بررسی رابطه بین خصوصیات فیزیکوشیمیایی و اشکال فرسایش صفحه‌ای و شیاری در واحدهای مارنی استان زنجان

Introduction
Marls are one of the most important sedimentary units in Iran, which have high sedimentation and erodibility in terms of physical-chemical properties. This property of marls has caused a lot of environmental and construction damage, and therefore it is necessary to study the erosion and sedimentation of marl units. The factors affecting marl erosion are very many, and it has a very complex process, so that it is a function of external factors such as rainfall distribution and internal factors such as physical properties of soil and clay minerals. Accordingly, in studying the erosion and sedimentation potential of marls, it is necessary to pay careful attention to the type, physical and chemical properties and their relationship with the formation and spread of erosion types, as well as to the weather conditions, hydraulic and hydrological behaviors, topographic conditions, and current land use. It is obvious that a general judgment based on quantitative figures and numbers about the results of the research conducted, which is case-specific and regional, is not possible and scientific. Accordingly, it is not possible and logical to use the results obtained from them with complete confidence on a wide scale. But what is certain is that the approaches mentioned are steps that have been taken based on the knowledge and study of marls and confirm that the strategies for estimating erosion and sedimentation in marl areas cannot be based 100% on the common principles in the presented models that are used in watershed management today, but rather it is necessary to provide scientific and practical guidelines on how to investigate erosion and sedimentation potential in marls by completing the studies and research. In addition, the approaches mentioned should be calibrated and tested repeatedly in climatic conditions, topography, and in marl areas that differ in terms of physical and chemical properties. The occurrence and formation of types of erosion in marls is so widespread that it requires special research on the types of marls with erosive forms. Determining the physical, mechanical, and chemical characteristics of marls and investigating the relationship between the type of erosion and these characteristics are very effective and practical in determining and adopting effective strategies to curb erosion and sedimentation of marl fields, but they have received less attention in watershed plans. The result has been the implementation of management and implementation of operations, which, especially before the 1981, led to the failure of plans and the intended goals were not achieved. The occurrence and formation of types of erosion in marls is so wide that it requires special research in relation to types of marls with erosion forms.
This research investigated the physical and chemical characteristics, forms of erosion and intensity of sedimentation of marl units in Zanjan province.
Materials and Methods
This study investigated the physical and chemical properties, erosion patterns, and sedimentation intensity of marly units in Zanjan province. To analyze the physical and chemical properties of marly units, 120 samples were taken from marly materials of marly units at two depths of 0-10 and 0-30 cm. To prepare the erosion profile map of marly units, 366 working units were created by combining marly unit maps, elevation maps above sea level, slope maps, slope direction maps, and land use maps in a GIS environment, eliminating duplicate units, and processing them. Then, using satellite images, aerial photographs, and conducting field visits and controls, along with completing the BLM scoring tables, the type and profile of erosion in each of the working units were determined. This study investigates the physical and chemical properties, forms of erosion and sedimentation intensity of marl units in Zanjan province. To analyze the physical and chemical properties of marl units, sampling of marl materials of marl units in two depths of 0-10 and 0-30 cm was performed on 120 samples. To provide a map of erosion of marl units by combining maps, marl units, altitude map, slope map, direction map and land use together in GIS environment and by removing duplication and processing units, 366 work units were created. Then, using satellite images, aerial photographs and field study and controls along with completing the BLM method score tables, the type and appearance of erosion in each of the work units was determined. The obtained data were analyzed using SAS and SPSS statistical programs.
Results and Discussion
Study of erosion forms in marl units
Based on field studies, the water erosion process is the main erosion process in the region. In general, all the marl units under study have erosion and, according to the physicochemical and environmental characteristics (climate, slope, vegetation, etc.), have different erosion forms. The main erosion forms in the marl units of Zanjan province include raindrop erosion, surface erosion, furrow, ditch, tunnel erosion, thousand-valley erosion, and mass erosion.
Comparison of different erosion forms with t-test
Different water erosions are seen in marl units, but the dominant erosions in them are sheet and furrow erosion. Therefore, statistical studies have been conducted for these two erosions. Based on the results of comparing pairwise means of erosion using the t-test method for the two dominant erosions, surface and groove, it has been observed that characteristics such as organic matter percentage (OC), sodium absorption ratio (SAR), liquid limit (LL), and plasticity index (PI) have significant differences in both erosions.
Studying the effect of physical and chemical variables on erosion forms of marly units
Based on the results obtained from variance analysis and comparison of the means related to sheet and groove erosion forms using Duncan's method, the variables of organic matter percentage (carbon percentage), sodium absorption ratio, fluid limit and plasticity index in these two forms of erosion in the marly units of Zanjan province have significant differences, and in other variables, this difference and difference is not significant. Therefore, it is possible to use these characteristics and variables to separate these two forms of erosion in the marly units of the studied area. 3-4- Studying the relationship between the physicochemical properties of marly units and erosion forms since the environmental and physicochemical conditions required for the creation and development of erosion forms are different. Therefore, the erosion forms existing in these marly units are not at the same level in terms of both erosion form and expansion and abundance. Most of these erosion forms can be observed in the studied marl units with different frequency and extent. However, in terms of frequency and extent, the dominant erosion forms in them are surface or sheet erosion, groove and channel erosion. Of course, gully and mass erosion also have a significant frequency and extent in most of the studied marl units. Based on the results obtained, the physicochemical elements in the groove erosion form are more than the plate erosion form, and in fact, it indicates an increase in these elements from plate erosion to groove erosion. Except for the variables Silt, Electrical Conductivity (EC) and Absorbable Phosphorus (PAV), other elements and variables in groove erosion are more than in plate erosion. Accordingly, it can be said that in the groove erosion form, the physicochemical variables are more concentrated and focused, which is due to the greater erosion intensity than in the plate erosion state. Based on the results obtained from the T-test, analysis of variance using the F-test and comparison of means using the Duncan method, the




Researches in Earth Sciences       17(1) 2026




physicochemical characteristics of sheet and groove erosion forms of marly units, among the 22 physicochemical variables recorded and studied, of these erosion forms, the variables of organic matter percentage (OC), sodium absorption ratio (SAR), liquid limit (LL) and plasticity index (PI) in both surface and groove erosion types had significant differences and it was possible to distinguish between the two erosion forms based on them. Of course, this does not mean that there is no difference between these two erosions in other variables and physicochemical characteristics. Because there are also differences and differences between other variables. But from a statistical point of view, it is said that it is not significant. Therefore, in this regard, these four variables are introduced as distinguishing characteristics between these two erosion forms among marly units existing at the provincial level in this study.
Conclusion
The erosion forms present in the marls of Zanjan province include raindrop erosion, surface erosion, furrow erosion, ditch erosion, tunnel erosion, thousand-valley erosion, and mass erosion. However, since the environmental and physicochemical conditions required for the creation and development of erosion forms are different, the erosion forms present in these marl units are not uniform in terms of both the type of erosion form and the extent and frequency. In terms of frequency and extent, the dominant erosion forms in them are surface or sheet erosion, furrow erosion, and channel erosion. Of course, ditch and mass erosion also have a significant frequency and spread in most of the marl units studied. An examination of the differences and changes in the physicochemical properties of the marly working units at two depths of 0-10 and 0-30 cm using the t-test method showed that the marly working units at the above two depths had a high correlation coefficient in most of the physicochemical variables and had significant differences in the variables silt, cation exchange capacity (C.E.C), organic matter percentage (O.C), neutralizable matter percentage (lime percentage) (TNV), dissolved sodium content (NaSol), sodium absorption ratio (SAR), chlorine content (Cl), sulfate (So4), and liquid limit (LL). Based on the results obtained from the T-test, analysis of variance using the F-test and comparison of means using the Duncan method, the physicochemical characteristics of the surface and groove erosion forms of marly units were recorded and studied among 22 physicochemical variables. Of these erosion forms, the variables of organic matter percentage (OC), sodium absorption ratio (SAR), liquid limit (LL) and plasticity index (PI) had significant differences in both surface and groove erosion types, and it is possible to distinguish between these two erosion forms based on them. Therefore, in this regard, these four variables are introduced as distinguishing characteristics between these two erosion forms among the marly units existing in Zanjan province in this study.