Using 137Cs to estimate wind erosion and dust deposition on grassland in Inner Mongolia-selection of a reference site and description of the temporal variability

Abstract

Aims The aims of this study were to identify areas of wind erosion and dust deposition and to quantify the effects of different grazing intensities on soil redistribution rates in grasslands based on the 137 Cs technique. Because the method uses a reference inventory as threshold for erosion or deposition, the classification of any other site as source or sink for dust depends on the accurate selection of this reference site. Methods Measurements of 137 Cs inventories and depth distributions were carried out at pasture sites with predominant species of Stipa grandis and Leymus chinensis which are grazed with different intensities. Additional measurements were made at arable land, plant-covered sand dunes and alluvial plains. Wind-induced soil erosion and dust deposition rates were calculated from 137 Cs inventories by means of the "Profile-Distribution" and the "Mass Balance II" models. Results The selection of the reference site was based on fluid dynamical and process-determining parameters. The chosen site should meet the following four conditions: (i) located at a summit position with obviously low deposition rates, (ii) sufficient vegetation cover to prevent wind erosion, (iii) plane to exclude water erosion and (iv) in the wind/dust shadow of a higher elevation. The measured reference inventory of 137 Cs was 1967(±102) Bqm −2 located at a summit position of moderately grazed Leymus chinensis steppe. The 137 Cs inventories at other sites ranged from 1330 Bqm −2 at heavily grazed sites to 5119 Bqm −2 at river deposits, representing annual average soil losses of up to 130 tkm −2 and deposits of up to 540 tkm −2 , respectively. The calculated annual averages of dust depositions at ungrazed Leymus chinensis sites were related to the dust storm frequencies of the last 50 years resulting in a description of the temporal variability of annual dust depositions from about 154 tkm −2 in the 1960s to 26 tkm −2 at recent times. Based on this quantification already 80% of the total dust depositions can be related to the 20 years between the 1960s and the end of the 1970s and only 20% to the time between 1980 and 2001.Conclusions 137 Cs technique is a promising method to assess the effect of grazing intensity and land use types on the spatial variability of wind-induced soil and dust redistribution processes in semi-arid grasslands. However, considerable efforts are needed to identify a reliable reference site, because erosion and deposition induced by wind may occur at the same places. The combination of the dust deposition rates derived from 137 Cs profile data with the dust storm frequencies is helpful for a better reconstruction of the temporal variability of dust deposition and wind erosion in this region. The calculated recent deposition rates of about 20 tkm −2 are in good agreement with data of other authors.

137Cs-Based Variation of Soil Erosion in Vertical Zones of a Small Catchment in Southwestern China

“…The variability of 137 Cs reference inventories were presented as (1) the differences in 137 Cs reference inventories between different latitudes and longitudes and between the southern and northern hemispheres, which showed a close relationship with the geographical locations where nuclear tests were conducted in the last century [31]; (2) a variability at different elevations of the same latitude and longitude, with the change in elevation also being the main factor inducing variation in annual precipitation. In areas where wet precipitation takes the leading role, the average annual precipitation was the key factor influencing the 137 Cs reference inventories.…”

Plutonium concentrations link soil organic matter decline to wind erosion in ploughed soils of South Africa

“…Such differences between the three agroecosystems may not only be attributed to slightly differing soil properties (Table 1, S4) but to regional 430 environmental conditions and atmospheric circulation patterns (distance between the agroecosystems is about 100-300 km), as found elsewhere (e.g. Funk et al, 2011;Xu et al, 2017;Meusburger et al, 2020).…”

The Impact of Residences and Roads on Wind Erosion in a Temperate Grassland Ecosystem: A Spatially Oriented Perspective

“…Temperate grassland ecosystems are an important source of dust resulting from wind erosion. The Xilingele grassland is located in the agro-pastoral ecotone and is a part of the wind-eroded areas in northern China [29]. It was found that the increased intensity of human activities caused extensive soil degradation [10].…”