RELATIVE MOBILITIES OF ATRAZINE, 5 ATRAZINE DEGRADATES, METOLACHLOR, AND SIMAZINE IN SOILS OF IOWA

The relative mobilities of atrazine -chloro-4-ethylamino-6-isopropylam ino-s-triazine), five atrazine degradates, metolachlor hylphenyl]-N-[2 -methoxy-1-methylethyl]-acetamide), and simazine (2-chloro-4,6-bis-[et hylamino]-s-triazine) were determined in both surface and subsurface s oils from five locations in Iowa by soil thin-layer chromatography (ST LC). Based on mobility of the compounds, four groups were identified f rom this study. Deethylatrazine (2-chloro-4-amino-6-isopropylamino-s-t riazine) was the most mobile compound. The intermediate mobility group included atrazine, deisopropylatrazine (2-chloro-4-ethylamino-6-amino -s-triazine), and didealkylatrazine (2-chloro-4,6-diamino-s-triazine). The less mobile group included metolachlor and simazine, and the near ly immobile group consisted of ammeline (4,6-diamine-s-triazine-2-ol) and hydroxyatrazine hydroxy-4-ethylamino-6-isopropylamino-s-triazine). A clear division between the intermediate and less mobile group was n ot seen in all soils. Mobilities of all eight compounds in this study were negatively correlated with soil organic matter content (p less th an or equal to 0.05) and positively correlated (except for didealkylat razine) with sand content (p less than or equal to 0.05). The greatest degree of mobility for the compounds studied was seen in Fruitland (s andy) and Nashua (sandy clay loam) subsurface soils, which also had th e least organic matter contents. The mobility relationship of atrazine , deethylatrazine, and deisopropylatrazine in this study (deethylatraz ine greater than or equal to atrazine greater than or equal to deisopr opylatrazine) is consistent with groundwater monitoring reports. Simil ar mobilities of atrazine, deisopropylatrazine, and dideallcylatrazine in some soils of this study suggest that didealkylatrazine is mobile enough to reach groundwater and therefore should be looked for in rout ine monitoring.