Which soil feature elevates the risk of well contamination from herbicides?

• A. Limestone bedrock
• B. Sand
• C. High water table
• D. All of these

Answer: (D)

Understanding groundwater vulnerability helps explain why multiple soil features can raise the risk of herbicide contamination. The key idea is that contaminants reach wells more easily when there is little soil filtration, a short distance to groundwater, or direct pathways.

Coarse soils like sand have large pore spaces and allow water and dissolved herbicides to move downward quickly with minimal resistance, so contaminants can reach a well sooner. A high water table places groundwater close to the surface, shortening the travel distance and reducing natural attenuation, which increases the chance that herbicides reach a well before they are filtered or degraded. Limestone bedrock, especially when fractured (karst), creates routes that bypass much of the soil’s filtration, giving contaminants direct pathways to groundwater.

Because each of these conditions separately increases vulnerability, having any combination of them raises the risk, making “All of these” the best answer.