Which characteristic makes pesticides more likely to move into groundwater?

Which characteristic makes pesticides more likely to move into groundwater?

• A. Pesticides which have low water solubility
• B. Pesticides which are strongly absorbed
• C. Pesticides which have a long persistence
• D. Both B and C

Answer: (C)

The factor that increases the chance of pesticides moving into groundwater is how long the chemical stays intact in the environment. When a pesticide persists, it degrades slowly, so it remains in the soil long enough for water to move through the soil profile and potentially carry it down toward groundwater. This longer window of opportunity makes leaching more likely, especially with permeable soils and rainfall or irrigation driving water downward. In contrast, low water solubility means the compound doesn’t dissolve well in water, so it doesn’t travel easily with percolating water, and strong adsorption to soil means it sticks to soil particles instead of moving with water. If a chemical were both strongly adsorbed and persistent, its movement would still be limited by adsorption. So the trait that best explains increased movement into groundwater is long persistence.

The factor that increases the chance of pesticides moving into groundwater is how long the chemical stays intact in the environment. When a pesticide persists, it degrades slowly, so it remains in the soil long enough for water to move through the soil profile and potentially carry it down toward groundwater. This longer window of opportunity makes leaching more likely, especially with permeable soils and rainfall or irrigation driving water downward.

In contrast, low water solubility means the compound doesn’t dissolve well in water, so it doesn’t travel easily with percolating water, and strong adsorption to soil means it sticks to soil particles instead of moving with water. If a chemical were both strongly adsorbed and persistent, its movement would still be limited by adsorption. So the trait that best explains increased movement into groundwater is long persistence.