جستجوی مقالات مرتبط با کلیدواژه "loamy sand" در نشریات گروه "آب و خاک"

The aim of this study was to investigate the effect of application of 0, 1.5, 3, and 4.5% of crude oil, kerosene, and gasoline on spontaneously and mechanically dispersible clay in three texturally different soils of clay loam, loamy sand, and sandy loam. In general, the results showed that the percentage of spontaneously dispersible clay in soils treated with kerosene and gasoline was significantly higher than that treated with crude oil by, respectively, 34% and 44%. Mechanically dispersible clay in soils treated with kerosene and gasoline were significantly higher than that of the crude oil treaded soils by nearly two folds. The percentage of spontaneously dispersible clay in the loamy sand soils was significantly higher than that of the clay loam and the sandy loam soils by nearly 21% and 57%, respectively. While mechanically dispersible clay in loamy sand soil was significantly less by about 31% than that in clay loam soil and about 32% more than that in sandy loam soil. In general, increasing the application rates of petroleum products increased the percentage of spontaneously and mechanically dispersible clay at low levels, but decreased the mentioned attributes at higher levels. The results showed that different levels of petroleum products had significant effects on dispersible clay. Therefore, the results of this study can provide the necessary information about the effect of petroleum materials on the amount of dispersible clay, as one of the soil strength and cohesion criteria and other related characteristics. This information can be used in making the necessary decisions for management and reclamation of different types of oil-contaminated soils, and for using petroleum compounds to protect the soil against erosion.

Oil pollutants are inevitable consequence of rapid population growth and the process of industrialization. Their spread in soil can affect many soil properties, especially aggregate stability. Particle size distribution and aggregate stability are of the main physical and hydraulic characteristics of soil that study of these indices are the basis of soil conservation strategies and are very important parameters in identifying the status of soil structure. Iran is an oil-rich country and the effect of different petroleum compounds on aggregate stability and stability indices including mean weight diameter and geometric mean diameter of aggregates in soils of different textures have not been studied so far. Therefore, this study aimed to investigate the effect of different levels of crude oil, kerosene, and gasoline as the three high-consumption petroleum products on the stability of aggregates in three soils with clay loam, sandy loam, and loamy sand textures.

In this study, the effect of 0, 1.5, 3.5, and 4.5% levels of crude oil, kerosene, and gasoline on the stability of aggregates in clay loam, loamy sand, and sandy loam soils was investigated in a factorial completely randomized design experiment. Studied stability indices were the mean weight diameter and geometric mean diameter of aggregates deterimined using both dry and wet sieving approaches. Finally, the results of the research were analyzed using EXCEL and SAS statistical softwares and the means of each separate treatment as well as their interactions compared using the Duncan's multiple range test at the 5% level.

The results showed that the mean dry weight of aggregate diameters in the loamy sand and sandy loam soils were significantly lower than that of the clay loam soil by nearly 72% and 56%, respectively. The reductions were about 78% and 69% for the dry geometric mean diameter of aggregates. Furthermore, the dry mean weight diameter of aggregates in the soils treated by kerosene and gasoline were more than that of the crude oil- treated soils by nearly 17% and 25%, respectively. The mentioned increaments were about 22% and 35% for the dry geometric mean diameter. The wet mean weight diameter of aggregates in the loamy sand soils was significantly higher than that of the clay loam and sandy loam soils by nearly 20% and 35%, respectively. Furthermore, the wet geometric mean diameter of aggregates in the loamy sand soils was significantly higher than that of the clay loam and sandy loam soils by nearly 91% and 12%, respectively. The wet mean weight diameter of aggregates in the soils treated by kerosene and gasoline was significantly lower than that of the crude oil- treated soils by nearly 32% and 8%, respectively. Furthermore, the wet geometric mean diameter of aggregates in the soils treated by kerosene and gasoline was significantly lower than that of the crude oil- treated soils by nearly 34% and 14%, respectively.

Generally, results indicated that the application of low levels of petroleum products significantly increased the wet and dry mean weight diameter of aggregates and geometric mean diameter of aggregates; whereas, high levels reduced the above-mentioned attributes. The results of this study can be used in both aspects of identifying and monitoring the properties of oil-contaminated soils for their remediation and making appropriate management decisions, as well as conservation of soils against the destructive erosion phenomenon.

Different viscosity and dielectric constants in petroleum productscause physicochemical interactions in the porous fluid electrolyte system, followed by changes in the physical and mechanical properties of the soil. Shear strength of surface soil is one of the most important mechanical properties influencing determination and prediction of soil erosion as a global problem. Penetration resistance is also another mechanical properties of soil that affects tillage operations, plant growth, and soil biological activities and has an important role in seed germination, root growth and development, and crop yield. This study aimed to investigate the effect of application of 0, 1.5, 3.5, and 4.5% of three types of common petroleum products including crude oil, kerosene, and gasoline on shear strength and penetration resisstance of three calcareous soils with clay loam, loamy sand, and sandy loam textures. Results showed that the mean value of shear strength in loamy and sandy loam soils compared to that of clay loam soils was significantly higher by nearly 100 and 35%, respectively, and the penetration resistance in loamy sand soils compared to that of clay loam and sandy loam soils was significantly lower by nearly 83% and 88%, respectively. The mean value of shear strength in soils mixed with kerosene and gasoline compared to that of the soils mixed with crude oil was significantly higher by nearly 17 and 15%; and penetration resistance was significantly higher by nearly 61 and 53%, respectively. In general, the application of 1.5, 3, and 4.5% of oil products caused a significant increase in soil shear strength by about 58, 47, and 14%, respectively, and also caused a significant increase in soil penetration resistance by about two times in all cases compared to that of control.

One of the most important soil and environmental pollutants, particularly around refineries and oil pipelines are oil pollutants which can affect on soil properties. Water repellency, as one of the important soil physical properties, can also be affected by different pollutants in different soils. Therefore, the aim of this study aimed is to evaluate the effect of 0, 1.5, 3, and 4.5% levels of crude oil, kerosene and gasoline on the static (soil-water contact angle) and dynamic (water droplet penetration time) water repellency in clay loam, loamy sand, and sandy loam soils. The results showed that the mean value of dynamic water repellency in loamy sand soil was significantly more than of clay loam and sandy loam soils by 27 times and the mean value of static water repellency in loamy sand and sandy loam soils was significantly more than of clay loam soil by 7% and 1%, respectively. Furthermore, the mean value of dynamic water repellency in soils treated with kerosene and gasoline were significantly lower than crude oil-treated soils by 100% and 96%, respectively and were respectively lower by 19% and 15% for the mean value of static water repellency. In general, petroleum products caused a significant increase in water repellency and the maximum value of water repellency was observed in the crude oil-treated soils.

Salinity and organic matter deficiency are the main problems of soils in arid and semi-arid regions. The use of residues in presence of salinity may affect soil properties differently. In this research, the effect of zero, 1. 5%, 3%, and 4. 5% application of pistachio residues and electrical conductivity (salinity) of water including three levels of 4, 8, and 12 dS m-1 were investigated on water repellency of soils with three different textures, namely, silty clay, loamy, and loamy sand. The static and dynamic water repellencies were determined by measuring soil-water contact angle and water penetration time. The mean values of soil-water contact angle for clay, loam, and sandy loam soils were 70±2. 5º, 65±2. 6º, and 62 ±3. 4º, and water droplet times (WDPT) were about 35±2. 6, 26±1. 6, and 18±0. 6 s, respectively. Accordingly, static water repellency of the fine textured soil was more than that of the medium and coarse textured soils by 3% and 7%, respectively, while the dynamic water repellency was 24% and 95% more, respectively. Salinity had no significant effect on static or dynamic water repellency. However, the salinity of 12 dS. m-1 increased the static water repellency of clay soil by 7%. The residues increased the static and dynamic water repellency of soils, except in silty clay soil where the effect of residues on static water repellency was not significant. In general, salinity levels had no significant effect on the mean values of the static and dynamic water repellency of soils; whereas application of residues (except for 4. 5% residues) increased both static and dynamic water repellency. Furthermore, since the applied residues were probably not fully decomposed in the time period used in this study, it is recommended that longer or different time periods be used in the future studies.