Evaporative sodium salt crust development and its wind tunnel derived transport dynamics under variable climatic conditions
Evaporative sodium salt crust development and its wind tunnel derived transport dynamics under variable climatic conditions
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DOI：
10.1016/j.aeolia.2016.09.003
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发表时间：
2016-12-01
期刊：
影响因子：
3.3
通讯作者：
Wiggs, Giles F. S.
中科院分区：
文献类型：
--
作者：
Nield, Joanna M.;Neuman, Cheryl McKenna;Wiggs, Giles F. S.
盐湖（或短暂的湖泊）可能是重要的灰尘来源，但它们通常被不同矿物的盐壳所覆盖，这给灰尘排放预测带来了不确定性。尽管结壳矿物学对排放潜力很重要，但人们对以下方面知之甚少：（一）温度和相对湿度的短期变化对这些结壳的可蚀性的影响;（二）结壳退化和矿物学对粉尘排放风速阈值的影响。我们对排放不是由跃变者的影响驱动的系统的理解特别差。本文介绍了一个风洞研究中，粉尘排放量的跳跃颗粒的情况下，测量了一套气候条件和盐壳类型常见的Sua潘，博茨瓦纳。据发现，在黎明和清晨的气候条件下，结壳是不发射的，与炎热和干燥的白天条件相比，在炎热和干燥的白天条件下，粉尘排放的风速阈值似乎变化很大，这取决于盐结壳的物理化学。值得注意的是，发现富硫酸钠结壳比氯化钠结壳更易发射，而两种结壳的降解形式比新鲜、连续结壳的发射阈值低。从这项研究的结果是在现场测量和确认，从盐结皮表面的粉尘排放可以发生没有跃移，虽然垂直通量的数量级低于（类似于10微克/米/秒）比风成系统夹带是由颗粒的影响。(C)2016作者由爱思唯尔公司出版
Playas (or ephemeral lakes) can be significant sources of dust, but they are typically covered by salt crusts of variable mineralogy and these introduce uncertainty into dust emission predictions. Despite the importance of crust mineralogy to emission potential, little is known about (i) the effect of short-term changes in temperature and relative humidity on the erodibility of these crusts, and (ii) the influence of crust degradation and mineralogy on wind speed threshold for dust emission. Our understanding of systems where emission is not driven by impacts from saltators is particularly poor. This paper describes a wind tunnel study in which dust emission in the absence of saltating particles was measured for a suite of climatic conditions and salt crust types commonly found on Sua Pan, Botswana. The crusts were found to be non-emissive under climate conditions characteristic of dawn and early morning, as compared to hot and dry daytime conditions when the wind speed threshold for dust emission appears to be highly variable, depending upon salt crust physicochemistry. Significantly, sodium sulphate rich crusts were found to be more emissive than crusts formed from sodium chloride, while degraded versions of both crusts had a lower emission threshold than fresh, continuous crusts. The results from this study are in agreement with in-situ field measurements and confirm that dust emission from salt crusted surfaces can occur without saltation, although the vertical fluxes are orders of magnitude lower (similar to 10 mu g/m/s) than for aeolian systems where entrainment is driven by particle impact. (C) 2016 The Authors. Published by Elsevier B.V.