Which option is NOT a geophysical method typically used to sense hazardous waste underground?

• A. Metal detection
• B. Ground-penetrating radar
• C. Resistivity
• D. Paint filter test

Answer: (D)

Sensing hazardous waste underground relies on measuring physical properties of the subsurface so we can see anomalies without disturbing the ground. The paint filter test doesn’t do that—it’s a simple lab screening used to decide if a waste sample contains free liquids for regulatory purposes. It tells you about the liquid content of a material, not about conditions beneath the soil or rock. In contrast, metal detection, ground-penetrating radar, and resistivity all probe subsurface properties: metal detection uses electromagnetic fields to locate buried metal objects, ground-penetrating radar sends radar waves and analyzes reflections to image buried features, and resistivity measures how easily electric current flows through the ground to infer moisture or contaminant-filled zones. So the paint filter test is not a geophysical method for sensing underground waste, which is why it’s the correct choice.