What property of a pesticide increases its risk of movement with surface runoff?

The correct choice is high solubility, as this property significantly affects the behavior of pesticides when applied to the environment. Pesticides that are highly soluble in water are more likely to dissolve and be carried away with surface runoff. When rain or irrigation occurs, these soluble pesticides can easily mix with water and travel over the soil surface, potentially reaching nearby water bodies or infiltrating into groundwater.

In contrast, pesticides with high volatility tend to evaporate easily into the atmosphere rather than moving with surface runoff. High toxicity refers to the harmful effects of the pesticide but does not directly influence its physical movement in environmental conditions. High viscosity can actually hinder movement, as more viscous substances are thicker and flow less easily, thereby reducing their capacity to be carried away by water. Thus, high solubility increases the risk of a pesticide being transported with surface runoff, making it a critical factor in understanding its environmental impact.