Formation and Movement of¹⁴C-Atrazine Degradation Products in a Sandy Loam Soil Under Field Conditions

Abstract

Formation and distribution of14C-atrazine degradation products in the top 120 cm of soil were determined over 16 mo under field conditions in an Estherville sandy loam. After 16 mo, 78% of applied14C was still present in the soil. By 2 mo after treatment (MAT),14C had moved to the 30- to 40-cm depth; however, movement to depths greater than 40 cm was not observed. Greater than 98% of the14C remaining in the soil profile after 16 mo was in the top 20 cm. Twenty-seven percent of the14C applied was atrazine 16 MAT. Atrazine was the predominant14C-compound in soil below 10 cm. Hydroxyatrazine (HA) was the major degradation product in the top 10 cm of soil. The proportion of14C as HA in the top 10 cm increased from 15% 2 MAT to 37% 16 MAT. Deethylatrazine (DEA) was the predominant degradation product at the 10- to 30-cm depth and accounted for up to 23% of the14C present in the 10- to 20-cm depth. Deisopropylatrazine (DIA) accounted for less than 6% of the radioactivity recovered at any soil depth. The proportion of DEA and DIA increased while the proportion of HA decreased as soil depth increased, indicating that DEA and DIA are more mobile in soil than HA. Detection of HA at depths greater than 10 cm appears to be due to in situ degradation of atrazine previously moved to that soil depth. The large amount of14C remaining in the soil 16 MAT suggests that a large pool of atrazine and its degradation products are present in the soil for an extended period following application and have the potential to contaminate ground water.

Atrazine behaviour in the different pedological horizons of two Argentinean non‐till soil profiles

“…The increasing rate of atrazine mineralization throughout all the incubation period observed in the BC horizon could indicate a natural contamination of atrazine‐degrading micro‐organisms from the surface reaching the subsoil through fissures in the soil profile because of the presence of an argilic horizon (Bt) (Jury & Flühler, 1992). Sorenson et al. (1993, 1994) showed a higher mobility of atrazine in a clay loam profile than in a sandy profile.…”

Use of Field Lysimeters To Determine 14C-Dicamba Persistence and Movement in Soil

“…Previously, we have also successfully used large field lysimeters (0.3 m diam by 0.9 to 1.0 m deep) to determine the degradation and movement of 14 Catrazine and its major metabolites in three soils in Minnesota (11)(12)(13). These lysimeters were inserted into the soil, 14 C-herbicide applied to the soil, and corn plants grown in and around the lysimeters.…”

Fate of a Symmetric and an Asymmetric Triazine Herbicide in Silt Loam Soils

“…Leachate collected from monitoring columns in the silt loam in this study and a clay loam (32) and sandy loam (12) indicated that water moved through the soils and was capable of leaching 14 C-compounds. Greater leaching of 14 C in the silt loam and clay loam (32) than in the sandy loam (12) appears to be a function of the greater water holding capacity of these soils.…”

“…Radioactivity in the silt loam decreased to 64% of applied 4 MAT, compared to 75 and 80% in the sandy loam (12) and clay loam (32) soils, respectively. Total radioactivity in the silt loam and sandy loam soils did not decrease after the 4-MAT sampling and was 68 and 78%, respectively, 16 MAT.…”

“…A fence was constructed to control access to the plots. 14 C-atrazine (0.85 MBq) in 5 ml methanol was applied to the center 10 cm of the column, 2.5 cm below the soil surface on May 20, 1988 as previously described (12) to minimize volatilization losses. Following application, three corn (Zea mays L.) seeds were planted in the center of each column.…”