Which term describes the process by which sediments can harbor pesticides and release them over time?

• A. Evaporation
• B. Degradation
• C. Adsorption
• D. Sedimentation

Answer: (C)

Sediments act like sponges for pesticides because pesticides can adhere to the surfaces of sediment particles, especially organic-rich matter and clays. This adhesion is adsorption, creating a reservoir where the chemicals are bound to the solid phase rather than freely dissolved in water. Over time, and under changing conditions such as pH, salinity, temperature, or organic content, those bound molecules can desorb back into the water, causing a delayed or prolonged release. In contrast, evaporation involves water turning to vapor and doesn’t describe storage in sediments; degradation means the chemical breaks down rather than being stored and released; sedimentation is the settling of particles, not the mechanism of binding and later releasing pesticides.