Non-polar pesticides tend to sorb to soil/sediments via bonds with which component?

• A. Water in solution
• B. Clay minerals
• C. Organic matter in soil/sediments
• D. Atmospheric gases

Answer: (C)

Non-polar pesticides are hydrophobic, so they prefer to leave water and partition into nonpolar organic matter in soils and sediments. Organic matter—like humus and other decayed plant and animal material—offers nonpolar regions and a large surface area that attract these compounds through van der Waals forces and hydrophobic interactions. This makes organic matter the primary sorption site, controlling how much pesticide is held in the solid phase versus remaining dissolved, which in turn affects mobility and persistence. Clay minerals can contribute some sorption, but for non-polar pesticides the dominant interaction is with organic matter. Water in solution is the phase the pesticide leaves, and atmospheric gases aren’t a driving factor here.