Quantifying the effect of geomorphology on aeolian dust emission potential in northern China

Abstract

Representation of dust sources remains a key challenge in quantifying the dust cycle and its environmental and climatic impacts. Direct measurements of dust fluxes from different landform types are useful in understanding the nature of dust emission and characterizing the dynamics of soil erodibility. In this study we used the PI‐SWERL® instrument over a seasonal cycle to quantify the potential for PM10 (particles with diameter ≤10 μm) emission from several typical landform types across the Tengger Desert and Mu Us Sandy Land, northern China. Our results indicate that sparse grasslands and coppice dunes showed relatively high emission potentials, with emitted fluxes ranging from 10−1 to 101 mg m−2 s−1. These values were up to five times those emitted from sand dunes, and one to two orders of magnitude greater than the emissions from dry lake beds, stone pavements and dense grasslands. Generally, PM10 emission fluxes were seen to peak in the spring months, with significant reductions in summer and autumn (by up to 95%), and in winter (by up to 98%). Variations in soil moisture were likely a primary controlling factor responsible for this seasonality in PM10 emission. Our data provide a relative quantification of differences in dust emission potential from several key landform types. Such data allow for the evaluation of current dust source schemes proposed by prior researchers. Moreover, our data will allow improvements in properly characterizing the erodibility of dust source regions and hence refine the parameterization of dust emission in climate models. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Spatially variable provenance of the Chinese Loess Plateau

“…These findings do not contradict the traditional view that northern China deserts are important sources for the CLP loess, but do point to the importance of precipitation, riverine transport, and floodplain deflation in the generation of dust deposited on the CLP. Deserts proximal to the CLP may have played an important role in contributing some of the finer sediments (<10 μm) to the loess (Cui et al, 2019)-we note that that provenance of the finer fraction cannot be addressed at this time using detrital zircon geochronology given current analytical limitations. However, because the >10 μm fraction composes the majority of loess sediments of the CLP (Sun et al, 2002), fluvial processes, and by extension the spatial and temporal distribution of precipitation driving fluvial transport and floodplain desiccation, must also be considered for models aimed at explaining Asia dust production (Yang et al, 2007).…”

On the formation of desert loess

“…Thus alluvial plains and dry riverbeds with mixed grain-size sediments are a possible source of coarse silt. Such surfaces have been identified as major sources of fine sediment for aeolian transport to desert soils in the Mojave Desert (Sweeney et al, 2013; Cui et al, 2019) and for loess deposits in the Illi basin (Fitzsimmons et al, 2019). In the Sahara and its margins, patchy interdune lacustrine and playa deposits dating to the African humid period are widespread (Lézine et al, 2011) and may be an important source of silt (e.g., Ehrmann et al, 2017).…”

“…Resuspension of fines as a result of reactivation of vegetation-stabilized dunes represents a further potential source of silt for loess deposits downwind. The availability of abundant saltating sand grains and a high content of trapped fines results in high emissions from such landforms (Cui et al, 2019). Many dune areas in the southern and western Sahara and its margins were stabilized by vegetation and soil formation during the early Holocene African Humid Period (Felix-Henningsen et al, 2009).…”

“…Sweeney et al (2011) hypothesize that the high and uniform rates of dust emission from dune areas (mean 0.1443 g/m 2 /s) are related to the constant reworking of the upper few centimeters of the surface sand by the wind, exposing more sediment for emission of dust. In a geographically extensive study of dust emission potential in Chinese deserts using the same methodology, Cui et al (2019) found that the highest dust emissions in dune areas were from coppice dunes, where abundant fine material trapped by vegetation exists in conjunction with actively saltating sand. Emissions from active dune areas were 5 times lower than from coppice dunes as a result of a low (2%) content of fines.…”

A cross-comparison of threshold friction velocities for PM10 emissions between a traditional portable straight-line wind tunnel and PI-SWERL

“…Most studies that used the PI-SWERL have been focused on studying the dust emission potential of different soil surfaces at various friction velocities in different regions in the world, e.g., the Namib Desert in Namibia (von Holdt et al, 2017), the Tengger and Mu Us Desert in Northern China (Cui et al, 2019), coastal dunes in California, USA (Mejia et al, 2019), the Colorado Plateau in the USA (Fick et al, 2020), Yellow Lake Playa, USA (Sweeney et al, 2016), Athabasca Oil Sands Region in Canada (Wang et al, 2015), and the Mongolian steppe (Munkhtsetseg et al, 2016). Others aimed to compare the dust emission potential of the PI-SWERL to a wind tunnel, for similar friction velocities (Sweeney et al, 2008;Kavouras et al, 2009;King et al, 2011).…”