Small Diameter Passive Diffusion Bag Samplers (PDBs) are used in place of purging and low-flow sampling methods in groundwater monitoring wells less than 2-inches diameter to obtain representative, discrete interval samples of Volatile Organic Compounds under natural groundwater flow conditions. Because these samplers are smaller in diameter than our Equilibrator for 2-inch wells, they are longer in length to obtain sufficient sample volume for analysis.
The PDBs are installed in the saturated screen zone where natural groundwater flow refreshes the water in contact with the samplers. VOC molecules enter and exit the sampler’s semi-permeable membrane based on the concentration gradient between the well water and the sampler, maintaining a dynamic concentration equilibrium. After sufficient deployment time the PDBs are removed and the contents emptied into VOA bottles using a “juice box straw” emptying device.