Which process can lead to pollution of water supplies during pesticide handling?

Backflow is a process that can lead to the contamination of water supplies during pesticide handling due to the reversal of water flow in a system. This occurs when there is a pressure difference between two points in a water distribution system, causing potentially contaminated water from a pesticide application to flow back into clean water sources. Proper backflow prevention measures, such as using an air gap or check valves, are essential to protect drinking water supplies from hazardous substances.

In contrast, evaporation refers to the transformation of liquid pesticide into vapor, which does not directly contaminate water supplies but may affect air quality or lead to pesticide drift. Drip irrigation is a method of delivering water directly to plant roots and is generally considered an efficient irrigation technique that does not involve the risk of backflow contamination. Filtration is typically a process used to remove impurities from water rather than a method that would lead to pollution. Therefore, understanding the mechanics of backflow is critical for ensuring safe pesticide handling and preventing environmental contamination.