What is photo-decomposition of herbicides primarily caused by?

The primary cause of photo-decomposition of herbicides is sunlight exposure. When herbicides are applied to the environment, they can interact with solar radiation, which leads to chemical changes. This process occurs when the energy from sunlight breaks down the chemical structure of the herbicide molecules, rendering them less effective or completely inactive. Photo-decomposition can significantly influence the persistence of herbicides in the environment and is an important factor in their overall degradation and impact on ecosystems.

In contrast, while microbial action in the soil and absorption by organic matter can also affect herbicide degradation, they relate more to biodegradation processes and sorption rather than the specific breakdown induced by sunlight. Temperature variations can influence the rate of chemical reactions, but they do not directly cause photo-decomposition, which specifically involves light energy.