Fine dust emissions from active sands at coastal Oceano Dunes, California

Yue Huang,Itzhak Katra,Thomas E Gill,Jasper F Kok,Nitzan Swet,Raleigh L Martin,Livia S Freire,Richard L Reynolds

doi:10.5194/acp-19-2947-2019

Abstract

Abstract. Sand dunes and other active sands generally have a low content of fine grains and, therefore, are not considered to be major dust sources in current climate models. However, recent remote sensing studies have indicated that a surprisingly large fraction of dust storms are generated from regions covered by sand dunes, leading these studies to propose that sand dunes might be globally relevant sources of dust. To help understand dust emissions from sand dunes and other active sands, we present in situ field measurements of dust emission under natural saltation from a coastal sand sheet at Oceano Dunes in California. We find that saltation drives dust emissions from this setting that are on the low end of the range in emissions produced by non-sandy soils for similar wind speed. Laboratory analyses of sand samples suggest that these emissions are produced by aeolian abrasion of feldspars and removal of clay-mineral coatings on sand grain surfaces. We further find that this emitted dust is substantially finer than dust emitted from non-sandy soils, which could enhance its downwind impacts on human health, the hydrological cycle, and climate.

Highlights

Dust emission by wind-blown processes produces important effects on the Earth system, including modulating the radiation budget (Miller et al, 2006; Kok et al, 2017), modifying cloud microphysics (DeMott et al, 2015) and the hydrological cycle (Ramanathan et al, 2001; Miller et al, 2004), and producing risks to human health (Burnett et al, 2014)
We find that dust emitted from the sand sheet at Oceano differs from dust emitted from non-sandy soils in two key ways
The second key difference is that dust emitted from the Oceano site is substantially finer than size-resolved dust emitted from non-sandy soils under natural saltation (Fig. 3a), and it is significantly finer than dust measured in situ over North Africa (Fig. 3b), which likely accounts for a majority of the world’s dust emissions (Prospero et al, 2002; Engelstaedter et al, 2006)

Summary

Introduction

Dust emission by wind-blown (aeolian) processes produces important effects on the Earth system, including modulating the radiation budget (Miller et al, 2006; Kok et al, 2017), modifying cloud microphysics (DeMott et al, 2015) and the hydrological cycle (Ramanathan et al, 2001; Miller et al, 2004), and producing risks to human health (Burnett et al, 2014) Despite these critical impacts, simulations of dust emissions in current climate models have large uncertainties, in predicted rates and spatial patterns of dust emissions (Engelstaedter et al, 2006; Huneeus et al, 2011; Kok et al, 2014b; Evan et al, 2015). Sandblasting can emit dust in four primary ways: 1. fragmentation of aggregates of clay-sized (< 2 μm in diameter) and silt-sized (2–63 μm in diameter) fine particles in the soil (Kok, 2011); Published by Copernicus Publications on behalf of the European Geosciences Union

Methods

Results

Discussion

Conclusion