Hitting the bull`s-eye in groundwater sampling
Many of the commonly-used groundwater sampling techniques and procedures have resulted from methods developed for water supply investigations. These methods have persisted, even though the monitoring goals may have changed from water supply development to contaminant source and plume delineation. Unfortunately, the use of these methods can result in an incorrect understanding of the contaminant concentrations and system geochemistry, often overestimating or underestimating the true values or the extent of a plume. It was discovered, during investigations of potential contaminant transport by mobile colloidal particles, that traditional purging and sampling were disrupting the aquifer and sand pack materials. The disruption was caused by the stress of high water velocities and/or water surging in the wells due to sampling with bailers and high-speed submersible pumps. This left no conclusive way to determine whether collected particulates in the samples were naturally occurring or due to the disturbance caused by the sampling device/approach. Such induced stresses can cause grain flow within the sand pack and/or exceed the cohesive forces of aquifer mineral cementation, resulting in excessive and artificial sample turbidity. This increased turbidity can radically alter analytical results for water samples, causing spurious in creases in analyzed metal concentrations.
- OSTI ID:
- 509246
- Journal Information:
- Pollution Engineering, Vol. 29, Issue 6; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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