Abstract:

PM10 emission largely depends on the characteristics of the saltation process, which involves the movement of aggregate and isolated particles. Studies analyzing the relationship between the fragmentation of saltating aggregates and the dust emission along the fetch distance are very scarce. The objective of the present study was to analyze, on a loamy texture soil, the changes in the size distribution of the eroded sediment along the fetch distance under field conditions. Changes in the particle size distribution of the transported material were measured at four different heights above the soil surface every 25 m on a 200 m plot, during three strong wind erosion events. Statistically significant differences were found both for particle size distribution and aggregation when comparing the eroded sediment at the windward and leeward sides of the experimental plot. A greater proportion of coarser particles was found as the distance traveled by the eroded sediment increased. From the change in average particle size distribution at the beginning and at the end of the 200 m experimental plot, it was estimated that around 12% of the particles smaller than 62.5 μm were lost by vertical transport (dust plume) producing an average concentration of 48 µg m−3 at 2 m height and 200 m fetch. Under the conditions of this experiment, a soil aggregate transported by saltation was fragmented at a rate of 38% every 100 m traveled (R2 = 0.88; p < 0.001). Particle size analysis of the eroded sediment and open-air PM10 concentration measurements indicated that the fragmentation of aggregates during saltation can be considered as the main mechanism of dust emission on this soil.

Author affiliation: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Buschiazzo, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina

Author affiliation: de Oro, Laura Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Abstract:

PM10 emission largely depends on the characteristics of the saltation process, which involves the movement of aggregate and isolated particles. Studies analyzing the relationship between the fragmentation of saltating aggregates and the dust emission along the fetch distance are very scarce. The objective of the present study was to analyze, on a loamy texture soil, the changes in the size distribution of the eroded sediment along the fetch distance under field conditions. Changes in the particle size distribution of the transported material were measured at four different heights above the soil surface every 25 m on a 200 m plot, during three strong wind erosion events. Statistically significant differences were found both for particle size distribution and aggregation when comparing the eroded sediment at the windward and leeward sides of the experimental plot. A greater proportion of coarser particles was found as the distance traveled by the eroded sediment increased. From the change in average particle size distribution at the beginning and at the end of the 200 m experimental plot, it was estimated that around 12% of the particles smaller than 62.5 μm were lost by vertical transport (dust plume) producing an average concentration of 48 µg m−3 at 2 m height and 200 m fetch. Under the conditions of this experiment, a soil aggregate transported by saltation was fragmented at a rate of 38% every 100 m traveled (R2 = 0.88; p < 0.001). Particle size analysis of the eroded sediment and open-air PM10 concentration measurements indicated that the fragmentation of aggregates during saltation can be considered as the main mechanism of dust emission on this soil.

EEA Anguil

Author affiliation: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Buschiazzo, Daniel Eduardo. INTA. Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Abstract:

PM10 emission depends on the texture and the aggregation state of a soil. A decisive but less studied factor is the saltation fraction of the soil (fraction between 100 and 500 μm). Six soils of contrasting textures were selected, and a wind tunnel study was carried out under three different saltation conditions: increased saltation, in which a sample of the saltation fraction was added to the air stream prior to the soil bed; no saltation added, in which the soil bed eroded without the addition of extra saltation fraction; and only saltation, in which the saltation fraction was injected into the air stream in the absence of the soil bed. Results indicated that the saltation efficiency for PM10 emission increased with the fine fraction content of the soil and decreased with the sand content, but this process showed a complex behavior depending on the cohesion and stability of the aggregates. An index for describing the saltation efficiency of the studied soils was proposed based on the combination of three parameters: the PM10 content, the amount of saltation fraction available in the soil surface, and an aggregation parameter (clay × organic matter content). Increasing the saltation rate increased the PM10 emission from the eroding soil bed, except for the sandy soil. Results suggest that the main mechanisms of PM10 emission under saltation conditions differ according to the soil texture: detachment of the PM10 adhered to the grains of sand predominates on sandy soils and fragmentation on finer soils, but both processes occur together on high-emitting soils of intermediate textures.

EEA Anguil

Author affiliation: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina.

Author affiliation: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Buschiazzo, Daniel Eduardo. INTA. Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Abstract:

Wind erosion starts when the threshold wind velocity (μ t ) is exceeded. We evaluated the sensitivity of μ t to determine the wind erosion susceptibility of soils under variable climatic conditions. Three years field data were used to calculate μ t by means of the equation μ t = ū - σ Φ -1 (γ), where ū is the mean wind speed (m s -1 ), σ the ū standard deviation (m s -1 ), γ the saltation activity and Φ the standard normal distribution function of γ. Saltation activity was measured with a piezoelectric sensor (Sensit). Results showed that ū of the whole studied period (3.41 ms -1 ) was lower than μ t (7.53 ms -1 ), therefore, wind erosion was produced mainly by wind gusts. The μ t values ordered in the sequence: Winter (6.10 ms -1 ) < Spring (8.22ms -1 ) = Summer (8.28 m s -1 ) < Autumn (26.48 m s -1 ). Higher μ t values were related to higher air humidity and lower wind speeds and temperatures. The μ t values did not agree with the erosion amounts of each season, which ordered as follows: Summer (12.88 t ha -1 ) > Spring (3.11 t ha -1 ) = Winter (0.17 t ha -1 ) = Autumn (no erosion). Low μ t and erosion amounts of Winter were produced by a scarce number of gusts during eroding storms. We concluded that μ t is useful as an index of soil susceptibility to wind erosion of different climatic periods. The use of a unique μ t value in wind erosion prediction models can lead to erroneous wind erosion calculations.

Author affiliation: de Oro, Laura Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Buschiazzo, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Abstract:

Wind erosion largely depends on saltation. Nevertheless, the effect of the composition of the saltation fraction of different textured soils is poorly understood, as is the relative influence of both saltation and soil properties on wind erosion. In order to answer these questions, wind erosion of six differently textured soils were simulated with a wind tunnel. The following saltation conditions were considered: injected saltation, in which the saltation fraction of each soil was added to the soil bed; no saltation, in which the soil eroded naturally, without injection of its saltation fraction; and only saltation, in which the saltation fraction was injected in absence of the soil bed. Results indicated that total erosion amounts increased as a function of the abrasion energy of the saltating particles but also with decreasing aggregation rate of the saltation fraction. The aforementioned agrees with a lower aggregate stability and higher amounts of the erodible fraction of sandy soils. Though saltation of individual sand grains produced impacts of higher kinetic energy on the soil surface of sandy soils than of fine textured soils, the relative erosion (quotient between the erosion occurred with and without saltation) was higher in finest soils, indicating a larger effect of saltation, probably due to the larger fragmentation of aggregates in these soils. Results of this study indicated that both the composition of the saltating fraction and also the intrinsic properties of the soil determined wind erosion.

Author affiliation: Avecilla, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Panebianco, Juan Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Author affiliation: Buschiazzo, Daniel Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina