Fate of 14C-Atrazine in a Silt Loam Soil

Abstract

Formation of ¹⁴C-atruzine degradation products and their distribution in the top 90 cm of a silt loam soil was determined during 16 months in the field. After 16 months. 68% of the applied 14C was still present in the soil. By 12 months after treatment (MAT). ¹⁴C leached to 70–80 cm. Atrazine accounted for 24% of the applied ¹⁴C remaining 16 MAT, and was the predominant ¹⁴C-compound below 10 cm through 16 MAT. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil comprising 13% of ¹⁴C present I MAT and increasing to 24% by 12 MAT. Predominant degradation products at depths greater than 10 cm were HA and deethylatrazine (DEA). Deisopropylatrazine (DIA) accounted for less than 6% of the radioactivity recovered at any soil depth. Deethyldeisopropylatrazine (DEDIA) was detected in soil extracts 2 MAT indicating further degradation of DIA and DEA. The proportion of DEA and DIA increased while the proportion of HA decreased at increasing soil depths indicating that DEA and DIA are more mobile in soil than HA. The large amount of ¹⁴C remaining in the soil 16 MAT, and the depth within the soil profile at which it is found, suggest that atrazine and its degradation products have the potential to persist and move deeper in the soil and possibly contaminate ground water supplies.

Key Words:

• Leaching
• ground water quality
• ¹⁴C-herbicides