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The influence of dynamic chamber design and operating parameters on calculated surface-to-air mercury fluxes

机译:动态腔室设计和运行参数对计算出的地面空气汞通量的影响

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摘要

Dynamic Flux Chambers (DFCs) are commonly applied for the measurement of non-point source mercury (Hg) emissions from a wide range of surfaces. A standard operating protocol and design for DFCs does not exist, and as a result there is a large diversity in methods described in the literature. Because natural and anthropogenic non-point sources are thought to contribute significantly to the atmosphere Hg pool, development of accurate fluxes during field campaigns is essential. The objective of this research was to determine how differences in chamber material, sample port placement, vertical cross sectional area/ volume, and flushing flow rate influence the Hg flux from geologic materials. Hg fluxes measured with a Teflon chamber were higher than those obtained using a polycarbonate chamber, with differences related to light transmission and substrate type. Differences in sample port placement (side versus top) did not have an influence on Hg fluxes. When the same flushing flow rate was applied to two chambers of different volumes, higher fluxes were calculated for the chamber with the smaller volume. Conversely, when two chambers with different volumes were maintained at similar turnover times, the larger volume chamber yielded higher Hg fluxes. Overall, the flushing flow rate and associated chamber turnover time had the largest influence on Hg flux relative to the other parameters tested. Results from computational fluid dynamic (CFD) modeling inside a DFC confirm that the smaller diffusion resistance at higher flushing flows contributes to the higher measured flux. These results clearly illustrate that differences in chamber design and operation can significantly influence the resulting calculated Hg flux, and thus impact the comparability of results obtained using DFC designs and/or operating parameters. A protocol for determining a flushing flow rate that results in fluxes less affected by chamber operating conditions and design is proposed. Application of this protocol would provide a framework for comparison of data from different studies.
机译:动态助焊剂室(DFC)通常用于测量各种表面上的非点源汞(Hg)排放。不存在用于DFC的标准操作协议和设计,结果,文献中描述的方法存在很大差异。由于认为自然和人为的非点源对大气中的汞池有很大贡献,因此在野战期间开发精确的通量至关重要。这项研究的目的是确定腔室材料,样品端口位置,垂直横截面积/体积和冲洗流量的差异如何影响地质材料产生的汞通量。用聚四氟乙烯室测得的汞通量要比用聚碳酸酯室测得的高,但与透光率和基材类型有关。样品端口位置(侧面与顶部)的差异对汞通量没有影响。当将相同的冲洗流量应用于两个不同体积的腔室时,对于较小体积的腔室,计算出的通量更高。相反,当两个具有不同体积的腔室保持相似的周转时间时,较大体积的腔室会产生较高的汞通量。总体而言,相对于其他测试参数,冲洗流速和相关的腔室周转时间对汞通量的影响最大。 DFC内部的计算流体动力学(CFD)建模结果表明,较高的冲洗流量时较小的扩散阻力有助于较高的测得通量。这些结果清楚地表明,腔室设计和操作上的差异会显着影响最终计算出的汞通量,从而影响使用DFC设计和/或操作参数获得的结果的可比性。提出了一种确定冲洗流量的协议,该流量可导致通量受腔室操作条件和设计的影响较小。该协议的应用将为比较不同研究的数据提供一个框架。

著录项

  • 来源
    《Atmospheric environment》 |2010年第2期|194-203|共10页
  • 作者单位

    Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557, USA;

    Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557, USA;

    Department of Civil Engineering, Lamar University, Beaumont, TX 77710, USA;

    Department of Mechanical Engineering, Lamar University, Beaumont, TX 77710, USA;

    Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557, USA;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    dynamic flux chamber; atmosphere/surface exchange; mercury; flux; emissions; geologic materials;

    机译:动态通量室大气/表面交换;汞;通量排放地质材料;

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