Which of the following is NOT a process that causes pesticides to break down after application?

The correct answer indicates that atmospheric degradation is not recognized as a process that directly contributes to the breakdown of pesticides after they have been applied.

Atmospheric degradation generally refers to the effects of environmental factors, such as sunlight, temperature variations, and wind, which can alter the chemical composition of substances in the atmosphere. While atmospheric conditions play a role in how pesticides behave once they are in the environment, they do not constitute a specific process by which pesticides are broken down in the same manner as the other listed processes.

In contrast, photo degradation involves the breakdown of chemicals through the action of sunlight, microbial degradation refers to the breakdown by microorganisms like bacteria and fungi, and chemical degradation relates to the changes within the chemical structure of the pesticide due to reactions with other chemicals or environmental factors. Each of these processes specifically contributes to how pesticides are degraded in the environment, making atmospheric degradation distinct from them in terms of its role in pesticide breakdown.