Which process does NOT contribute to the breakdown of pesticides after application?

Atmospheric degradation refers to the breakdown of substances through reactions with components in the atmosphere, such as sunlight, water vapor, and other gases. While atmospheric processes can influence the fate of pesticides, this option is considered not as direct in contributing to the breakdown of pesticides after application compared to the other methods listed.

Photo-degradation, for instance, involves the breakdown of pesticides through the action of sunlight, which can significantly alter or degrade many chemicals present in pesticides. Microbial degradation is the process where microorganisms such as bacteria or fungi metabolize pesticides, leading to their breakdown in the soil. Chemical degradation involves chemical reactions that can occur in the environment, further breaking down pesticide compounds into less harmful substances.

In contrast, atmospheric degradation is generally a broader category that might not specifically target the chemical interactions relevant to the immediate breakdown of pesticides, making it less relevant in this context.