Iowa Pesticide Applicator Practice Exam

What happens during a temperature inversion that affects pesticide drift?

1. Vertical air movement increases

2. Air near the ground is warmer than above

3. Horizontal air movement predominates

4. Humidity is eliminated

The correct answer is: Horizontal air movement predominates

During a temperature inversion, the air temperature actually increases with height, which is the opposite of normal atmospheric conditions where it decreases as altitude increases. This phenomenon causes the air near the ground to be cooler than the air above it, creating a stable layer that can trap pollutants, including pesticide particles, close to the surface. The stable conditions during a temperature inversion typically lead to reduced vertical air movement, meaning that any pesticide particles released into the air remain suspended rather than being dispersed upward. Instead, horizontal air movement becomes more prevalent. As a result, the pesticides can drift over greater distances in a horizontal direction, which can lead to potential off-target application and environmental concerns. This increased horizontal air movement is significant for understanding how pesticides can be carried away from the intended application area. The other options do not accurately describe the effects of a temperature inversion in relation to pesticide drift. Vertical air movement does not increase; instead, it diminishes during an inversion. The characterization of air near the ground being warmer is incorrect as the ground air is typically cooler. Lastly, humidity may still be present, but it is not eliminated; rather, it can affect the behavior of pesticide particles in the air differently.