Abstract

A 3D dry deposition scheme for particulate matter (PM) is presented as a Free-Libre and Open-Source Software (FOSS) library, DePaSITIA (RSE SpA). This combines some advanced formulations for the deposition mechanisms of sedimentation, inertial impaction, turbulent impaction and interception. The scheme also considers bouncing effects. The input quantities relate to the canopy elements (Leaf Area Density, leaf equivalent diameter, leaf shape, orientation and roughness parameters), the transporting fluid (local mean velocity, friction velocity) and the particulate matter (PM local mean concentration, median diameter and density). The deposition scheme is coupled with a well-known Lagrangian Stochastic model for pollutant dispersion, the Open-Source code SPRAY-WEB (Università del Piemonte Orientale et al.). The coupled numerical solution is validated on a laboratory test case representing the dispersion of particulate matter from two line sources within a canopy atmospheric boundary layer. The deposition interfaces are represented by the trees of a scaled spruce forest. Validation refers to the average vertical profile of the deposited mass (not the mean concentration) normalized by the above-canopy mean concentration. Some inter-comparisons are also reported considering uniform Leaf Area Density, the additional effects of molecular diffusion, the height-dependent relative contribution of each deposition mechanism and an alternative deposition scheme. The results of this test case are available as a FOSS tutorial. Considering the Fractional Bias obtained for the deposited mass (FB = 27%), this numerical solution seems suitable to simulating stationary dispersion phenomena within complex canopy boundary layers, assessing the height-dependent dry deposition fluxes of atmospheric PM. The current numerical solution might be improved and applied to elevated obstacles such as electric insulators.

Article Highlights

1. •

   Development of a height-dependent dry deposition scheme 37 for particulate matter, coupled with a pollutant dispersion code.

2. •

   Validation on a vertical profile of deposited pollutant mass.

3. •

   Assessment of each deposition mechanism; availability of the code and tutorial as Open-Source Software; possible application to any elevated or ground-level 3D obstacle.

中文翻译：

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颗粒物的干沉降方案，结合著名的拉格朗日随机模型进行污染物扩散

摘要

一种针对颗粒物（PM）的3D干法沉积方案作为自由软件和开源软件（FOSS）库DePaSITIA（RSE SpA）提出。它结合了一些先进的配方，用于沉积，惯性碰撞，湍流碰撞和拦截的沉积机理。该方案还考虑了弹跳效应。输入量涉及冠层元素（叶面积密度，叶当量直径，叶形状，方向和粗糙度参数），输送流体（局部平均速度，摩擦速度）和颗粒物（PM局部平均浓度，中值直径和密度）。沉积方案与著名的拉格朗日随机模型用于污染物扩散，即开源代码SPRAY-WEB（Universitàdel Piemonte Orientale等）。该耦合数值解在一个实验室测试案例中得到了验证，该案例代表了来自冠层大气边界层内两个线源的颗粒物的分散。沉积界面由鳞片状云杉林的树木表示。验证是指通过冠层以上平均浓度归一化的沉积物质的平均垂直剖面（不是平均浓度）。还报告了一些相互比较，其中考虑到均匀的叶面积密度，分子扩散的其他影响，每种沉积机理的高度相关的相对贡献以及其他沉积方案。该测试用例的结果可作为FOSS教程获得。考虑到沉积质量的分数偏差（FB = 27％），该数值解似乎适合于模拟复杂冠层边界层内的平稳弥散现象，评估大气PM的高度相关干沉降通量。当前的数值解决方案可能会得到改进，并应用于诸如电绝缘体之类的高处障碍物。

文章重点

1. •

   针对颗粒物的高度相关的干式沉积方案37的开发，以及污染物扩散代码。

2. •

   在沉积污染物质量的垂直剖面上进行验证。

3. •

   评估每种沉积机理；代码和教程作为开源软件的可用性；可能适用于任何高架或地面3D障碍物。