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首页> 外文期刊>Ground Water Monitoring & Remediation >Macro- And Micro-purge Soil-gas Sampling Methods For The Collection Of Contaminant Vapors
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Macro- And Micro-purge Soil-gas Sampling Methods For The Collection Of Contaminant Vapors

机译：宏观和微观净化土壤气体采样方法收集污染物蒸气

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摘要

Purging influence on soil-gas concentrations for volatile organic compounds (VOCs), as affected by sampling tube inner diameter and sampling depth (i.e., system volume) for temporary probes in fine-grained soils, was evaluated at three different field sites. A macro-purge sampling system consisted of a standard, hollow, 3.2-cm outer diameter (OD) drive probe with a retractable sampling point attached to an appropriate length of 0.48-cm inner diameter (ID) Teflon~R tubing. The macro-purge sampling system had a purge system volume of 24.5 mL at a 1-m depth. In contrast, the micro-purge sampling systems were slightly different between the field sites and consisted of a 1.27-cm OD drive rod with a 0.10-cm ID stainless steel tube or a 3.2-cm OD drive rod with a 0.0254-cm inner diameter stainless steel tubing resulting in purge system volumes of 1.2 and 7.05 mL at 1-m depths, respectively. At each site and location within the site, with a few exceptions, the same contaminants were identified in the same relative order of abundances indicating the sampling of the same general soil atmosphere. However, marked differences in VOC concentrations were identified between the sampling systems, with micro-purge samples having up to 27 times greater concentrations than their corresponding macro-purge samples. The higher concentrations are the result of a minimal disturbance of the ambient soil atmosphere during purging. The minimal soil-gas atmospheric disturbance of the micro-purge sampling system allowed for the collection of a sample that is more representative of the soil atmosphere surrounding the sampling point. That is, a sample that does not contain an atmosphere that has migrated from distance through the geologic material or from the surface in response to the vacuum induced during purging soil-gas concentrations. It is thus recommended that when soil-gas sampling is conducted using temporary probes in finegrained soils, the sampling system use the smallest practical ID soil-gas tubing and minimize purge volume to obtain the soil-gas sample with minimal risk of leakage so that proper decisions, based on more representative soil-gas concentrations, about the site can be made.
机译：在三个不同的现场地点，评估了对细颗粒土壤中临时探针的采样管内径和采样深度（即系统体积）的影响对挥发性有机化合物（VOC）对土壤气体浓度的净化影响。大型吹扫采样系统由一个标准的空心3.2厘米外径（OD）驱动探针组成，该探针带有一个可伸缩的采样点，该采样点连接到适当长度的0.48厘米内径（ID）的Teflon〜R管上。大型吹扫采样系统在1米深处的吹扫系统体积为24.5 mL。相比之下，现场的微吹扫采样系统略有不同，由外径为1.27厘米，内径为0.10厘米的不锈钢管或外径为3.2厘米，内径为0.0254厘米的驱动杆组成。不锈钢管在1米深处产生的吹扫系统体积分别为1.2和7.05 mL。除了少数例外，在每个站点和站点内的位置，都以相同的相对丰度顺序识别了相同的污染物，这表明对相同的一般土壤大气进行了采样。但是，在采样系统之间发现了VOC浓度的显着差异，微型吹扫样品的浓度比相应的大型吹扫样品高27倍。较高的浓度是在吹扫期间对周围土壤大气的最小干扰的结果。微吹扫采样系统对土壤气体的最小干扰使得可以收集更能代表采样点周围土壤大气的样品。即，不包含响应于在清除土壤-气体浓度期间感应的真空而从远处穿过地质材料或从表面迁移的气氛的样品。因此，建议在细粒土壤中使用临时探针进行土壤-气体采样时，采样系统使用最小的内径的土壤-气体管道，并最小化吹扫量，以获得泄漏风险最小的土壤-气体样品，以便适当可以根据更具代表性的土壤气体浓度来确定该地点。

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