Determining controls on aeolian dust emissions: analysis of dynamic processes at Etosha Pan, Namibia.

被风吹来的矿物气溶胶（风尘）的排放、运输和沉积是地球陆地-大气-海洋-生物圈系统的关键组成部分;影响气候[1]、海洋施肥[2]、营养物运输[3]、空气质量和人类健康[4]。先进的数值模式提供了预测未来全球大气粉尘负荷和含营养物质的粉尘羽流输送路径的主要手段[5]。由于粉尘的相对影响取决于颗粒的矿物学和地球化学成分，而这主要取决于它们最初被夹带的陆源，因此，对可侵蚀物质起源的准确了解，确定排放源区域和关于侵蚀过程驱动因素的数据是全球粉尘排放建模的先决条件[6]。致力于利用遥感数据检测和绘制大规模粉尘源区域的地貌学研究已经将处于干燥阶段的短暂湖泊（浅湖或干湖）确定为区域和全球重要的粉尘源[7，8]。在这些区域内，洪水期间经常补充细沉积物的储存，在干燥时，可能会受到风蚀的影响[9]。然而，现有数值模型的相对复杂性仍然局限于代表这些重要源区的粉尘排放[10]。虽然迄今为止的研究已经提供了对风沙系统的一般了解，但沉积物被风从干盐湖表面侵蚀的过程本身就很复杂[11]。这是由于控制侵蚀沉积物可用性的环境驱动因素的动态变化（即，结壳、隆起等的产生和分解）沉积物地球化学和大气条件的变化[12]。因此，通过洪水事件的动态沉积物可用性的固有复杂性产生高空间（即，子模型网格）和时间（即，季节性和年际）排放源的不均匀性，这在从现有粗尺度遥感观测开发的模型参数化中描述得很差[13]。本研究的目的是调查复杂的控制沉积物的可用性，以完善我们的理解是什么定义的本地规模的发射率的沉积物从短暂的湖泊。随着最近发射的具有高空间和时间分辨率的新卫星传感器（例如，PlanetScope和ESA的Sentinel），一个新的机会存在，以确定特定的“热点”粉尘排放位置，并确定时空动态的控制沉积物的风蚀。结合对侵蚀沉积物的矿物学和地球化学成分的分析，这将有助于改进这些重要源区粉尘产生的限制控制参数，从而改进对排放影响的评估，以应对未来不断变化的环境条件。

The emission, transport, and deposition of windblown mineral aerosols (aeolian dust) represents a critical component in the Earth's land-atmosphere-ocean-biosphere system; impacting climate [1], ocean fertilisation [2], nutrient transport [3], air quality and human health [4]. Sophisticated numerical models offer the principal means of forecasting future global atmospheric dust loading and transport pathways of nutrient-laden dust plumes [5].As the relative impact of dust depends on the mineralogical and geochemical composition of theparticles, which is primarily determined by the terrestrial sources from which they are initially entrained, an accurate knowledge of the origin of erodible material, the identification of emission source areas, and data on the drivers governing eroding processes are a prerequisite for global dust emissions modelling [6]. Geomorphological studies dedicated to the detection and mapping of large-scale dust source areas using remote sensing data have identified ephemeral lakes in their dry phases (pans or playas) as regionally and globally significant dust sources [7,8]. Within these regions, stores of fine sediment are frequently replenished during flooding periods which, on drying, can become susceptible to aeolian erosion [9]. However, the relative sophistication of existing numerical models remains limited in representing dust emissions from these significant source regions [10].Whilst research to date has provided a general understanding of the windblown dust system, the processesby which sediment is eroded from the playa surface by wind areinherently complex [11]. This is due to dynamic variability in the environmental drivers that control sediment availabilityforerosion (i.e., the creation and breakdown of crusting, heaving, etc.) in response to variations in sediment geochemistry and atmospheric conditions [12]. Thus, inherent complexities in dynamic sediment availability through flooding events generate high spatial (i.e., sub-model grid) and temporal (i.e., seasonal and interannual) heterogeneityin emission sources, which are poorly depicted in model parametrisations developed from existing coarse-scale remote sensing observations [13]. The purpose of this research is to investigatethecomplex controls on sediment availability to refine our understanding of what defines the local-scale emissivity of sediment from ephemeral lakes. With the recent launch of new satellite sensors with high spatial and temporal resolution (e.g., PlanetScopeand ESA's Sentinel), a novel opportunity exists to identify specific 'hot-spot' dust emissionlocations and to characterise the spatio-temporal dynamics of controls on sediment availability for aeolian erosion. Combined with analysis of the mineralogical and geochemical composition of eroded sediment, this willallow for improvements in constraining control parameters of dust production from these significant source regions and thus improve assessments of the effects of emissions in response to changing environmental conditions in the future.