Effect of moisture variation on sulfate concentration in a buck solonetz soil

Abstract

Sulfate concentration in the equilibrium solutions of a black solonetz soil was different at each moisture content. In the sub‐surface horizons a decrease in soil moisture up to about 35 percent resulted in a gradual increase of sulfate concentration. However, with further decrease in moisture the sulfate concentration increased abruptly. Variation of sulfate concentration appears to alter significantly certain cation ratios in the equilibrium solutions.     

The effect of four calcium‐based amendments on soil aggregate stability of two sandy topsoils

The structural stability of soil is a physical characteristic that affects soil degradation processes. Calcium‐based amendments, such as calcium carbonate, calcium sulfate, and calcium oxide/hydroxide, have been shown to improve the stability of soil aggregates. This study seeks to determine which calcium‐based soil amendments, and at what concentration, are the most efficient in improving aggregate stability of sandy topsoils derived from granitic and metamorphic parent materials, and to analyze the mechanisms involved. In the pot experiment, soils amended with CaCO₃, CaCl₂, and CaSO₄ did not present significant differences in aggregate stability compared to the control or among each other. In contrast, Ca(OH)₂ soil amendment brought the greatest stability to the soil aggregates. A dose of 1% Ca(OH)₂ significantly increased the stability of soil aggregates. This effect is due to the reaction of Ca(OH)₂ with atmospheric CO₂ which leads to the formation of CaCO₃, a delayed reaction not showed by the other soil amendments tested. Likewise, the greater solubility of Ca(OH)₂ compared to CaCO₃ exerts a greater aggregation effect on soil. Thus, the mechanism of action of Ca(OH)₂ is related to cementation, rather than flocculation. Future studies should be carried out to demonstrate the effectiveness of Ca(OH)₂ under field conditions.     

MnSO_4浸种对马铃薯幼苗质量及产量形成的影响

以"克新13"马铃薯为材料,通过盆栽试验,利用不同浓度的硫酸锰浸种处理,通过测定马铃薯幼苗的地上部干重、地下部干重、壮苗指数、叶片叶绿素含量、根系活力及产量等指标的变化,研究硫酸锰对马铃薯幼苗质量及产量的作用效应。结果表明:适宜浓度硫酸锰(0.06%~0.09%)浸种处理能有效地提高叶绿素含量和根系活力,促进幼苗地上部和地下部干物质积累,提高壮苗指数,从而提高幼苗质量和产量;硫酸锰过量,则抑制了马铃薯幼苗的正常生长,从而影响了产量的形成。     

基于微观特性分析风积沙粉体掺入提高混凝土的抗冻性

为研究冻融-盐浸环境下风积沙粉体混凝土的微观特性,设计了强度等级为C35、C25的风积沙粉体混凝土,在浓度为0%、3%、6%硫酸镁溶液中采用快冻法进行抗冻性试验,同时借助核磁共振技术、场发射扫描电镜及能谱分析研究其孔隙特征、微观形貌及水化产物。结果表明,风积沙粉体的掺入显著提高混凝土的抗冻性,且适当提高强度等级,有利于提高风积沙粉体混凝土抗冻性,其中强度等级为C35的风积沙粉体混凝土在6%MgSO_4溶液中可承受高达425次冻融循环;相对于基准组,风积沙粉体混凝土中有发育状况良好的针柱状产物钙矾石、纤维状产物石膏生成,填充因冻胀应力作用产生的裂隙,使其内部有害及多害孔数量低于普通混凝土29.78%,抗冻性增强。     

Sulfur metabolism in Allium cepa is hardly affected by chloride and sulfate salinity

Salinity as a major agricultural problem can affect crop growth and quality. Onion (Allium cepa L.) plant contains a wide variety of sulfur-containing compounds which may be involved in plant protection against salt stress. In the current study, a similar reduction in growth caused by chloride and sulfate salts was observed when onion was exposed to equimolar concentrations of Na⁺. Also, no difference was observed for shoot/root ratio and dry matter content of roots and shoots. Plants accumulated Na⁺ and the respective anions (chloride and sulfate) which in turn caused changes in the content of other nutrients. The content of potassium and calcium was decreased more than the other elements by both sodium salts. Sulfate salinity resulted in substantial increase in total sulfur and sulfate content but chloride salinity affected neither the total sulfur nor sulfate content of the roots and shoots, only in onion exposed to 200 mM chloride salt, those of roots and shoots were reduced. Furthermore, the water-soluble non-protein thiol content as well as the content of alliin remained rather unaffected. In conclusion, either salts affected the uptake and distribution of sulfate in onion, but had no or only a minor effect on the plant sulfur metabolism.     

Adsorption of anionic surfactant (sodium dodecyl sulfate) on silica

The adsorption of an anionic surfactant sodium dodecyl sulfate (SDS) on a negatively charged silica was studied to provide a better understanding of surfactant adsorption phenomena in an electrostatic repulsion environment between surfactant and soil. The adsorption experiment was conducted under different electrolyte concentration and pH. Results indicated that adsorption happened with hydrophobic interaction, although electrostatic repulsion was generated between SDS and silica surface. The adsorption amount decreased with decreasing electrolyte concentration and increasing pH due to the increase of electrostatic repulsion. The influence of electric potential near the silica surface on the adsorption was confirmed with the modified Langmuir adsorption equation, 1-pK basic Stern model and zeta potential. Because silica is ubiquitous in soils and the water environment, the adsorption characteristics of an anionic surfactant is important when we consider the fate of an anionic surfactant in the environment. The result is also useful when considering the fate of agricultural chemicals which contain negative charge and hydrophobic sites.     

酸性硫酸盐土酸消长的水动力机制研究

以不同土壤湿度、不同干湿交替周期和原状土自然风干 8个处理进行酸性硫酸盐土 (简称ASS)室内模拟实验。通过对模拟过程内土壤pH、总硫化物性酸度和未氧化双氧水可氧化硫、交换性酸度、硫派生的实际酸度、KCl可提取硫等指标的动态变化过程的跟踪测定和分析显示 ,土壤水分条件是制约ASS酸度及酸形态转化的重要动力机制 ,可导致ASS酸度和酸形态的有规律变化。ASS产酸量和洗酸量受干湿交替周期制约     

不同浓度硫酸盐对水稻土中异化铁还原过程的影响

研究不同电子受体之间的竞争关系对揭示厌氧水稻土中微生物作用导致的氧化还原过程变化机理具有重要的理论意义。本研究采用土壤泥浆厌氧培养、人工合成氧化铁体系接种土壤浸提液厌氧培养及接种铁还原菌纯培养等试验方法,通过向培养体系中添加SO24-,探讨了硫酸盐作为竞争电子受体对不同铁还原体系中Fe（Ⅲ）还原的影响。结果表明,在2种水稻土的泥浆培养过程中,Fe（Ⅲ）还原速率均随着SO24-浓度增加而降低,但Fe（Ⅱ）的最终累积量却较对照处理有明显的增加。添加硫酸盐对Fe（Ⅲ）还原速率（k）的影响表现为：石灰性水稻土〉酸性水稻土;而最终Fe（Ⅱ）累积增加率则为：酸性水稻土〉石灰性水稻土。由接种不同水稻土浸提液的培养试验看出,添加SO24-后Fe（Ⅲ）还原受到显著的抑制,但随着培养时间延长Fe（Ⅲ）还原反应依然可以进行,并且Fe（Ⅱ）累积量最终达到与CK相同的水平。在接种铁还原菌的纯培养试验中,添加SO24-对供试的4株铁还原菌的Fe（Ⅲ）还原过程并未产生抑制效应,表明铁还原菌本身并不受硫酸盐的影响。     

Biofortification of onion bulb with selenium at different levels of sulfate

In this research experiment, two commercial onion cultivars (Allium cepa L., cvs. Dorrcheh and Cebolla Valenciana) were grown in sand culture and exposed to two levels of selenium (Se) (0 and 25?µM) and two levels of sulfate (1 and 3?mM). According to the results obtained, addition of 25?µM Se in combination with 3?mM sulfate was not only effective in significant increase of onion bulb yield, but it significantly increased Se concentration of bulb. By considering the average consumption of onion in central Iran, the daily intake of Se via consumption of Se-biofortified onion is estimated to be 68.4–77.2?µg in spring and summer and 72.6–117.1?µg in fall and winter. These amounts of daily intakes of Se is higher than the sufficient levels of Se recommended by world health organization (WHO) but less than the maximum tolerable level of Se (400?µg Se per day) for human.