In Situ Measurements of Dynamic Bacteria Transport and Attachment in Heterogeneous Sand-Packed Columns

Area of Science:

• Environmental Science
• Geology
• Microbiology

Background:

• Understanding bacterial contaminant transport in groundwater is crucial for effective prevention and regulation.
• Discrepancies between field and lab studies highlight gaps in knowledge of bacterial transport in heterogeneous geological systems.

Purpose of the Study:

• To develop and demonstrate a new experimental approach for *in situ* quantification of dynamic bacterial transport and attachment in geologic media.
• To directly measure bacterial attachment coefficient distributions in groundwater.

Main Methods:

• Radiolabeling *Escherichia coli* with positron-emitting radioisotopes.
• Utilizing three-dimensional (3D) positron emission tomography (PET) imaging to quantify bacterial transport and distribution.
• Comparing experimental results with a 3D numerical model using a first-order irreversible attachment model.

Main Results:

• The highest bacterial attachment was observed at the interfaces between sand layers oriented orthogonal to the flow direction.
• A 3D numerical model accurately predicted bacterial attachment based on the experimental PET data.
• Demonstrated the ability to directly measure attachment coefficient distributions.

Conclusions:

• The new radiolabeling and 3D PET imaging approach provides a transformational method for studying bacterial transport in groundwater.
• This technique improves the understanding of bacterial fate and transport mechanisms in complex geological environments.
• Accurate prediction of bacterial transport can be achieved by incorporating local geologic conditions and improved model parametrization.