Effects of Urban Surface Roughness on Potential Sources of Microplastics in the Atmospheric Boundary Layer
Effects of Urban Surface Roughness on Potential Sources of Microplastics in the Atmospheric Boundary Layer
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DOI：
10.1007/s10546-022-00763-0
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发表时间：
2022-12
影响因子：
4.3
通讯作者：
Yuanfeng Cui;Shuolin Xiao;M. Giometto;Qi Li
中科院分区：
文献类型：
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作者：
Yuanfeng Cui;Shuolin Xiao;M. Giometto;Qi Li
了解城市环境中排放的微塑料（MPs）的本地运输，例如街道和高速公路上的车辆轮胎磨损，是量化其全球运输周期的必要第一步。通过将微塑料近似为重颗粒，我们使用大涡模拟（LESs）进行数值模拟，以了解空间组织源和复杂的城市表面粗糙度如何影响其运输。考虑了三种情况，即：(i)空间均匀源和（ii）空间组织源，以及（iii）具有明确解析的粗糙度元素的空间组织源。结果表明，在无建筑物的空间组织源中，源在流向上的非均质性仅影响垂直浓度分布。相反，横向影响剖面，其中纵坐标和域高度分别为。对建筑物的模拟表明，建筑物阻碍了颗粒的传输，颗粒在建筑物的背风侧积聚，其特征是尾流湍流和相对静止的流动。在冠层子层内，由于风的减小，颗粒的重力沉降作用更加显著。因此，颗粒的逃逸分数比无建筑物时要小，并且随着建筑物高度和建筑平面面积分数的增加而减小。最后，通过寻找合适的标量位移高度和标量粗糙度长度，我们发现重粒子仍然存在一个类似于被动标量的惯性子层（ISL）。本研究强调，对于空间组织的颗粒源，由于城市粗糙度引起的动量下降和重力沉降共同影响重颗粒的输运，这意味着表面非均质效应可以在量化城市起源的微塑料的大气输运中发挥重要作用。
Understanding the local transport of microplastics (MPs) emitted from the urban environment, such as those from vehicle tire wearing in streets and highways, is a necessary first step for quantifying their global transport cycle. By approximating microplastics as heavy particles, we conduct numerical simulations using large-eddy simulations (LESs) to understand how spatially organized sources and complex urban surface roughness affect their transport. Three sets of cases are considered, namely: (i) spatially uniform source and (ii) spatially organized source, and (iii) spatially organized source with explicitly resolved roughness elements, respectively. Results suggest that for a spatially organized source without buildings, source heterogeneity in streamwise direction only influences the vertical concentration profile up to. In contrast, that in spanwise direction influences the profile till, wherezandare the vertical coordinate and the domain height, respectively. Simulations with buildings reveal that the buildings impede the transport of particles and particles accumulate on the leeward side of the buildings, which are characterized by wake turbulence and relatively quiescent flow. Within the canopy sub-layer, the gravitational settling effect of the particles becomes more significant because of the reduced wind. Because of that, the escape fraction of particles is smaller than in cases with no buildings and it decreases with increasing building heighthand increasing building plan area fraction. Finally, by finding suitable scalar displacement heightand scalar roughness length, we find that similar to a passive scalar, an inertial sub-layer (ISL) still exists for heavy particles. This study highlights that for spatially organized particle sources, the momentum sinks due to urban roughness and the gravitational settling jointly affect the transport of heavy particles, which implies that the surface heterogeneity effect can be substantial in quantifying the atmospheric transport of microplastics of urban origins.