The effect of time on the components of wind erosion flux in the southeast of Lake Urmia basin

Abstract
Background and objectives: The main reason for soil loss in arid and semiarid regions is wind erosion. About 40 percent of lands have potential to wind erosion. In Iran due to the drying of a large area of the Lake Urmia and creating the salt marshes and abundant salt plains, it has recently been one of the main problem in this region. Due to the location of this lake, it will become one of the main sources of dust and wind erosion in northwestern of Iran. Determination of the wind erosion flux and its components will be useful for choosing appropriate solutions for this problem. Reliable field measurement of the amount of soil loss will not be possible if there is no satisfactory equipment. Several wind erosion samplers have been developed so far. But the most recommendable one is the BSNE (Big Spring Number Eight) sampler that was made and used by Donald Fryrear to gather the suspended particles.
Materials and methods: In order to trap the suspension and saltation particles from the wind erosion, 14 poles with four BSNE samplers installed on each of them at height of 0.15, 0.5, 1 and 2 m above the soil surface were installed in a circular pattern with a 100 m radius on a land area of 3.14 ha. Also, in order to trap the creeping particles, 14 sediment traps which the opening of them was in the same level with ground were installed at a radial distance of 20 cm from each BSNE pole. For 6 months (from March - August 2017) the eroded particles were collected and weighed. Then the suspension (Isus), saltation (Isal) and creeping (Ic) fluxes were calculated.
Meteorological information was obtained from Khosroshahr Weather Agency during the research period, which was at the closest distance from the study area. In order to investigate the effect of sampling time on suspension, saltation and creeping fluxes, a completely randomized experiment was designed with three replications. Duncan's test was used to compare the means. Statistical analysis was performed by SPSS software and charts drawn by EXCEL software. In order to determine the vertical profile of the suspension flux, the data obtained from the BSNE samplers at four heights (0.15, 0.5, 1 and 2 m ) was used.
Results: Findings of this study showed that the effect of sampling time was significant on Ic, Isal and Isus (p≤0.01) and on total flux (It)(p≤0.05). The results of mean comparing showed that the highest of It was obtained in March and July (2.091 and 2.0153 ton.h-1.mon-1, respectively) due to the high speed of strongest wind (16 and 18 m.s-1, respectively) and lack of plant cover in March and dry soil surface in July (Monthly rainfall was zero). The lowest of It was obtained in April (0.1007 ton.h-1.mon-1) due to high monthly rainfall (78.3 mm) and high moisture of soil surface. Totally, the wind erosion in the study area was 11.028 ton.h-1.y-1. The Isus decreased with increasing the height of soil surface and the power equation was the best one to explain these profile.
Conclusion: There was a negative correlation between Ic (wind erosion section), Isus and It fluxes with monthly rainfall and positive correlation with speed of strongest wind. The mean It was maximum in March and July and minimum in April. The results showed that a large part of the particles were moving at a height of less than 15 cm above the soil surface.