[MIS06-03] Low dust generation from active sand dunes
キーワード：Aeolian processes, Dust source, Atmospheric PM10, Wind tunnel, Dust emission
Several studies have indicated that mineral dust is generated from regions covered by sand, proposing that sand dunes might be important sources of dust emission. Aeolian abrasion was proposed as the dominant mechanism for that dust generation. However, the hypothesis of dust emission from active sands under natural aeolian (by wind) conditions was not tested. This study integrates targeted wind tunnel experiments and field observations with mathematical modeling to explore aeolian dust emission from sands. The results from the wind tunnel experiments indicate no dust emission under shear velocities below the saltation threshold. The initial content of dust-sized particles (>63 µm) in the sand was found to impact the measured atmospheric PM10 concentration. The experiments identify clay coating removal as the dominant mechanism of dust emission over time in typical active sand dunes (<2% dust content) with the inclusion of re-emission of the existing dust-sized particles (<63 µm). This was supported by the field measurements conducted in the Oceano sand dunes (California). Despite the common assumption, aeolian abrasion have a minor role in PM10 dust generation from active sands, demonstrating very low dust generation over time. The overall dust emission from sand dunes to the atmosphere is at the low end of the range produced by other dust-soil sources. The new quantitative information obtained can be implemented as more realistic parametrization of dust loading from sand areas to the atmosphere to reduce the existing uncertainties in dust and climate models.