Particle Dry Deposition From the Ambient Atmosphere: The Role of Particle-Surface Interactions

空气中的颗粒物在维持地球能量平衡、维持生态系统和影响全球化学物种循环方面发挥着至关重要的作用。不幸的是，我们对影响这些颗粒物的过程的理解，从排放到它们的最终命运，还远远没有完成。一个特别的不足涉及我们对通过干沉积从大气中去除颗粒物的有限了解。该项目的总体目标是确定影响空气中颗粒物干沉积的最重要因素，重点是颗粒物与植被表面之间的相互作用。有三个具体目标：1)为几种颗粒-表面相互作用机制开发改进的数学公式，2)通过风洞试验验证这些公式，以及3)通过开发和验证冠层内沉积模型将这些公式应用于野外条件。目标1将通过改进通过粘性下层的湍流传输、静电吸引和再悬浮领域的现有配方来实现。目标2将通过在风洞中使用可通过荧光测量的单分散的尿氨酸颗粒进行沉积和再夹带测量来实现。最后，将通过开发一个模型来实现目标3，该模型将冠层内的空气悬浮浓度和植被要素的几何形状用作模型输入。测量已知粒度分布的周围化学物质的干沉降量将允许验证该模型。这项研究的结果将使人们能够更好地了解影响自然表面颗粒干沉积的最重要过程。反过来，这将产生更准确的干沉积预测，作为大气传输模型的一个组成部分。

Airborne particles play a vital role in maintaining the earth's energy balance, sustaining ecosystems and influencing global cycles of chemical species. Unfortunately, our understanding of the processes affecting these particles, from emissions to their ultimate fate, is far from complete. A particular deficiency concerns our limited knowledge of particle removal from the atmosphere by dry deposition. The overall goal of this project is to determine the most important factors influencing dry deposition of airborne particles, focusing on interactions between particles and the surface of vegetation. There are three specific objectives: 1) to develop improved mathematical formulations for several mechanisms of particle-surface interaction, 2) to verify these formulations through wind tunnel tests, and 3) to apply the formulations to field conditions by developing and verifying an in-canopy deposition model. Objective 1 will be achieved by improving existing formulations in the areas of turbulent transport through the viscous sublayer, electrostatic attractions, and resuspension. Objective 2 will be achieved by conducting deposition and reentrainment measurements in a wind tunnel using monodisperse uranine particles that can be measured by fluorescence. Finally, objective 3 will be achieved by developing a model that relates airborne concentrations within the canopy and geometry of the vegetation elements are used as model inputs. Measurement of dry deposition of ambient chemical species with known size distributions will allow verification of the model. The results of this study will enable a better understanding of the most important processes influencing particle dry deposition onto natural surfaces. This, in turn, will yield more accurate prediction of dry deposition as a component of atmospheric transport models.