Which of the following is the correct ordering for groundwater risk at historical herbicide manufacturing sites? Atrazine, Dalapon, Endothall, Ethylbenzene

Which of the following is the correct ordering for groundwater risk at historical herbicide manufacturing sites? Atrazine, Dalapon, Endothall, Ethylbenzene

• A. Atrazine
• B. Dalapon
• C. Endothall
• D. Ethylbenzene

Answer: (C)

Groundwater risk in this context follows how readily a chemical can move with infiltrating water from a historical release into the groundwater. The chemical with the highest potential to reach groundwater is the one that is highly soluble in water and does not bind strongly to soil, so it can travel downward quickly before it degrades. Endothall fits that pattern: it dissolves well and has relatively weak soil sorption, so releases from an old herbicide manufacturing site are more likely to leach into groundwater than the others listed. Atrazine, while persistent and mobile, can sorb to some soils and may degrade over time, reducing downward transport in many scenarios. Ethylbenzene tends to volatilize and biodegrade more readily, which reduces its groundwater persistence, and Dalapon, though mobile, generally does not present leaching potential as high as Endothall under typical site conditions. So Endothall represents the highest groundwater risk among these substances in this historical-site context, making it the best choice.

Groundwater risk in this context follows how readily a chemical can move with infiltrating water from a historical release into the groundwater. The chemical with the highest potential to reach groundwater is the one that is highly soluble in water and does not bind strongly to soil, so it can travel downward quickly before it degrades. Endothall fits that pattern: it dissolves well and has relatively weak soil sorption, so releases from an old herbicide manufacturing site are more likely to leach into groundwater than the others listed. Atrazine, while persistent and mobile, can sorb to some soils and may degrade over time, reducing downward transport in many scenarios. Ethylbenzene tends to volatilize and biodegrade more readily, which reduces its groundwater persistence, and Dalapon, though mobile, generally does not present leaching potential as high as Endothall under typical site conditions. So Endothall represents the highest groundwater risk among these substances in this historical-site context, making it the best choice.