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Role of natural attenuation in modeling the leaching of contaminants in the risk analysis framework

机译：自然衰减在风险分析框架中对污染物的淋溶建模中的作用

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摘要

Natural attenuation (NA) processes occurring in the subsurface can significantly affect the impact on groundwater from contamination sources located in the vadose zone, especially when mobile and readily biodegradable compounds, such as BTEX, are present. Besides, in the last decades several studies have shown natural attenuation to take place also for more persistent compounds, such as Polycyclic Aromatic Hydrocarbons (PAHs). Nevertheless, common risk analysis frameworks, based on the ASTM RBCA (Risk Based Corrective Action) approach, do not include NA pathways in the fate and transport models, thus possibly leading to an overestimation of the calculated risk. The aim of this study was to provide an insight on the relevance of the different key natural attenuation processes usually taking place in the subsurface and to highlight for which contamination scenarios their inclusion in the risk-analysis framework could provide a more realistic risk assessment. To this end, an analytical model accounting for source depletion and biodegradation, dispersion and diffusion during leaching was developed and applied to several contamination scenarios. These scenarios included contamination by BTEX, characterized by relatively high mobility and biodegradation rate, and PAHs, i.e. a more persistent class of compounds. The obtained results showed that BTEX are likely to be attenuated in the source zone due to their mobility and ready biodegradation (assuming biodegradation constant rates in the order of 0.01-1 d~(-1)). Instead, attenuation along transport through the vadose zone was found to be less important, as the residence time of the contaminant in the unsaturated zone is often too low with respect to the time required to get a relevant biodegradation of BTEX. On the other hand, heavier compounds such as PAHs, were found to be attenuated during leaching since the residence time in the vadose zone can reach values up to thousands of years. In these cases, even with the relatively slow biodegradation rate of PAHs, in the order of 0.0001-0.001 d~(-1), attenuation can result significant. These conclusions were also confirmed by comparing the model results with experimental data collected at an hydrocarbon-contaminated site. The proposed model, that neglects the transport of NAPLs, could be easily included in the risk-analysis framework, allowing to get a more realistic assessment of risks, while keeping the intrinsic simplicity of the ASTM-RBCA approach.
机译：在地下发生的自然衰减（NA）过程会显着影响位于渗流区的污染源对地下水的影响，尤其是在存在流动且易于生物降解的化合物（例如BTEX）时。此外，在最近的几十年中，一些研究表明，对于持久性较强的化合物，例如多环芳烃（PAH），也会发生自然衰减。尽管如此，基于ASTM RBCA（基于风险的纠正措施）方法的常见风险分析框架并未在命运和运输模型中包括NA途径，因此可能导致对计算出的风险的高估。这项研究的目的是深入了解通常在地下发生的各种关键自然衰减过程的相关性，并强调将其纳入风险分析框架可为哪些污染情景提供更现实的风险评估。为此，开发了一种分析模型，该模型考虑了淋洗过程中的源耗竭和生物降解，扩散和扩散，并将其应用于几种污染情景。这些情况包括以较高的迁移率和生物降解率为特征的BTEX污染以及PAH（即更具持久性的化合物）。获得的结果表明，BTEX可能由于其流动性和易于生物降解而在源区中被衰减（假定生物降解恒定速率约为0.01-1 d〜（-1））。取而代之的是，发现沿通过渗流区的传输的衰减不那么重要，因为污染物在不饱和区内的停留时间通常相对于BTEX进行相关生物降解所需的时间太短。另一方面，由于在渗流带中的停留时间可以达到数千年，因此发现较重的化合物（如PAHs）在浸出过程中会减弱。在这些情况下，即使PAHs的生物降解速度相对较低，大约为0.0001-0.001 d〜（-1），衰减也会显着。通过将模型结果与在烃污染现场收集的实验数据进行比较，也证实了这些结论。所提议的模型忽略了NAPL的传递，可以轻松地包含在风险分析框架中，从而可以对风险进行更现实的评估，同时保持ASTM-RBCA方法的内在简单性。

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  • 来源
    《Journal of Environmental Management》 |2013年第15期|395-403|共9页
  • 作者

    Iason Verginelli; Renato Baciocchi;

  • 作者单位

    Laboratory of Environmental Engineering, Department of Civil Engineering and Computer Science Engineering, University of Rome 'Tor Vergata', Via del Politecnico 1,00133 Rome, Italy;

    Laboratory of Environmental Engineering, Department of Civil Engineering and Computer Science Engineering, University of Rome 'Tor Vergata', Via del Politecnico 1,00133 Rome, Italy;

  • 收录信息 美国《科学引文索引》(SCI);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    vadose zone; natural attenuation; source depletion; leaching; risk assessment;

    机译：渗流区;自然衰减源耗尽;浸出风险评估;

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