Which type of pesticide is least likely to leach into groundwater?

The choice indicating that a pesticide with a solubility of 44 PPM is least likely to leach into groundwater is correct because solubility plays a significant role in a substance’s potential to move through soil and into groundwater. A pesticide with lower solubility in water is less likely to dissolve and move through the soil, thereby reducing the risk of leaching into groundwater.

Higher solubility means that the pesticide can easily dissolve in water, increasing the likelihood of leaching when it rains or when watering occurs. Therefore, the pesticide with a solubility of 44 PPM suggests relatively low solubility, making it less mobile in the soil and, consequently, less likely to enter the groundwater system.

Volatility, molecular weight, and heavy application rates are factors that can affect pesticide behavior, but they do not directly relate to the solubility aspect. Highly volatile pesticides can evaporate quickly, while low molecular weight may make it easier for a substance to migrate through the soil. Heavy application rates can lead to increased concentrations in the environment but do not specifically address solubility or leaching potential.