The Nature of the Pedogenic and Geoinformatics Distribution of Iron Oxides in Different Physiographic Units

The study was conducted within different physiographic units in central and northern Iraq to find out the nature of the effect of these units on the genetic distribution of iron oxides within the soil pedon. Sex Soil pedons representing the nature of the variability of the physiographic units were elected, in addition to taking 34 surface samples representing the nature of the variability of the soil units horizontally within the physiographic units to prepare maps of the spatial distribution of iron oxides based on geospatial technologies, Soil Pedons described the morphology and wavelength 5 YR for Soil pedon located within the mountainous region that was affected by iron oxides The results showed that the highest content of iron oxides was in the mountainous physiographical unit in the surface horizon Mollic horizon while the lowest content of oxides was in the physiographical unit of the river basin. The Geoinformatics distribution maps revealed 3 class of iron oxides, the low class, the medium class, and the high class. The most abundant class was the moderate class, with an estimated area of about 1051.8575.


Introduction
The term physiographic is used to indicate the nature of the topography of large areas in terms of varying heights in totality and the geographical shapes that result in one physiographic unit [1].Soil survey operations depend on their office and field work for preparing soil maps and classifying them by studying the factors and processes of soil formation and development and the extent of their impact on soil variation horizontally represented by soil units and vertically represented by internal soil characteristics within soil pedon.These operations require revealing the nature of the environmental system and its elements, which include the units of Physiography, soils, and the characteristics of their geographical areas.To diagnose and classify soils, the physiographic units and landforms are studied geographically and topologically through their heights based on aerial photographs or remote sensing techniques and finding the geomorphological and physiographical relationships that link this topography and affect the pedological characteristics of the soil.It also shows the importance of studying the physiographic units in the office based on aerial photographs or remote sensing techniques to clarify the boundaries separating the image units and in the field by counting them as one of the main environmental requirements in the morphological documentation form, which requires the person in charge of the soil survey and classification process to document all external soil characteristics represented by the elements of the physiographic units.Soil surface aspects and internal characteristics are represented by the pedological characteristics of the soil surface for the preparation of soil maps as a final stage for soil survey and classification operations.The soils of Iraq differ among themselves as a result of the different factors and processes of their formation and development, and these factors and processes differ from one physiographic region to another, in addition to the presence of locational differences within one physiographic unit, and these differences are due to the difference in height, especially the micro-relief difference, and to the difference in material The origin, climatic and local conditions, as well as the natural vegetation and permeability, and thus this effect will be reflected in the pedological characteristics of the soil.Iron oxides are one of the main components of the earth's crust and constitute about 5.1% of the rocks and 3.8% of the soil.It is released through the weathering of iron-manganese minerals in the form of precipitated oxides [2] and is often the result of genetics or through Weathering of primary minerals [3] and iron oxides have a very significant effect on the physical properties of the soil, such as soil color [4] showed that the free oxide content in soil depends on the degree of its development.[5] Buzzini (1991) also showed that the content of free oxides in developed soils is more than that of undeveloped soils.He also found that the degree of soil development greatly affects the content of these oxides.[6] confirmed that free iron oxides are often found associated with soil separations forming compounds.differ in their characteristics.These oxides are among the important compounds in various types of soils because of their clear influence on the chemical and physical properties of the soils in them.[7] stated that the formation of iron oxide compounds in the soil depends mainly on the parent material and the intensity of weathering.[5] mentioned that the values of the results of iron oxides increase with the decrease in the size of the soil separations and that the largest value was present within the clay separations, and from here he reached the conclusion that there is a joint movement of free iron oxides with the clay separations.[8] confirmed that the vertical distribution of iron oxides corresponds to the vertical distribution of clay separations in most of the selected pedons within Erbil and Tikrit.Total, free, and crystallized iron oxides were also dominant in soil pedons Erbil and Tikrit.[9] mention The values of free iron oxides varied within different units of environment between desert and sedimentary soils, as well as among the soil soils of the single environment.[10] It was concluded that the pedogenic distribution of iron oxides is consistent with the clay content.[11] mention A remote sensing technique was used to forecast the presence of soil minerals, particularly iron, in the research area and The anticipated soil mineral maps for the research region were created to depict the soil characterization and total iron spread at the study site.The findings of this study could aid in determining the spatial distribution of specific soil qualities in Sulaimaniyah, Iraq.The study aims to know the nature of the genetic distribution of iron oxides in the selected soil pedons and the horizontal distribution within the soil units in different physiographic units as well as prepare a map of the distribution of iron oxides in the different physiographic units using geoinformatics techniques.

Study Area
Several investigations and exploratory field tours were conducted within the study area to identify the nature of the physiographic units and their impact on soil formation and the nature of the distribution of vegetation cover.Three physiographic units were identified within the mountainous, hill, and river basin units.The first site was chosen within the mountainous physiographic unit in Sulaymaniyah Governorate, which is located in northeastern Iraq, between longitude 22-03-59-44-E and latitude 37-12-38-35 N-and within the village of Bazian, which is 30 km from the center of Sulaymaniyah Governorate.The second site is within the undulating physiographic unit within Kirkuk Governorate Northern Iraq between longitudes E 44-07-55-45 and latitudes 27-10-45-35-N in the village of Qara Hanjir.Pedons representatives of the soils of the study area were identified in Figure 1.Other surface samples were sampled by ten samples.The third site within the physiographic unit identified the river IOP Publishing doi:10.1088/1755-1315/1259/1/0120253 basin in the district of Alton Kobri, located between the longitudes 44-07-55-45-E and two latitudes 35-45-10-21-N.It identified Pedons representative of the soils of the study area, and Surface samples were taken and distributed according to the different physiographic units so that they are representative of these units.

Fieldwork/Morphological Characteristics
The samples representing the soils of the study sites were excavated within the physiographic units, and the surface and subsurface diagnostic horizons were diagnosed based on the morphological description form and the morphological characteristics of the horizon, horizon thickness, color in dry and wet conditions, soil texture, soil structure, soil consistency, Root distribution, Soil horizon boundary, with documenting the prevailing morphological features within the soil pedon according to soil survey manual [12].

Physical and Chemical Properties
It was estimated after taking soil samples from the field, which are models of the horizons of surface and subsurface soil deposits.The samples were air dried, then ground and passed through a sieve with a diameter of 2 mm, in preparation for conducting physical and chemical mineral measurements.Soil compositions (sand, silt, and clay) were estimated using the international absorbent method described by [13], and reported in [14].The bulk density was estimated according to [15].Soil pH was measured by making an extract (1:1), using a device ((pH Meter), and according to [14].The electrical conductivity of the soil was measured by making an extract (1:1), using an (Ec Meter) device [14].The organic matter was estimated according to [16].The cation exchange capacity was estimated according to [17].Calcium carbonate (lime) was determined by [16].iron was determined according to [18].A map of the spatial distribution of iron oxides was prepared according to a method IDW in the program ARC GIS.

The Effect of the Physiographic Site on some Morphological Characteristics of the Soils of the Study Sites
The results of the morphological description represented by the color of the soil for the selected sites in the study sites indicate that there is a state of variation in the nature of the dominant color class, due to the influence of the nature of the physiographic sites, both within the main and secondary physiographic units on a large scale, and the accompanying influence on the nature of the activity of soil formation factors and processes, especially climate.(Rain and temperature) as well as the effect of the vegetation cover factor, which is one of the effective factors in soil formation and development, as well as the impact of the nature of the physiographic site on the nature of the site conditions for each hill, especially the topographic and the degree of slope, whose impact is reflected in the surface and internal characteristics of the beds and comes in the forefront of the type and nature of horizons Color, texture, and these factors helped, individually or collectively, to create a kind of variation in the horizontal surface of the soil unit and the internal vertical of the body of the treadmill.The results indicate the morphological description of soil pedon located in the Bazian region, which is located within the physiographic unit (the mountainous region), indicating that the dominant color was reddish-brown in its different degrees if the wavelength was 5 YR, and the values of the intensity of the color brightness were between 5-6 in the dry state.As for the values of color purity, It was between 2-4 in the dry state, while in the wet state, the dominant color class was dark reddish brown and the value of the intensity of color brightness was between 3-6 and the purity of the color was between 2-4, while in the physiographic unit of wavy nature and hills the dominant color class was In the dry yellowish-brown or pale yellowish-brown state if the light wavelength values are 10 YR The value of the color brightness in the dry state was 6, the value of the color chroma was 3-4, while the color class prevailing in the wet state was yellowish-brown, and the value of the brightness of the color was 4-5, while the values of the color chroma were 3-4 as well.As for the physiographic unit, the river basin, the nature of the dominant color was pale yellow-brown.The values of the intensity of color brightness were 6 and the chroma of the color was 4 in the dry condition, while in the wet condition, the color was pale yellowish-brown and the color brightness was 4 while the chroma of the color was also 4.
The difference in the nature of the color components of the genetic horizons in the soil pedons is due to the influence of the nature of the physiographic location as well as the influence of the parent material, so the difference in the wavelength of light, as well as the values of brightness intensity and color chroma, reflect the nature of the internal characteristics of the genetic horizons and the extent of the genetic development that they went through in the previous time The dominance of the dark color indicates the nature of the effect of the content of the decomposed organic matter as well as the increase in the moisture content in it, as well as the presence of iron minerals, especially the minerals hematite, biotite, and alkene.The color of the soil is determined depending on its content of the main components, as the yellow or red color indicates The presence of some types of iron oxides, for example, the yellow color may indicate the dominance of the mineral goethite, while the red color may indicate the dominance of the mineral hematite, while the pale white color indicates the dominance of the mineral calcite and dolomite [19].
Table 1.The activity of some pedogenic processes is responsible for the formation of color or the group of colors that make up the soil pedon.The presence of forests in the mountainous physiographic unit and the undulating hills unit, while the presence of some of the dominant trees in the river basin had a role in changing the color of the soil horizontally and vertically within the soil unit, in contrast to the areas located within the river basin unit that suffers from continuous additions due to inundation and floods, and therefore it was not allowed It has time to develop soil color.
It is located within the developed soils because it contains the superficial diagnostic horizon, molecular, and the gain horizon (Horizon B) Argillic, which represents the horizon of collecting some colloidal materials transferred from the surface horizons and collecting them in the subsurface horizons as a result of the activity of some pedogenic processes, especially the processes of loss, illuvial, and removal of calcification, which helped to form a horizon Some materials, including clay and carbonate minerals, are collected, which are among the basic aspects of the formation of earning horizons, according to what was mentioned in [18].And the climatic conditions represented by the increase in rainfall helped this region to diversify the vegetation cover, especially trees, as well as the relatively long life span and topography to activate some pedogenic processes responsible for the formation of the gain horizon which refers to the movement of soil components from the surface horizons to the subsurface horizons, especially carbonates and separable Clay may indicate a state of dissolution and transport in this region as a result of increased precipitation, which leads to the removal of binders and then the movement of soil components with depth, and this is consistent with [20].
The results of the morphological characterization Table (1) indicate the internal characteristics of the soil bed, which is characterized by a dark color, especially for the surface diagnostic horizons, for the presence of good content of organic matter.It was also observed that the color persists with the depth of the horizon that follows it.The activity may be due to the dark color development process, which works to mix organic materials with the components of Mineral soil and give the soil a dark color.The color of the soil in the wet state ranged from dark reddish brown at wavelength YR10 at the surface horizon A to reddish brown at the horizon 1Ck at wavelength YR5.The value of value ranged between (3-6), while the value of chroma ranged from (2-3), but in the dry state, Soil color ranged from reddish gray at wavelength YR5 in the surface horizon A to light reddish brown in the horizon.

Particle Size Distribution
The results indicate that the pediments located within the physiographic unit of the mountainous region have a high content of clay, then silt, then sand, as it reflects the nature of the clay origin material of this soil, as it is noted in the first pediment that the percentage of clay increased in the subsurface horizons, as it ranged from (300-410).gm.kg -1 and the increase in mud in horizon B may be attributed mainly to the role of the climate factor mainly to increase the rate of rainfall in addition to the role of the vegetation cover and the parent material.This is consistent with what was indicated by [21] that the process of transporting mud and its sedimentation is a pedogenic process that requires the presence of precipitates higher than evaporation that helps disperse and carry mud and transport it from the surface horizons to the subsurface horizons.
As for the second volume, it did not show any pattern of clay separation, as its lowest value on the horizon was Ck3 and the highest value on the horizon was Ck2.The discrepancy between clay separations in the first and second batches is attributed to the effect of the physiographic unit.The value of the silt for the first batch ranged between (210-505) gm.kg-1.The lowest value was in the horizon Ck3 and the highest value was in the horizon Ck2, while the value in the second volume ranged between (189-470) g.kg-1The lowest value in the horizon Ck3 and the highest value in the horizon Ck1, and it is noted that the silt distribution is irregular during the first and second units, and this is attributed to the nature of the parent material and the variation in sedimentation processes.The distribution of sand was low in the first place, ranging between (115-380) g.kg-1.The lowest value was in the Btk horizon and the highest was in Ck3.The reason for the decrease in the percentage of sand is due to the type of calcareous-clay parent material, the weathering conditions, and the type of wind and water sediments.As for the distribution of sand in the second volume, it was different, due to the nature of the parent material and the variation in sedimentation processes.The results indicated that the vaults located within the physiographic unit (undulating area) did not show the requirements for the investigation and diagnosis of the mud horizon, despite the presence of slightly high content of clay joints with the depth of the subsurface horizon in both the third and fourth vaults.The reason for this may be attributed to the fact that this resource is located in a sloping area, and the slope increases the movement of water to the side in the direction of the slope and thus reduces the entry of water into the soil body, which led to a decrease in the activity of soil formation processes and the transfer of soil components towards the surface horizons, and this is consistent with [20].The content of the clay separation for the third batch ranged between (355-420) g.kg -1 , the lowest value in the Bk horizon and the highest value in the horizon 1Ck.As for the fourth volume, it ranged between (365-430) gm.kg-1, the lowest value in Ck2 and the highest value in Ck2As for the silt distribution, it decreased with depth in both the third and fourth volumes, as it ranged between (225-270) gm.kg -1 .The lowest value is in the horizon Ck1 and the highest value is in the subsurface horizon Bk for the third volume, while the fourth volume is (210-480) gm.Kg -1 .The lowest value in the horizon Ck2 and the highest value in the surface horizon A. The variation in silt ratios may be associated with the parent material and weathering conditions consistent with [22].As for the total sand separation, it ranged between (340-420) g.kg-1, the lowest value in the horizon Bk and the highest value in the horizon 1Ck for the third volume, while the fourth volume ranged between (13-425) g.kg -1 , the lowest value in the horizon A and the most expensive Ck2 value, and this discrepancy may be attributed to the parent material.The results indicate that the minerals located within the physiographic unit (the river basin) showed an opposite pattern to the minerals of the mountainous region and the undulating region, as the predominance was for the sand separation, then clay, then silt, as the content of the total sand separation ranged between (460-486) g.kg -1 less.A value on the horizon A and the highest value of Ck1 for the fifth grade, while it ranged between (440-516) g.kg-1, the lowest value on the horizon Ck2 and the highest value of Ck1.As the rise and fall in the total sand sediment content are affected by the nature of sedimentation and the physiographic location, and this is consistent with [23] We note from the results that the content values of the clay separation ranged between (294-330) g.kg -1 .The lowest value is in the horizon Ck1 and the highest value is in the surface horizon A for the fifth volume.As for the sixth volume, the content of the clay separation ranged between (294-322) g.kg -1 .The lowest value in Ck2, and the highest value in horizon A. This is due to the exposure of the transported particles to breakage during the transport process and repeated sedimentation.As for the distribution of sedimentary silts, it ranged between (208-220) g.kg -1 , the lowest value in the horizon Ck2 and the highest value in the horizon Ck1 for the fifth grade, while the sixth grade ranged between (190-240) g.kg -1 , the lowest value in the horizon Ck1 and the highest value On the horizon Ck2.We note the agreement of textures between the fifth and sixth blocks, and this is due to the similarity in the physiographic location of these units and the nature of the sedimentation conditions, and this is consistent with [23].

Chemical properties
The results of Table (2) indicate that there is a discrepancy in the organic matter content of the pots located within the main and secondary physiographic units.It was noted from Table (2) that the values of the organic matter for the crevices located within the physiographic unit (the mountainous region) ranged between (34.1-5.3)g.It was consistent with the spectral behavior of this horizon, as the value of its spectral reflectivity reached (26% for horizon A) at a wavelength of approximately 1900 nm, and this was confirmed by [24] that increasing the content of organic matter in the soil affects clearly and effectively The values of the spectral reflectivity of the soil, which means that the higher the organic matter content in the soil, the lower the spectral reflectivity values of the soil.As for the organic matter content of the pits located within the physiographic unit (the corrugated area) ranged between (31.0-4.4)g.kg-1.The lowest value is in the subsurface horizon Ck1 of the third pit and the highest value in the surface diagnostic horizon A of the fourth pit, and this is attributed to the vegetation of With pine trees and the natural vegetation prevailing in this region, as mentioned above in the morphological description, and this applies with what was indicated by [22] that the soil content of organic matter depends mainly on the vegetation cover, root group systems, and climatic conditions.As for the deposits located within the physiographic unit (the river basin), they showed a different pattern in the values of the organic matter content, as they ranged between (11-4.2) g.This is because these soils are newly formed and undeveloped sediments.The values of the cation exchange capacity of the containers located within the physiographic unit (the mountainous region) ranged between (16.61-24.52)cmol of a kg-1 charge.This is due to the high content of clay and silt, and this is consistent with [23] who indicated that the dominance of the silt separation leads to an increase in the cationic exchange capacity.The values of the cation exchange capacity of the pots located within the physiographic unit (undulating and hill) ranged between (24.87-13.38)centimos of charge.kg-1 is the lowest value in the subsurface horizon Ck2 for the fourth pot, and this is due to the increase in calcium carbonate, which negatively affects the exchange capacity values.Cationic compounds in the soil, as they work to encapsulate clay and silt particles that have great importance in the exchange capacity, and instead, they work to reduce the surface area of these joints and thus reduce the values of the cationic exchange capacity, and this is consistent with [22] and the highest value in the surface diagnostic horizon A for the fourth degree, and this is due to the content of organic matter in the soil, as the exchange capacity values increase with the increase in the soil content of organic matter, and this is consistent with [25].
As for the values of the exchange capacity of the pots located within the physiographic unit (the river basin), they ranged between (10.96-13.57)centimoles of a kg-1 charge.The lowest value is in the C1 horizon and the highest value is in the surface diagnostic horizon A for the fifth pot.The unit, compared to the main physiographic units, indicates a decrease in its content of organic matter, as well as an increase in its content of separated sand, and these results are consistent with [26].
The values of calcium carbonate minerals for the gauges located within the physiographic unit (wavy area) ranged between (236-380) g.kg-1.The lowest value is in the surface diagnostic horizon A of the fourth gauge and the highest value is in the surface diagnostic horizon A of the third gauge.It is noted from the results that the gain horizon is Bk for the third degree, and this reflects the successive effect of the surface addition processes of carbonate minerals in the surface horizon, which were transferred from oceanic sites due to the processes of erosion and water sedimentation that helped to accumulate carbonates.As a result of the availability of suitable moisture, it helped to dissolve and transport carbonate minerals from the surface horizons and collect them in the horizons close to the surface.kg-1 and this is consistent with what was mentioned by [27].As for the reservoirs located within the physiographic unit (the river basin), the carbonate content ranged between (305-256) g.kg-1.The lowest value is in the subsurface horizon, C2, for the fifth reservoir, and the highest value is in the subsurface horizon, C2, for the sixth reservoir.It is noted through the results.These deposits showed a similar pattern in the decrease in the values of calcium carbonate distribution, and due to the fact that the parent material is Alluvium sedimentary materials, there are no significant differences in the carbonate content in these deposits, and this is consistent with [22].As the values of calcium carbonate for the soil pedon located within the physiographic units (the mountainous region) ranged between (396-112) g.The continuous dissolving and transport of this component with depth, and may be associated with chemical conditions that make the carbonate in its dissolved form and in the form of solutions or suspensions and thus facilitate its movement with the soil solution.Decalcification process It is noted from the results, Table (2), that the values of the interaction scores for all study areas located within its main and secondary physiographic units ranged from neutral to low basal, and this is consistent with [28,29]), and that this range is due to the factors and processes of soil formation as well as the effect of calcium carbonate, and this is consistent with [30].
The results shown in Table (2) indicate a decrease in the electrical conductivity values of the soils of the study areas, and this indicates that the study soils are not saline.

3.3.1.Iron Oxides
The results in Table 2 indicated a variation in the values of total iron oxides for the soil values of the study areas within their physiographic units, due to the amount and distribution of rainfall in the study areas and the accompanying variation in the nature and density of vegetation cover, as well as a state of variation in the nature of the parent material.These factors, together or individually, helped to cause a state of variation in the activity of different weathering processes, especially chemical ones, which helped to release iron in its free nature in the soil at different rates within the study sites [31].As the values of iron oxides for the burials located within the physiographic unit (the mountainous region) ranged between (9.02-3.72)g.kg-1, the lowest value in the subsurface horizon Ck3 for the first burial ground and the highest value in the surface diagnostic horizon A for the first burrow, as this horizon was characterized by a brown color Dark reddish as mentioned in the morphological description, and this high value is due to the containment of these soils to dark minerals, as this is consistent with [31] and is also attributed to the high soil content of organic matter and clay separation, and to the influence of the type of vegetation from the prevailing forest trees In the study area and within the mountainous unit.The values of iron oxides for the pots located within the physiographic units (wavy area) ranged between (1.8-8.63), with the lowest value in the surface horizon A of the third pot and the highest value in the surface characterization A of the fourth pedon.[32,33] where confirmed the presence of a highly significant positive relationship between the content of organic matter and free iron oxides.As for the pits located within the physiographic unit (the river basin), the values of iron oxides ranged between (4.31-265) g.This decrease is attributed to the fact that these soils are sedimentary, undeveloped, with low content of organic matter, and separated by clay.

Spatial distribution of iron oxides
It is noted from the table that the values and content of iron oxide varied horizontally also within the soil units located in different physiographic units, if they were somewhat high in the mountainous unit, due to the original material, as well as the somewhat development of soils in these units due to the influence of climate with the nature of the prevailing vegetation cover, so it was higher The content in the tenth sample was 9.12, while the content of oxides decreased horizontally within the soil units located within the physiographic unit, the wavy hills, if the highest content was at the sample 14 and its value was 6.38.If it was 1.89 at sample 32, then the reason is certainly due to the nature of the soils of this undeveloped unit and that it is young newly formed soil.The figure shows the distribution map of the spatial distribution of iron oxides, depending on the content of surface samples in each physiographic unit, if this predictive map includes three classes of iron oxides for the physiographic units, as the area of the low class reached 918.79, at a rate of 3.269, and the area of the medium class reached 1051.85, at a rate of 5.04, and the area of the high class reached 606.38, at an average 7.02, as iron oxides showed superiority within the physiographic unit of the mountainous region, followed by the undulating region and the river basin.Table 3.

Conclusions
The iron oxides affected the variation of the morphological characteristics represented by the variation of the wavelength, the values of the intensity of the color brightness (value), and the chroma, and thus the effect on the variation of the soil color within the different physiographic units if the reddish color dominant roloc in the mountainous physiographic unit.Variation in the values of total iron oxides within one physiographic unit (undulating area).This variation is attributed to the density of vegetation cover, as it decreased in the third pedon with a decrease in the content of organic matter
Table of the morphological characteristics of the soil pedon within the physiographic units.

Table 2 .
Table of the physical and Chemical properties of the soil pedon of the study area.

Units Soil Surface Sample Fe O Total
Table of Fe O Oxides Total for Soil Surface Sample of the study area.

Table 4 .
Table of Classes of the spatial distribution of iron oxide content within physiographic units..1398874.138098 3.269191 Moderate 1051.85754.138128 6.026819 5.043164 High 606.385 6.026826 9.119953 7.026296