GSI Environmental Inc., Austin, TX, United States.
GSI Environmental Inc., Houston, TX, United States.
Sci Total Environ. 2021 Aug 25;784:146928. doi: 10.1016/j.scitotenv.2021.146928. Epub 2021 Apr 6.
In recent years, there has been a growing recognition of the importance of sewers as preferential pathways for vapor intrusion. This pathway involves volatile organic compound (VOC)-impacted vapor migration through the interior of pipes or conduits towards the potential receptor. A number of research initiatives have been undertaken to improve the understanding of this pathway which, in turn, supports development of sampling methods to evaluate whether it is a concern at a given site. One aspect of the conceptual model that is important to understanding the potential risk of sewer vapor intrusion is the degree to which VOC concentrations vary over time. This paper presents results of field sampling conducted in Texas, Utah, and California to explore temporal variability of chlorinated VOC concentrations in sewer vapor over different timescales. These results, along with results from other studies, suggest that wide ranges of VOC concentrations can occur at given sampling locations. However, long-term temporal variability (months to years) is much higher than short-term variability (days). The timescale over which the variations occur has implications on sampling methods and frequency. The results suggest that multiple grab samples collected over a longer time period, such as on a quarterly basis, are more appropriate for characterizing the long-term average sewer vapor concentrations than single time-integrated samples collected over a period of hours to days. Because time-integrated samples can often be logistically more difficult to collect, an understanding of the timescale of variability may help practitioners balance field logistics considerations with data adequacy when characterizing VOC concentrations in sewers.
近年来，人们越来越认识到污水管道是蒸气侵入的优先途径。这种途径涉及挥发性有机化合物 (VOC) 污染的蒸气通过管道或管道内部迁移到潜在受体。已经开展了许多研究活动来提高对这一途径的理解，这反过来又支持了开发采样方法的工作，以评估在特定地点是否存在这种途径。了解污水蒸气侵入潜在风险的概念模型的一个重要方面是 VOC 浓度随时间变化的程度。本文介绍了在德克萨斯州、犹他州和加利福尼亚州进行的现场采样结果，以探讨不同时间尺度下污水中氯化 VOC 浓度的时间变化。这些结果以及其他研究的结果表明，在给定的采样地点，可能会出现广泛的 VOC 浓度范围。然而，长期的时间变化（数月至数年）比短期变化（数天）高得多。变化发生的时间尺度对采样方法和频率有影响。结果表明，与在数小时至数天内采集的单次积分样本相比，在较长时间内（例如每季度）采集多个单次采集样本更适合描述长期平均污水蒸气浓度。由于积分样本通常在收集方面具有更大的后勤困难，因此了解变化的时间尺度可能有助于从业人员在描述污水中 VOC 浓度时平衡现场后勤考虑因素和数据充分性。
