Interactive effect of slope aspect and rainfall intensity on soil permeability compared to acidic rainfalls

Document Type : Original Article


1 Department of Soil Conservation and Watershed Management Research, Kerman Agricultural and Natural Resource Research Center, Agricultural Research, Education and Extension Organization, Kerman, Iran

2 Department of Watershed Management Engineering, Faculty of Natural Resource, Tarbiat Modares University, Noor, Iran


Introduction: The amount of soil permeability depends on the size of the holes, concentration of liquid, and surface tensile force. In fact, factors affecting the initial porosity are also effective in permeability. The results of different research show that soil permeability has been prioritized in different researches. In Iran, various research has been conducted on soil physical and chemical properties and their relationship with permeability. This study was conducted based on infiltration field measurements under simulated rainfall conditions in order to determine the penetration rate and interaction effect between slope aspect and intensity of precipitation relative to acidic precipitation on Aghajari and Gachsaran formations .
Material and methods: In this study, in order to determine the interactive effect between slope aspect and rainfall intensity in soil permeability compared to acidic precipitation in the deposits of Gachsaran and Aghajari formations due to the existence of petroleum pollutants and air pollution, a part of Gypsum and Margha watersheds of Izeh city with an area of 1202 and 1609 hectares, respectively, were selected. Then, soil permeability was sampled at 16 points with three replicates in rangeland land use in the northern, southern, eastern, and western aspects of Gachsaran and Aghajari formations at different rainfall intensities of 1 and 1.25 mm/min and in precipitation of distilled water, as well as the acidity of 4 and 5 were performed using Kamphorst rain simulator.
Results and discussion: The results showed that in Aghajari formation, the interaction effect of slope aspect and rain intensity, as well as rainfall intensity had the highest sensitivity and slope aspect had the lowest sensitivity to soil permeability compared to acid rains. However, the Gachsaran formation showed uniformity changes compared to acidic precipitation and showed positive effects on slope aspect and rain intensity and interactive effect of slope aspect and rain intensity in almost all three concentrations. In addition, by increasing the amount of soil permeated with acid rains, the amount of soil porosity increased, which this case was due to this type of contamination on the main ingredients of soil and washing soil bonds. Of course, slope aspect due to there are a different amount of clays in both Aghajari and Gachsaran formations, so is more influence in soil permeability than acidic precipitations, as well as the existence of different organic matter in the main aspects of the slopes, especially in the northern and eastern slope aspects, creates a more complex situation in electrical charge changes, which necessitates further research to understand this complex mechanism.
Conclusion: In general, by increasing the acidic degree and increasing the penetration time, soil properties were changed, including the resistance characteristics and bearing capacity of the soil, which in turn, due to the amount of clay and different organic matter, caused more influence of acidic precipitation on soil permeability.


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