enters the drains as Fe2+ and is there oxidized by T. ferrooicidans and deposited as hydrated ferric oxide. Once the soil becomes acid enough for T. ferrooxidans to multiply, the rate at which pyrite oxidizes increases several-fold, and at c. pH 3 iron appears in the drainage water in the ferric form. Liming seems to decrease the rate of Oxidation. 相似文献
3.
在假定土壤对酸碱的缓冲作用全由表面基团反应所控制的基础上,建立了一个描述可变电荷土壤酸碱滴定曲线的模型,并在计算机上对实验结果进行了模拟。结果表明,本模型可以较好地描述土壤酸碱滴定曲线,提供土壤的酸强度(Ka)和酸容量(St),并可进一步提供土壤的酸缓冲容量曲线。本模型对了解和认识土壤酸化和吸附等过程具有一定的意义。 相似文献
4.
The linear diffusion of H ion from a series of soil blocks, containing essentially H and Ca only as exchangeable cations, into a sink solution maintained at pH 5·2, has been studied. In three separate series of experiments, first the total concentration of diffusible H, then the amount of diffusible H in the pore solution, and finally the amount of exchangeable H associated with the solid phase have been successively varied. Account has also been taken of the variation in activity ratio: aH/√a ca. The effect on the resulting flux and diffusion coefficients of the ion has been related to the H buffer power of the soil. The impedance factor of the ion through the liquid pathway is slightly lower than that for other cations determined in soil. The diffusive flux of H occurs through the liquid pathway, and the contribution of solid-associated H is small, except possibly at low H ion solution concentrations. 相似文献
5.
THE RELATIONSHIP BETWEEN OXIDATION-REDUCTION POTENTIALS AND OXYGEN-DIFFUSION LEVELS IN SOME WATERLOGGED ORGANIC SOILS 总被引：2，自引：0，他引：2
W. ARMSTRONG 《European Journal of Soil Science》1967,18(1):27-34
In valley and blanket-bog peat, oxygen-diffusion rates and corresponding oxidation-reduction potentials have been measured, and the relationship between them expressed graphically. Oxygen-diffusion rates were obtained ‘polarographically’, and the Pt cathode also served as the redox indicator-electrode. Plateau-shifts towards more positive potentials made it necessary to use the reduced voltage setting of ?0.48 v for oxygen determinations. These plateaushifts correlate with a lowering of the oxygen content, and an increase in acidity, or, perhaps, with the type of buffer systems found in peat. The ratio redox potential/oxygen diffusion is not constant. At very low oxygen values there is a relatively large increase in redox potential per unit of oxygen, but, as oxygen approaches 2 × 10?8 g O2cm?2min?1, the ratio becomes much lower, while variations become more obvious. rH values calculated according to Jeffery (1961), show that, in peat of high iron content at pH 6, the first traces of oxygen correspond to an rH 1.10–1.20 (E6, 50–120; reduced and oxidized iron probably present), while above 2 × 10?8 g O2 cm?2min?1 the rH is greater than 1.20 and oxidized iron probably predominates. Thus oxidized soil, as defined by Jeffery, may be maintained at very low oxygen levels. It is suggested that oxygen diffusing from plant roots into these peats will oxidize reduced soil products, and thereby protect the plant. 相似文献
6.
华南红壤的交换性碱和交换性酸 总被引：2，自引：2，他引：2
本文提出了一个同时测定土壤的交换性酸和交换性碱的简易方法。将土壤的交换性酸和交换性碱区分为:Na-交换性酸、Ba-交换性酸和SO4-交换性碱、F-交换性碱。用推荐的方法,在野外对华南地区由不同母质发育的砖红壤、赤红壤、红壤等10个剖面进行了测定。结果表明,红壤类土壤含有相当量的交换性碱,但其数量比交换性酸少。酸性母质发育的土壤的交换性酸和交换性碱量大于由基性岩发育的土壤者。红壤的交换性酸和碱的量随电性盐浓度的增高而增大,浓度大于0.1N后,数量基本不变。 相似文献
7.
Diffusion coefficients of soil phosphate calculated from flux to chloride form of anion-exchange resin-paper, assuming total depletion of the labile pool at the boundary, were too small and unrealistic. Thus not all the phosphate in the labile pool contributed to the diffusion process while being desorbed at constant pH in the presence of an indifferent anion—Cl—from the resin-paper. Desorption relationships under these conditions, using CaCl2 at atmospheric CO2 pressure, were markedly different from the relationship between the long-term 32P-exchangeable phosphate and the corresponding pore-solution concentrations. In the same soil containing different amounts of labile phosphate, a different desorption relationship was found for each phosphate level. The constant proportionality between amount of phosphate diffusing into resin-paper and square root of time was indicative of a constant concentration at the boundary. The resin-paper: soil system was therefore considered as an infinite composite medium in which diffusion through both resin-paper and soil were rate-limiting. The constant boundary concentrations were estimated by the use of the diffusion coefficients in the resin-paper, the phosphate adsorption isotherm for the resin-paper and the desorption relationship for each phosphate level in the soil. Diffusion coefficients, calculated using the boundary concentration appropriate to each phosphate level, were related to the slopes of the corresponding desorption relationships, resulting in values of the impedance factor similar to those found for K diffusion under similar conditions. The resin-paper method, however, does not provide an accurate enough measure of the diffusion coefficient of soil phosphate to be of any practical use. Until better and simpler methods are found, the diffusion coefficient may be calculated using the slopes of the desorption relationship and the separately determined value of the impedance factor. 相似文献
8.
土壤磷酸盐位是研究土壤磷有效度的具有相对能量意义的概念,它的提出为研究土壤磷的问题开辟了一条新的途径[2,3,11].磷位值是土壤有效磷的强度指标,把它运用于土壤需磷诊断上,使它成为指导磷肥施用的有用工具,在当前生产上有一定意义. 相似文献
9.
10.
苏南水稻土对铜离子专性吸附的初步研究 总被引：3，自引：1，他引：3
六十年代以来,土壤对多价离子特别是重金属离子的专性吸附,已日益成为土壤化学领域中一个受人注意的问题。土壤胶体中铁、锰、铝、硅等氧化物及其水合物和土壤有机质是专性吸附的主要载体[12,16,17,19,20,21],它们对许多重金属元素的专性吸附所引起的富集过程,起着控制这些金属元素在土壤溶液和海水中浓度的作用[9,15,18];一些微盒营养元素在土壤中的移动及其对植物的有效性,也深受土壤中氧化物胶体的专性吸附的影响[11,14,21]。因此,铁、锰等水合氧化物对重金属离子的专性吸附的研究,不仅是土壤化学领域,而且也是土壤环境保护和地球化学等领域中的重要研究课题。 相似文献
11.
Cadmium sorption was measured in 10 agricultural soils with pH ranging from 4.5 to 7.9, and total Cd content from 0.27 to 1.04 μg g?1 dry soil. With initial Cd concentrations of 0.5 to 100.0 μM, sorption from 0.002 M CaCl2 was described by the Freundlich adsorption equation but the gradients of the isotherms increased when the initial concentrations were below 0.5 μm. This indicates that there are specific sites of differing sorption energy; differences between soils in the gradients of the isotherms at low initial concentration could largely be accounted for by their contents of ‘free’ Fe2O3. When initial concentrations were below 0.5 μm there was a linear relationship between the quantity of Cd sorbed and the final concentration in solution. This relationship held with all soils except that of lowest pH from which there was a net loss of Cd to the solutions. Desorption was measured from three soils with contrasting pH. With the soil of lowest pH, over 80 per cent of sorbed Cd was desorbed to 0.002 m CaCl2 and up to 30 per cent to 100 or 500 μm solutions of heavy metal chlorides. In contrast, only very small proportions (<1.25 per cent) were desorbed from the other soils with pH 6.7 and 7.8. The results indicate that Cd is strongly sorbed by soils of pH of above 6.0 when added in amounts comparable to additions in sewage sludges or phosphatic fertilizers, and illustrate the importance of liming as a means of reducing the mobility of this metal in soils. 相似文献
12.
研究了镍在６种不同性质土壤中活性的动力学。结果表明,土壤活性镍随时间变化的规律可用双常数速率方程很好地加以描述。参数ｋ反映了变化过程的速率,即ｋ值愈大者,其变化的速率愈小。 相似文献
13.
Cation exchange characteristics of the K:Ca saturated forms of five soils were measured at 25°C and 50°C. The rates of isotopic exchange of 42K and 45Ca were too fast to be measured except that of 42K in the K:Ca Harwell soil at 25°C. The slower isotopic exchange of K in this soil was attributed to the presence of a zeolite, clinoptilolite. The intra-particle diffusion coefficient, Di, of K in this soil increased with K-saturation to a maximum at about 40 per cent K, probably because of the ‘blocking’ action of the larger hydrated Ca ions at small K-saturations in clinoptilolite. The CEC, measured by isotopic exchange along the K:Ca adsorption isotherm, decreased with increasing temperature probably because some interlayer spaces collapsed. The standard free energy, enthalpy, and entropy changes were negative for the reaction Ca-soil+2K+? 2K-soil+Ca++. These results seem to show that K is more strongly bound than Ca by the soil and that the Ca-preference shown by the isotherm at small external electrolyte concentration is caused by entropy changes in solution. Calculated activity coefficients of the exchangeable ions changed with K-saturation similarly at both temperatures but values at 50°C were smaller than at 25°C. 相似文献
14.
介绍了国外关于土壤微生物磷测定方法的研究进展 ,讨论了常用的几种方法所存在的问题 ,介绍了主要操作过程要求。对我国 5种主要母质类型的土壤 (pH 3 .3～ 7.4,1molL- 1KCl)的对比研究表明 ,我国土壤采用氯仿熏蒸、0 .5molL- 1NaHCO3在 1∶2 0土水比提取测定无机磷 (Pi)、并以同时测得的培养土壤微生物的磷的回收率作为计算常数得到的结果最佳。测定的大多数南方土壤的微生物磷占土壤全磷的比例小于 1 .5 % ,微生物碳磷比值大于 3 0∶1 ,反映南方土壤磷的生物活性较低 ,土壤微生物对磷的作物供应调节能力不强。 相似文献
15.
酸性土壤磷分级新方法建立与生物学评价 总被引：10，自引：0，他引：10
土壤磷分级方法可用于估算土壤有效磷数量、不同土壤磷组分库数量及其对土壤有效磷的补充能力。以云南赤红壤、黄红壤及湖北棕红壤为供试材料,运用张守敬方法、蒋柏藩方法及本文提出的新方法,对三种酸性土壤和其石灰改良后的土壤磷进行分级研究,探讨石灰改良对酸性土壤磷组分数量及其生物有效性的影响。结果表明:Ca2-P、Al-P和Fe-P是酸性土壤主要的有效磷源,O-P(闭蓄态磷)也是潜在有效磷源,土壤中活性有机磷库相对比较稳定,可转化为高活性有效磷源供植物吸收利用。与两种经典磷分级方法相比,新方法将O-P划分为O-Al-P和O-Fe-P,O-Fe-P较好地反映了石灰处理与对照之间的土壤磷植物有效性差异。 相似文献
16.
The two-surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2-7.6; 0.8-24.2 per cent CaCO3) from the Sherborne soil series, which are derived from Jurassic limestone. High-energy P adsorption capacities (x″m) ranged from 140–345 μg P/g and were most closely correlated with dithionite-soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed (x″m 6–51 ml/μg P). The low-energy adsorption capacities (x″m) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO3 but not with per cent CaCO3, pH, or dithionite-soluble Fe. Total surface areas of CaCO3 in the soils ranged from 4.0 to 8.5 m2/g soil. Low-energy P adsorption capacities agree reasonably with values (100 pg P/m2) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates (k″= 0.08–0.45 ml/μg P) than by limestones (k～10.0 ml/μg P). Low-energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co-adsorbed P. 相似文献
17.
采用随机区组和裂区设计,通过盆栽和根箱模拟试验研究了石灰性土壤,在水分充足的条件下施磷及磷、铁对柠条生长发育及根际土壤养分有效性的影响。盆栽试验结果表明,柠条的生物产量随着施磷水平的增加而增加;在低磷或磷胁迫条件下,柠条的地上部生长受到抑制,根冠比增大,土壤pH值迅速降低。根箱模拟试验发现,不同的铁、磷施肥配比对柠条生物产量的影响不同,当磷和铁的施用量分别为P2O50.15 g kg-1 和FeSO4·7H2O0.03g kg-1时能明显提高柠条的生物量。不同铁、磷配比对柠条根际土壤有效磷含量影响的根际范围是0-6 mm之间,在此范围内供试土壤有效磷含量随距离快速下降,并与根际土壤pH值呈反比。柠条对根际土壤pH的调控主要受磷水平的影响,而施铁水平对根际和根外土壤pH值的影响比较小。 相似文献
18.
Exchange reactions between 0.0in AlCl3 solutions of different pH and Ca-saturated montmorillonite, vermiculite, illite, and soils from the Park Grass Experiment at Rothamsted and the Deerpark Experiment, Wexford, Ireland, showed that Al3+ and Al(OH)2+ were adsorbed from solutions of pH > 4.0 and Al3+ and H+ from solutions of pH < 3.0. When Al was adsorbed, the cation exchange capacity of Ca-saturated soils and clays increased. Conventional Ca: Al exchange isotherms showed that Al3+ was strongly preferred to Ca2+ on all soils and clays. The equilibrium constant for Ca: Al exchange, K, was identical for soils before and after oxidizing their organic matter and did not vary, for any exchanger, with Al-saturation or the initial pH of the AlCl3 solution. This proved the validity of the procedure used for calculating exchangeable Al3+. K values for Ca:Al exchange favoured Al3+ in the order: vermiculite > Park Grass soil > Deerpark soil > illite > montmorillonite. The influence of surface-charge densities of the clay minerals on this order is discussed and a method proposed and tested for calculating the K value of a soil from its mineralogical composition. 相似文献
19.
Zejiang Cai Minggang Xu Boren Wang Lu Zhang Shilin Wen Suduan Gao 《Journal of Soils and Sediments》2018,18(9):2893-2903
Purpose
Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.Materials and methods
Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH4+) and nitrate plus nitrite (NO3??+?NO2?).Results and discussion
All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol(+) kg?1 compared to 2.82 and 4.19 cmol(+) kg?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol(+) kg?1 per pH unit increase for both straws compared to 6.25 cmol(+) kg?1 per pH unit from the manure. The NO3??+?NO2? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.Conclusions
While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.20.
《Communications in Soil Science and Plant Analysis》2012,43(8):699-715
Abstract A buffer is generally a mixture of a weak acid and a salt of the same weak acid. Hence it can neutralize both acids and bases, and thus resists marked changes in pH of a system. Yet systematic change in pH of a buffer caused by addition of an acidic substance can be used to indicate the total acidity represented by the change in buffer pH. Since acid soil is itself a buffer, when it is added to a buffer mixture for the purpose of measuring its acidity or lime requirement (LR), the resulting double‐buffer suspension (soil‐buffer) is a relatively complex system. Much of the complication in interpreting the changes in buffer pH brought about by mixing soil and buffer stems from the facts: i) that much of the acidity is pH‐dependent, and ii) that quick‐test methodology involves reaction of only a fraction of the total soil acidity with the buffer. Marked change in relative amounts of H ions dissociating from the soil‐SMP‐buffer system at soil‐buffer pH 6.9 and above accounts for relatively wide variations between buffer‐indicated and CaCO3 incubation‐measured LR of low LR soils. Similarly, decreased reactivity of H+ in high organic matter soils and increased reactivity of H in acid‐leached soils cause errors in buffer‐indicated LR. Awareness of these principles helps avoid pitfalls of existing buffer methods, and has led to incorporation of the double‐buffer feature for improving the SMP method. 相似文献