In this quick activity about pollutants and groundwater (page 2 of PDF under Water Clean-up Activity), learners build a model well with a toilet paper tube. Learners use food coloring to simulate pollutants and observe how they can be carried by groundwater and eventually enter water sources such as wells, rivers, and streams. This activity is associated with nanotechnology and relates to linked video, DragonflyTV Nano: Water Clean-up.