What type of chemicals are mainly used for agricultural purposes in water systems?

The correct choice refers to synthetic organic chemicals, which are extensively used in agricultural practices, including herbicides, insecticides, and fungicides. These compounds are specifically designed to manage pests and enhance crop production. Their systematic application in agriculture is crucial for improving yield and protecting plants from various threats.

Synthetic organic chemicals are often formulated to target specific pests or problems, providing precision in agricultural management. This is important as it allows for more effective interventions, increasing productivity while managing potential environmental impacts.

While inorganic minerals play roles in agriculture, such as fertilizers, synthetic organic chemicals are more prominently used for pest control. Volatile compounds and heavy metals do not typically serve the main purpose of enhancing agricultural productivity, thus making them less relevant in this context.