**12. Clay minerals in loesses**

128 Soil Erosion Studies

Dimension 84cm×120cm×160cm

a. The reservoir and the splashing part of the rainfall simulator are made of Plexiglas with

b. 12 volts electrical motor is located on special small balls for easier movement of the

c. The metal stand of the equipment slides and is adjustable from 140 to 180 centimeters in order for the reservoir and falling plate to be adjusted on the slope for being completely

d. Metal frame of plot: This frame is hammered on the ground, just under the part which produces rainfall. All resulted runoff and sediment from rainfall are collected and

Elevation of falling drops above slope 1.45m Average aperture diameter 0.66 mm Area of plot 1.008 m2

Voltage of electrical motor of equipment 12 volts Capacity of reservoir of equipment 80 liters

thickness of 8 mm. The capacity of these two parts is 80 liters.

**11. Different parts of the equipment are as follows** 

reservoir. This prevents falling of drops in one point.

horizontal and the equipment to be used on slopes.

directed to the outlet which are collectable.

Initial velocity of drops 0 Number of capillary tubes 204 Length of tubes 8 mm

Picture 5. Plot of rain fall simulator

Table 3. Specification of rainfall simulator

Clay minerals are the main factors in attachment of silt particles in loesses, therefore, play important role in erodibility and physical-chemical properties of loesses (Khormali and Kehl, 2010). About 23 samples from the top 20 centimeters of materials (one sample from each land unit) were analyzed for determination of clay minerals by X-ray diffraction (XRD) method. In general, clay minerals are about %10 in different samples. The rest are other minerals, majority of them are Quartz, then Feldspar and Carbonate calcium. For purization of clay and removing chemical substances which act as cement, sodium acetate normal in 80 degrees centigrade, for oxidation of organic matter, oxygen peroxide %30 and for removing Iron oxide, sodium dithionate were used. Then pure clay of each sample was separated using sedimentation method.

For the peaks of XRD to be obvious, facilitating identification of clay mineral types, five analyses with different treatments were performed as follows (Moore and Reynolds,1989):


Figure 6 shows a XRD difractogram from land unit A-SRE-1.

Fig. 6. XRD difractogram of loess of land unit A-SRE-1. letters MG, MGG, K and KT written on peaks show MgCl2, MgCl2 - Ethylene Glycol, KCl and KCl-heated treatments of clay tiles.
